The prognostic value of defibrillators in cardiac resynchronization therapy (CRT) for primary prevention remains debatable. Predicting ventricular arrhythmias (VAs) before implantation is useful for deciding whether to add a defibrillator to a CRT device. This study aimed to determine the risk factors for VA events after CRT device implantation and to construct a scoring model. A total of 153 patients who underwent CRT device implantation, with no history of sustained ventricular tachycardia or ventricular fibrillation (including 25 patients with CRT pacemakers) and with follow-up period >
1 year after implantation were included. We assessed VA events requiring implantable cardioverter-defibrillator therapy and sustained VA events requiring clinical treatment. During a mean follow-up of 6.3 years, 24 patients (16%) received therapy for VA. Multivariate analysis revealed age ≤ 70 years (hazard ratio [HR] 2.936, P = 0.037), administration of tolvaptan (HR 11.259, P <
0.001), and coronary artery disease (HR 2.444, P = 0.045) were independent predictors for VA events. Risk scores were assigned based on the HR for each predictor, and the population was divided into 3 risk groups (low: 0 points
moderate: 1-3 points
high: 4-5 points). VAs occurred less frequently in the low-risk group than in the other risk groups (low: 8.1%
moderate: 18%
high: 21%) (log-rank, P <
0.001). No significant differences in mortality were observed between the groups, whereas hospitalization for heart failure occurred more frequently in the high-risk group than in the other groups. In conclusion, a scoring system using specific background information may help predict VA events in prophylactic CRT recipients.