Coronary Artery Disease - STEMI Case #5 - Question #2 Answer

She is taken for coronary angiography, and a large posterior descending coronary artery was found to be thrombotically occluded. This was treated with a drug-eluting stent.

On hospital day three, she becomes suddenly hypotensive with a blood pressure of 60/40 mm Hg and heart rate of 120 beats per minute. Her cardiac physical examination remains unchanged. A pulsus paradoxus of 16 mm Hg is present, and she is still wheezing on examination. She is taken for emergency coronary angiography, and her stent is widely patent. Right heart catheterization shows that the diastolic pressures are elevated and equal. The oxygen saturation measured in the right atrium was 63%, right ventricle 63% and pulmonary artery 65%. There is a small V wave in the pulmonary capillary wedge pressure tracing.

An arterial pressure tracing is below:

pulsus

Which of the following is the likely diagnosis?

A. Acute ventricular septal defect

B. Acute left ventricular free wall rupture

C. Acute mitral valve regurgitation

D. Right ventricular infarction

 

A left ventricular free wall rupture causes sudden accumulation of blood in the pericardium and cardiac tamponade, which can be rapidly fatal. Normally, the pericardium and heart chambers can expand as the heart fills; however, with cardiac tamponade from a large pericardial effusion or constrictive pericarditis, this is not able to occur. As a person inspires, venous return is increased to the right heart, and the interventricular septum bulges to the left, impairing left ventricular filling, reducing left heart cardiac output and thus decreasing systemic pressure (increasing the pulsus paradoxus). As a person exhales, right ventricular filling decreases, and the left heart fills, causing the interventricular septum to bulge to the right, impairing right ventricular filling. Recall that severe asthma and chronic obstructive pulmonary disease, or COPD, exacerbations can increase the pulsus paradoxus as well. The arterial pressure tracing provided in the case question above shows a large pulsus paradoxus.

The diastolic pressures in the cardiac chambers are elevated and equal, as every chamber pressure influences the other in the setting of cardiac tamponade due to the fact that the heart is not able to expand as mentioned above.

An acute ventricular septal defect causes an oxygen “step-up” in the right heart because oxygenated blood crosses through defect from the left ventricle, increasing the oxygen saturations in the right heart chambers (right ventricle and pulmonary artery).

Acute mitral valve regurgitation causes a large V wave in the pulmonary capillary wedge pressure tracing. A right ventricular infarction causes hypotension and can occur in the setting of inferior or posterior MI, but there is no pulsus paradoxus. The treatment for a right ventricular infarction is IV fluids.