Key result
In patients receiving right pectoral ICDs, mean defibrillation thresholds were unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% fixed tilt waveform (14.9 J vs 14.2 J; P=0.8).
Why the study?
Does waveform tuning improve defibrillation thresholds compared to a fixed tilt waveform in patients receiving right pectoral implantable cardioverter defibrillators?
RCT (n=91)
1:1
Does waveform tuning improve defibrillation thresholds compared to a fixed tilt waveform in patients receiving right pectoral implantable cardioverter defibrillators?
Absolute Event Rate: 14.9% vs 14.2%
p-value: p=0.8
Waveform tuning does not significantly improve defibrillation thresholds in patients receiving right pectoral ICDs compared to a fixed tilt waveform, suggesting implant testing remains important for these devices.
Tuned waveforms confer no DFT advantage in right pectoral ICDs; confirms fixed-tilt sufficiency and extends null evidence on waveform optimization.
AIMS: Assess defibrillation thresholds (DFTs) with right active pectoral implantable cardioverter defibrillator (RICDs). Defibrillation thresholds in patients receiving RICDs are regarded as 'high' and potentially improved by waveform optimization (tuning). However, this has not been systematically tested. METHODS AND RESULTS: Patients receiving RICDs [Single chamber (VVI) = 16, DDD = 32, cardiac resynchronization therapy (CRT) = 43] were randomized to either 50/50% fixed tilt (FT) or tuned waveform (3.5 ms time constant based). Defibrillation threshold was tested with a binary search protocol in single coil anodal configuration. Then RICDs were compared with left-sided placements. Baseline patient characteristics in FT (n = 54) and tuned (n = 37) were similar (65 ± 14 years, 71% male, Left ventricular ejection fraction 31 ± 13%; and proportions VVI/DDD/Cardiac resynchronization therapy defibrillator). Tuning reduced Phase 1 by 15% and Phase 2 by 45%. For FT vs. tuned: high voltage impedance was 61.9 ± 13.2 vs. 64.5 ± 12.7 Ω (P = 0.33) and mean DFT 14.2 ± 8.8 vs. 14.9 ± 9.2 J (P = 0.8). When high voltage impedance was >62 Ω (mean 73.6 ± 8.6 Ω), DFT was identical [FT 13.0 ± 7.9 J vs. tuned 12.0 ± 5.9 J (P= 0.7)]. Defibrillation thresholds exceeded 20 J (600 V) in >20% of patients [FT 11/54 (20.4%) vs. tuned 12/37 (32%) patients]. Defibrillation threshold with RICD was greater and exhibited wider dispersion compared with left ICDs (n = 54) under similar conditions. CONCLUSION: This first randomized trial investigating DFTs with right ICDs confirms relatively higher DFTs with RICDs than reported for left pectoral ICDs. However, DFTs were generally unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% tilt waveform. Implant testing may be preferred with RICDs. CLINICAL TRIAL NUMBER: NCT00873691.
No takes yet. Share an insight, caveat, or question.
Varma et al. (2016) conducted an RCT in Patients receiving right active pectoral implantable cardioverter defibrillators (RICDs) (n=91). Tuned waveform (3.5 ms time constant based) vs. 50/50% fixed tilt (FT) waveform was evaluated on Mean defibrillation threshold (DFT) (p=0.8). In patients receiving right pectoral ICDs, mean defibrillation thresholds were unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% fixed tilt waveform (14.9 J vs 14.2 J; P=0.8).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: