Medical Student Clinical Pearl – October 2019
Alex Pupek
Faculty of Medicine
Dalhousie University
CC4
Class of 2020
Reviewed and Edited by Dr. David Lewis
All case histories are illustrative and not based on any individual
Case
A 70F with a history of bladder CA, HTN and 4.9cm AAA presented to the Emergency Department (ED) and was Triaged as Level 3 with a chief complaint of generalized weakness. Initial assessment was significant for hypotension and low-grade fever with dysuria elicited on history; she was started on Ceftriaxone with a working diagnosis of urosepsis. Bloodwork and imaging studies were sent to rule out other potential sources of infection.
She had a mild leukocytosis of 12.4, pH of 7.23 and a lactate of 5.0. Point-of-care urinalysis was unremarkable. The chest x-ray revealed an enlarged cardiothoracic ratio of 0.62 compared to 0.46 ten months previously, concerning for a pericardial effusion.
Upon reassessment, the patient appeared unwell with slight mottling to the skin, cool extremities and tenuous blood pressure; point of care ultrasound revealed a large pericardial effusion. Interventional cardiology was paged; the patient was moved to the trauma area and an emergent pericardiocentesis was performed: 360cc of bloody fluid was removed. The pericardial drain was left in situ.
Post-procedure bloodwork included a troponin of 216 and CK of 204. The patient was admitted to the Cardiac Care Unit and discharged within a week’s time.
Pericardial Effusions and The Role of Point-of-Care Ultrasound (POCUS)
The normal pericardial sac contains up to 50 mL of plasma ultrafiltrate [1]. Any disease affecting the pericardium can contribute to the accumulation of fluid beyond 50mL, termed a pericardial effusion. The most commonly identified causes of pericardial effusions include malignancy and infection (Table 1).
Table 1 – UpToDate, 2019 – Diagnosis and Treatment of Pericardial Effusions
Evaluation of the pericardium with point-of-care ultrasound includes one of four standard views: parasternal long axis, parasternal short axis, subxiphoid and apical (Figure 1). A pericardial effusion appears as an anechoic stripe or accumulation surrounding the heart. Larger effusions may completely surround the heart while smaller fluid collections form only a thin stripe layering out posteriorly with gravity. Seen most commonly post-cardiac surgery, pericardial effusions may be loculated and compress only a portion of the heart. [1,2] (Table 2)
Figure 1[1]
Table 2 [2]
Both the pericardial fat pad and pleural effusions can be mistaken for pericardial effusions. The parasternal long-axis view is most helpful to accurately define the effusion with the descending aorta, posterior to the mitral valve and left atrium, serving as a landmark: the posterior pericardial reflection is located anterior to this structure. Fluid anterior to the posterior pericardial wall is pericardial, whereas a pleural effusion will lie posterior. The pericardial fat pad is an isolated dark area with bright speckles, located anteriorly; unlike fluid, it is not gravity dependent. Rather than competing with the cardiac chambers for space within the pericardial sac, the fat pad moves synchronously with the myocardium throughout the cardiac cycle. [1,2] (Figure 2)
Figure 2[1]
A pericardial effusion discovered on POCUS in the ED may be mistaken for tamponade, leading to inappropriate and invasive management in the form of pericardiocentesis.[2]
Patient tolerance of pericardial effusions depends on the rate by which they accumulate. As little as 150-200 mL of rapidly accumulating effusion can cause tamponade whereas much larger amounts of slowly accumulating fluid can be well tolerated. Pericardial effusions formed gradually are accommodated by adaptations in pericardial compliance. A tamponade physiology is reached once the intrapericardial pressure overcomes the pericardial stretch limit.[2] (Figure 3)
Figure 3[2]
The core echocardiographic findings of pericardial tamponade consist of:
- a pericardial effusion
- diastolic right ventricular collapse (high specificity)
- systolic right atrial collapse (earliest sign)
- a plethoric inferior vena cava with minimal respiratory variation (high sensitivity)
- exaggerated respiratory cycle changes in mitral and tricuspid valve in-flow velocities as a surrogate for pulsus paradoxus
In the unstable patient with clinical and echocardiographic findings of tamponade, an emergent pericardiocentesis is indicated.[2]
A retrospective cohort study of non-trauma emergency department patients with large pericardial effusions or tamponade, ultimately undergoing pericardiocentesis, found that effusions identified by POCUS in the ED rather than incidentally or by other means saw a decreased time to drainage procedures, (11.3 vs 70.2 hours, p=0.055).[3]
Point of care ultrasound is a valuable tool during the initial evaluation of the undifferentiated hypotensive emergency department patient but should be interpreted judiciously and within clinical context to avoid unnecessary emergency procedures.
Additional Images
From GrepMed
echocardiogram-pericardial-tamponade-alternans-effusion
References
- Goodman, A., Perera, P., Mailhot, T., & Mandavia, D. (2012). The role of bedside ultrasound in the diagnosis of pericardial effusion and cardiac tamponade. Journal of emergencies, trauma, and shock, 5(1), 72.
- Alerhand, S., & Carter, J. M. (2019). What echocardiographic findings suggest a pericardial effusion is causing tamponade?. The American journal of emergency medicine, 37(2), 321-326.
- Alpert, E. A., Amit, U., Guranda, L., Mahagna, R., Grossman, S. A., & Bentancur, A. (2017). Emergency department point-of-care ultrasonography improves time to pericardiocentesis for clinically significant effusions. Clinical and experimental emergency medicine, 4(3), 128.
