Defibrillation efficacy testing: Long-term follow-up and mortality

Aims: Extensive defibrillation threshold testing is no longer necessary to perform as devices have become more effective. We assessed the lowest effective defibrillation (LED) level at implantation and before hospital discharge and related this to outcome. Methods and results: One hundred and twenty-seven consecutive patients with biphasic shock and active can devices were studied at intraoperative and predischarge testing. A subgroup of 67 patients had ≥3 VF inductions at implant. Improvement was defined when LED decreased by ≥3 J. The LED was significantly higher at implantation compared with predischarge (P < 0.001). Improvement was seen in 73/ 127 patients (58%). In the group with ≥3 VF inductions, an implantation LED > 9 J was related to a lower LVEF (P < 0.01); 34/67 patients (51%) had improvement in LED. During follow-up, 18/127 patients died, four received heart transplantation. No different outcome was observed in patients with and without improvement. However, for those with ≥3 VF inductions, an independent predictor of mortality was implantation LED >9 J without improvement on the second test. Safety margin <10 J was not related to mortality. Conclusion: Repeated defibrillation efficacy testing before hospital discharge may confirm that a relatively high defibrillation energy is required. This is related to a higher mortality in long-term follow-up.

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