Implantable cardioverter-defibrillator programming and electrical storm: Results of the OBSERVational registry On long-term outcome of ICD patients (OBSERVO-ICD).

Background: Electrical storm (ES) is defined as 3 or more episodes of ventricular fibrillation (VF) or ventricular tachycardia (VT) within 24 hours and is associated with increased cardiac and all-cause mortality.

Objective: The purpose of this study was to test whether aggressive implantable cardioverter-defibrillator (ICD) programming can be associated with ES.

Methods: The OBSERVational registry On long-term outcome of ICD patients (OBSERVO-ICD) is a multicenter, retrospective registry enrolling all consecutive patients undergoing ICD implantation from 2010 to 2012 in 5 Italian high-volume arrhythmia centers. Clinical history and risk factors were collected for all patients, as were ICD therapy-related variables such as detection zones and delays. The total number of arrhythmic episodes and therapies delivered by the ICD were collected through out-of-hospital visits and remote monitoring.

Results: The registry enrolled 1319 consecutive patients, of whom 62 (4.7%) experienced at least 1 ES during follow-up (median 39 months). Patients who experienced ES had a significantly lower VF detection zone (P = .002), more frequently had antitachycardia pacing therapies programmed off during capacitor charge (P = .001), and less frequently had an ICD set with delayed therapies for VT zones (P = .042) and VF zone (P = .036). Patients who experienced ES had a significantly higher incidence of death and heart failure-related death compared to patients with no ventricular arrhythmias and patients with unclustered VTs/VFs (P = .025 and P <.001, respectively).

Conclusion: Patients with ES had a more aggressive ICD programming setup, including lower VF detection rates, shorter detection times, and no antitachycardia pacing therapies during capacitor charge. This kind of ICD programming potentially could increase the likelihood of ES and the related risk of death.