Early Surgery Lowers Risk of MACE in Asymptomatic Aortic Stenosis vs Watchful Waiting

Mark Banovic, MD, PhD

Results of the AVATAR trial provide support for early aortic valve replacement compared to watchful waiting, due to an apparent reduction in risk of adverse cardiovascular events, for patients with asymptomatic severe aortic stenosis and normal ejection fraction.

Presented at the American Heart Association (AHA) 2021 Scientific Sessions, results of the trial, which included a population of more than 150 patients with a median follow-up of 32 months, demonstrate early surgical aortic valve replacement (SAVR) was associated with a 54% reduction in risk of a composite cardiovascular end point and a 60% reduction in risk of heart failure hospitalization or all-cause mortality.

“Our data deliver the additional degree of evidence needed to support the decision for early surgery and reassure a clinician when caring for a patient with severe asymptomatic aortic stenosis and normal left ventricular function. In such cases of low surgical risk and absence of other major health conditions, one may advocate for an early surgery for select patients,” said Marko Banovic, MD, PhD, lead investigator of the trial and an associate professor of cardiology at University Clinical Center of Serbia and the University of Belgrade Medical School in Serbia, in a statement from the AHA.

Led by Banovic and a team of colleagues, the Aortic Valve Replacement Versus Conservative Treatment in Asymptomatic Severe Aortic Stenosis (AVATAR) trial was designed with an interest in improving outcomes among asymptomatic patients with severe aortic stenosis and normal LVEF. An investigator-initiated, prospective, multinational, randomized, controlled, parallel group, event-driven trial, AVATAR was conducted in 9 centers across 7 European countries, was conducted from June 2015 to September 2020, and enrolled a population of 157 patients.

The primary outcome of interest for the trial was a composite end point including all-cause mortality, acute myocardial infarction, stroke, or hospitalization for heart failure. The 157 patients were randomly allocated to receive early SAVR or a conservative treatment. Those randomized to surgery were expected to undergo surgery within 8 weeks of randomization and patients in the conservative treatment group received risk factor and comorbidity management but were not referred to surgery unless patients experienced onset of aortic stenosis-related symptoms, reduction in LVEF to less than 50%, or a peak aortic jet velocity increase per year by more than 0.3 m/s on follow-up echocardiography.An event-driven trial, AVATAR was designed with a target of at least 35 events.

For inclusion in the trial, patients needed to be at least 18 years of age with severe aortic stenosis according to standard echocardiographic criteria and negative exercise testing. Of the 157 patients included in the study, 78 were randomized to early surgery and 79 were randomized to conservative treatment. The overall patient population had a mean age of 67 years, 57% were men, and the overall median follow-up was 32 months. Of note, the median follow-up time among the surgery group was 28 months and the median follow-up time among the conservative treatment group was 35 months.

During the follow-up period, 39 primary end point events occurring, including 13 in the early surgery group and 26 in the conservative treatment group. Investigators pointed out 92.3% of those randomized to early surgery underwent SAVR and the operative mortality rate among these patients was 1.4%. In their intention-to-treat analysis, early surgery was associated with a significantly lower incidence of the primary composite end point compared to those receiving conservative treatment (HR, 0.46 [95% CI, 0.23-0.90]; P=.02).

When assessing a composite of hospitalization for heart failure or all-cause mortality, results suggested a lower incidence of these events occurred among those randomized to early surgery compared to conservative treatment (HR, 0.40 [95% CI, 0.19-0.84]; P=.013). Additional analysis indicated there were no statistically significant differences observed for other secondary end points, including all-cause mortality, first heart failure hospitalizations, major bleeding, or thromboembolic complications, but trends were consistent with the primary outcome.

“Managing an asymptomatic patient with severe aortic stenosis can make for a much more difficult decision since valve replacement is not needed to improve the person’s quality of life, and the risk of sudden cardiac death is perceived to be low—around 1% per year, though still higher than in the general population,” Banovic added, in the aforementioned statement.

This study, “Aortic Valve ReplAcemenT versus Conservative Treatment in Asymptomatic SeveRe Aortic Stenosis: The AVATAR Trial,” was presented at AHA 2021 and simultaneously published in Circulation.