Objectives: The aim of this study was to assess coronary blood flow during intraaortic balloon counterpulsation by direct measurement.
Background: In a majority of human studies, increased coronary blood flow during intraaortic balloon counterpulsation measured by indirect techniques has not been consistently demonstrated.
Methods: Hemodynamic variables and coronary blood flow velocity (20-MHz Doppler-tipped catheter) data were measured in 19 patients requiring intraaortic balloon pumping for clinical indications (11 patients had acute myocardial infarction [9 with shock], 6 had unstable angina, 1 had acute mitral regurgitation and 1 was at high risk undergoing angioplasty). Hemodynamic data, mean and phasic diastolic flow velocity and velocity-time integrals (computed from digitized waveforms) were analyzed during periods of 1:1 balloon counterpulsation.
Results: Intraaortic balloon pumping decreased systolic pressure (6 +/- 10%, p < 0.001) and increased diastolic pressure (80 +/- 30% from baseline, p < 0.001) without changing RR interval. Peak phasic, mean coronary flow velocity and diastolic flow velocity integral were significantly increased (115 +/- 115%, 67 +/- 61%, 103 +/- 81%, respectively, all p < 0.001) during intraaortic balloon pumping. In addition, although a wide splay of data was evident due to operator set variations in balloon inflation and deflation timing, the greater increases in diastolic flow velocity integral (DFVi) occurred in patients with basal systolic pressure < or = 90 mm Hg (% delta DFVi = 102 - 0.1.[unaugmented systolic pressure], SEE = 21.7 mm Hg, r = 0.30, p < 0.001).
Conclusions: Intraaortic balloon pumping unequivocally and significantly augments proximal coronary blood flow velocity, nearly doubling the coronary flow velocity integral in most patients. This mechanism may be a significant means of ischemia relief in hypotensive patients.