Copyright © 1992 by the European Society of Cardiology.
© 1992 The European Society of Cardiology
Investigation of impaired coronary vasodilator reserve in the guinea pig heart with pressure induced hypertrophy
Department of Academic Cardiology, St Mary's Hospital Medical School London W2, U.K
Received 14 February 1991; revised 21 June 1991; .
Correspondence Dr D. O'Gorman, Dept. of Academic Cardiology, Q.E.Q M. Wing, St Mary's Hospital, Paddington, London W2 I NY, U.K.
Abstract
Impaired coronary reserve and increased minimal coronary resistance have been documented in several animal models of left ventricular hypertrophy. There is controversy whether the increased minimal coronary resistance is due to vascular or extravascular causes. To test the hypothesis that pressure-overloaded left ventricular hypertrophy (LVH) is associated with a vascular defect, studies were performed using isolated buffer-perfused guinea pig hearts taken 72 ±6 days post-aortic banding (L VH n=13) and compared to sham-operated controls (n=12). The pressure flow relationship was determined over the range 3070 mmHg. We defined an extravascular compression index as the percentage increase in flow during maximal arteriolar dilation when systolic forces were excluded during prolonged diastole (2±0.2s). In LVH, coronary reserve was reduced (141±5.5% v 231.7 ±24.1%) P <0.01 and minimal coronary resistance was increased (4.55± 0.44 v 3.70±0.37 mmHg. ml1. min1. g1) P<0.05. The extravascular compression index was increased in LVH (36.8± 1.4 v 30.5±2.3%) P<0.05. Systole caused a greater increase in resistance in the LVH group than in controls (l.73±0.26 v 0.95±0.14 mmHg. ml1. min1.g1) P<0.05. These data indicate that during diastole there is impaired minimal coronary resistance of vascular origin. Systole impaired flow to a greater extent in hypertrophied hearts, further reducing the coronary reserve.
Key Words: Left ventricular hypertrophy coronary blood flow coronary reserve
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