Use of ACE inhibitors in aortic stenosis
QWhy are ACE inhibitors contraindicated in aortic stenosis?
AIn patients without the obstruction to left ventricular outflow that occurs in aortic stenosis, a decrease in systemic vascular resistance (as occurs in exercise) results in increased cardiac output so that blood pressure is subsequently maintained.
In contrast, if severe aortic stenosis is present, cardiac output cannot increase in response to decreased systemic vascular resistance. As a result blood pressure falls, leading to hypotension and syncope.
ACE inhibitor usage would exacerbate the blood pressure fall, although the magnitude of this effect and its precise relationship to the severity of aortic stenosis remains unknown.
Although there have been small studies showing ACE inhibition can be tolerated in some patients with aortic stenosis, studies with larger numbers of subjects are needed.
ACE inhibition is likely to be well tolerated in asymptomatic patients with only mild aortic valve obstruction. Several studies have shown these patients can increase cardiac output in response to exercise and thus should respond normally to a change in systemic vascular resistance.
At the other end of the spectrum, patients with severe symptomatic aortic stenosis require valve replacement and ACE inhibitors are contraindicated.
Professor Gregory Lip, consultant cardiologist, professor of cardiovascular medicine, City Hospital, Birmingham