ABNORMAL CORONARY VASCULAR-RESPONSE TO EXERCISE IN DOGS WITH SEVERE RIGHT VENTRICULAR HYPERTROPHY

Measurements of right coronary artery blood flow, aortic and right ventricular (RV) pressures and heart rate were radiotelemetered during strenuous, spontaneous exercise in normal dogs and dogs with severe RV hypertrophy induced by chronic (5-6 mo.) pulmonary artery stenosis. With fixed pulmonic stenosis dogs with RV hypertrophy exhibited a decrese (P < 0.01) in arterial pressure during exercise. Under these conditions, exercise increased right coronary artery blood flow and decreased right coronary vascular resistance less (P < 0.05) in dogs with RV hypertrophy compared with normal. This attenuated response of right coronary artery blood flow of dogs with RV hypertrophy was not observed when arterial pressures remained at preexercise vaules during exercise. Regardless of changes in arterial pressures during exercise, all dogs with RV hypertrophy demonstrated a striking postexercise coronary hyperemia (P < 0.01), suggesting a perfusion deficit of the hypertrophied RV during exercise. A fundamental defect in the ability of the coronary circulation of the severely hypertrophied RV to provide sufficient nutrient supply during elevated metabolic demands of exercise is suggested.