Tuesday, August 7, 2012

Tamponade or PE?

Today we discussed a tricky case of a patient with both a pericardial effusion and a pulmonary emobolism. When they developed shock, the question became is this tamponade or a massive PE?

On physical exam, both groups of patients will have:
- sinus tachycardia
- hypotension
- high JVP

In tamponade: muffled heart sounds, pericardial friction rub, pulsus paradoxus

In massive PE: signs of DVT

Note that an increased pulsus (ie>10 mmHg) can also be seen in other conditions: profound hemorrhagic shock, obstructive lung disease... and massive pulmonary embolism!

In an unstable patient, bedside investigations would include an ECG...

ECG findings of tamponade: 
- sinus tachycardia
- low voltages (ie less than 5 in limb leads, less than 10 in precordial leads)
- pericarditis findings: ST elevation, PR depression
- electrical alternans (beat-to-beat variation in QRS amplitude, caused by swinging of the heart in the pericardial fluid) - rare but very specific.

ECG findings of pulmonary embolism:
- sinus tachycardia
- atrial arrhythmias
- S1Q3T3-rare but specific ECG pattern
- non-specific ST/T wave changes
- precordial T-wave inversion (Rt heart strain pattern)

To definitively sort these two out, an echocardiogram is needed. 

Echocardiogram findings of massive PE:
- Increased RV size
- Decreased RV function
-Tricuspid regurgitation

Echocardiogram findings of tamponade:
- RA/RV diastolic collapse
- ventricular interdependence: reciprocal respiratory variation in volume in right and left heart, as well as flows across AV valves (as in figure above).
- IVC full, collapses by less than 50% on inspiration

Check out this NEJM review on Acute Cardiac Tamponade

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