Is CRT Optimization Obsolete? A Referral Center's Experience

Abstract

Background: Cardiac resynchronization therapy (CRT) is a well-established therapy for patients with heart failure (HF). However, 30% of HF patients do not show any improvement in clinical status after CRT implantation. In this study, we report our echocardiography-based CRT optimization methodology, in daily practice at our CRT referral center.

Methods: We included 350 ambulatory patients, who were referred to our center for optimization after CRT implantation. A protocol-driven echocardiographic approach for adjusting mechanical dyssynchrony, whereby adjusting for ventriculoventricular (VV) delays with strain and atrioventricular (AV) delays with Doppler echocardiography was performed. We defined changes in left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) classes as outcome variables in the evaluation of the CRT outcomes.

Results: Optimization was obtained in 288 (82%) patients. VV and AV timings were adjusted to 61% and 51%, respectively. In 3%, biventricular pacing was turned off and in 3% left ventricular (LV) only pacing was programmed. The LVEF and NYHA class showed significant improvements in all patients who underwent CRT optimization.

Conclusions: CRT optimization remains valuable in improving LVEF and functional status measured using the NYHA class in all patients receiving CRT devices.

Keywords: CRT-optimization; cardiac resynchronization therapy; strain rate imaging.

Fig. 1.

Measuring left ventricular (LV) dyssynchrony with peak longitudinal strain derived from strain rate imaging (SRI). The method used to measure dyssynchrony with SRI. Peak longitudinal strain curves from the mid-septum (left panel) and mid-lateral wall (right panel) in a patient undergoing mechanical delay pre-cardiac resynchronization therapy (CRT) optimization of 260 ms – 90 ms = 170 ms, measured from the opening of the aortic valve to the maximal strain of the mid-septum and mid-lateral wall in the left ventricle. Mechanical dyssynchrony is exhibited. Post-CRT optimization of the mechanical delay between the mid-septum and the mid-lateral walls was reduced to 260 ms – 250 ms = 10 ms. AVC, aortic valve closed; AVO, aortic valve open; MVC, mitral valve closed; MVO, mitral valve open.

Fig. 2.

CRT modulation. Abbreviations: N, number (n = 350); VV, VV interval programming; AV, AV interval modification; allP, VV, and AV combined; NoC, no changes were necessary; LV, LV only pacing; AF, VV interval adaptation in patients with atrial fibrillation; Off, pacing mode switched off; noOpt, no changes could be made. Suboptimal VV intervals were adjusted in 215 patients, while the AV settings were modified in 178 patients according to the iterative method. Both VV and AV interval (allP) optimizations were performed in 141 patients, while no changes were necessary (NoC) in 62 patients. Device settings were already optimal at baseline. CRT was programmed in 9 patients to LV only. In 29 patients, VV programming only could be performed due to underlying atrial fibrillation (AF). The CRT was turned off in 10 patients because they did not have dyssynchrony (Off) at baseline. Furthermore, optimization failed (noOpt) in 15 patients due to arrhythmias. VV, ventriculoventricular; AV, atrioventricular; LV, left ventricle; CRT, cardiac resynchronization therapy.

Fig. 3.

LVEF improvement after CRT optimization. Abbreviations: LVEF, left ventricular ejection fraction; CRT, cardiac resynchronization therapy; Pre, before CRT implantation; Post, after CRT implantation but before CRT optimization; Opt, after CRT optimization. The median LVEF prior to CRT implantation was 30%. After implantation, there was a significant improvement in median LVEF to 35%. After CRT optimization, the median LVEF further improved to 39% (p 0.04). There were 344 patients with LVEF measurements available.

Fig. 4.

LVEF improvement after CRT optimization in responders and non-responders. Abbreviation: N, number; R LVEF, responders left ventricular ejection fraction; NR LVEF, non-responders left ventricular ejection fraction; NR after Opt, number of non-responders after optimization; All, all non-responders; $>$, increase in LVEF; =, no difference in LVEF; , decrease in LVEF; Post, post CRT implantation but before CRT optimization; Opt, after CRT optimization; CRT, cardiac resynchronization therapy. Based on the selection criteria for R and NR, there were 184 R and 160 NR at baseline. LVEF showed significant improvements before and after optimization in both the R and NR groups.

Fig. 5.

Improvements in NYHA class after CRT optimization. Abbreviations: Pre, before CRT implantation; Post, after CRT implantation but before CRT optimization; Opt, after CRT optimization; NYHA, New York Heart Association classification; CRT, cardiac resynchronization therapy. After CRT implantation, the NYHA class improved in all 350 patients, while the NYHA class further improved after optimization, with a greater number of patients exhibiting NYHA class I (104 patients). After optimization, 198 patients were in NYHA class II. The number of patients in NYHA classes III and IV were reduced to 46 and 2 patients, respectively, meaning the optimization resulted in a significant improvement p 0.01.