Bicuspid Aortic Valve – An important incidental PoCUS finding?

Bicuspid Aortic Valve – An important incidental PoCUS finding?

Medical Student Pearl

 

Khoi Thien Dao

MD Candidate – Class of 2023

Dalhousie Medicine New Brunswick

Reviewed by: Dr. David Lewis


Case:

A 58-year-old male presents to Emergency Department with sudden onset of chest pain that is radiating to the back. He was also having shortness of breath at the same time of chest pain. The patient later reveals that his past medical history only consists of “bicuspid valve”, and he takes no medication. On examination, he was uncomfortable, but no signs of acute distress. His respiratory and cardiac exam were unremarkable for reduced air sound, adventitious sound, heart murmur, or extra heart sound. ECG was normal and initial cardiac markers were within normal range. His chest x-ray is normal.

You are aware that with his medical presentation and a history of bicuspid aortic valve, you need to consider associated concerning diagnosis (aortic root aneurysm and aortic dissection) within the differential (myocardial infarct, congestive heart failure, pneumonia, etc.).


Bicuspid Aortic Valve

Bicuspid aortic valve is one of the most common types of congenital heart disease that affects approximately one percent of population. There is a strong heritable component to the disease. Bicuspid aortic valve occurs when two leaflets fused (commonly right and left coronary leaflets) and form a raphe, a fibrous ridge1. The fusion of the leaflets can be partial, or complete, with the presence or absence of a raphe1. Bicuspid aortic valve disease is associated with increasing risks for valve calcification, which lead to aortic stenosis or regurgitation secondary to premature degeneration1. This congenital heart defect is also a well-known risks factor for aortic dissection and aortic dilatation. Reports have estimated prevalence of aortic dilation in patients with bicuspid aortic valve ranging between 20 to 80 percent, and that the risks of aortic dilation increase with age2. Increases risk of aortic dilatation in bicuspid valve disease also leads to a significantly greater risk for aortic dissection2.3.

The majority of patients with bicuspid aortic valve are asymptomatic with relatively normal valve function and therefore can remain undiagnosed for many years. However, most patients with bicuspid aortic valve will develop complications and eventually require valve surgery within their lifetime. Early diagnosis, while asymptomatic, can enable close follow-up for complications and early intervention with better outcomes. However, asymptomatic individuals are rarely referred for echocardiography.

With increasing use of cardiac PoCUS by Emergency Physicians, there are two scenarios where increased awareness of the appearance of bicuspid aortic valve and its complications may be of benefit.

  1. Known bicuspid aortic valve patients presenting with possible associated complications
  2. Undiagnosed bicuspid aortic valve patients presenting with unrelated symptoms undergoing routine cardiac PoCUS

This clinical pearl provides a review of the clinical approach to bicuspid aortic valve and its associated complications and provides guide to enhancing clinical assessment with PoCUS.


Clinical Approach:

Although bicuspid aortic valve commonly presents as asymptomatic, a detailed focused cardiac history can assess for clinical signs and symptoms related to valve dysfunction and its associated disease, such as reduced exercise capacity, angina, syncope, or exertional dizziness1. Information about family history with relation to cardiac disease is essential for a clinician’s suspicion of heritable cardiovascular disease. Red flag symptoms that shouldn’t be missed such as chest pain, back pain, hypertensive crisis, etc. should be specifically identified. They are indicators for possible emergent pathologies that should not be missed (for example: acute MI, aortic dissection, ruptured aortic aneurysm, etc.)

Physical examination findings in patients with bicuspid aortic valve include, but not limited to, ejection sound or click at cardiac apex/base, murmurs that have features of crescendo-decrescendo or holosystolic. Clinical signs of congestive heart failure such as dyspnea, abnormal JVP elevation, and peripheral edema may also be present.


Core Cardiac PoCUS:

With cardiac PoCUS, it is important to obtain images from different planes and windows to increase the complexity of the exam and to be able to be confidently interpreting the exam. There are four standard cardiac view that can be obtained: parasternal short axis (PSSA), parasternal long axis (PSLA), subxiphoid (sub-X), and apical 4-chamber view (A4C). Each cardiac view has specific benefits.

Parasternal Long Axis

With the PSLA, the phased-array transducer is placed to the left sternum at 3rd or 4th intercostal with transducer orientation pointing toward patient’s right shoulder. Key structures that should be seen are Aortic Valve (AV), Mitral Valve (MV), Left Ventricle (LV), pericardium, Right Ventricle (RV), Left Ventricular Outflow Tract (LVOT), and portion of ascending and descending aorta8. It is primarily used to assess left ventricular size and function, aortic and mitral valves, left atrial size8. Furthermore, pericardial effusions and left ventricular systolic function can be assessed.

Parasternal Long Axis

 

Parasternal Short Axis

Using the same transducer position as the PSLA the transducer can be centered to the mitral valve and rotated 90 degrees clockwise to a point where the transducer marker points to patient’s left shoulder to obtain the PSSA. With this orientation, one can assess for global LV function and LV wall motion8. Furthermore, with five different imaging planes that can be utilized with this view, aortic valve can be visualized in specific clinical contexts.

Parasternal Short Axis

 

Apical 4-Chamber

The apical 4-chamber view is generated by placing the transducer at the apex, which is landmarked just inferolateral to left nipple in men and underneath inferolateral of left breast in women. This view helps the clinician to assess RV systolic function and size relative to the LV8.

Apical 4-Chamber

 

Subxiphoid

The subxiphoid view can be visualized by placing a transducer (phased-array or curvilinear) immediately below the xiphoid process with the transducer marker points to patient’s right. The movements of rocking, tilting, and rotation are required to generate an optimal 4-chamber subcostal view. A “7” sign, which consists of visualizing the border between liver and pericardium, the septum, and the RV and LV that looks like number 7. This view allows user to assess RV functions, pericardial effusion, and valve functions8. In emergency setting, it can be used for rapid assessments in cardiac arrest, cardiac tamponade, and global LV dysfunction8.

From –  the PoCUS Atlas

Subxiphoid labelled

 

7 Sign


PoCUS Views for Aortic Valve Assessment

In assessing the aortic valve, the PSSA and PSLA can be best used to obtain different information, depending on clinical indications. Both views can be used to assess blood flows to assess stenosis or regurgitation. However, the PSLA view includes the aorta where clinician can look for aortic valve prolapse or doming as signs of stenosis and its complications, like aortic dilatation. On the other hand, PSSA are beneficial when assessing the aortic valve anatomy.

Parasternal Long Axis

From PoCUS 101

Parasternal Short Axis

From – the PoCUS Atlas


PoCUS Appearance of Normal Aortic Valve (Tricuspid) vs Bicuspid Aortic Valve

With PSSA view, the normal aortic valve will have three uniformly leaflets that open and form a circular orifice during most of systole. During diastole, it will form a three point stars with slight thickening at central closing point. The normal aortic valve is commonly referred to as the Mercedes Benz sign.

Parasternal Short Axis – Normal Tricuspid AV – Mercedes Benz Sign and 3 cusp opening

Pitfall

However, the Mercedes Benz Sign sign can be misleading bicuspid valve disease when three commissure lines are misinterpreted due to the presence of a raphe. A raphe is a fibrous band formed when two leaflets are fused together. It is therefore important to visualize the aortic valve when closed and during opening, to ensure all 3 cusps are mobile. Visualization of The Mercedes Benz sign is not enough on its own to exclude Bicuspid Aortic Valve.

Apparent Mercedes sign when AV closed due to presence of raphe. Fish mouth appearance of the same valve when open confirming bicuspid aortic valve

Bicuspid Aortic Valve

Identification requires optimal valve visualization during opening (systole). Appearance will depend on the degree of cusp fusion. In general a ‘fish mouth’ appearance is typical for bicuspid aortic valve.

