Of fads, fashion, surrogate endpoints and dual RAS blockade

Dual renin-angiotensin system (RAS) blockade, mostly by combining an angiotensin converting enzyme (ACE) inhibitor with an angiotensin receptor blocker (ARB), is increasingly used in patients with hypertension and diabetes and/or proteinuria and in those with resistant heart failure. However, in the zest of achieving greater nephroprotection and cardioprotection, even patients with uncomplicated essential hypertension are not uncommonly treated with dual RAS blockade.

In 2003 the COOPERATE trial, seemed to confirm that dual RAS blockade was beneficial and that proteinuria reduction was synonymous with nephroprotection. This study had to be withdrawn recently attesting to the suspicion that the data looked to good to be true. Moreover, the large prospective ONTARGET data argue against a nephroprotective effect of dual RAS blockade and together with renal findings from ACCOMPLISH, cast doubt on albuminuria/proteinuria being a reliable surrogate endpoint for renal outcome. Although in heart failure, dual RAS blockade had some benefit without reducing mortality, there remains a distinct safety issue with regard to hyperkalemia and elevated creatinine. Neither in ischaemic heart disease nor in left ventricular hypertrophy had dual RAS blockade any benefits when compared with single RAS blockade. Of note, the combination of an ACE inhibitor with an ARB was recently shown to reduce the risk of dementia. All dual RAS blockade may be created equal and the combination of valsartan with aliskiren, a direct renin inhibitor will be evaluated in diabetic patients in the prospective, randomized ALTITUDE study.

For the time being, given the adverse effects and lack of consistent survival benefits, the use of dual RAS blockade should be avoided unless ironclad data emerge to the contrary.