Heart failure severity, inappropriate ICD therapy, and novel ICD programming: a MADIT-RIT substudy.

Background: The effects of heart failure (HF) severity on risk of inappropriate implantable cardioverter-defibrillator (ICD) therapy have not been thoroughly investigated. We aimed to study the association between HF severity and inappropriate ICD therapy in MADIT-RIT.

Methods: MADIT-RIT randomized 1,500 patients to three ICD programming arms: conventional (Arm A), high-rate cut-off (Arm B: ≥200 beats/min), and delayed therapy (Arm C: 60-second delay for ≥170 beats/min). We evaluated the association between New York Heart Association (NYHA) class III (n = 256) versus class I-II (n = 251) and inappropriate ICD therapy in Arm A patients with ICD-only and cardiac resynchronization therapy with defibrillator (CRT-D). We additionally assessed benefit of novel ICD programming in Arms B and C versus Arm A by NYHA classification.

Results: In Arm A, the risk of inappropriate therapy was significantly higher in those with NYHA III versus NYHA I-II for both ICD (hazard ratio [HR] = 2.55, confidence interval [CI]: 1.51-4.30, P < 0.001) and CRT-D patients (HR = 3.73, CI: 1.14-12.23, P = 0.030). This was consistent for inappropriate ATP and inappropriate ICD therapy < 200 beats/min, but not for inappropriate shocks. Novel ICD programming significantly reduced inappropriate therapy in patients with both NYHA III (Arm B vs Arm A: HR = 0.08, P < 0.001; Arm C vs Arm A: HR = 0.17, P < 0.001) and NYHA I-II (Arm B vs Arm A: HR = 0.25, P < 0.001; Arm C vs Arm A: HR = 0.28, P < 0.001).

Conclusion: Patients with more severe HF are at increased risk for inappropriate ICD therapy, particularly ATP due to arrhythmias < 200 beats/min. Novel programming with high-rate cut-off or delayed detection reduces inappropriate ICD therapies in both mild and moderate HF.