Atrial Fibrillation as a Prognostic Factor for All-Cause Mortality in Patients With Transthyretin Amyloid Cardiomyopathy

Background Atrial fibrillation/atrial flutter (AF/AFL) are common manifestations of transthyretin amyloid cardiomyopathy (ATTR-CM) but have not been found to be predictive of mortality. Objectives This analysis aimed to examine whether baseline or historical AF/AFL at enrollment was prognostic for all-cause mortality. Methods In the ATTR-ACT (Tafamidis in Transthyretin Cardiomyopathy Clinical Trial), a 30-month study of tafamidis vs placebo for ATTR-CM, AF/AFL was evaluated as an independent prognostic factor for all-cause mortality using Cox proportional hazards modelling. The impact of AF/AFL on tafamidis efficacy was explored by adding an interaction term for AF/AFL status and treatment. Results ATTR-ACT enrolled 441 patients with ATTR-CM (median age 75 years; 90% male); 314 (71.2%) had baseline or historical AF/AFL at enrollment. AF/AFL was an independent prognostic factor for all-cause mortality after adjusting for covariates prespecified in the ATTR-ACT model (treatment, genotype, New York Heart Association functional class; HR: 0.550; 95% CI: 0.368-0.821) but not in an expanded stepwise model selection analysis including 23 covariates (blood urea nitrogen and N-terminal pro–B-type natriuretic peptide concentration, 6-minute walk test distance, genotype, treatment, and global longitudinal strain were prognostic [P < 0.01]). The interactions between tafamidis treatment and AF/AFL for all-cause mortality (P = 0.33) and changes in Kansas City Cardiomyopathy Questionnaire Overall Summary score (P = 0.83) and 6-minute walk test distance (P = 0.82) were not significant. Conclusions In ATTR-ACT, baseline or historical AF/AFL was prognostic for all-cause mortality in analyses with limited adjustment but not after accounting for additional indicators of disease severity. Baseline or historical AF/AFL did not impact the efficacy of tafamidis treatment. (Safety and Efficacy of Tafamidis in Patients With Transthyretin Cardiomyopathy [ATTR-ACT]; NCT01994889)