The LRT (Low Risk TAVR) trial did not find any significant differences in the rate of all-cause mortality between low-risk patients undergoing transcatheter aortic valve implantation (TAVI) and a historical control group of low-risk patients undergoing surgical aortic valve replacement. LRT is the first TAVI study to have US FDA approved investigational device exemption for low-risk patients.
Writing in the Journal of the American College of Cardiology, Ron Waksman (MedStar Washington Hospital Center, Washington, DC, USA) and colleagues comment that NOTION (Nordic Aortic Valve Intervention)—the only randomised trial to date to evaluate TAVI in low-risk patients—found that TAVI “compared favourably”, in terms of 30-day mortality, with surgical aortic valve replacement in low-risk patients. However, they add that this study also showed that TAVI with an early generation self-expanding device was “associated with significantly higher permanent pacemaker rates and paravalvular aortic regurgitation”. Therefore, the aim of LRT was to evaluate TAVI, with new-generation devices, in a low-risk US population.
Waksman et al report that, in the study, 200 low-risk patients (STS-PROM score ≤3% and absence of comorbidity that would increase surgical risk) underwent transfemoral TAVI with a balloon-expandable (Sapien 3, Edwards Lifesciences) or self-expanding device (CoreValve, Evolut R, Evolut PRO, Medtronic). The outcomes of these patients were then compared with a historical control group of 719 low-risk patients who underwent surgical aortic valve replacement, with the primary endpoint being all-cause mortality at 30 days.
Hospital length of stay was significantly shorter in TAVI patients and the rate of postoperative atrial fibrillation was higher in the surgical patients. However, the rates of permanent pacemaker implantation and moderate paravalvular leak were low in both groups—in fact, the rates of pacemaker implantation and moderate paravalvular leak were the lowest seen in all major TAVI studies so far. “This may be explained by the use of predominantly newer generation balloon-expandable devices in younger patients [approx. six years younger than those of the intermediate-risk populations in PARTNER 2 and SURTAVI] with less aortic annular calcification and less pre-existing conduction system disease, and improved implantation techniques,” Waksman et al comment.
There were no significant differences between TAVI and surgery patients in terms of the primary endpoint, with all 200 TAVI patients being discharged alive within 30 days of the TAVI procedure and zero mortality and zero disabling stroke at 30 days in this group. The authors comment: “It is important to highlight that except for the sponsor (MedStar Washington Hospital Center, Washington, DC, USA), enrolling centres in the LRT trial were not high-volume centres or experienced centre. As such, these results truly represent contemporary real-world TAVI practice in the USA.”
They observe that, unlike for higher risk populations, TAVI may not provide a mortality benefit (over surgery) for low-risk populations. They say, therefore, that the benefit of TAVI for these patients “may be shorter hospital length of stay, swifter recovery, and superior prosthesis haemodynamics”.
Post-surgery haemodynamics were not available for the surgical cohort, so a comparison could not between the groups could not be made. However, according to the authors, the mean gradient and valve areas seen in the TAVI group of the LRT trial were comparable to those seen in the TAVI arm of the PARTNER 2 Sapien 3 intermediate-risk.
Concluding, Waksman et al write: “TAVI is safe in low-risk patients with symptomatic severe aortic stenosis, with low procedural complication rates, short hospital length of stay, zero mortality and zero disabling stroke at 30 days.”
Waksman told Cardiovascular News: “The LRT study sends a strong signal that TAVI for low-risk patients is a safe and effective alternative to surgical aortic valve replacement for this population with symptomatic aortic stenosis. We anticipate that the pivotal trials will corroborate the LRT results and FDA will expand the labelling of TAVI for the low-risk population.”
The study was presented at the 2018 European Society of Cardiology (ESC) Congress (25-29 August, Munich, Germany).