Regional differences in survival after ICD implantation

Background: The implantable cardioverter-defibrillator (ICD) remains the cornerstone in the prevention of sudden cardiac death. Cost-effectiveness depends on survival after implantation. In Belgium there are unexplained major differences in 3-year mortality after ICD implantation. Centre volume and socio-economic differences might affect survival after implantation.

Methods: In total, 9647 patients underwent a first ICD implantation between February 2010 and 2016 in Belgium and were retrospectively compared for demographics, 30-day and 3-year mortality. Chi-squared and Mann-Whitney U tests were used to determine differences across centre volume.

Results: Low-volume centres treated patients with different characteristics and implanted more patients with ischaemic heart disease (50.2 vs 47.9%, p = 0.002), in primary prevention (66.7 vs 62.0%, p < 0.001) and with overall more comorbidities. Kaplan-Meier survival analysis showed a significant higher 3-year mortality in low-volume centres (16.3 vs 11.4%, p < 0.001). After adjudication with a multivariable Cox model, centre volume remained an independent predictor of 3-year mortality (low volume HR 1.300 [95% CI 1.124-1.504]. However similar 30-day mortality (0.6% in low vs 0.5% in high volume centres, p = 0.393) suggests that implantation related determinants alone are insufficient to explain the long-term survival difference. Socio-economic factors like regional average income (wealth) and overall survival (health) also were associated with the survival difference between low- and high-volume centres.

Conclusions: There exist large survival differences after ICD implantation between implanting centres in Belgium that cannot only be explained by a volume-outcome effect. Centres size and characteristics are inhomogeneous and vary according to different socio-economic variables. Some of these variables are also significantly associated with survival and warrant further investigation.