Left Untreated, Moderate Aortic Valve Stenosis Has High Mortality Risk

Aortic valve stenosis (AVS) is an incidental finding in many patients who require coronary artery bypass grafting (CABG). Although aortic valve replacement (AVR) is indicated when AS is severe, experts have struggled with crafting evidence-based recommendations in the presence of mild or moderate AS, which has led to inconsistent practices and surgical guidelines.

In an effort to identify the long-term outcomes for moderate AS and pinpoint the threshold at which patients with untreated AS should undergo AVR, a team of surgeons from the Mayo Clinic conducted a review of 312 patients with mild or moderate AS — defined as an aortic valve area (AVA) of 1-2 cm² — who underwent isolated CABG between 1993 and 2006. The researchers then compared the patients to a control group of AS-free subjects who underwent CABG in the same period.

In the study, patients with untreated moderate AS had significantly lower late survival rates than those with mild or no AS. After adjusting for age, ejection fraction, heart failure, creatinine, diabetes, and peripheral vascular disease, patients with moderate AS were more likely to die than those with mild or no AS.

Patients with AVAs of 1-1.25 cm² — the upper limit of moderate AS — experienced the highest rate of late postoperative mortality, as they were more than twice as likely to die.

The study authors hypothesized that the prognostic impact of untreated moderate AS results from the disease’s progressive nature. The estimated average decline in AVA is 0.1 cm²/year, and at that rate, AS that is approaching the upper limit of moderate disease could progress to severe stenosis within 2 or 3 years of CABG.

The authors suggested that further clinical trials are needed to define AS severity thresholds, as well as determine whether AVR should be performed earlier.