Can the Renin-Angiotensin System Protect Against Stroke? A Focus on Angiotensin II Receptor Blockers

Abstract

From a patient's perspective, stroke is the most devastating form of cardiovascular disease, representing the number one cause of permanent disability in the United States. Treatment of hypertension significantly reduces the risk of stroke; however, it is unclear whether all antihypertensive agents are equivalent in this regard. Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce the risk of cardiovascular events, including stroke. Although attenuation of the renin-angiotensin system (RAS) is often credited with the blood pressure-independent effects of this class of agents, this hypothesis has not been confirmed with regard to the end point of stroke. In fact, drugs that activate the RAS, such as diuretics and dihydropyridine calcium channel blockers, are as effective or superior to ACE inhibitors for stroke prevention. Angiotensin II receptor blockers (ARBs) selectively block the angiotensin II subtype I receptor, which results in a reflexive increase in levels of angiotensin II and unopposed activation of angiotensin II subtype 2 receptors. Clinical trials comparing ARBs with active controls have reported significant reductions in stroke in ARB-treated patients. Data on ARBs and other drugs that activate the RAS (diuretics and dihydropyridine calcium channel blockers) support a potential role for the RAS in protecting against stroke. Ongoing trials with ARBs are evaluating stroke as a primary end point, and results should help to further elucidate the role of ARBs in this disease. Until then, it is prudent to treat hypertension with an agent or combination of agents that are likely to result in a rapid and sustained reduction in blood pressure, taking into consideration patient characteristics, comorbidities, tolerability, and cost.