Appropriate ICD therapy for slow-rate VT predicts increased risk of appropriate therapy for high-rate VT/VF in the MADIT-RIT trial

Abstract

Background: Data on the association between appropriate therapy for slow rate ventricular arrhythmias and subsequent appropriate therapy for high-rate ventricular arrhythmias is limited. Therefore we investigated predictors for high-rate appropriate therapy in the MADIT-RIT population, incorporating time-dependent ICD therapies. Methods: The MADIT-RIT study randomized 1500 patients with a prophylactic indication for ICD or CRT-D to one of three ICD programming arms: (A) conventional programming (VT zone ≥ 170 bpm);(B) high-rate cut-off (VT zone ≥ 200 bpm) and (C) prolonged 60 sec. delay before therapy. A multivariate Cox model with best subset regression was used to identify predictors of high-rate appropriate therapy and to assess the effect of slow-rate appropriate therapy (VT-zone 170-199 bpm) on high-rate appropriate VT/VF therapy (>200bpm). Results: During a mean follow-up of 1.4±0.6 years, 186 out of 1500 (12.4%) patients received appropriate therapy. Slow-rate appropriate therapy was the strongest predictor of subsequent high-rate appropriate therapy, although we only identified 7 patients who in the same episode had a slow VT that was accelerated by ATP. Conventional ICD programming (arm A) was identified as an independent predictor of high-rate appropriate therapy when compared with arm C, but not when compared to arm B (Table). Other significant predictors of high-rate appropriate therapy are listed in the Table. View this table: Factors associated with increased risk of appropriate therapy >200 bpm in MADIT-RIT Conclusion: Slow-rate appropriate therapy was associated with significantly increased risk of high-rate appropriate therapy.