Does adaptive pacing work in patients with HF, LBBB, and intact AV conduction? 

Adaptive cardiac resynchronisation therapy (CRT) did not reduce the risk of death or intervention for heart failure (HF) decompensation compared with conventional CRT in patients with HF, left bundle branch block (LBBB), and intact atrioventricular (AV) conduction, according to the AdaptResponse trial.

“Although CRT offers health benefits to patients with symptomatic HF, a prolonged QRS duration, and a reduced ejection fraction, up to 30% of the patients have been classified as non-responders to conventional CRT,” said Dr Bruce Wilkoff (Cleveland Clinic, OH, USA) [1]. “Pacing the left ventricle only may be superior to biventricular pacing if conduction to the right ventricle is intact” [2]. The AdaptResponse trial (NCT02205359) randomised 3,618 patients with HF, LBBB, and intact AV conduction 1:1 to adaptive CRT, switching between left ventricular pacing and biventricular pacing based on the patients’ AV and heart rhythm, or conventional CRT [3]. The primary endpoint was death from any cause or intervention for HF decompensation.

The primary endpoint was not met, and the trial was stopped after the third interim analysis due to futility. The event rate was 33.7% in the conventional CRT group and 30.8% in the adaptive CRT group (HR 0.89; P=0.077). Similarly, secondary endpoints did not reach a statistically significant difference between the 2 study groups. Finally, Dr Wilkoff mentioned that a post-hoc analysis showed that participants in the adaptive CRT group with ≥85% synchronised left ventricular pacing had a significantly lower rate of mortality and intervention for HF decompensation than patients in the conventional CRT group (HR 0.76; P=0.0037).

1. 1. Mullens W, et al. JACC. 2009;53(9):765–773.
   2. Vernooy K, et al. Nat Rev Cardiol. 2014;11(8):481–493.
   3. Wilkoff BL, et al. Adaptive versus conventional cardiac resynchronization therapy in patients with heart failure: primary results from the AdaptResponse global randomized trial. Late-Breaking Science Day 2, EHRA 2023, 16–18 April, Barcelona, Spain.

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