Can Inhibition of the Renin-Angiotensin System Have a Cardioprotective Effect?

The inhibition of the renin-angiotensin system (RAS) has important effects on different parameters of left ventricular function. Chronic inhibition of the RAS avoids hypokalemia and potassium losses by increasing aldosterone release. This potassium-sparing effect is likely to prevent cardiac arrhythmia. Inhibition of the RAS reverses cardiac hypertrophy in renovascular and in spontaneously hypertensive rats (SHR), but not in DOCA salt hypertensive rats. Inhibition of the RAS also reverses the decrease in myocardial contractility, as demonstrated by the reversion of isoenzyme profile of cardiac myosin in renovascular hypertensive rats. In DOCA salt hypertensive rats, RAS inhibition has no effect on blood pressure or on cardiac contractility. Despite its peripheral vasodilatory property, inhibition of the RAS does not increase heart rate in relation to a direct negative chronotropic effect of angiotensin II inhibition and to the absence of activation of the baroreflex system. When RAS is activated, its inhibition has a coronary vasodilatory effect, but this coronary vasodilation is associated with a decrease in perfusion pressure and with an increase in intrinsic cardiac contractility. These concomitant effects lead us to conclude that inhibition of RAS probably has no important beneficial effect on the oxygen demand/oxygen supply ratio in the myocardium distal to the coronary artery stenosis.