Angiotensin-converting enzyme inhibitors and coronary artery disease

State-of-the-Art lecture. Statins and blockers of the renin-angiotensin system: vascular protection beyond their primary mode of action

In addition to their primary mode of action, statins and blockers of the renin-angiotensin system possess common additional properties that are under active investigation. The inhibition of cellular proliferation, the restoration of endothelial activity, the inhibition of platelet reactivity, and an antioxidant potential are only a few examples of shared effects that target the arterial wall. These and other properties may eventually become exploited for the improved treatment of cardiovascular diseases and of other diseases apparently unrelated to the cardiovascular field, including inflammation and cancer. This review analyzes the current knowledge on the pleiotropic properties of these classes of drugs. Direct comparison indicates that study of the associations among these drugs may eventually disclose additive or synergistic effects that, perhaps even at lower dosages, may provide improved vascular protection and a strong alliance against several atherogenic mechanisms.

Bradykinin-induced preconditioning in patients undergoing coronary angioplasty

OBJECTIVES

The purpose of this study was to determine whether administration of bradykinin reproduces the cardioprotective effects of ischemic preconditioning (PC) in patients undergoing percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Experimental studies suggest that activation of the bradykinin B2 receptor is an important trigger of ischemic PC. However, it is unknown whether bradykinin can precondition human myocardium against ischemia in vivo. Multicenter clinical trials have demonstrated an anti-ischemic effect of angiotensin-converting enzyme inhibitors, which has been postulated to result from potentiation of bradykinin; however, direct evidence for an anti-ischemic action of bradykinin in patients is lacking.

METHODS

Thirty patients were randomized to receive a 10-min intracoronary infusion of bradykinin (2.5 microg/min) or normal saline. Ten minutes later they underwent PTCA (three 2-min balloon inflations 5 min apart).

RESULTS

In control patients, the ST-segment shift on the intracoronary and surface electrocardiogram was significantly greater during the first inflation than during the second and third inflations, consistent with ischemic PC. In bradykinin-treated patients, the ST-segment shift during the first inflation was significantly smaller than in the control group, and there were no appreciable differences in ST-segment shift during the three inflations. Measurements of chest pain score and regional wall motion during inflation (quantitative two-dimensional echocardiography) paralleled those of ST-segment shift. Infusion of bradykinin had no hemodynamic effects and no significant adverse effects. Thus, intracoronary infusion of bradykinin before PTCA rendered the myocardium relatively resistant to subsequent ischemia, and the degree of this cardioprotective effect was comparable to that afforded by the ischemia associated with the first balloon inflation in control subjects. In a separate cohort of seven patients given the same dose of bradykinin, coronary hyperemia resolved completely within 10 min after the end of the infusion, indicating that bradykinin-induced vasodilation cannot account for the protective effects observed during the first balloon inflation.

CONCLUSIONS

Bradykinin preconditions human myocardium against ischemia in vivo in the absence of systemic hemodynamic changes. Pretreatment with bradykinin appears to be just as effective as ischemic PC and could be used prophylactically to attenuate ischemia in selected patients undergoing PTCA.

Estrogen replacement therapy and cardiovascular protection: lipid mechanisms are the tip of an iceberg

Cardiovascular disease remains a major cause of mortality among postmenopausal women. After menopause, atherogenesis is promoted by a number of metabolic and vascular changes. A multitude of observational clinical studies have come to the conclusion that estrogen replacement therapy (ERT) reduces cardiovascular risk by approximately 50% and that estrogen's favorable effects on the lipid profile can explain only 25-50% of the overall observed reduction. Estrogens are now known to have potent anti-atherogenic properties through lipid and non-lipid mechanisms; both will be highlighted in view of the recent literature. Estrogens induce favorable changes on lipids and lipoproteins, partly by increasing HDL-cholesterol and decreasing both LDL-cholesterol and lipoprotein (a). Non-lipid mechanisms of estrogen action include decreasing insulin resistance, serum fibrinogen, factor VII and plasminogen activator inhibitor-1 (PAI-1). Moreover, estrogens maintain endothelial cell integrity, decrease expression of adhesion molecules, lower systemic blood pressure, promote vasodilatation, decrease platelet aggregability, inhibit vascular smooth muscle cell proliferation, possess potent antioxidant and calcium antagonist activities, inhibit adrenergic responses and downregulate platelet and monocyte reactivity. Also mentioned are recent reports linking estrogen to the renin-angiotensin system, relaxin, serotonin and homocysteine. What was once thought of as a simple action is now being increasingly appreciated as a complex, multifaceted mechanism, which serves to prove that estrogen is a powerful cardiovascular agent.