Parasternal Short Axis – Fish Mouth Opening – Fusion L & R Coronary Cusps – Bicuspid Aortic Valve

In the parasternal long axis view the aortic valve can form a dome shape during systole, and prolapse during diastole, rather than opening parallel to the aorta. This is called systolic doming. Another sign that can be seen in PSLA view is valve prolapse, when either right or non-coronary aortic valve cusps showed backward bowing towards the left ventricle beyond the attachment of the aortic valve leaflets to the annulus. This can be estimated by drawing a line joining the points of the attachment.

Systolic doming

 

Diastolic prolapse and systolic doming

 

 

 


PoCUS Appearance of the Complications of Bicuspid Valve Disease

In patients presenting with chest/back pain, shock or severe dyspnea who have either known or newly diagnosed bicuspid valve disease, PoCUS assessment for potential complications can be helpful in guiding subsequent management.

Complications of bicuspid aortic valve include aortic dilatation at root or ascending (above 3.8cm) and aortic dissection 5-9.

Dilated aortic root, from – sonomojo.com

Aortic root dilatation – Normal maximum = 40mm

 

Aortic root dilatation with dissection

Valve vegetations or signs of infective endocarditis are among the complications of severe bicuspid valve5-9

Aortic valve vegetations


General Management of Patients with Bicuspid Valve in the Emergency Department

Management of bicuspid aortic valve disease is dependent on the severity of the disease and associated findings.

For a patient with suspicious diagnosis of bicuspid valve disease, a further evaluation of echocardiography should be arranged, and patient should be monitored for progressive aortic valve dysfunction as well as risk of aortic aneurysm and dissection. Surgical intervention is indicated with evidence of severe aortic stenosis, regurgitation, aneurysm that is > 5.5cm, or dissection1.


How accurate is PoCUS for Aortic Valve assessment?

Bicuspid aortic valve disease is usually diagnosed with transthoracic echocardiography, when physical examination has revealed cardiac murmurs that prompt for further investigation. However, patients with bicuspid valve disease frequently remain asymptomatic for a prolonged periods. Michelena et al. (2014) suggested that auscultatory abnormalities account for 60 to 70% diagnostic echocardiograms for BAV in community10.

While there are no published studies on the utility of PoCUS for the diagnosis of bicuspid aortic valve, there are studies on the use of PoCUS as part of the general cardiac exam. Kimura (2017) published a review that reported early detection of cardiac pathology when PoCUS was used as part of the physical exam 9. Abe et al. (2013) found that PoCUS operated by expert sonographer to screen for aortic stenosis has a sensitivity of 84% and a specificity of 90% in 130 patients 11. In another study by Kobal et al. (2004), they found that PoCUS has a specificity of 93% and sensitivity of 82% in diagnosing mild regurgitation12.

There are also limitations of using PoCUS to assess for bicuspid aortic valve disease, or valve disease in general. Obtaining images from ultrasound and interpretation are highly dependent on user’s experiences to assess for the valve9. Furthermore, research is needed to investigate the use of PoCUS in lesser valvular pathology.

 

When a new diagnosis of bicuspid aortic valve is suspected, a formal echocardiogram should be arranged, and follow-up is recommended.


Summary 

  • Bicuspid aortic valve is often asymptomatic and undiagnosed until later in life
  • Patients with known bicuspid aortic valve disease are closely followed and may require surgical intervention in the event of complications
  • Diagnosis of bicuspid aortic valve requires careful visualization of valve closing and opening during diastole and systole
  • The increased use of PoCUS by Emergency Physicians as an adjunct to cardiac examination may result in increased diagnosis of bicuspid  aortic valve. These may be related to the presentation or incidental findings
  • In patients presenting to the Emergency Department with known or newly diagnosed bicuspid aortic valve disease, consider if a complication is related to their presentation
  • In patient with incidental finding of bicuspid aortic valve disease refer for cardiology follow up

 


References

  1. Braverman, A. C., & Cheng, A. (2013). The bicuspid aortic valve and associated aortic disease. Valvular heart disease. Philadelphia: Elsevier, 179-218.
  2. Verma, S., & Siu, S. C. (2014). Aortic dilatation in patients with bicuspid aortic valve. N Engl J Med370, 1920-1929.
  3. Della Corte, A., Bancone, C., Quarto, C., Dialetto, G., Covino, F. E., Scardone, M., … & Cotrufo, M. (2007). Predictors of ascending aortic dilatation with bicuspid aortic valve: a wide spectrum of disease expression. European Journal of Cardio-Thoracic Surgery31(3), 397-405.
  4. Tirrito, S. J., & Kerut, E. K. (2005). How not to miss a bicuspid aortic valve in the echocardiography laboratory. Echocardiography: A Journal of Cardiovascular Ultrasound and Allied Techniques22(1), 53-55.
  5. Baumgartner, H., Donal, E., Orwat, S., Schmermund, A., Rosenhek, R., & Maintz, D. (2015). Chapter 10: Aortic valve stenosis. The ESC textbook of cardiovascular imaging. European Society of Cardiology.
  6. Fowles, R. E., Martin, R. P., Abrams, J. M., Schapira, J. N., French, J. W., & Popp, R. L. (1979). Two-dimensional echocardiographic features of bicuspid aortic valve. Chest75(4), 434-440.
  7. Shapiro, L. M., Thwaites, B., Westgate, C., & Donaldson, R. (1985). Prevalence and clinical significance of aortic valve prolapse. Heart54(2), 179-183.
  8. Gebhardt, C., Hegazy, A.F., Arntfield, R. (2015). Chapter 16: Valves. Point-of-Care Ultrasound. Philadelphia: Elsevier, 119-125.
  9. Kimura, B. J. (2017). Point-of-care cardiac ultrasound techniques in the physical examination: better at the bedside. Heart103(13), 987-994.
  10. Michelena, H. I., Prakash, S. K., Della Corte, A., Bissell, M. M., Anavekar, N., Mathieu, P., … & Body, S. C. (2014). Bicuspid aortic valve: identifying knowledge gaps and rising to the challenge from the International Bicuspid Aortic Valve Consortium (BAVCon). Circulation129(25), 2691-2704.
  11. Abe, Y., Ito, M., Tanaka, C., Ito, K., Naruko, T., Itoh, A., … & Yoshikawa, J. (2013). A novel and simple method using pocket-sized echocardiography to screen for aortic stenosis. Journal of the American Society of Echocardiography26(6), 589-596.
  12. Kobal, S. L., Tolstrup, K., Luo, H., Neuman, Y., Miyamoto, T., Mirocha, J., … & Siegel, R. J. (2004). Usefulness of a hand-carried cardiac ultrasound device to detect clinically significant valvular regurgitation in hospitalized patients. The American journal of cardiology93(8), 1069-1072.
  13. Le Polain De Waroux, J. B., Pouleur, A. C., Goffinet, C., Vancraeynest, D., Van Dyck, M., Robert, A., … & Vanoverschelde, J. L. J. (2007). Functional anatomy of aortic regurgitation: accuracy, prediction of surgical repairability, and outcome implications of transesophageal echocardiography. Circulation116(11_supplement), I-264.
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Resuscitative Transesophageal Echo

Resuscitative TEE – the whats, the whys and the hows…. A brief review of the literature, examples of use and a proposed cardiac arrest protocol

Dr. David Lewis

Professor, Dalhousie Department of Emergency Medicine


Download SlidesPoCUS Rounds – TEE – Nov 2022



Further Reading

Introduction to Transesophageal Echo – Basic Technique

   http://pie.med.utoronto.ca/tee/

ACEP NOW – How to Perform Resuscitative Transesophageal Echocardiography in the Emergency Department

 

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Volume Status Assessment in ED: Beyond the Vitals

Dr. Rawan Alrashed (@rawalrashed)

PEM Physician

PoCUS Fellow

Reviewed and edited by: Dr. David Lewis

Case

A 55 year old man known to have hypertension, diabetes, atrial fibrillation, chronic kidney disease presenting with 1 week H/O fever, SOB, chest pain, cough, fatigability, looking distressed on exam with HR 110, SpO2 of 86% on RA and BP of 87/45. No audible crackles or gallop rhythm, bilateral pitting edema noticed.

