Cardiac Contractility Modulation and Arrhythmic Burden in Heart Failure: Mechanistic Rationale, Clinical Evidence, and Future Perspectives

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Abstract
Cardiac contractility modulation (CCM) is an implantable device-based therapy that delivers biphasic, non-excitatory electrical signals to the ventricular myocardium during the absolute refractory period. By enhancing contractile performance without inducing depolarization or altering ventricular activation, CCM acts as bioelectronic myocardial conditioning. Current evidence supports its use in selected patients with symptomatic heart failure, reduced or mildly reduced left ventricular ejection fraction, narrow QRS duration, persistent symptoms despite guideline-directed medical therapy, and no indication for cardiac resynchronization therapy. In this population, CCM improves functional status and quality of life, whereas evidence for reductions in mortality or recurrent heart failure hospitalization remains less definitive. Whether CCM also reduces arrhythmic burden remains uncertain. Candidates for CCM frequently exhibit atrial and ventricular remodeling, neurohormonal activation, implantable cardioverter-defibrillators, and vulnerability to atrial fibrillation, ventricular arrhythmias, and device therapies. Mechanistically, CCM may render the failing myocardium less arrhythmogenic through coordinated effects on calcium handling, electromechanical remodeling, fibrosis-related substrate, contractile efficiency, and heart-failure stability. However, pivotal trials were not designed to assess arrhythmic endpoints, leaving the relationship between CCM and arrhythmic burden insufficiently characterized. This review summarizes CCM evidence, mechanistic rationale, available arrhythmic signals, device-related considerations, and future research priorities for prospective studies in this evolving field.