Lowering of blood pressure and coronary blood flow in isolated systolic hypertension

Background In essential hypertension, the lower limit of autoregulation of coronary flow shifts to higher perfusion and the hypertensive ventricle is at a higher than normal risk of ischemia, and less able to tolerate acute r eduction of coronary perfusion pressure. Little is known about pattern of c oronary flow in isolated systolic hypertension, a pathologic condition in w hich the elevated systolic blood pressure is associated with a lower than n ormal vascular compliance and normal or slightly greater than normal mean a rterial pressure and vascular resistance. Objective To evaluate the effects of rapid normalization of blood pressure on coronary blood flow in isolated systolic hypertension. Methods We subjected 20 patients with isolated systolic hypertension to int raoperative hemodynamic and transesophageal echocardiographic monitoring du ring peripheral vascular surgery. Coronary flow velocity integrals and diam eters in the left anterior descending coronary artery were evaluated under baseline conditions and after normalization of blood pressure, which occurr ed spontaneously during anesthesia (10 cases; group 1A) or was induced by i nfusion of nitrate (10 cases, group 1B). Results After normalization of systolic blood pressure integrals decreased significantly only for patients in group 1A; percentage changes of diameter were significantly greater for patients in group 1B, Therefore, coronary b lood flow after normalization of systolic blood pressure increased for pati ents in group 1B (by 28 +/- 25%) and decreased for patients in group 1A (by 30 +/- 21%), Changes in integrals were inversely related to those in diame ter (r = -0.72, P < 0.001); for patients in group 1A changes in coronary pe rfusion pressure and diameter were related to those of integrals (r = 0.94; P < 0.0005). Conclusions In isolated systolic hypertension, despite there being similar changes of the systolic blood pressure, administration of nitrates caused a marked increase of coronary flow through direct effects on coronary circul ation, whereas spontaneous normotension was associated with a significant r eduction of coronary flow. Coron Artery Dis 12:259-265 (C) 2001 Lippincott Williams and Wilkins.