So, you are asking yourself should your next step be Fluids or Diuresis ??

Background

Patient presenting to the emergency department as critically ill with shock status presents a challenge in the initial hour to balance their fluid requirements with their volume status to reach an improvement in hemodynamics without causing harm.

Volume status assessment and fluid responsiveness have been investigated using multiple measures ranging from physical examination to laboratory work up to invasive measures. Despite all that, no single or multiple factor have been sensitive or specific enough to guide further fluid management. Currently, PoCUS is progressing widely in aiding the emergency physician to take a decision in assessing patient’s  fluid vs vasopressor vs diuretic needs and guide further resuscitation. PoCUS is noninvasive, readily available, reproducible test that can be augmented with other measures to guide fluid management (1).

 

Pathophysiology

To simplify fluid responsiveness, patients are assessed on accordance of the Frank-Starling curve. Patients will respond to fluid administration if they are on the ascending portion of the Starling curve and no benefit will be added if they are at a plateau where more harm can occur which is difficult to be predict form physical examination solely (2).

 

Figure 1: Frank Starling Law

 

Fluid Challenge

Traditionally volume responsiveness has been assessed by small fluid bolus challenge. A safer alternative to this is passive leg raise (PLR) which is an autotransfusion where you mobilize about 300-500 ml of intravascular volume from the lower limb to the heart by raising the patient legs from 0o to 45o. A Pre-Post assessment of stroke volume within 30-90 sec from PLR can be done to measure the difference where change of 10% consider to be responsive.

This have been shown to have a sensitivity of 77% to 100%, and a specificity of 88% and 99% (1).

 

Figure 2: Passive Leg raising technique (uptodate)

 

Volume Status Assessment

PoCUS have been used in volume status assessment and fluid responsiveness using multiple surrogates which can be classified as follows for simplification:

  1. Cardiac PoCUS: core and advanced.
  2. Stroke volume Assessment: VTI of LVOT/Carotid artery.
  3. Vascular Assessment: IVC, IJV.
  4. Venous Congestion: Hepatic, portal, & intra-renal doppler.
  5. Lung PoCUS.

 

1) Cardiac PoCUS

The target of Cardiac PoCUS is to assess for possible causes of hypotension and shock status using the RUSH or SHoC protocol (3).

 

Figure 3: SHoC Protocol (3).

 

2) Cardiac Output Assessment

Two measures can be used to assess fluid responsiveness: the left ventricular outlet tract (LVOT) and the carotid artery where you assess the velocity time integral (VTI) representing the column of blood passing through the vessel through time. This can be used as surrogate of fluid responsiveness before and after the PLR where a change of 10-15% consider as fluid responsive (4).

 

a. LVOT measurements

Cardiac output variation of greater than 14% has a high positive predictive value for the patient being fluid responsive while values less than 10% are associated with a high negative predictive value (1)

Cardiac output (mL/min) = Stroke Volume (mL/cycle) x Heart Rate (bpm)

Stroke Volume= LVOT area    x    LVOT VTI

 

PoCUS Technique (4)

  • Using the cardiac phased array probe to get apical 5 chamber view and parasternal long axis view.
  • Apical five chamber view, with visualization of the LVOT (A).
  • Pulsed wave Doppler interrogation of the LVOT. The interrogation window is placed just above the aortic valve, and the line of interrogation is positioned parallel to the long-axis of the LVOT itself (B).
  • Measuring the area under the curve of the LVOT Doppler waveform to derive the velocity time integral (C) .
  • Diameter of the LVOT, measured from a parasternal long-axis view (D)

Figure 4: Stroke volume measurement at the LVOT.

 

 

b. Common Carotid Artery

Two measurement are applied to the carotid artery: the carotid blood flow and the corrected carotid flow time index. These measure are recently established in the field of cardiac output assessment and accuracy is still under debate with further studies needed.

 

  • The carotid blood flow is the integral of blood volume that is ejected through the carotid artery with each cardiac cycle. An increase of carotid blood flow by 20% after PLR is indicative of fluid responsiveness with a sensitivity of 94% and specificity of 86% (6).

 

  • The corrected carotid flow time index  (CFTI) representing the flow time between the onset of systole and the closure of the aortic valve as the duration of the full cardiac cycle. A change in the CFTI of 25% following PLR was found to have high specificity but a low sensitivity accordingly a cutoff values of 10% to 15% are more typical, still further studies are needed to specify the accurate cut off value (4).

 

PoCUS Technique (4,5)

a. The linear transducer is placed at approximately at the level of the thyroid cartilage, with the orientation marker pointed toward the patient’s head (A).

b. The Carotid artery identified in long-axis and the bulb before the bifurcation visualized and the doppler is applied within 2–3 cm proximal to the carotid bulb, interrogation line (green) has also been angled to make it more parallel to the long-axis of the artery.

c. The Doppler angle correction cursor is placed parallel to the direction of blood flow with insonation angles <60° .

d. Carotid artery Doppler waveform with measurement of the systolic flow time (SFT) and total cycle time (CCT).

e. Calculate the corrected flow time index using the following formula (Figure-5):

                                           CFTI=SFT/√CCT

f. Calculate the carotid blood flow using velocity time integral tracing and carotid diameter (Intima to intima)  then apply it in this formula (Figure-6):

                                     blood flow=π×(carotid diameter)2/4×VTI×heart rate

 

Figure-5: Corrected Carotid Flow Time Index Measurement (4).

 

Figure-6: Carotid Blood Flow measurement (5).

 

 

 

3) Vascular Assessment

a. Inferior vena cava (IVC)

Measurements of IVC diameter and respiratory variation with the collapsibility index as a predictor of fluid responsiveness was found to be having pooled sensitivity and specificity of 63% and 73% respectively (7).  

PoCUS Technique (8)

  • Use the curvilinear or phased array probe.
  • placed in the sub-xiphoid space with the transducer flat against the abdomen identifying RA and gradually fanning the probe until the intrahepatic IVC can be identified.
  • The probe is then rotated 90 degrees with the marker toward patient head to obtain the IVC in long axis view.
  • IVC diameter is measured 2 cm inferior to the cavo-atrial junction or about 1 cm inferior to the branching of the hepatic veins (Figure 7).
  • M-mode can be used to track IVC collapse during inspiration in spontaneously breathing patients.

Figure-7: IVC and measurement of respiratory variation (Collapsibility Index)

 

Measurements:

Collapsibility Index (Caval Index)

The collapsibility index=(maximal vessel diameter – minimal vessel diameter)÷maximal vessel diameter

It has been demonstrated that venous collapsibility may be inversely proportional to CVP: a 1 mmHg change in central venous pressure correlates to about 3.3% change in IVC collapsibility (9).

