2. Additional echocardiographic imaging /evaluation.

Early detection and management of cardiac tamponade is an essential skill in emergency and critical care medicine. Cardiac tamponade can be quickly and accurately identified by bedside point of care ultrasound (PCU). Physical exam findings, EKG, and chest x-ray abnormalities are less sensitive and specific than 2D echo.

While all of the above choices should be employed during initial PCU, tamponade physiology is most readily and accurately identified by right ventricular (RV) diastolic collapse in M-mode. IVC plethora with blunted collapsibility is very sensitive, but notoriously nonspecific for cardiac tamponade. Of note, transvalvular Doppler inflow velocities, or flow velocity paradoxus, is also accurate to diagnose tamponade but is less specific than diastolic collapse in M-Mode, and considerably more challenging in image acquisition and skill.

Incorporation of both the right ventricle and mitral valve anterior leaflet across the parasternal (or in this case, subcostal) axis in M-mode allows the provider to reliably detect right ventricular wall collapse during the diastolic phase of the cardiac cycle (i.e., the phase between mitral valve opening and closure).

Figure 2.  Demonstration of landmarks for M-Mode.

With M-mode, any posterior motion of the right ventricle free wall during mitral valve opening (demonstrated by anterior motion of anterior mitral valve leaflet) is recognized as chamber collapse and tamponade physiology, which was indeed the case in this patient (See Figure 3). Preparation for US-guided pericardiocentesis was planned and cardiology consulted.

Figure 3.  M-Mode view through RV free wall and Mitral valve. RV free wall collapse occurs during mitral valve opening in M-Mode. White arrow demonstrates posterior wall movement of RV Wall during diastole.

Formal STAT Echo read was obtained 1 hour later, confirming tamponade physiology. Pericardiocentesis was then successfully performed via para-apical approach under US guidance, with a large serosanguinous pericardial effusion (>600 ml) aspirated. Within minutes, the patient’s tachycardia improved and her respiratory distress resolved, confirming the diagnosis of tamponade. Fluid studies demonstrated a hemorrhagic pericardial effusion with negative cultures and cytology. Her rivaroxaban was discontinued, a pericardial catheter kept in place until drainage of <50 ml/day, and antibiotics administered for the bacterial pneumonia. The patient was transferred back to the floor in stable condition 3 days later.

Final diagnosis: acute hypoxic respiratory failure secondary to early hemorrhagic pericardial tamponade in setting of rivaroxaban for chronic atrial fibrillation.

Take home point: pericardial effusion with tamponade occurs along a spectrum of widely-variable clinical presentations (more often silently than catastrophically in medical patients). While PCU can easily identify the presence or absence of a pericardial effusion, M-mode visualization of right ventricular free wall collapse during diastole should also be examined to quickly and accurately identify early tamponade physiology.


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