Implantable cardioverter-defibrillators: a long-term view

No long-term data on implantable cardioverter-defibrillators (ICDs) exist in Australasia.

We examined all patients receiving a new ICD implant at Wellington Hospital between January 2001 and December 2005 to determine long-term outcomes in this patient population.

Follow-up data were collected and Kaplan-Meier curves were constructed for survival and long-term outcomes, and Cox proportional hazard model was used for calculation of hazard ratio.

In the study period, 138 new ICDs were implanted, and the mean follow-up time was 84 ± 16 months. Patients were predominantly male (76%), 75% were European, 20% were Maori. Median age was 59 years (range 16-80 years). In 47% of patients, there was an ischaemic substrate. A secondary-prevention indication was present in 77%. The 7-year survival rate was 72%. No difference in mortality was observed between primary- and secondary-prevention groups. The 7-year appropriate therapy rate was 55%. The appropriate shock rate was greater in secondary prevention than in primary-prevention patients was observed (hazard ratio = 2.11, 95% confidence interval 1.16-3.85, P= 0.01). Over the study period, inappropriate therapy rate was 25%. This was more common in patients with prior atrial fibrillation (hazard ratio = 3.57, 95% confidence interval 1.80-7.09, P < 0.001). The median device longevity was 6.8 years.

This is the first long-term follow-up study of ICD patients in New Zealand. We observed a low mortality rate when compared with other published registries, but a similar rate of both appropriate and inappropriate shock therapy.