EVIDENCE FOR A SYSTEMIC DEFECT OF RESISTANCE-SIZED ARTERIOLES IN HYPERTROPHIC CARDIOMYOPATHY

Background: To investigate whether the abnormalities of coronary arterioles observed in association with hypertrophic cardiomyopathy represent a generalized phenomenon, both forearm and coronary vasodilator reserve were measured in 12 patients with hypertrophic cardiomyopathy. Methods: Forearm vasodilator reserve was evaluated by measuring minimal forearm vascular resistance (R(min), the ratio of mean intra-arterial pressure to peak forearm blood flow measured by venous plethysmography) under conditions of maximal postocclusive reactive hyperemia. Results: In a subgroup (n = 5) of patients, the intra-arterial infusion of sodium nitroprusside combined with arterial occlusion did not produce additional vasodilation, indicating that the ischemic stimulus was indeed maximal. Coronary reserve was quantitated by measuring left ventricular blood flow (N-13-ammonia and positron emission tomography) and coronary resistance at baseline and after intravenous dipyridamole (0.56 mg/kg). R(min) was significantly greater in patients than in a group of age- and sex-matched controls. The percentage change in coronary resistance after dipyridamole was significantly related to R(min), whereas no correlation was found between change in coronary resistance and individual septal thickness values. Conclusions: Independent of cardiac hypertrophy, systemic and coronary arterioles of patients with hypertrophic cardiomyopathy are affected by an abnormality that may contribute to the clinical evolution of this syndrome.