ULTRASOUND ZOOM
On Cardiac Tamponade By Anna Culhane, MD, PGY-3
University of Miami / Jackson Health System
INTRODUCTION As an emergency physician, when I think of diagnosing cardiac tamponade, my mind immediately goes to the traditionally taught Beck’s triad of muffled heart sounds, low blood pressure, and distended neck veins. However, I have learned through experience that muffled heart sounds are difficult to hear in a noisy emergency department, hypotension is not always present, and neck veins are mostly elusive. A major concern for all emergency physicians is that cardiac tamponade can quickly decompensate into cardiac arrest. While a crash cart situation may sound exciting for some, it is disruptive and unsettling for most healthcare staff and most importantly terrible for the patient. It is relatively easy to diagnose a pericardial effusion. However, it is extremely difficult to convince consultants that there is an impending tamponade, especially in the face of normal blood pressures. This challenge appears to increase exponentially at night. How can we convince our consultants to spring out of bed at 3:00 am for a procedure on a patient with stable vital signs? Here is where a systematic cardiac point-of-care ultrasound (POCUS) might just do the trick. We know POCUS is quick and efficient. A 2017 study on 73 patients compared the diagnosis of tamponade with POCUS to that with CT scans, and demonstrated that POCUS led to decreased pericardiocentesis times (11.3 vs. 70.2 hours, P=0.055) and a shorter length of hospital stay (5.1 vs. 32
Edited by Leila Posaw, MD, MPH
Emergency Ultrasound Faculty, Jackson Memorial Hospital
7.0 days, P=0.222).1 To diagnose tamponade with POCUS, there are six questions that need careful evaluation. When these six findings are all present on a patient, they should prompt a response even from the most obstinate consultant.
FRAMEWORK A phased array transducer should be used to obtain cardiac views and answer the six questions listed below. These views include the inferior vena cava (IVC), parasternal long axis (PSLAX), parasternal short axis (PSSAX), sub-xiphoid (SX), apical four chamber (AP4C), and IVC size and collapsibility. B-mode, M-mode, and pulse wave Doppler modes are useful. The questions that need to be answered to diagnose tamponade are: 1. Is there a pericardial effusion, and how big is this? 2. Is there right atrial collapse during filling? 3. Is there right ventricular collapse during filling? 4. Is the inferior vena cava plethoric? What is the collapsibility index? 5. Is the respiratory variation of the mitral and tricuspid valve inflow velocities exaggerated? 6. Is the direction of blood flow in the hepatic veins reversed? But first, what is cardiac tamponade? Cardiac tamponade is a syndrome that results from the compression of the heart by a pericardial effusion, which impedes normal cardiac function and results in hemodynamic compromise and obstructive shock. EMpulse Summer 2021
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A normal heart is surrounded by a small amount of physiologic effusion which serves several useful functions, for example lubrication. Several conditions, such as infection, trauma, inflammation, and cancer may lead to the accumulation of larger effusions. Consider the case of a 26-year-old woman with a history of end stage renal disease who presented to our emergency department with dyspnea. Upon arrival, she was considered “stable” with a heart rate of 88 and blood pressure of 111/92. However, our careful systematic POCUS examination revealed a large pericardial effusion and the looming threat of cardiac tamponade.
Step 1a: Is there a pericardial effusion?
A pericardial effusion appears as a dark, anechoic collection typically surrounding the heart. However, in the setting of dissection, trauma, or cardiac surgery, it may present as a small, localized effusion. Physiological pericardial effusions are usually less than 50 mL and are visualized during systole. If an effusion is appreciated during both systole and diastole, we can assume that it is most likely greater than 50 mL. Additionally, effusions can be categorized as simple or complicated with septations, strings, and floating debris. Even though a pericardial effusion can be visualized in any of the four standard views, the preferred views to visualize an effusion are the PSLAX (Video 1) and SX (Video 2). On our exam, we found a large, anechoic
