Left ventricular pressure is an important determinant of coronary oscillatory flow amplitude

Abstract

We studied the effect of cardiac contraction on coronary arterial flow with vasomotor tone (control) and during maximal vasodilation with adenosine in the isolated blood-perfused rat heart at constant perfusion pressure (105 mmHg) with a left ventricular balloon (n = 6). Ventricular pressure was changed by volume changes and contractility via postextrasystolic potentiation. Contractility was expressed as the slope of the end-systolic pressure-volume ratio, elastance. Constant vasomotor flow was judged from stable diastolic flow. Coronary flow reduction (diastolic minus systolic flow, δCBF, ml . min −1 . g −1 ) due to contraction was related to developed ventricular pressure (devP LV ) and developed elastance (devE LV , systolic minus diastolic elastance) by multiple regression: δCBF = S p . devP LV + S E . devE LV + I, where S p and S E represent changes in coronary blood flow due to changes in devP LV and devE LV , respectively, and I is the intercept. In the control, δCBF = (0.016 ± 0.008) . devP LV + (0.0022 ± 0.0009) . devE LV + (0.29 ± 0.77); during vasodilation, δCBF = (0.046 ± 0.011) . devP LV + (0.009 ± 0.0053) . devE LV + (2.50 ± 2.56). Diastolic flow increased by a factor of 4.06 ± 1.57 (SD) during vasodilation. The increases in diastolic flow, S p , and S E were not different. We conclude that vasodilation has similar effects on diastolic flow and flow amplitude without affecting the relative contributions of ventricular pressure and contractility