Coronary circulation in hypertension and aging: an experimental study

Purpose. This study was undertaken to examine adverse changes in coronary hemodynamics associated with hypertension, aging, and excessive salt intake. To dissociate from the possible effects of atherosclerosis, the study was done in rats because they do not develop atherosclerosis. Moreover, this strain of spontaneously hypertensive rats (SHR) develops hypertension similar to essential hypertension in man.Methods. Systemic and coronary hemodynamics, left ventricular mass, and collagen content in normotensive and SHR of various ages and given different treatments were determined.Results. Compared with normotensive Wistar-Kyoto rats, coronary blood flow reserve was lower and minimal coronary vascular resistance was higher in SHR of all ages; an age-related decrease in flow reserve and an increase in minimal vascular resistance were observed for both strains of rats. In very old rats with isolated systolic hypertension, an increase in left ventricular collagen was associated with coronary insufficiency; antihypertensive therapy nearly normalized both measures. In SHR excessive salt intake increased pressure, increased collagen deposition in myocardial interstitium and perivascularly, and impaired coronary circulation; angiotensin II receptor blocker therapy prevented fibrosis and improved coronary hemodynamics.Conclusion. In conclusion, these data indicate that considerable coronary insufficiency associated with hypertension, aging, and salt overload exists in the absence of atherosclerotic coronary changes. Perivascular fibrosis within myocardium may significantly contribute to the coronary vascular impairment.