Estimating the Effects of MTEER in U.S. Practice: A Transportability Analysis of the COAPT Trial.

backgroundAlthough mitral transcatheter edge-to-edge repair (MTEER) was approved for secondary mitral regurgitation after the COAPT trial, findings of other MTEER trials have been mixed, raising questions about the applicability of the COAPT results to contemporary clinical practice.

objectivesWe used transportability methods to estimate the treatment effects of COAPT trial interventions applied to 2 target populations: 1) trial-eligible patients representative of U.S. clinical practice; and 2) treatment-candidate patients with secondary mitral regurgitation representative of U.S. clinical practice, regardless of trial eligibility.

methodsWe identified patients from the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy (TVT) Registry who were treated with MTEER for secondary mitral regurgitation from March 14, 2019 to September 30, 2023. To select trial-eligible individuals, we applied COAPT trial eligibility criteria to the TVT Registry sample. We used inverse odds of participation weighting to standardize patient-level COAPT data to the data distribution of each target population sample and estimated treatment-specific outcomes. The primary outcome was heart failure hospitalization at 2 years. We also examined 10 secondary outcomes, including all-cause death.

resultsOur analyses included 614 COAPT trial patients and 15,275 TVT Registry patients, of which 7,289 were COAPT trial-eligible. Trial-eligible TVT Registry patients were less likely to have ischemic cardiomyopathy (34.1% vs 60.8%) and more likely to have 4+ mitral regurgitation (79.4% vs 47.9%) compared with trial patients. We estimated that compared with medical therapy alone, MTEER in conjunction with other COAPT interventions (eg, optimization of medical therapy) in the trial-eligible population would result in 2-year absolute risk reductions of 17.0% for heart failure hospitalizations (95% CI: -28.7% to -5.7%) and 15.4% for all-cause death (95% CI: -26.6% to -5.2%), effect sizes similar to those estimated in the trial (P for difference between the trial and target populations >0.05 for both outcomes). The estimated treatment effect for heart failure hospitalizations in the broader treatment-candidate target population was also similar to that in the COAPT trial (P for difference = 0.90).

conclusionsAlthough COAPT trial patients had different baseline characteristics than patients undergoing MTEER in contemporary U.S. practice, we estimated that treatment effects would be similar had real-world patients received COAPT trial interventions, under the assumptions required for transportability (eg, conditional exchangeability across data sources, positivity of trial participation).