 

IVC diameter (cm) CI (%) CVP (mmHg)
<1.5 100% <0-5 Volume depleted
1.5-2.5 >50% <10 Less predictive of responsiveness
1.5-2.5 <50 >10
>2.5 0% >20 Volume overload

 

Important to note that sole interpretation of the IVC for volume assessment was found to be poorly correlating and thus should be used in conjunction with  other measures and integrated on patient presentation (9).

 

b. Internal Jugular Vein (IJV)

Internal jugular vein is used for the assessment of the central venous pressure in comparable way to IVC. A small study of non-ventilated patients who were simultaneously undergoing CVP monitoring, a mean IJV diameter of 7 mm correlated with a CVP of 10 mmHg (8). 

Collapsibility index of the IJV with change of 39% consider the patient as volume depleted but this carries a limitation of the intrabdominal/ intrathoracic pressure effects (4).

PoCUS Technique

  • Use the linear Probe
  • Identify the IJV in transverse plane then rotate the probe 90o toward the patient head.
  • Image of IJV is obtained where it narrows into a paintbrush appearance (Figure 8).
  • The height where the IJV tapers correlates with jugular venous distension.
  • The IJV diameter is measured using M-mode through several respiratory cycles, and the end expiratory diameter is used as the final measurement.

Figure-8: Internal Jugular vein

 

4)Venous Congestion (VEXUS):

This includes assessment of the Hepatic/Portal/Intrarenal veins wave forms which has been correlated to the level of venous congestion thus estimating the end organ volume effects.

Hepatic Vein Doppler mainly reflects the right atrium filling pattern, portal and intrarenal venous Doppler provide additional information about right atrial filling pressure and its correlation with congestive organ injury (10).

 

PoCUS Technique (9)

Hepatic Vein Doppler

  • The probe is placed over the liver in the subcostal position to visualize the middle hepatic vein. Pulsed-wave Doppler is used 2-4 cm from where the hepatic vein drains into the IVC.

Findings: The waveform of the hepatic vein is reversed with higher velocities seen in diastole in states of volume overload. In severe volume overload, retrograde flow is seen in systole (Figure 9)

 

Figure-9: Hepatic vein doppler different wave forms (11).

 

Portal Vein Doppler

  • Moving towards the portal vein, the transducer is placed in the right mid-axillary line

Findings: Flow through the portal vein is normally monophasic, but in the presence of hypervolemia, pulsatility will be present. This can be quantified using the pulsatility index where a pulsatility index greater than 50% indicates severe volume overload.

 

Figure 10: Portal vein doppler wave forms (11).

 

Intra-renal Doppler

  • The curvilinear transducer is placed on the posterior axillary line

Findings: A normal Doppler waveform is continuous. With increasing venous congestion, there is a decrease in the systolic component of the wave with progression to biphasic (systolic/diastolic phases), and with severe renal congestion, there is complete absence of systolic flow showing only diastolic phase.

 

Figure 11: Intra-renal doppler wave forms (11).

 

Figure-12: the change in the venous doppler according to progression of venous congestion (10).

 

Figure -13: VExUS grading system for venous congestion using IVC and different venous doppler wave form for categorization.

 

5)Lung Ultrasound 

A meta-analysis showed that LUS is 88% sensitive and 90% specific for acutely decompensated heart failure and was more sensitive at detecting pulmonary edema than CXR (8).

Another meta-analysis determined the sensitivity and specificity of ultrasound for detection of pleural effusions as 93% and 96% respectively. The sensitivity approaches 100% with pleural effusions >100 mL in volume (8).

PoCUS Technique

  • Use the linear or curvilinear probe.
  • In longitudinal plane, along the midclavicular, midaxillary line then the posterior-lateral point.

Findings:

  • B-lines are hyperechoic vertical lines extending from the pleura down to the bottom of the US image (Figure 14). Two or fewer B-lines in each section is considered normal
  • Pleural effusion can be identified with presence of V-sign (extension of vertebral line proximal to the diaphragm (Figure-15) .  

 

Figure 14: B-Lines

Figure 15: Pleural effusion

 

 

 

 

 

 

 

 

 

 

Case Conclusion

Patient was found to have reduced LV function with Dilated IVC and CI of 15%, VExUS grade 2. Assessment of COP after PLR didn’t show a proper change thus patient was started on diuretic and respiratory support with consideration of inotropic support. 

Conclusion

The table below (8) shows a summary of the evidence related to the different used marker for volume assessment from physical exam to the use of PoCUS. Thus, it is imperative that we do not rely on one single tool, but rather integrate both pertinent physical examination and POCUS findings for better probability of coming to the right decision.

 

 

References

  1. Pourmand A, Pyle M, Yamane D, Sumon K, Frasure SE. The utility of point-of-care ultrasound in the assessment of volume status in acute and critically ill patients. World J Emerg Med. 2019;10(4):232-238. doi:10.5847/wjem.j.1920-8642.2019.04.007.
  2. Praveen P., Shanmugam L., Prasath, P. A review of role of lung ultrasound and clinical congestion score in acute left ventricular failure. International Journal of Advances in Medicine. 2020;7. 720. 10.18203/2349-3933.ijam20201130.
  3. Atkinson P, Bowra J, Milne J, et al. International Federation for Emergency Medicine Consensus Statement: Sonography in hypotension and cardiac arrest (SHoC): An international consensus on the use of point of care ultrasound for undifferentiated hypotension and during cardiac arrest – CORRIGENDUM. CJEM. 2017;19(4):327. doi:10.1017/cem.2017.31.
  4. Millington SJ, Wiskar K, Hobbs H, Koenig S. Risks and Benefits of Fluid Administration as Assessed by Ultrasound. Chest. 2021;160(6):2196-2208. doi:10.1016/j.chest.2021.06.041.
  5. Ma IWY, Caplin JD, Azad A, et al. Correlation of carotid blood flow and corrected carotid flow time with invasive cardiac output measurements. Crit Ultrasound J. 2017;9(1):10. doi:10.1186/s13089-017-0065-0.
  6. Marik PE LA, Young A, Andrews L. The use of bioreactance and carotid Doppler to determine volume responsiveness and blood flow redistribution following passive leg raising in hemodynamically unstable patients. Chest. 2013;143(2):364-370. doi:10.1378/chest.12-1274.
  7. Long E, Oakley E, Duke T, Babl FE. Does Respiratory Variation in Inferior Vena Cava Diameter Predict Fluid Responsiveness: A Systematic Review and Meta-Analysis. Shock (Augusta, Ga). 2017;47(5):550-559.
  8. Kearney, D., Reisinger, N., & Lohani, S. (2022). Integrative Volume Status Assessment. POCUS Journal7(Kidney), 65–77.
  9. Argaiz Eduardo R, Koratal A., Reisinger N. Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography. Kidney360
  10. Galindo P, Gasca C, Argaiz ER, Koratala A. Point of care venous Doppler ultrasound: Exploring the missing piece of bedside hemodynamic assessment. World J Crit Care Med. 2021;10(6):310-322. Published 2021 Nov 9. doi:10.5492/wjccm.v10.i6.310.
  11. Dinh, V. (n.d.). Vexus ultrasound score – fluid overload and venous congestion assessment. POCUS 101. Retrieved March 29, 2022, from https://www.pocus101.com/vexus-ultrasound-score-fluid-overload-and-venous-congestion-assessment/. 

 

 

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PoCUS in Early Pregnancy – a review

PoCUS in Early Pregnancy – a Resident Clinical Pearl (RCP)

Dr. Victoria Landry, R3

Integrated Family Medicine Emergency Medicine Program

Saint John, NB

Edited by Dr. Rawan AlRashed, PoCUS fellow

Copyedited by Dr. Mandy Peach

PoCUS use by the emergency physician for the diagnosis of uncomplicated intrauterine pregnancy have been proven to be affective in expiditing patient management and decreasing the length of stay in the emergency department. In a metanlaysis done by Stein et.al. emergency physiscain performed PoCUS was found to be 99.3% sensitive in ruling out ectopic pregnancy by detecting an Intauterine pregnancy (IUP). In this review, ultrasound findings in the first trimester will be highlighted.

