Clinical guidelines don’t recommend valve replacement for patients with severe aortic stenosis (AS) demonstrating normal flow and low gradients. But maybe they should, according to new research published in JACC: Cardiovascular Imaging.
Over a mean follow-up of 652 days, those patients displayed the following mortality rates: 28 percent for conservative treatment, 11 percent for transcatheter aortic valve replacement (TAVR) and 12 percent for surgical aortic valve replacement (SAVR). After adjustment for baseline risk factors, TAVR and SAVR were associated with greater survival by 51 and 45 percent, respectively, when compared to conservative treatment.
“Our study found intervention to be associated with better survival than conservative therapy among NFLG (normal flow-low gradient) patients, similar to results found in another study that evaluated patients with low gradient severe AS,” wrote lead researcher Oren Zusman, MD, with Rabin Medical Center in Tel Aviv, Israel, and colleagues.
“This finding is in contrast with other research that found no benefit of AVR in this patient group, or similar long-term mortality when comparing asymptomatic NFLG patients with those with moderate AS. However, these studies included asymptomatic patients with very few TAVR patients. By contrast, our study focused only on symptomatic patients and included a substantial number of TAVR patients.”
A total of 303 NFLG patients in the single-center study were included in the final analysis—149 conservative treatment, 114 TAVR and 40 SAVR. They all displayed the following characteristics via echocardiogram: aortic valve area of less than one square centimeter, mean gradient of less than 40 millimeters of mercury and a stroke volume index of at least 35 milliliters per square meter.
“The results of our study suggest that for symptomatic patients with an AVA of ≤1.0 cm2 and normal flow, individual judgment on appropriateness of intervention might be more important than adherence to a specific gradient cutoff,” the authors wrote. “This strategy is reasonable, because patients with a mean gradient of 30 to 35 mm Hg can progress to higher gradients in less than 1 year and, because gradients, as with other biologic processes, exist on a spectrum and do not neatly fit into categories defined by simple cutoffs.”
Zusman et al. said larger randomized studies are necessary to substantiate their findings and test the outcomes of AVR in a broader group patients with NFLG AS. They also suggested “different parameters should be sought to yield a better threshold for intervention.”
In a corresponding editorial, Blase A. Carabello, MD, with the East Carolina Heart Institute, wrote Zusman and colleagues’ study “adds to a host of data that tell us that if you have symptoms due to severe AS, AVR is indicated in most cases.”
However, Carabello pointed out it is often difficult to determine whether a patient’s symptoms are due to AS. He suggested observing a patient during exercise—which could induce symptoms of AS—or performing imaging for aortic valve calcium as additional tools to assess the severity of AS.
“The study by Zusman et al. confirms that severe symptomatic AS is a lethal disease that should be treated with AVR even in normal flow low gradient cases,” Carabello wrote. “When the patient’s AVA is 0.6 cm2 and the mean gradient is 75 mm Hg, the decision is easy. When these parameters are less severe or discordant, we must obtain more data. … Considering the safety of implanting both surgically and transcatheter aortic valves in current practice, in most cases it seems wise to err on the side of valve replacement in this difficult group of patients.”