Road Exposure After Cardioverter-Defibrillator Implantation and its Potential Influence on Reported Motor Vehicle...

Many individuals transiently reduce their road exposure (kilometers or hours of driving per month) after receiving an implantable cardioverter-defibrillator (ICD). This markedly influences interpretation of monthly crash risks, but very few studies describe real-world road exposure after ICD implantation. We obtained 18 years of population-based health and driving data for drivers undergoing ICD implantation in British Columbia, Canada. We estimated drivers' monthly "road exposure relative to baseline" (RERB) after ICD implantation (0 = complete cessation of driving; 1 = road exposure unchanged), using clinical data to infer the duration of compulsory driving restrictions, and using published data to account for incomplete adherence to restrictions and voluntary reductions in road exposure by month since implantation. We then used estimated RERB to calculate exposure-adjusted crash risks. Among 3,454 primary prevention ICD recipients, RERB-adjusted crash rate in the first month after implantation was not significantly different than among matched controls (mean recipient RERB = 0.29; adjusted incidence rate ratio [aIRR] = 2.22, 95% CI 0.72 to 6.87), but sensitivity analyses suggested that crash rate adjusted for a plausible lower-bound RERB estimate was ∼5-fold higher than among controls. Among 3,070 secondary prevention ICD recipients, RERB-adjusted crash rate in the first 6 months after implantation was not significantly different than among matched controls (mean recipient RERB = 0.50; aIRR = 1.11, 95% CI 0.77 to 1.61), but sensitivity analyses indicated that crash rate in the first 3 months after implantation adjusted for a plausible lower-bound RERB estimate was ∼2-fold higher than among controls. In conclusion, the substantial transient reductions in road exposure after ICD implantation should inform interpretation of monthly crash risks.