Indication: Confirmed or suspected pregnancy with abdominal pain, vaginal bleeding, syncope, or hypotension(2)

Technique

Start with trans-abdominal ultrasound (TAUS) (1,2)

  • Use abdominal probe (deep penetration, wide field view; use “obstetrics” or “gynecology” preset)
  • Acoustic window is a full bladder (anechoic structure in the near field). Uterus is a homogenous structure beneath bladder
  • Place abdominal probe midline longitudinally/sagitally immediately superior to symphysis pubis with probe marker toward patient’s head. Adjust depth so uterus is in middle of screen. Sweep left and right till uterus disappears in each view.
  • Rotate probe 90° into transverse plane with marker toward patient’s right side. Sweep up and down till uterus disappears in each view.
  • To improve image: Turn the gain down, sweep slowly

Then Consider the use of transvaginal ultrasound (TVUS) if available, and qualified to use  (1)

  • Requires empty bladder, Patient in lithotomy position.
  • Ultrasound gel on probe, latex condom over top (ensure no air bubbles), then sterile lubricant
  • Reference mark toward ceiling (in sagittal orientation), insert 4-5cm into vagina, sweep left and right
  • Turn probe 90° C to be in coronal plane and marker to the right of the patient – sweep anterior and posterior

General principles (1)

  • follow the endometrial stripe (echogenic line within uterus) along its entire course (left to right in longitudinal view, cervix to fundus in transverse view), looking for evidence of a pregnancy
  • You are trying to rule in an intrauterine pregnancy (IUP) (as opposed to rule out an ectopic) – assume all pregnancies are ectopic until proven otherwise(2)

 

Figure 1 – Longitudinal/sagittal view (TAUS): (1)

Figure 2 – Transverse view (TAUS): (1)

Discrimination zone (βHCG levels below which you cannot see an IUP)(2, 3)

  • TVUS – βHCG 1500-2000 mlU/ml
  • TAUS – βHCG 5000-6000 mlU/ml
  • If No definite IUP (NDIUP) above these levels, strongly consider ectopic!

Findings:

Inutrauterine pregnancy

  • The “double ring sign is the earliest sign of a definitive IUP. Diagnosing an intrauterine pregnancy (IUP) requires visualization of all 3 structures inside the uterus. (1,2)
  • Decidual reaction – hyperechoic (white) line in uterus (2) represents endometrium thickening – begins around day 14 post-fertilization (1)
  • Gestational sac – anechoic (black) round area within decidual reaction, contains amniotic fluid, seen at 4-5wks (TVUS), 6wks (TAUS) (2)
  • Yolk sac +/- fetal pole within the gestational sac(2)
    • Yolk sac: circular echogenic layer, looks like a cheerio, visible when gestational sac is 10mm by TVUS (~5-6wks GA), 20mm by TAUS (~6-7wks GA) (1)
    • Fetal pole: echogenic structure; develops around the same time as yolk sac but visualized on US ~1wk later(1)

Figure 3 – Double ring sign(1)

Figure 4 – Double ring sign(4)

Figure 5 – Fetal pole(1)

Measurements

Mean sac diameter

  • Obtain sagittal view of gestational sac, measure height and length of sac using mean sac diameter calculation package, rotate probe 90º to obtain transverse view of gestational sac, measure width of sac
  • MSD (mm) + 30 = Gestational age (days)

 

Crown-rump length (CRL) = Top of skull to base of pelvis(1)

  • >5mm without visible fetal heart = unlikely to proceed to viability
  • CRL (mm) + 42 = gestational age (days)
  • The most accurate method of dating the pregnancy(3)

 

Fetal cardiac activity = proof of live IUP(1)

  • detectable ~6wks on TVUS (fetal pole is >5mm), 7-8wks on TAUS (fetal pole is >10mm) (1)
  • Normal IUP with fetal cardiac activity is reassuring!
    • absence of cardiac activity will likely result in miscarriage, presence of cardiac activity reduces risk of miscarriage (HR >100 consistent with good fetal outcome)
  • Technique(3)
    • Locate fetal pole, optimize depth, turn on M-mode (never doppler as it subjects fetus to high US energy and may be harmful)(1,2), place caliper over beating heart, measure and calculate heart rate
    • Note: must be within gestational sac, well away from uterine wall (don’t confuse with highly vascular decidual reaction)(1)
    • Normal FHR Ranges
      • 6-7wks: 100-120bpm
      • 8wks: 145-170bpm
      • 9+wks: 120-160bpm

 

Other findings and descriptions

No definitive intrauterine pregnancy (NDIUP) (2)

  • if any single criteria of IUP is missing

DDx for NDIUP(2):

  • Early normal pregnancy (βHCG below discrimination zone)
  • Threatened/spontaneous abortion
  • Anembryonic pregnancy (blighted ovum)
  • Molar pregnancy
  • Ectopic pregnancy

Threatened abortion: abnormal bleeding during pregnancy; normal IUP on US(3)

Inevitable abortion: vaginal bleeding with open os; normal IUP or product of conception (POC) near cervix on US(3)

Incomplete abortion: open os with retained POC; US shows anything from debris to embryo; abnormal uterine contents confirms dx(1)

Complete abortion: empty uterus + positive βHCG +/- closed os; same findings as for ectopic therefore requires formal US + serial βHCG(1)

Ectopic pregnancy (3)

  • NDIUP (no definitive intrauterine pregnancy) above βHCG in discriminatory zone
  • Scan adnexa for signs of ectopic
    • Tubal ring sign (thick hyperechoic ring around a tubal mass)
    • Ring of fire sign (also seen in corpus luteum cysts; high velocity flow seen on color doppler around the
    • gestational sac + fetal pole with cardiac activity outside the uterus is diagnostic of an ectopic
  • assess pouch of douglas for free fluid
  • suspicious for ectopic: ectopic mass, fluid in cul de sac, absent IUP, abnormal βHCG pattern (normally rises at least 50% in 48hr period)

Corpus luteal cyst(2,3)

  • develops due to growth, instead of normal regression, of corpus luteum
  • appears very similar to ectopic, but will move with the ovary in response to transducer manipulation instead of independent, tubal ring is thinner and less echogenic, cystic fluid is more clear and anechoic (rather than “clumpy” with echoes)
  • ovarian cyst characteristics: outside the uterus, circular, well circumscribed, do not taper to solid organs

Blighted ovum (anembryonic pregnancy)(1,2)

  • abnormally large gestational sac with no embryonic contents
    • gestational sac >20mm without yolk sac visible à suspect blighted ovum
    • >25mm without yolk sac visible à blighted ovum virtually certain (Eliminates diagnosis of ectopic)
  • Positive βHCG (higher than expected for GA)
  • Confirm with formal US

Molar pregnancy (1,3)

  • Tumor due to uncontrolled proliferation of trophoblasts (cells that surround blastocyst and later become the placenta)
  • Complete mole: no fetal/embryonic tissue; abnormally elevated βHCG >100,000 mIU/ml
  • Partial mole: may contain (abnormal) fetal structures
  • Presentation: hyperemesis, larger uterus than expected, vaginal bleeding, anemia, signs of hyperthyroidism, pregnancy-induced hypertension
  • US: appears as a “snowstorm” or “cluster of grapes” in uterus – fairly homogenous mass full of small, fluid-filled (black) holes; no detectable fetal cardiac activity
  • Needs gyne referral for surgical evacuation(2)

