Anti-ischemic effects of angiotensin-converting enzyme inhibitors: a future therapeutic perspective

The renin-angiotensin system and angiotensin-converting enzyme (ACE) are increasingly being implicated in the pathogenesis of coronary artery disease and its sequelae and the potential of ACE inhibitors to protect the heart is a topic that has emerged recently as a matter for scientific discussion. Experimental and clinical studies have shown the beneficial effects of ACE inhibitors on the metabolism, function and structure of healthy and damaged hearts and these data support the concept of both primary and secondary cardioprotection with this class of drugs. Animal studies have demonstrated the potential beneficial effects of ACE inhibition at a variety of sites, including improvement of endothelial function, inhibition of platelet aggregation, prevention of atherosclerotic lesions and inhibition of myointimal proliferation, extending the concept to a more general definition of cardiovascular protection with ACE inhibitors involving both the heart and the vessels. ACE inhibitors prevent stimulation of smooth muscle cell angiotensin-II (A-II) receptors, thereby blocking both contractile and proliferative actions of A-II. In addition, ACE inhibition of kininase inhibits the breakdown of bradykinin, a direct stimulant of nitric oxide release from the intact endothelial cell. Thus, at the cellular level ACE inhibition shifts the balance of ongoing mechanisms in favour of those promoting vasodilatory, anti-aggregatory, antithrombotic and antiproliferative effects. Although these data have not all been validated in human studies, the reduction of ischemic events in studies of ACE inhibition in left ventricular dysfunction (LVD) and, more recently, also in patients without LVD, cannot be explained solely by improved hemodynamics, and it is possible that actions on the endothelium, the atherosclerotic process and platelets are at least in part responsible. So, the available data underlie the potential benefits of ACE inhibition in the field of ischemic heart disease and atherosclerosis; the results of ongoing studies in humans looking more directly at the influence of ACE inhibitors in this setting are awaited with interest.