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Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Introduction Cardiac resynchronisation therapy (CRT) in the form of His bundle CRT and left bundle area CRT can be more effective than the gold standard, biventricular pacing (BVP). In BVP scar burden is known to predict response whether this is true for these novel modalities is not known. Purpose The purpose of this study was to determine whether left ventricular scar burden assessed using cardiac MRI can be used to predict the electrical and acute haemodynamic response to two novel CRT modalities. Methods Patients with standard CRT indications were recruited. They underwent a pre-procedure cardiac MRI, with late gadolinium enhancement (LGE) to quantify scar. His bundle CRT (His CRT) and left bundle area CRT (LBA CRT) were attempted. The electrical response was measured using high precision non-invasive mapping ECGi (CardioInsight, Medtronic). The haemodynamic response was measured with a high precision protocol. We investigated the impact of scar and baseline electrical characteristic on ECGi and haemodynamic response. Results 26 patients were recruited (85% male, mean age 69 ± 10, with ischaemic cardiomyopathy in 35%). LGE was observed in 96% of cases and the mean (range 1-39%). We found a significant correlation between scar extent and the electrical response with both modalities. There was a significant correlation between a lower scar burden and better electrical response. For His CRT the reduction in left ventricular activation time was better with lower scar burden (R= 0.77, p < 0.01, Picture 1), for LBA CRT for reduction in left ventricular activation was also better with lower scar burden (R = 0.53, p = 0.05, Picture 2). With His CRT there was also a significant correlation between lower scar extent and better acute haemodynamic response ( R = 0.6, p = 0.002) but this was not observed with LBA CRT (R = 0.07, p = 0.77). Conclusion Left ventricular myocardial scar can be used to predict the electrical response to two different conduction system CRT modalities.

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation. Background HOPE-HF was a randomised, placebo-controlled, cross-over trial of AV-optimised His bundle pacing in patients with heart failure (LVEF ≤40%), a PR interval (≥200ms) and without left bundle branch block.1,2. In this analysis we studied the impact of baseline PR interval and acute blood pressure change at the optimal AV-delay on the placebo-controlled effect of His bundle pacing on the trial endpoints of peak VO2 (primary) and patient symptoms (using the Minnesota Living with Heart Failure Questionnaire). Methods and Results 167 patients were successfully implanted and randomised to 6 month blocks of pacing and placebo. We performed a non-invasive, high-precision protocol to calculate the optimal AV delay and associated acute blood-pressure response at randomisation. To test the impact of the baseline PR interval and acute BP response on the placebo-controlled effect of AV-optimised His bundle pacing on endpoints we compared Bayesian ordinal regression models and the relative explained variance (REV) of variables in the model. There was weak evidence that His-bundle pacing improved peak VO2 across all patients (OR 1.31, 95% CrI 0.86 to 2.01, Pr(OR > 1)=89%). The baseline PR interval had little impact on this benefit (REV 0%), and the blood pressure response was more likely (88% vs 12%) to be predictive. However, there was strong evidence that overall AV-optimised His-bundle pacing improved patient symptoms as compared to placebo (OR 1.58, 95% CrI 1.04 to 2.40, Pr(OR>1)=98%). Again, the baseline PR interval had little impact on this benefit (REV 0%) and the blood pressure response was much more likely (97% vs 3%) to be predictive. Higher acute BP increments led to greater placebo-controlled improvements in MLWHF at 6-months. Conclusion An individual’s acute BP response with AV-optimised His-pacing is a powerful predictor of their placebo-controlled improvement in symptoms (MLWHF) at 6-months. This can form the basis of patient selection for future studies and clinical practice.