Pitfalls

  • Pseudogestational sac (1, 3)
    • contains no yolk sac, usually more irregularly shaped or pointy-edged than a true gestational sac, border is not as echogenic, and fluid may contain some echoes
    • Intrauterine fluid collections occur in 9-20% of ectopic pregnancies
    • Unless all 3 criteria met for double ring sign, pt requires formal US
  • Extrauterine pregnancy(1)
    • Recognize uterine tissue and always confirm bladder-uterus juxtaposition(2)
  • Interstitial and cornual ectopic pregnancies(1)
    • Rare but dangerous – tend to rupture later therefore produce more rapid hemorrhage than other ectopics
    • Myometrium around interstitial and cornual pregnancies is thin and uneven(2)
    • Measure the “myometrial mantle” (the thinnest part of myometrium around the gestational sac) – should be >5-7mm thick (thinner is concerning for cornual or interstitial ectopic pregnancy) (2)
  • Multiple pregnancies(2)
    • In multiple gestation, each fetus needs to meet the criteria for IUP
    • Heterotopic pregnancies = combined IUP and ectopic pregnancy
      • Risk is 1:30,000 in general population
      • Risk increases to 1:100 with fertility treatment (e.g. IVF)

Figure 7 – Extrauterine pregnancy(1)

Figure 8 – Normal myometrial mantle(1)

Figure 9 – Cornual ectopic pregnancy(1)

Key points(1)

  • False positive IUP can have devastating consequences
  • Any positive βHCG + no definitive IUP = presumed ectopic
    • Pt stable + no free fluid à formal US + quantitative βHCG
      • If no ectopic mass, repeat formal US and βHCG in 48hrs with consideration of patient risk of ectopic pregnancy
      • Follow up with OB to be arranged
    • Always consider other diffrerntail diagnosis for patient presentation before discharging them home.

Figure 10 – Clinical application(2)

 

References:

  1. Socransky, S., &amp; Wiss, R. (2016). Obstetrical EDE. In Essentials of point-of-care ultrasound: The EDE book (pp. 61-90). The EDE 2 Course.
  2. Long, N. (2020, March 02). VanPOCUS: 1st Trimester Obstetrics • LITFL • Ultrasound Library. Retrieved October 15, 2020, from https://litfl.com/vanpocus-1st-trimester-obstetrics/
  3. Dinh, V. (n.d.). Obstetric/OB Ultrasound Made Easy: Step-By-Step Guide. Retrieved October 15, 2020, from https://www.pocus101.com/obstetric-ob-ultrasound-made-easy-step-by-step-guide/
  4. Flores, B., Smith, T., & Joseph, J. (n.d.). OB/Gyn. Retrieved October 15, 2020, from https://www.thepocusatlas.com/obgyn-1

 

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Advanced cardiac echo – a review of E-point septal separation

Dr. Kyle Traboulsee, PoCUS Fellow

Reviewed by Dr. David Lewis

Copyedited by Dr. Mandy Peach

Background:

Often hypotensive, or acutely dyspneic patients, present to the emergency department in significant distress, and emergency physicians must work quickly to evaluate, stabilize, and treat these patients. In the past, determining whether there was a cardiac etiology to these presentations often relied solely on history, physical exam, and varies biochemical markers. Point-of-care ultrasound has increasingly been adopted as a tool to assess cardiac function, and specifically left ventricular ejection fraction (LVEF). Different methods can be used to estimate LVEF (such as “eyeballing”, and the Simpson method), but they can have large inter-reader variability, and require significant cardiac PoCUS experience. E-point septal separation is a measurement of how close the anterior mitral valve leaflet comes towards the interventricular septum and has been shown to be a quick and easy method for estimating LVEF. (1)(2)

 

Anatomy/pathophysiology

               Blood flow is determined by pressure gradients, where blood will travel from areas of high pressure to low pressure. Such a pressure gradient exists between the left atrium and left ventricle. During diastole, the left ventricle relaxes, and the intraventricular pressure decreases until the pressure falls below that of the left intra-atrial pressure. When the left atrial pressure exceeds the left ventricular pressure, the mitral valve opens, and blood passively flows from the high(er) pressure atrium to the lower pressure ventricle. This occurs early in diastole, and the flow of blood from atrium to ventricle is further assisted by an atrial contraction (termed atrial kick) later in diastole. In a healthy individual the atrial-ventricular (A-V) gradient is sufficient to open the mitral valves and bring the anterior mitral leaflet in proximity (or contact) with the intraventricular septum. (1)(2)(3)

In the case of reduced LVEF, the diastolic pressure inside the left ventricle increases due to a decreased ability to eject blood during systole. This can occur due to several reasons, but often result in left ventricular dilation to compensate and preserve LVEF. As LVEF decreases, the ventricular diastolic pressure increases, and the atrial-ventricular (A-V) gradient decreases, leading to a decreased flow rate from atrium to ventricle during diastole, and thus a decreased mitral valve opening. That, paired with LV dilation, leads to an increased (measurable) distance between the anterior mitral valve leaflet and the intraventricular septum during diastole, which can be used as a surrogate marker for left ventricular function. (1)(2)(3).

 

PoCUS Technique

The E-point septal separation measurements will be made using a parasternal long axis (PLAX) view

Obtaining PLAX view

Steps:

  • Place probe at the left parasternal border, just caudal to manubrium (second intercostal space), perpendicular to the chest. Ensure the probe indicator is placed towards to the patient’s right shoulder.
  • Slowly slide the probe down each successive intercostal space, as well as medially (not exceeding patient midline), and laterally, until the highest quality images are obtained (this will likely be around 3-5th intercostal space, left parasternal border, but may differ from patient to patient)
  • Once the best view has been located from step 2, slowly rotate the probe to elongate the left ventricle as much as possible. The probe may need to be rocked (heeled) to center the image.

The optimal PSL image includes the left ventricle (LV) in continuity with the aortic outflow tract. The right ventricle will be near field, the left atrium far field, and the mitral valve, aortic valve, and LV cavity are in between (in the middle of the field).  The apex of the left ventricle will be screen left. (4)(5).

Parasternal long axis view- probe orientation (6)              Parasternal long axis view-anatomy (7)

Parasternal long axis view: normal (own image)

EPSS measurements

EPSS measurements are commonly obtained using M-mode.

  • Once a parasternal long axis view (PLAX) is obtained, turn on M-mode, and place the cursor over the apical tip of the anterior mitral valve leaflet.
  • The M-mode will demonstrate movement of the anterior mitral leaflet, with respect to the intraventricular septum. The image should show 2 peaks per heart cycle, under a hyperechoic line. The first, larger peak (E), represents the initial opening of the mitral valve from passive blood flow in early diastole caused by the A-V gradient. The second, usually smaller peak (A), represents the atrial kick, occurring later in diastole. This M mode image is commonly referred to as a “cloudy sky over two hills”
  • Measure the distance from the top of the E wave to the intraventricular septum. (1)(5)

A normal EPSS measurement with M-mode (8)

PSL: normal EPSS, M-mode (own image)

An abnormal EPSS measurement with M-mode (8)

EPSS measurements can alternatively be measured in B mode

  • Once a parasternal long axis view (PLAX) is obtained, ensure anterior mitral valve leaflet and septum are well visualized over 3-5 cardiac cycles
  • Freeze the image and cycle through the previous 3-5 cardiac cycles, stopping on the image where the anterior mitral valve leaflet lies closest to the intraventricular septum.
  • Measure the distance between the tip of the anterior mitral valve leaflet and the intraventricular septum.

