Introduction: Conduction system pacing is a novel way for delivering cardiac resynchronisation therapy (CRT). This may deliver more effective ventricular resynchronisation than the gold standard, biventricular pacing (BVP). In BVP scar burden is known to impact response but whether this is true for conduction system pacing is unknown.
Methods: Patients with standard CRT indications were recruited. They underwent a pre-procedure cardiac MRI, with late gadolinium enhancement to assess scar. Scar burden was quantified as the percentage of the amount of myocardium for each segment and the whole of the left ventricle (total scar). Conduction system pacing with both His bundle CRT (HB-CRT) and left bundle area CRT (LBA-CRT) was attempted in everyone, and the modality that delivered the narrowest QRS duration was selected. The electrical response was measured using non-invasive mapping (ECGi, CardioInsight, Medtronic). The haemodynamic response was measured with a high precision protocol. We investigated the impact of scar on the electrical and haemodynamic response.
Results: A total of 26 patients were recruited, 85% male, mean age 69 ± 10 years, ischaemic cardiomyopathy in 35% and mean QRS duration 160 ± 15. LGE was observed in 96% of cases, mean total scar burden was 13 ± 12% (range 1–39%). We found a significant correlation between amount of scar and both the electrical and acute haemodynamic response (Figure 1). Patients with a lower scar burden obtained a greater improvement in both electrical resynchronisation (R=0.55, 95% CI 0.21–0.77, p<0.01, for reduction in left ventricular activation time [LVAT]), and acute haemodynamic response (R=0.5, 95% CI 0.18–0.76, p=0.005 for increase in acute systolic blood pressure).
Conclusion: Conduction system pacing appears to be less effective in patients with a high left ventricular scar burden. We observed a strong correlation between scar burden and both ventricular electrical resynchronisation and acute haemodynamic response. This information may help patient selection for conduction system CRT. Alternative CRT modalities or combinations of modalities warrant further investigation in this challenging group of patients. ❑