Timing of Cardiac Resynchronization Therapy Following Stable Medical Therapy in Patients With Heart Failure.

BACKGROUND Guidelines' recommendations for cardiac resynchronization therapy (CRT) implantation in selected patients with heart failure (HF) exist. However, data on the best timing for CRT implantation after the achievement of stable medical therapy (SMT) and its association with outcomes are currently lacking. OBJECTIVES The aim of this study was to investigate the timing of CRT implantation after the achievement of SMT, associated patient profiles, and clinical outcomes in a real-world HF population. METHODS Patients with HF treated with SMT derived from the Swedish ICD and Pacemaker Registry who received CRT between 2007 and 2020 were included in the study. Patient characteristics associated with a shorter or longer time to CRT implantation were assessed using multivariable logistic regression, and associations between the time from SMT to CRT implantation and clinical outcomes (mortality and morbidity) were analyzed using multivariable Cox regression. RESULTS Of the 9,409 patients, 43.8% received CRT at <3 months of achieving SMT, 34.9% between 3 and 9 months, and 21.3% after 9 months. The time from SMT to CRT implantation decreased significantly over the study period. Independent determinants of shorter time to implantation included recent HF hospitalization, previous implantation of a defibrillator, and greater use of guideline-directed medical therapy, whereas a history of HF >6 months and ischemic heart disease were associated with a longer time. After adjustments, there was a 9% lower risk of cardiovascular death with a shorter time from SMT to CRT implantation of <3 months vs 3-9 months (P = 0.045). A delayed time of >9 months vs 3-9 months was associated with a 13% higher risk of cardiovascular death/HF hospitalization, a 12% higher risk of cardiovascular death (P = 0.040), and an 11% higher risk of first HF hospitalization (P = 0.013). CONCLUSIONS Time from the achievement of SMT to CRT implantation decreased over the study period. Delayed CRT implantation beyond 3 months was associated with higher cardiovascular mortality compared with earlier implantation after GDMT optimization.