It’s the middle of a busy shift – the kind of shift where you keep putting off even a brief break to satisfy your aching hunger or appease your bulging bladder – and you are on your way to see just one more patient in need. You know that eventually you will be able to do what is needed to bring your body back towards homeostasis and your mind out of the fog. “After this next patient…” you promise yourself.
On exam he appears obese and in no acute distress with vital signs showing a temperature of 97.8, a pulse of 88, a blood pressure of 117/92, respiratory rate of 22, and a pulse ox of 95% on room air. His lungs actually sound quite clear. His sternotomy scar looks good and his heart is regular with a 2/6 slightly harsh systolic ejection murmur. His abdomen is non-tender and his legs show symmetric trace edema with a negative Homan’s sign bilaterally.
You order a CBC, chem-7, troponin, BNP, chest x-ray and EKG along with oxygen 2 liters by nasal canula. You are about to go empty your bladder and get a bite to eat, but this plan gets derailed by four nurses with burning questions, three critical lab values, two new patients in the “to be seen” box, and a PMD holding on line-3. When you finally finish up that business, the EMT hands you the EKG he just did on your 72-year-old with trouble breathing 12 days post CABG. The EKG is shown below.
What does the EKG show? What should you do next?
The EKG shows low voltage in the limb leads, which can be a pre-existing finding, but should always make you consider a pericardial effusion. The differential diagnosis of low voltage on the EKG, which is usually defined as all limb leads having a effective R + S amplitude of <5mm, includes pneumothorax, pericardial effusion, COPD, amyloidosis, myocardial scar, and scleroderma. Of these, the first two are the most acutely life threatening, and both can be ruled out with ultrasound, with or without the help of a chest X-ray. In this patient who is recently post-op from cardiac surgery, a bedside scan of the pericardium can help you determine if he has a pericardial effusion, and more importantly, if tamponade physiology is also present.
The two labeled ED ultrasound/echo images here show a large pericardial effusion which was later confirmed by a formal echocardiogram. In “real-time” imaging, the patient’s bedside ultrasound demonstrated sonographic signs of cardiac tamponade: diastolic right ventricular and right atrial collapse.
An image from a normal echocardiogram is shown for comparison. The cardiac chambers and the pericardial effusion are black or anechoic, the myocardium is echoic, and the pericardium is bright white or hyperechoic.
Orientation is aided by remembering that the right ventricle is always closest to the sternum and thus at the top of any parasternal view. (RV = Right Ventricle, LV = Left Ventricle). These images were obtained via the subxiphoid approach, so a small wedge of liver can be seen at the top of the image. The patient remained stable, but was admitted to the ICU, where the cardiologist emergently performed an ultrasound guided pericardiocentesis.