Cardiovascular risk in patients with mild renal insufficiency: implications for the use of ACE inhibitors

Abstract

We review the evidence linking mild renal insufficiency (MRI) with increased cardiovascular risk. MRI is associated with a number of cardiovascular risk factors, including nighttime hypertension, and increased levels of lipoprotein (a), homocysteine, asymmetric dimethyl-arginine, and inflammation and insulin resistance markers and mediators. Epidemiologic evidence associates coronary artery disease and nephrosclerosis, a frequent cause of early renal insufficiency in the elderly. In a middle-aged general population MRI was found in 8% of women and 9% of men, but was not associated with cardiovascular disease. Nonetheless, in a representative sample of middle-aged British men the risk of stroke was 60% higher for the sub-group with MRI: in people at high cardiovascular risk (mostly coronary disease), the HOPE study found a 2-fold (unadjusted) or 1.4-fold (adjusted) higher incidence of cardiovascular outcomes with MRI. The combined incidence of cardiovascular death, myocardial infarction and stroke increased with the level of serum creatinine. Several studies have examined the cardiovascular risk associated with MRI in hypertension. In HDFP, as in HOPE, cardiovascular mortality increased with serum creatinine (five-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). The risk associated with renal insufficiency was independent of other classic cardiovascular risk factors. Two trials of hypertensives with low risk (HOT and a small Italian trial) found that cardiovascular outcomes approximately doubled in subjects with MRI. Another study (MRFIT) found that it was not baseline creatinine, but its increase on follow-up that predicted future cardiovascular disease. These observational data suggest that regardless of etiology MRI is a strong predictor of cardiovascular disease and is found in 10% of populations at low cardiovascular risk and in up to 30% of those at high risk. No prospective therapeutic trials aimed at reducing the cardiovascular burden in people with MRI are available. Subgroup analyses of the HOPE study indicate that angiotensin-converting enzyme (ACE) inhibition with ramipril is beneficial and does not increase the risk of such side effects as acute renal failure or hyperkalemia. Thus the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since MRI identifies a group at high risk that appears to benefit most from treatment. Moreover, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of early renal insufficiency for cardiovascular disease and prognosis with various therapeutic options.