Reduced vasodilator response of the right coronary artery to myocardial ischemia in the hypertrophied right ventricle.

The reduced reactive hyperemic response of the right coronary artery (RCA) to brief coronary occlusion was assessed in dogs with pressure-induced right ventricular hypertrophy (RVH). Right coronary reactive hyperemia was observed in normal dogs and in dogs with pressure-induced RVH. RVH was induced by chronic pulmonary artery banding in eight 3- to 6-month-old dogs, and reactive hyperemia responses to coronary occlusion lasting for 5, 10, 15, 20, 30, 45, and 60 sec were compared to those in normal dogs. In dogs with RVH, the peak reactive flow rate and excess blood flow debt repayment after the release of 5- to 60 sec RCA occlusion were markedly attenuated. The calculated minimum coronary resistance was higher in RVH dogs than in normal dogs (p < 0.02). The occlusion time that produced one-half of the maximum %PRHc, T1/2, was significantly (p < 0.01) shorter in RVH dogs than in normal dogs, where %PRHc = (peak reactive flow rate baseline flow rate)/(baseline flow rate). T1/2 in RVH dogs varied inversely with right ventricular systolic pressure. Therefore, blood flow in the RCA in RVH is characterized by an attenuated flow response to acute myocardial ischemia, suggesting inadequate development of the coronary vasculature supplying the hypertrophied ventricle.