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Image 2: Parasternal long-axis view of the heart demonstrating a pericardial effusion. (RV=right ventricle, LV=left ventricle, Ao=aorta, LA=left atrium)
Dx: Not Your Typical Viral Infection
You allow the patient to remain in whatever position is most comfortable for her and begin explaining to her that you see a small collection of fluid around her heart (Image 2). She seems indifferent as you begin explaining that her viral infection could have led to pericarditis and development of a small pericardial effusion that requires further testing. “As long as you make me feel better, doc, do whatever you have to do…” she replies in between her dry, hoarse coughs.
You walk your intern through the rest of the bedside cardiac ultrasound and even though the effusion is not large, you double-check to make sure there are no signs of early tamponade physiology and no other obvious issues with the patient’s cardiac output or wall motion. You give your intern teaching point #2: “Don’t stop your evaluation just because you find something abnormal. Make sure you follow through and complete the rest of the exam or ultrasound.”
In your institution, patients with pericarditis are admitted to the hospital so you order the tests you know your internal medicine colleagues will want to have: EKG, CXR, CBC, CMP, ESR, CRP, cardiac enzymes, LDH, TSH, Free T4, HIV, and a QTB. You defer the rheumatologic and neoplastic workup and potential biopsy option to them.
As you are wrapping up your shift with your intern, you are greeted with a smile and a big thank you from the patient being wheeled upstairs for admission. With all of the influenza and viruses you have been seeing this season, you knew you would eventually come across something unexpected. You turn to your intern for your final teaching point on the case: “Being able to find that needle in a haystack is what differentiates great doctors from the rest. Then again, sometimes its just better to be lucky than good.”
Tips & Tricks for Performing a Bedside Cardiac Ultrasound to Evaluate for Pericardial Effusion
01 Bedside ultrasound is the stethoscope of the future. Ultrasound is more sensitive and specific than physical exam alone in assessing for the presence of a pericardial effusion. Especially in patients where it can be difficult to determine if a pericardial friction rub or diminished heart sounds are present, perform a bedside cardiac ultrasound.
02 Use a low frequency transducer with a small footprint (e.g. a 1-5 MHz phased array transducer).
03 Place the patient in a supine or left lateral decubitus position to bring the heart anteriorly in the chest wall and closer to the probe.
04 Pericardial effusions will appear as a black or anechoic collection of fluid anterior to the descending thoracic aorta.
05 Effusions are typically categorized by the following guidelines:
06 Small effusions are generally confined to the area just posterior to the left ventricle when the patient is lying supine. For this reason, it is very important to increase the depth of your scan to evaluate the region posterior to the heart.
07 Large effusions will appear circumferentially around the heart and you may see the heart swinging in the bag of fluid with each contraction.
08 Note that loculated effusions can be seen anywhere in the pericardial space.
09 Effusions from viral infection, uremia, or recent myocardial infarction can contain fibrinous material and appear more heterogenous on bedside ultrasound.
10 When you see a pericardial effusion, determine if there is any evidence of cardiac tamponade. On ultrasound, cardiac tamponade should be suspected if you see end-diastolic right ventricular or right atrial collapse in the appropriate clinical setting. Avoid the pitfall of confusing normal right-sided systolic contraction with abnormal diastolic collapse.
11 Remember that large pleural effusions can mimic the appearance of a pericardial effusion on bedside ultrasound. Make sure you visualize the descending aorta and see how the hypoechoic fluid courses in relationship to the aorta. Pericardial effusions will be seen layering out anterior to the descending aorta (between the aorta and the heart) on a parasternal long-axis view of the heart. Pleural effusions will run posterior to the aorta on a parasternal long-axis view.
Brady Pregerson (@TheSafetyDoc) manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more info visit EMresource.org.
Teresa S. Wu (@TeresaWuMD) is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa EM Program in Phoenix.