EFFECTS OF INTRAAORTIC BALLOON PUMPING ON SEPTAL ARTERIAL BLOOD-FLOW VELOCITY WAVE-FORM DURING SEVERE LEFT MAIN CORONARY-ARTERY STENOSIS

Objectives. We sought to evaluate the effect of intraaortic balloon pu mping on the phasic blood velocity waveform into myocardium with sever e coronary artery stenosis. Background. In the presence of severe coro nary artery stenosis, it is not clear whether intraaortic balloon pump ing augments intramyocardial inflow during diastole or changes systoli c retro grade blood flow from the myocardium to the extramural coronar y arteries. Methods. Using anesthetized open chest dogs (n = 7), we in troduced severe stenosis in the left main coronary artery lo reduce th e poststenotic pressure to approximately 60 mm Hg (>90% diameter steno sis). Septal arterial blood flea velocities were measured with a 20-MH z, 80-channel ultrasound pulsed Doppler velocimeter, Left anterior des cending arterial flow, aortic pressure and poststenotic distal coronar y pressure were measured simultaneously. The diastolic anterograde flo w integral and systolic retrograde flow integral were compared in the presence and absence of intraaortic balloon pumping. Results. Although intraaortic balloon pumping augmented diastolic aortic pressure, this pressure increase was not effectively transmitted through stenosis. S eptal arterial diastolic flow velocity was not augmented, and left ant erior descending arterial flow was unchanged during intraaortic balloo n pumping. Conclusions. In the presence of severe coronary artery sten osis, intraaortic balloon pumping failed to increase diastolic inflow to the myocardium and did not enhance systolic retrograde flow from th e myocardium to the extramural coronary artery. Thus, the major effect of intraaortic balloon pumping on the ischemic heart with severe coro nary artery stenosis may be achieved by reducing oxygen demand by syst olic unloading.