Prognostic relevance of new onset arrhythmia and ICD shocks in primary prophylactic ICD patients.

BACKGROUND: The prognostic relevance of new onset arrhythmias compared to ICD shocks in ICD patients is not well known.
OBJECTIVES: Aim of the study was to evaluate the prognostic relevance of new onset atrial fibrillation (AF) or ventricular arrhythmias (VT/VF) compared to ICD shocks in primary prophylactic ICD-patients.
METHODS: A total of 622 of 1955 (32%) patients of the prospective single-centre ICD-registry Ludwigshafen with primary prophylactic ICD indication and sinus rhythm (SR) at baseline without history of AF were analyzed. All patients underwent an ICD implantation between 1992 and 2012.
RESULTS: During the median follow-up time of 6 years, 200 (32%) ICD patients developed new AF and 249 (40%) patients new VT/VF. There was an approximately 10% increase of 5-year mortality rate depending on the type of new onset arrhythmia (no arrhythmia 19%, new AF 28%, new VT 36% and new VF 55% 5-year mortality). In a multivariate analysis, new onset of AF or VT/VF was an independent predictor for increased mortality whereas VT shocks and inappropriate ICD shocks were not.
CONCLUSION: More than half of primary prophylactic ICD patients with SR at baseline develop new AF or VT/VF after 6 years. New onset arrhythmias of AF and VT/VF are independent prognostic factors for increased mortality in primary prophylactic ICD patients. ICD shocks itself, inappropriate or appropriate, are not additionally associated with a worse outcome. These results support the hypothesis that in clinical practice rather the arrhythmia than the ICD shock itself is responsible for a deteriorated prognosis.