Cardiac Resynchronization Therapy—Emerging Therapeutic Approaches

Neal A. Chatterjee, E. Kevin Heist

Cardiac resynchronization therapy (CRT) is an important therapeutic tool in the management of patients with heart failure and electrical dyssynchrony. In appropriately selected patients, landmark randomized controlled trials have demonstrated morbidity and mortality benefit beyond standard goal-directed medical therapy. Current guidelines emphasize the greatest clinical efficacy of CRT in patients with symptomatic heart failure, left bundle branch block, and wide QRS duration (> 150 ms). Other relevant considerations include the presence of atrial fibrillation, the presence of AV block, the etiology of cardiomyopathy, the presence of masked left-sided conduction delay, and the impact of comorbidities that might predict poor clinical response. At the time of CRT implantation, key considerations include targeting of the left ventricular (LV) lead to sites of greatest electrical and/or mechanical delay, the use of quadripolar versus bipolar LV pacing leads, evaluation of multiple pacing vectors to maximize electrical resynchronization, and in select instances pre-procedure imaging of the coronary venous anatomy to help guide decision-making at the time implant. Post-implant care includes the selective use of atrio-ventricular and inter-ventricular optimization algorithms, mitigation of right ventricular pacing, recognition, and treatment of suboptimal biventricular pacing, as well as management by a multi-disciplinary team of cardiovascular specialists. Emerging therapeutic strategies for patients eligible for CRT include the use of endocardial LV pacing, novel LV pacing options including multi-point pacing, His bundle pacing, and the integration of remote monitoring platforms that may identify patients at risk for clinical worsening.