Defibrillation threshold testing does not predict clinical outcomes during long-term follow-up: a meta-analysis

Defibrillation threshold (DFT) testing at the time of implantable cardioverter defibrillator (ICD) implantation is widely used in clinical practice, but reliable data supporting its routine use are lacking. We undertook a meta-analysis to evaluate the efficacy of DFT testing compared to no DFT testing at the time of ICD implantation.

We searched the MEDLINE and EMBASE databases for studies evaluating the effect of DFT testing on total mortality and ventricular arrhythmias during follow-up. Risk ratios (RR) with 95% confidence intervals (CI) were calculated using random effects modeling.

Eight studies involving 5,020 patients (3,068 undergoing DFT and 1,952 not undergoing DFT) were included. Of those, only one study was randomized. Reasons for not performing DFT included patient characteristics (four studies), center's standard practice (three studies), or randomization (one study). Median follow-up was 24 months. Overall, the quality of the included studies was rather poor. On the basis of the pooled estimate across the studies, DFT testing did not reduce total mortality or ventricular arrhythmias at follow-up (RR = 0.94, 95% CI 0.74-1.21; P = 0.65 and RR = 1.19, 95% CI 0.85-1.68; P = 0.30, respectively). No individual study had a major impact on the estimated RR or the statistical significance based on a sensitivity analysis.

Recognizing the limited quality of current studies in the area of DFT testing and outcomes, available data suggest that DFT testing at the time of ICD implantation does not appear to predict total mortality and ventricular arrhythmias during follow-up. Large randomized controlled trials, adequately powered to detect clinical outcomes, are warranted.