College Answer

On palpation of the arterial pulse, a double peak was noted with each cardiac cycle.  List 4 conditions/situations  which can produce this phenomenon.

•    AS + AR
•    Severe AR
•     HOCM
•     IABP

Discussion

This is a phenomenon known as pulsus bisferiens. The typical cause for it is the combination of aortic stenosis and regurgitation. The four differentials listed above are the classical ones which one may find in any textbook (or in Wikipedia for that matter). The below-referenced article is from 1957, before balloon pumps, but it covers the topic well. The article from 1899 is even cooler, but perhaps less relevant in modern critical care.