PSL-Poor mitral valve opening (own image)

PSL view- abnormal EPSS measurement in B mode (9)

 

Interpretation

An EPSS < 7mm is considered normal

An EPSS >7 mm has been suggested as 87% sensitive and 75% specific for an EF <50% (10)

Another study suggested that an EPSS >7 mm was 100% sensitive and 51.6% specific for an EF<30% (11).

One MRI study came up with the following formula to calculate EF (4):

EF=75.5 – (2.5 x EPSS in mm)

 

Pitfalls

               Although a quick and relatively simple surrogate measurement for LVEF, there are some patient populations and situations in which EPSS may give in inaccurate estimate of cardiac function. Patients with mitral stenosis may have poor valve opening, leading to a high EPSS, in the context of an otherwise normally functioning left ventricle. Patients with aortic regurgitation may also have poor anterior mitral valve leaflet motion, and thus have a falsely high EPSS. For these reasons, it would be reasonable to apply color doppler across the mitral and aortic valves to assess for signs of regurgitant jets, as well as close assessment of the valves for signs of calcification. Off-axis measurement, regional wall motion abnormalities, and left ventricular hypertrophy may also result in false interpretations concerning LVEF (1)(3)(4).

 

Bottom line

               E-point septal separation is a relatively easy and reproducible technique that can be used to generate a quick estimation of left ventricular function and can help point towards a cardiac etiology in the undifferentiated patient.  It is important to keep in mind factors (as discussed) that may lead to false EPSS interpretations, and EPSS results should not preclude a more global cardiac assessment.

 

References:

  • Boon, S. C., Lopez Matta, J. E., Elzo Kraemer, C. V., Tuinman, P. R., & van Westerloo, D. J. (2020). POCUS series: E-point septal separation, a quick assessment of reduced left ventricular ejection fraction in a POCUS setting. Netherlands Journal of Critical Care, 28(3), 139–141.
  • Cisewski , D., & Alerhand, S. (2018, December). Fellow corner: E-point septal separation in the patient with congestive heart failure. ACEP // Home Page. Retrieved October 18, 2021, from https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/dece/fellow-corner-e-point-septal-separation-in-the-patient-with-congestive-heart-failure/.
  • Miller, T., Salerno, A., & Slagle, D. (2021, May 25). Advanced Critical Care Ultrasound: E-Point Septal Separation to Estimate Left Ventricular Ejection Fraction. EM resident . Retrieved October 2021, from https://www.emra.org/emresident/article/epss/.
  • Atkinson, P., Bowra, J., Harris, T., Jarman, B., & Lewis, D. (2019). Point-of-care ultrasound for Emergency Medicine and Resuscitation. Oxford University Press.
  • Socransky, S., & Wiss, R. (2016). Essentials of point-of-care ultrasound: The ede book. The EDE 2 Course, Inc.
  • SonoSpot, & SonoSpot. (2012, September 17). Sonotip&Trick: “I can’t get a good parasternal long view.” really? well, try this… Retrieved October 18, 2021, from https://sonospot.wordpress.com/2012/08/07/sonotiptrick-i-cant-get-a-good-parasternal-long-view-really-well-try-this/.
  • Roma, Ak, Sparks, M., Kelly, C., (@NephroP), A. K., Dowd, R., Crosson, D. A., Deepali, D., Singh, N., Andreea, Aya, S.A., A., Panchal, L. M. R., & Murthy, J. (2019, June 7). Introduction to focused cardiac ultrasound: The parasternal long axis view. Renal Fellow Network. Retrieved October 18, 2021, from https://www.renalfellow.org/2019/06/07/introduction-to-focused-cardiac-ultrasound-the-parasternal-long-axis-view/.
  • Miller, T., Salerno, A., & Slagle, D. (2021, May 25). Advanced Critical Care Ultrasound: E-Point Septal Separation to Estimate Left Ventricular Ejection Fraction. EM resident . Retrieved October 2021, from https://www.emra.org/emresident/article/epss/.
  • Satılmış Siliv, N., Yamanoglu, A., Pınar, P., Celebi Yamanoglu, N. G., Torlak, F., & Parlak, I. (2018). Estimation of cardiac systolic function based on mitral valve movements: An accurate bedside tool for emergency physicians in DYSPNEIC patients. Journal of Ultrasound in Medicine, 38(4), 1027–1038. https://doi.org/10.1002/jum.14791
  • Ahmadpour H, Shah AA, Allen JW, et al. Mitral E point septal separation: a reliable index of left ventricular performance in coronary artery disease. Am Heart J. 1983;106(1 Pt 1):21-8
  • McKaigney, C. J., Krantz, M. J., La Rocque, C. L., Hurst, N. D., Buchanan, M. S., & Kendall, J. L. (2014). E-point septal separation: A bedside tool for emergency physician assessment of left ventricular ejection fraction. The American Journal of Emergency Medicine, 32(6), 493–497. https://doi.org/10.1016/j.ajem.2014.01.045
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Alternative Rib Fracture Management in the ED

Alternative Rib Fracture Management in the ED – A Medical Student Clinical Pearl

Victoria Mercer, Clinical Clerk 3, DMNB

Reviewed and Copyedited by Dr. Mandy Peach

Rib fractures are a frequent presentation in the ED, occuring in approximately 10% of all injured patients with the primary causes being blunt chest trauma and MVAs(1,2).  The mainstay of treatment for rib fractures is analgesic control(1). When pain cannot be adequately managed, the patient is at a heightened risk of hypoventilation due to decreased thoracic mobility and secretion clearance, predisposing the patient to significant atelectasis(1,2).

Historically the pain from rib fractures has been managed with acetaminophen or NSAIDS and if these do not sufficiently alleviate the pain, opioids are used(1,3). Unfortunately, these methods often do not provide adequate pain control or in the case of opioids, come with a myriad of side effects such as nausea, vomiting, constipation, respiratory depression and the potential for dependency and abuse (1,4).

An alternative to traditional methods include regional techniques such as paravertebral or epidural nerve blocks. These interventions have been shown to effectively control pain in rib fractures(3,4). The downside to these interventions include being technically challenging and time consuming with significant complication risks and contraindications such as coagulation disorders (1,3).

The solution? A serratus anterior block 

An ultrasound guided blockade of the lateral cutaneous branches of the thoracic intercostal nerves was first described by Blanco et al. in 2013 for patients following breast surgery to manage their postoperative pain(5). This procedure has been adopted by many emergency departments for its convenience and practicality compared to epidural or paravertebral nerve blocks(3).

Serratus anterior blocks are less invasive and considerably more practical in the ED setting, providing paresthesia to the ipsilateral hemithorax for 12-36 hours (6).

The only absolute contraindications are patient refusal, allergy to local anesthetic and local infection(1).

Complications of a serratus anterior block include pneumothorax, vascular puncture, nerve damage, failure/inadequate block, local anesthetic toxicity and infection(1).

Serratus anterior blocks are only effective for the anterior two-thirds of the chest wall (3).

 

Figure 1. Ultrasound image of serratus anterior muscle and surrounding tissues with superficial or deep needle guides. Image from Thiruvenkatarajan V, Cruz Eng H, Adhikary SD. An update on regional analgesia for rib fractures. Current Opinion in Anaesthesiology. 2018;31(5):601–607.

How do you do it?

