Introduction: A strategy of routine ICD testing is under discussion. So far, few studies have addressed the potential clinical value of identification of patients with elevated defibrillation thresholds (DFTs). We investigated the relation between the DFT at implantation and the occurrence of appropriate ICD therapy.
Methods: After ICD implantation (n=419), routine defibrillation testing was performed with sequential shocks (15-25-35 joule). Cumulative incidences of appropriate ICD therapy were compared between patients with low (=15 joule) and elevated DFTs (>15 joule).
Results: In total 67 (16%) patients had an elevated DFT and 352 (84%) had a low DFT. The cumulative incidences of appropriate ICD therapy are shown in the Table (p=0.03). Elevated DFT and history of sustained VT were independently associated with appropriate therapy [HR 1.99 (95% CI 1.19-3.33)]; [HR 2.57 (95% CI 1.52-4.36)].
Conclusions: During routine testing, an elevated DFT was observed in one-out-of-six patients. The 1-2 year incidences of appropriate ICD therapy were twice as high in these patients as compared with patients with a low DFT. Our findings question whether routine testing can be omitted safely in all patients.