Heart Rhythm 2024: Early CRT Improves Cardiac Function in Mild to Moderate Heart Failure

A physician-initiated prospective, randomized clinical trial sponsored by The National Heart, Lung, and Blood Institute found that early cardiac resynchronization therapy (CRT) may slow the progression of heart failure in patients with mild to moderately reduced left ventricular ejection fraction (LVEF) and left bundle branch block (LBBB). Researchers presented these findings as late-breaking clinical science over the weekend at Heart Rhythm 2024 in Boston.
 
Approximately 6.7 million U.S. adults have heart failure, and the prevalence is expected to rise to 8.5 million by 2030.¹ Additionally, more than 30% of heart failure patients have conduction abnormalities. CRT, a pacemaker that corrects abnormal electrical conduction by simultaneously pacing the left and right heart chambers, is a well-established therapy for improving cardiac efficiency. According to the 2023 HRS guidelines on cardiac physiologic pacing, CRT can lead to improvement in survival time, decline in hospitalizations for heart failure, and stabilization of ventricular function.
 
To assess if CRT would improve or halt the progression of heart failure in patients with mild to moderately reduced LVEF and LBBB, Mayo Clinic researchers randomized clinical trial participants to receive either CRT-off (VVI RV pacing 40 bpm) or CRT-on (DDDR BIV pacing 60-150 bpm). After six months, the programming was reversed for another six months: patients who originally received CRT-off received CRT-on, and patients who originally received CRT-on received CRT-off. Patients who received CRT-off first experienced a significant reduction in left ventricular end-systolic volume (LVESV) only after the later CRT-on phase. Similarly, patients who received CRT-on first, followed by CRT-off, showed significant LVESV reduction in the initial CRT-on phase. Because LVESV remained lower than baseline even after the 12-month trial period, researchers concluded that the effects of CRT may persist for up to six months after CRT was turned off, indicating a CRT carry-over effect.
 
“In this study, we proposed use of CRT for patients to prevent the progression of mild to moderate heart failure,” said Yong-Mei Cha, M.D., cardiac electrophysiologist at Mayo Clinic in Rochester, Minn. “We confirmed early CRT improves cardiac systolic function in these patients, which supports HRS guidelines.
 
Looking ahead, the Mayo Clinic research team will investigate the long-term clinical outcomes of  CRT in patients with mild to moderately reduced LVEF and LBBB, further advancing the understanding of this treatment option.
 
The Heart Rhythm Society is the international leader in science, education, and advocacy for cardiac arrhythmia professionals and patients and is the primary information resource on heart rhythm disorders. Its mission is to improve the care of patients by promoting research, education, and optimal healthcare policies and standards. Incorporated in 1979 and based in Washington, D.C., it has a membership of more than 8,200 heart rhythm professionals from 94 countries. 

Reference 
¹ Bozkurt B, Ahmad T, Alexander KM, Baker WL, Bosak K, Breathett K, Fonarow GC, Heidenreich P, Ho JE, Hsich E. Heart failure epidemiology and outcomes statistics: a report of the Heart Failure Society of America. Journal of cardiac failure. 2023 Oct;29(10):1412.