The procedure is usually performed with the patient laying supine however the patient could also lay in a lateral decubitus position (1,3). Using a high frequency linear ultrasound probe (6-13MHz), identify the serratus anterior and latissimus dorsi muscles over the fifth rib in the mid-axillary line(1,3). Using an in-plane approach, insert the needle either superficial or deep to the serratus anterior and confirm correct needle placement by visualizing anaesthetic spread via ultrasound(1,3). According to May et al., superficial spreading tends to have a longer lasting analgesic effect(1). Place and secure a catheter to infuse the remainder of the bolus(1,3). Thiruvenkatarajan et al. recommend a bolus of 40ml of 0.25% levobupivacaine and a 50mm 18G Tuohy catheter needle(3).

See this excellent review by Dr. David Lewis on identifying rib fractures and their complications using ultrasound (start 3:08) as well as a review of the block and procedure (start 8:00)

Rib Fractures and Serratus Anterior Plane Block

References

  1.         May L, Hillermann C, Patil S. Rib fracture management. BJA Education. 2016 Jan 1;16(1):26–32.
  2.         Malekpour M, Hashmi A, Dove J, Torres D, Wild J. Analgesic choice in management of rib fractures: Paravertebral block or epidural analgesia? Anesthesia and Analgesia. 2017 Jun 1;124(6):1906–11.
  3.         Thiruvenkatarajan V, Cruz Eng H, Adhikary S das. An update on regional analgesia for rib fractures. Vol. 31, Current opinion in anaesthesiology. 2018. p. 601–7.
  4.         Tekşen Ş, Öksüz G, Öksüz H, Sayan M, Arslan M, Urfalıoğlu A, et al. Analgesic efficacy of the serratus anterior plane block in rib fractures pain: A randomized controlled trial. American Journal of Emergency Medicine. 2021 Mar 1;41:16–20.
  5.         Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: A novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013 Nov;68(11):1107–13.
  6.         Mayes J, Davison E, Panahi P, Patten D, Eljelani F, Womack J, et al. An anatomical evaluation of the serratus anterior plane block. Anaesthesia [Internet]. 2016 Sep 1 [cited 2021 Apr 18];71(9):1064–9. Available from: http://doi.wiley.com/10.1111/anae.13549

 

 

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PoCUS & COVID Severity

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Rib Fractures and Serratus Anterior Plane Block

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Scaphoid Fracture – Can PoCUS disrupt the traditional ‘splint and wait’ pathway?

 

PoCUS Fellow Pearl

Dr. Melanie Leclerc, CCFP-EM

MSK PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual


 

Case:

A 37 year old, right hand dominant, carpenter presents to your local ED with a complaint of right wrist pain. He was on a step-stool and lost his balance earlier today. He fell landing on his outstretched arm and had an acute-onset of radial-sided wrist pain. He denies any other injury. There are no neurologic complaints.

On exam, there is no visible deformity. The skin is closed and there is some swelling noted. The patient is tender over the anatomic snuff box as well as volarly over the scaphoid. There is pain noted with axial loading of the thumb. There is no other tenderness. ROM is within normal limits. The limb is distally neurovascularly intact.


X-rays are normal.

An occult scaphoid fracture is suspected. At this institution, patients with suspected occult scaphoid fracture are placed in a thumb spica splint and referred to the local hand surgeon to be seen in ~10-14 days for repeat assessment and X-ray.

Can Point of Care Ultrasound change this traditional “splint and wait” patient pathway?


 

Background:

Scaphoid fracture is a common presentation to the Emergency Department accounting for approximately 15% of all wrist injuries and 70% of carpal fractures. Up to 30% of the time, radiographs at initial presentation appear normal making fracture a commonly missed injury for Emergency physicians. A failure to recognize this injury can lead to chronic pain and functional impairment for patients. Particularly, fractures of the proximal pole (most distant to the blood supply) can lead to avascular necrosis (AVN) at high rates. Non-union can lead to scaphoid non-union advanced collapse (SNAC wrist) which can perpetuate further degenerative changes throughout the carpus. This can cause a significant impact on quality of life and occupation. Early detection of fracture could expedite fixation and possibly results in better outcomes. Further study in this area is needed.


 

Anatomy:

The scaphoid bone lies in the radial aspect of the proximal carpal row. It’s unique shape (“twisted peanut”), lends to easy recognition. It articulates proximally with the distal radius, distally with the trapezium, and on its’ ulnar aspect with the lunate to form the scapho-lunate interval. The blood supply to the scaphoid is unique in that the majority of it is retrograde. The dorsal carpal branch of the radial artery supplies the bone from distal to proximal. A small proportion of the blood supply originates at the proximal end. The boundary between the two supplies creates a “watershed” area prone to non-union and AVN.


 

Classification of Fractures:

Scaphoid fractures are classified by location. These regions are the proximal, middle and distal thirds which account for 20%, 75%, and 5% of the fractures respectively. The stability of fractures is determined by the displacement (>1mm) and angulation (scapholunate angle >60 and radiolunate angle >15). The Hebert Classification as endorsed by Traumapedia can be found below.


 

Traditional Imaging:

Imaging of these suspected injuries varies. Traditionally serial X-rays were used, but have been found to be poorly sensitive even several weeks after injury. Bone scan has also been used as an alternative due to it’s high sensitivity, but has poor specificity and provides no further information regarding the nature of the fracture. CT is relatively sensitive and specific and provides information for pre-operative planning. MRI is considered the gold standard, but is difficult to obtain in a timely manner in Canada.

Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89. doi: 10.1055/s-0039-1693147. Epub 2019 Jul 21. PMID: 32025360; PMCID: PMC7000269.


 

PoCUS Technique:

  • Linear probe

  • Consider waterbath, gel standoff pad, or bag of IV fluid

  • Scan with the wrist ulnarly deviated

  • Scan in the longitudinal and transverse orientations of volar, lateral and dorsal aspects

  • Place the probe in longitudinal orientation dorsally over lister’s tubercle of the radius and scan distally until the scaphoid is visualized in the snuff box. Scan radial to ulnar.

  • Rotate to the transverse orientation and scan through proximal to distal

  • Volarly, in the transverse plane, identify the tendon of the flexor carpi radialis (this lies radial to the easily identifiable palmaris longus tendon on exam). The scaphoid is found deep to this. Scan proximal to distal.

  • Rotate to the longitudinal orientation and scan radial to ulnar

 


 

Video Demonstration:

 


 

Findings:

  • Cortical disruption

  • Periosteal elevation

  • Hematoma


 

The Evidence:

  • Early advanced imaging (CT or MRI) compared to initial 2 week immobilisation proved more cost effective and had better patient oriented outcomes (ie. missed work).(7)
  • A systematic review and meta analysis of moderate to high quality studies published in 2018 found that ultrasound had a mean sensitivity of ~89% and specificity of ~90% for detection of occult scaphoid fractures.(1)
  • Similar results were also reported by another systematic review in 2018.(8)
  • Pocus was shown to have a comparable sensitivity to CT for occult scaphoid in a systematic review published in 2020.(2)

 

Limitations:

  • Only useful if positive
  • Operator experience dependent
  • US probe and frequency dependant
  • Potential for false positives due to injury of nearby structure causing hematoma
  • Potential for false positives in context of arthritis or remote trauma

 

Bottom line:

  • Useful if positive
  • Still need definitive test to further delineate fracture (ie: for operative planning)
  • Could expedite CT
  • Could expedite specialist follow-up
  • May improve ER physician diagnostic certainty
  • May improve patient trust and compliance with splinting
  • Further study is needed

 

Case Conclusion:

Scaphoid cortical disruption was visualized using PoCUS. After discussion with the hand surgeon, a CT Scan of the wrist was performed which confirmed a minimally displaced waste fracture of the scaphoid. The patient was splinted and seen the next day in clinic for discussion regarding operative management.


 

Further Review:

 

 


 

References

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  22. https://litfl.com/terry-thomas-sign
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