Cardiac resynchronization therapy pacemaker: critical appraisal of the adaptive CRT-P device

Abstract

Cardiac resynchronization therapy (CRT) is an effective and well-established therapy for patients suffering with heart failure, left ventricular (LV) systolic dysfunction (ejection fraction ≤35%), and electrical dyssynchrony, demonstrated by a surface QRS duration of ≥120 ms. Patients undergoing treatment with CRT have shown significant improvement in functional class, quality of life, LV ejection fraction, exercise capacity, hemodynamics, and reverse remodeling of LV, and ultimately, morbidity and mortality. However, 30%-40% of patients who receive a CRT device may not show improvement, and they are termed as non responders. The nonresponders have a poor prognosis; several methods have been developed to try to enhance response to CRT. Echocardiography-guided optimization of CRT has not resulted in significant clinical benefit, since it is done at rest with the patient in supine position. An ideal optimization strategy would provide continuous monitoring and adjustment of device pacing to provide maximal cardiac resynchronization, under a multitude of physiologic states. Intrinsic activation of the right ventricle (RV) with paced activation of the RV, even in the setting of biventricular (BiV) pacing, may result in an adverse effect on cardiac performance. With this physiology, the use of LV-only pacing may be preferred and may enhance CRT. Adaptive CRT is a novel device-based algorithm that was designed to achieve patient-specific adjustment in CRT so as to provide appropriate BiV pacing or LV-only pacing. This article will review the goals of CRT optimization, and implementation and outcomes associated with adaptive CRT.

Keywords: adaptive; cardiac resynchronization; heart failure; left and biventricular pacing; therapy.

Figure 1

Summary of aCRT algorithm. Notes: Reprinted from American Heart Journal, 163(5), Krum H, Lemke B, Birnie D, et al. A novel algorithm for individualized cardiac resynchronization therapy: rationale and design of the adaptive CRT trial, 747–752. Copyright (2012), with permission from Elsevier. Abbreviations: aCRT, adaptive cardiac resynchronization therapy; AV, atrio-ventricular; LV, left ventricular; BiV, bi-ventricular; VV, interventricular; DDD/R, dual chamber pacemaker with and without rate response.

Figure 2

Summary of aCRT study. Notes: Reprinted from Heart Rhythm, 9(11), Martin DO, Lemke B, Birnie D, et al. Investigation of a novel algorithm for synchronized left ventricular pacing and ambulatory optimization of cardiac resynchronization therapy: results of the adaptive CRT trial, 1807–1814. Copyright (2012), with permission from Elsevier. Abbreviation: aCRT, adaptive cardiac resynchronization therapy.

Figure 3

Summary of aortic velocity time integral (AoVTI) at randomization and at 6-months follow-up comparing aCRT to echo-guided optimization. Notes: Reprinted from Heart Rhythm, 9(11), Martin DO, Lemke B, Birnie D, et al. Investigation of a novel algorithm for synchronized left ventricular pacing and ambulatory optimization of cardiac resynchronization therapy: results of the adaptive CRT trial, 1807–1814. Copyright (2012), with permission from Elsevier. Abbreviations: aCRT, adaptive cardiac resynchronization therapy; CCC, concordance correlation coefficient.

Figure 4

Percent of patients improved in CCS during 6-month follow-up. Notes: Reprinted from Singh JP, Abraham WT, Chung ES, et al. Clinical response with adaptive CRT algorithm compared with CRT with echocardiography optimized atrioventricular delay: a retrospective analysis of multicentre trials. Europace. 2013;15(11):1622–1628 by permission of Oxford University Press. Abbreviation: aCRT, adaptive cardiac resynchronization therapy; ICD, implantable cardioverter-defibrillator; CCS, Clinical composite score.

Figure 5

Time to all-cause death or first heart failure hospitalization over the 12-month follow-up stratified by percent synchronized left ventricular pacing in the aCRT arm. Notes: Reprinted from Heart Rhythm, 10(9), Birnie D, Lemke B, Aonuma K, et al. Clinical Outcomes with synchronized left ventricular pacing: analysis of the adaptive CRT trial, 1368–1374. Copyright (2013), with permission from Elsevier. Abbreviations: CI, confidence interval; aCRT, adaptive cardiac resynchronization therapy; HF, heart failure; HR, hazard ratio; %sLVP, synchronized left ventricular pacing as a percentage of total ventricular pacing over the 12-month follow-up.

Figure 6

Time from heart failure hospitalization to all-cause readmission. Notes: This figure was published in J Am Coll Cardiol HF, 3(7), Starling RC, Krum H, Bril S, et al. Impact of a Novel Adaptive optimization algorithm on 30-day readmissions evidence from the adaptive CRT trial, 565–572. Copyright Elsevier (2015). Abbreviations: aCRT, adaptive cardiac resynchronization therapy; ECHO, echocardiographic optimization; HF, heart failure; CI, confidence interval.