3.2 Outcome
Over a median follow-up of 2.2 (IQR: 1.1-3.2) years, 74/749 (9.9%) patients developed PICM. In patients who developed PICM, LVEF decreased from a mean 56.6+/- 3.35% to 41.5 +/- 6.87%. The earliest incidence of PICM was at 6 months and the longest was at 6 years following implantation. Patients who developed PICM had a lower pre-implantation EF compared to those who did not develop PICM (56.6 ± 3.0 % Vs 57.5 ± 2.6; p-value 0.005) and higher RV pacing burden (median 98.2% [IQR 80.5 - 99.0 %] Vs 75.0 % [IQR 13.0 - 99.0 %]; p-value < 0.001).
3.3 Right ventricular pacing burden and outcome
The median RV pacing for the whole cohort was 81.0% (IQR 15.0 - 99.0 %). Most patients were in the extreme categories of pacing burden - 21.4 % having ≤ 10.0% RV pacing and 43.5% were paced > 90.0 % (Figure 1.a). So, the cohort was divided into three tertiles based on RV pacing percentage of 34.0% (33rd percentile) and 98.0% (67th percentile). The incidence of PICM in the first, second and third tertiles was 3.8%, 12.7%, and 14.6%, respectively (Chi-square p-value for trend < 0.001; figure 1.b).