Dispersion of repolarization increases after cardiac resynchronization therapy in patients who do not undergo left ventricular reverse remodelling

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Wellcome/EPSRC Centre for Medical Engineering

CardioInsight Inc.

Background

The effect of CRT on dispersion of repolarization and arrhythmic risk is unclear. LV epicardial pacing has been associated with increased dispersion of repolarization, which may be due to altered activation and repolarization sequence. However, while CRT-induced ventricular arrhythmias have been reported, evidence from large clinical trials suggest CRT has a favourable effect on arrhythmic risk, with a lower incidence of arrhythmia in patients who undergo LV reverse remodelling.

Purpose

To investigate the effect of CRT and LV reverse remodelling on dispersion of repolarization using electrocardiographic imaging (ECGi).

Methods

11 patients with heart failure and electrical dyssynchrony underwent ECGi after CRT implant and again at 6 months. Reconstructed epicardial electrograms were used to create maps of activation recovery intervals (ARI), an accepted surrogate for action potential duration, which were corrected for heart rate. LV ARI dispersion was calculated as the standard deviation of ARI across the LV epicardium. The methodology is summarized in figure 1.

Results

Mean age at implant was 74±10 years and 82% of patients were male. 64% had ischaemic aetiology of heart failure, and mean LV ejection fraction was 29±10%. 64% of patients had underlying LBBB, 28% had an RV-paced rhythm and 9% had RBBB. 8 patients had a ≥15% reduction in LV end-systolic volume (LVESV) with CRT at 6 months (volumetric responders). Example ARI maps for 1 patient are shown in figure 2A. There was a significant increase in LV ARI dispersion at 6 months compared to baseline (36.4±7.2ms vs 28.2±7.7ms; P=0.03) [Fig 2B]. In a multiple linear regression analysis, volumetric response was an independent predictor of relative change in LV ARI dispersion from baseline to 6 months (P=0.04). In a sub-analysis, for volumetric responders there was no significant difference in LV ARI dispersion between baseline and CRT at 6 months (36.4 ±6.1 vs 30.1±7.8 ms; P=0.1). In comparison, in volumetric non-responders there was a significant increase in LV ARI dispersion (38.3±1.2 vs 22.6±2.6 ms; P=0.01). The relative change in LV ARI dispersion from baseline to CRT 6-months was greater for volumetric non-responders compared to volumetric responders (70.7 ±21.3% vs 27.0 ±35.4%; P=0.04) [Fig 2C]. There was a moderate negative correlation between relative change in LV ARI dispersion and relative reduction in LVESV (R=-0.5), however this did not meet statistical significance (P=0.12) [Fig 2D].

Conclusion

CRT increases dispersion of repolarization at 6 months. However, this potentially arrhythmogenic effect of epicardial pacing was only observed in CRT non-responders, which is in keeping with previous evidence that LV reverse remodelling reduces risk of ventricular arrhythmia.

Acute hemodynamic response of epicardial and endocardial cardiac resynchronization therapy, His bundle pacing and left bundle branch pacing

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Medtronic

Background / Introduction

Endocardial pacing and conduction system pacing are emerging as alternative methods to deliver cardiac resynchronization therapy (CRT) and have been shown to achieve superior acute hemodynamic response (AHR) compared to conventional epicardial pacing. However, a direct comparison of all the methods of delivering CRT has not yet been performed.

Purpose

To directly compare the AHR of conventional CRT (BiV Epi), endocardial pacing (BiV Endo), His bundle pacing (HBP) and left bundle branch pacing (LBBP) during a temporary CRT study.

Methods

4 patients underwent a temporary CRT and hemodynamic study. Temporary pacing was achieved using quadripolar catheters in the right atrium and coronary sinus, and roving decapolar catheters in the right ventricle (RV) and left ventricle (LV) via retrograde aortic access. Hemodynamic assessment was performed with a PressureWire X (Abbott, CA, USA) in the LV cavity. AHR was calculated as the percentage improvement in LV dP/dtmax from baseline AAI or RV pacing (if underlying complete heart block).

Results

The patients had a mean age of 67.5 ±5.8 years and all had non-ischemic cardiomyopathy with severe LV impairment (mean ejection fraction 22.5 ±7.4%). 3 patients had left bundle branch block and 1 patient had complete heart block with an RV paced rhythm (mean QRS duration 157 ±24 ms). All methods of delivering CRT achieved a mean AHR of >10%, which is considered clinically significant and is predictive of LV remodelling at 6 months. Mean AHR during BiV Epi pacing was 12.6 ±5.0%. There was a trend towards higher AHR for BiV Endo pacing (23.6 ±7.6%), HBP (17.4 ± 9.5%) and LBBP (16.1 ±7.8%) as shown in figure 1, however there was no significant difference between groups on one-way analysis of variance (p = 0.348).

Conclusions

All methods of delivering CRT achieved an AHR >10%. The AHR during BiV Endo pacing, HBP and LBBP was higher than for BiV Epi pacing, but this did not reach statistical significance. Further investigation with larger studies is required to determine which method of delivering CRT achieves the best hemodynamic response.

Figure 1. Box plot of acute hemodynamic response (AHR) for conventional cardiac resynchronization therapy (BiV Epi), endocardial pacing (BiV Endo), His bundle pacing (HBP) and left bundle branch pacing (LBBP). Data displayed as median (solid line), mean (+), 1st and 3rd quartiles (box) and minimum and maximum values (whiskers). Abstract Figure 1