Cardiac Resynchronization Therapy, Remodeling, and Outcome in Patients With Amyloid Transthyretin Cardiomyopathy

Background: Transthyretin amyloid cardiomyopathy (ATTR-CM) has a specific pathophysiology, with myocardial stiffening and systolic dysfunction only in advanced stages. We aimed to investigate the response to cardiac resynchronization therapy (CRT) in ATTR-CM compared with heart failure. Methods: In this multicenter, observational study, patients with ATTR-CM receiving CRT (n=101) were matched to patients without amyloid cardiomyopathy by sex, age, and implantation type (CRT with versus without defibrillator versus conduction system pacing, upgrade versus first implant). We evaluated changes in QRS duration and echocardiographic parameters following CRT implantation and at the most recent available assessments. The study end points were all-cause death alone or combined with heart failure hospitalization. Results: Patients with ATTR-CM (median age, 76 [interquartile range, 72-83] years, 98% men, left ventricular (LV) ejection fraction 30% [26-33]) showed greater QRS shortening after CRT implantation (P=0.012), but not after a median of around 1 year (P=0.152). There were no significant differences in the absolute LV ejection fraction changes immediately after implantation (+7 [+2/+10] versus +3 [0/+9] units; P=0.124), or to the last echo (P=0.796), which was performed after 1.3 years in patients with ATTR-CM and 2.9 years in patients without amyloid cardiomyopathy. Patients with ATTR-CM had a shorter survival than controls (P<0.001 for both end points). Patients with ATTR-CM experiencing an early improvement in LV ejection fraction had a longer survival (log-rank, 4.3; P=0.038). Conclusions: Following CRT implantation, patients with ATTR-CM show QRS narrowing and improvement in LV ejection fraction, not different from patients without amyloid cardiomyopathy. Early favorable LV remodeling seems to be associated with a lower risk of all-cause death.