Introduction: Chronic high burden of right ventricular (RV) pacing is well known to cause deleterious effects on the left ventricular (LV) systolic function. However, there is variation in this effect with LV systolic function being maintained in some patients and worsening in others. We investigated characteristics amongst a cohort of patients with RV pacing burden greater than 40% to establish any specific risk factors associated with this effect.
Methods: We retrospectively examined records of 152 consecutive patients with RV pacing > 40% who underwent generator change (GC) or cardiac resynchronisation therapy (CRT) upgrade between July 2016 and July 2019 at Barts Heart Centre. All patients had LV assessment prior to initial pacing procedure and prior to GC or CRT upgrade with echocardiography. Case group included patients who underwent CRT upgrade (81 patients) with LV systolic dysfunction (ejection fraction EF ≤45%) and the controls were patients with preserved LV function who underwent only generator change (71 patients). Patients with underlying cardiomyopathies and complex congenital heart disease were excluded. Within the CRT upgrade group, factors affecting the development of LV systolic dysfunction were examined.
Results: Baseline characteristics are presented in Table 1. Primary indication for pacing for both cohorts were similar with principal reason being complete heart block (72%). Median RV pacing % in both cohorts were high, 99% vs 100%. Median time between implant and upgrade or GC were similar (CRT upgrade 8 years vs GC 9 years). Male predominance was significantly higher (p=0.008) in the upgrade cohort compared to the GC cohort. Presence of low pre-implant LV ejection fraction (<55%), history of ischaemic heart disease, presence of atrial fibrillation and chronic kidney disease were more prevalent in upgrade cohort compared to GC cohort (p<0.04). Within the CRT upgrade cohort, the effect of paced QRS duration and age at implant were examined using Spearman’s correlation coefficient. There was an inverse correlation between paced QRS duration and LV systolic function prior to upgrade (r= -0.64; p<0.01). A negative correlation was also observed between age at implant and time to diagnosis of LV systolic dysfunction since implant (r= -0.36; p<0.01). There was no statistically significant association between RV lead position (apical vs septum) with paced QRS duration (p=0.58) and LV systolic function (p=0.89).
Conclusion: Male gender, pre-implant LV ejection fraction (EF <55%), ischaemic heart disease, atrial fibrillation and chronic kidney disease may be associated with deterioration in LV function in patients who have a high burden of RV pacing. Wider paced QRS duration and age at implant may also be factors which influence development of pacing induced LV dysfunction. Further large prospective randomised studies are needed to determine aetiological factors in these patients.