Structural and functional adaptations within the myocardium and coronary vessels after antihypertensive therapy in...

The relationships between cardiac performance, coronary flow, minimal coronary vascular resistance and myocardial oxygen consumption (MVO2) were explored in isolated hearts from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) and in hearts from SHR given a combination of metoprolol and felodipine (selective calcium antagonist) for 35 weeks. Antihypertensive therapy markedly reduced arterial pressure and caused a substantial regression of left ventricular hypertrophy. An antegrade working-heart perfusion system was used, allowing measurements of stroke volume, coronary flow and MVO2 at varying pre- and afterloads. In untreated SHR cardiac function was reduced at low and enhanced at high perfusion pressure compared with WKY. Minimal coronary vascular resistance, which was greatly increased in SHR, was significantly reduced by treatment, allowing higher coronary flow for any given perfusion pressure and consequently a lower degree of oxygen extraction. In addition, at a given workload, MVO2 was reduced in both untreated and treated SHR. These results stress the importance of having adequate coronary perfusion within a hypertensive structurally redesigned coronary vascular bed in order to maintain cardiac performance. With antihypertensive therapy in SHR, an improved coronary flow capacity was created due to regression of the hypertensive vascular changes.