Association Between Use of WATCHMAN Device and 1-Year Mortality Using High-Dimensional Propensity Scores to Reduce Confounding

BACKGROUND: Previous observational studies showed left atrial appendage occlusions with the WATCHMAN device reduced 1-year mortality, which conflicted with evidence generated from randomized controlled trials. We proposed to use the high-dimensional propensity score (hdPS) to assist in nonactive comparator selection (prevalent user of medication) and compared 1-year mortality between patients with atrial fibrillation who received the WATCHMAN device (percutaneous left atrial appendage occlusion device [pLAAO]) and direct oral anticoagulants in 2 matched cohorts based on (1) traditional propensity score (PS) and (2) integrating traditional PS with information learned from hdPS. METHODS: Patients entered the cohort once diagnosed with atrial fibrillation in the 15% of Medicare fee-for-service claims database from 2011 to 2018. Patients could enter the study cohort upon receiving WATCHMAN or at an outpatient visit with an atrial fibrillation diagnosis, respectively. We used PS matching with a 1:3 ratio for patients in pLAAO and direct oral anticoagulant groups. In cohort 2, we implemented a multistep approach with information learned from hdPS. The Cox proportional hazards model was used to estimate hazard ratios of outcomes with 95% CIs. RESULTS: In cohort 1, we identified 1159 and 3477 patients in the pLAAO and direct oral anticoagulant groups with a mean age of 78.1 versus 77.5 years, 44.9% versus 40.8% of women, and a 1-year mortality rate of 8.02 versus 8.97/100 person-years (hazard ratio, 0.87 [95% CI, 0.69–1.09]). With the support of hdPS, in cohort 2, we excluded patients with malignant cancer and added frailty score in the PS model. We identified 953 and 2859 patients in the pLAAO and direct oral anticoagulant groups with a mean age of 78.1 versus 77.9 years, 47.2% versus 46.1% of women, and a 1-year mortality rate of 7.45 and 7.69/100 person-years (hazard ratio, 0.95 [95% CI, 0.73–1.24]). CONCLUSIONS: No association was found between pLAAO and 1-year mortality, which is consistent with existing evidence from randomized controlled trials. The hdPS approach provides an opportunity to improve nonactive comparator selection in traditional PS analysis.