60-year-old man with cardiogenic shock due to recent myocardial
infarction requires intra-aortic balloon counterpulsation (IABP) in
order to maintain adequate hemodynamics. During the past few minutes,
the patient’s mean arterial BP has decreased from 70 to 45 mm Hg, and
you suspect IABP malfunction. The action of the pump is timed
from the patient’s arterial BP tracing, and the balloon inflates with
every beat. To diagnose a potential problem, you change the timing
of balloon inflation to every third beat. The arterial pressure
waveform is shown in Figure 1.
Which of the following is the most likely cause of the patient’s
decrease in BP?