Renal Hypertension Impairs Coronary Hyperemia During Exercise

Williams, Maurice A., Renal Hypertension Impairs Coronary Hyperemia During Exercise. Doctor of Philosophy (Biomedical Sciences), August, 2003, 103 pp., 2 tables, 10 illustrations, bibliography, 180 titles. High blood pressure (hypotension) is a common disease that greatly impacts cardiovascular disease and quality of life making it a high priority for early detection and treatment. Hypertension is a major risk factor for coronary artery disease, heart failure, stroke and sudden death. The incidence of hypertension is increasing as the population ages. Exercise intolerance or exertional fatigue is a common complaint of patients with hypertension. We tested the hypothesis that the acute onset of renovascular hypertension results in a sustained, elevated sympathetic adrenergic stimulation of the heart which blunts the coronary hyperemic response and reduces the cardiac contractile response to exercise. Studies were conducted in chronically instrumented dogs before and after the acute onset of renosvascular hypertension of only 2 weeks. This degree of hypertension would normally go undetected or untreated by physicians. Short-term hypertension blunted coronary blood flow at rest and during each level of submaximal exercise. Hypertensive dogs showed a significant reduction in cardiac pump function during submaximal exercise compared to the responses in the normotensive dogs. These changes were very dramatic for such a short term of a mild hypertension. These studies were designed to examine mechanisms mediating the blunted coronary hyperemic response during exercise which imposes a limit on cardiac function. The results of these experiments addressed fundamental questions regarding alterations in neurohumoral control of cardiac contractile function and the mechanisms by which neurohumoral control of the heart is altered by hypertension. These studies should also clarify the mechanistic rationale for medical therapies to treat patients with hypertension.