Significant regional variation in use of implantable cardioverter-defibrillators in Denmark

Aims: Implantable cardioverter-defibrillator (ICD) treatment prevents sudden cardiac death in high-risk patients. This study examined geographical variation in ICD implantation rates in Denmark and potential causes of variation. Methods and results: We obtained numbers of ICD implantations in the 5 Danish regions and 98 municipalities during 2007-13 from the Danish Pacemaker and ICD Registry. Standardized implantation rates (SIRs) were computed as ICD implantations per 1 000 000 person-years, and age-and gender-standardized to the Danish population. We examined associations of the municipal SIR with mean age and Charlson Comorbidity Index score of ICD recipients, percentage of implantations with primary prophylactic indication, and distance from patient residency to ICD implanting centre. Based on 7192 ICD implantations, the nationwide SIR was 186 [95% confidence interval (CI) 182-190], ranging from 170 (95% CI 158-183) in the North Denmark Region to 206 (95% CI 195-218) in the Region of Zealand. Municipalities with higher patient comorbidity scores, higher percentages of implantations with primary prophylactic indication, and shorter distances to ICD implanting centres, had higher SIRs [differences between SIRs of municipalities in highest and lowest quartiles 22 (95% CI 10-34), 45 (95% CI 33-58), and 35 (95% CI 24-47), respectively]. Regional differences in SIRs decreased over time and had become insignificant during 2011-13. Conclusion: Implantable cardioverter-defibrillator implantation rates in Denmark varied significantly between regions but variation decreased during 2007-13. Geographical variation was associated with differences in patient comorbidity score, variation in use of primary prophylactic ICD treatment, and distance to ICD implanting centre.