Debate: angiotensin-converting enzyme inhibitors versus angiotensin II receptor blockers--a gap in evidence-based medicine.

In this article, 2 leading physicians debate the strength of outcome data on the efficacy of angiotensin-converting enzyme (ACE) inhibitors versus angiotensin II receptor blockers (ARBs) for reducing the incidence of cardiovascular, cerebrovascular, and renovascular events. Dr. Stephen G. Ball notes that the efficacy of ACE inhibitors for reducing the risk for myocardial infarction independent of their effects on blood pressure is controversial. In the Heart Outcomes Prevention Evaluation (HOPE) study, ramipril treatment in high-risk patients was associated with a 20% reduction in the risk for myocardial infarction; mean reduction in blood pressure was 3 mm Hg for systolic blood pressure and 1 mm Hg for diastolic blood pressure. The HOPE investigators propose that the 20% reduction was much greater than would be expected based on the observed blood pressure reduction. However, a meta-regression analysis of blood pressure reduction in >20 antihypertensive therapy outcome trials found that the reduction in myocardial infarction risk with ramipril observed in HOPE was consistent with the modest blood pressure reduction seen with that agent. Nevertheless, there are convincing data for prevention of myocardial infarction with ACE inhibitors in patients with heart failure, including those with heart failure after myocardial infarction, as well as supportive evidence from studies in patients with diabetes mellitus and concomitant hypertension. On the other hand, Dr. William B. White takes the position that ARBs are well-tolerated antihypertensive agents that specifically antagonize the angiotensin II type 1 (AT(1)) receptor and provide a more complete block of the pathologic effects of angiotensin II-which are mediated via the AT(1) receptor-than ACE inhibitors. The Evaluation of Losartan in the Elderly (ELITE) II study and the Valsartan Heart Failure Trial (ValHeFT) suggest that ARBs reduce the risk for mortality in patients with congestive heart failure. The Losartan Intervention for Endpoint (LIFE) Reduction in Hypertension trial also demonstrated beneficial effects of ARBs in the prevention of stroke events. The Irbesartan in Patients with Diabetes and Microalbuminuria (IRMA) study, the Irbesartan Diabetic Nephropathy Trial (IDNT), and the Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan (RENAAL) study demonstrated significant reductions in the rate of progression of renal disease in patients receiving ARBs, independent of effects on blood pressure. These data support the use of ARBs, in addition to the standard of care, in hypertensive patients with heart failure who are intolerant of ACE inhibitors, and also provide compelling evidence for their use in patients with hypertension and type 2 diabetes.