By Jeffrey Zimmet, MD, PhD
Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center
In this prospective, multicenter, single-arm trial, low-surgical risk patients with bicuspid aortic valve anatomy treated with transcatheter aortic valve replacement showed favorable results at three years, with low rates of death and disabling stroke.
Zahr F, Ramlawi B, Reardon MJ, et al. 3-year outcomes from the Evolut Low Risk TAVR Bicuspid Study. JACC Cardiovasc Interv 2024;17:1667-1675.
Aortic stenosis in patients with bicuspid aortic valve pathology presents special challenges for transcatheter aortic valve replacement (TAVR). The earliest studies of TAVR excluded bicuspid patients, and subsequent retrospective data suggested lower rates of device success and higher incidence of procedural complications and significant paravalvular regurgitation. Bicuspid valve aortic roots may be more elliptical than non-bicuspids, and the often severe and asymmetric leaflet calcification can hinder device anchoring and sealing at the annulus.
The Evolut Low Risk Bicuspid Study prospectively enrolled 150 patients with bicuspid aortic stenosis at 25 U.S. centers to receive TAVR with the self-expanding Evolut valve. Patients were estimated by local heart teams to have low surgical risk (< 3% risk of mortality within 30 days). The mean age was 70 years, and the median Society of Thoracic Surgery (STS) risk score was 1.3%. Patients younger than 60 years of age were excluded, as were those with significant aortopathy or ascending aortic diameter greater than 4.5 cm. Acute results were positive, with device success in 95.3% and only a single death and disabling stroke by 30 days. No patients had moderate or greater paravalvular leak.
Three-year follow-up was available for 128 patients (85.3%). At three years, the composite of all-cause mortality or disabling stroke was 4.1%. Endocarditis occurred in only two patients, and a total of three patients (2%) were diagnosed with clinical or subclinical leaflet thrombosis. Two patients required valve surgery with TAVR explant. The permanent pacemaker rate was 19.4%, with most of these occurring in the first year. Valve hemodynamics were very favorable at three years, with mean transvalvular gradient 9.1 ± 5.8 mmHg, 15% with mild paravalvular leak, and none with moderate or greater paravalvular leak.The authors reported that this represents the longest study of low-risk patients with bicuspid aortic stenosis treated with TAVR with low rates of mortality and disabling stroke, and favorable hemodynamics maintained at three years.
COMMENTARY
TAVR has been studied extensively in multiple populations since its commercial inception, but data on outcomes in bicuspid patients specifically have been lacking. The randomized NOTION-2 trial comparing TAVR to surgical aortic valve replacement (SAVR) in younger patients, presented earlier this year at EuroPCR, suggested similar overall short-term outcomes between TAVR and surgery in the overall trial. However, it also reported a nearly four-fold increased risk of death, stroke, or rehospitalization among the subset of patients with bicuspid anatomy treated with TAVR compared with SAVR. Notably, as TAVR has been applied to younger and healthier patients, the percentage with bicuspid anatomy increases. Registry data have suggested that, while only 5% of AS patients 80 years of age or older have bicuspid valves, that percentage increases to more than 20% in the 65- to 79-year-old range.
The current trial goes some distance toward allaying fears about TAVR outcomes in these patients. In the highly selected population enrolled in this study, patients had overall excellent outcomes, both from the immediate procedure and over the intermediate term at three years. Note that the valve used here was the self-expanding Corevalve device. Also, note that the balloon-expandable Sapien valve currently has significantly higher market share in the United States.
One clear message here is that choosing TAVR over SAVR for low-surgical risk patients with bicuspid valve anatomy is not necessarily wrong. However, remember that patients in this trial were evaluated by an experienced committee in each case. Patients with significant coronary disease or aortic dilatation were excluded, and patients with hostile device landing zone calcification also were disqualified. This demonstrates that experienced practitioners are able to select bicuspid patients who are likely to do well with TAVR, and yet the criteria for favorable vs. unfavorable bicuspid anatomy are not currently well-defined. If TAVR is considered for bicuspid aortic stenosis patients in this demographic, evaluation of TAVR candidacy should take into account each patient’s comorbidities and aortic anatomy. Candid assessment of the computed tomography scan by an experienced team should be undertaken before offering TAVR as a viable alternative to surgery for low-risk patients. Truly long-term data on these patients still are lacking, as are randomized data comparing TAVR with SAVR in these patients.
