Clinical predictors of atrial defibrillation thresholds with a dual-coil, active pectoral lead system

Etiology and Programming Effects on Shock Efficacy in ICD Recipients

BACKGROUND

We sought to assess the efficacy of high-energy shocks to restore rhythm and predictors of success in patients with sustained ventricular arrhythmias and implantable cardioverter defibrillator (ICD).

METHODS AND RESULTS

Data from 162 patients included in the UMBRELLA study that experienced one or more episodes of ventricular tachycardia (VT) for which ICD shocks of at least 30 Joules were delivered (appropriate high-energy shocks) were analyzed. In total, 456 ventricular arrhythmia episodes were registered. Forty four episodes (9.6%) from 39 patients (24%) had at least one ineffective high-energy shock delivered. Hypertrophic cardiomyopathy was more frequent among patients with unsuccessful shocks (10.3% vs 2.4%). Patients with ineffective shocks had higher proportion of sustained monomorphic ventricular arrhythmias (86.4%; the other 13.6% were sustained polymorphic and ventricular fibrillation [VF]) compared with patients with all their shocks effective (62.9%, P = 0.02). No statistical differences were found between groups in time from detection to the high-energy shock delivery, in tachycardia cycle length, or in antitachycardia pacing, but patients with ineffective high-energy shocks had higher proportion of previously ineffective low-energy shock (9.1% vs 0.5%, P = 0.01).

CONCLUSION

We found a substantial rate of ineffective high-energy shocks for the treatment of VT or VF in patients with ICD. High-energy shock efficacy seems to be reduced by hypertrophic cardiomyopathy and by the administration of previous low-energy shocks.

[ICD leads]

Implantable cardioverter-defibrillator (ICD) leads have to fulfill particular requirements: safe pacing and sensing, detection, and termination of ventricular tachyarrhythmias, if necessary by (multiple) high-energy shocks. At the same time, their implantation has to be simple, they need to provide excellent long-term stability and they must be completely and safely extractable. Numerous technical developments have enabled currently available ICD leads to fulfill these expectations to a high extent. However, some changes of lead design, materials, and manufacturing processes have led to increased lead failure, especially in two lead models (Medtronic Sprint Fidelis®, St. Jude Medical Riata®). The high rate of lead failure was identified only several years after market release, in part because there are no appropriate registries of ICD leads. This review presents background and developments of ICD lead technology and their association with the clinical usage of ICD therapy. To also benefit patients with only slightly-to-moderately increased risk of ventricular tachyarrhythmia, optimum ICD therapy requires optimal leads and sufficiently experienced implanters.

Defibrillation testing in patients with atrial fibrillation

Implantable cardioverter defibrillator implantation in patients with atrial fibrillation (AF) is complicated by the need for anticoagulation during defibrillation testing. In this retrospective study, we evaluated the factors associated with successful cardioversion of AF during ventricular defibrillation testing and the safety of our local anticoagulation protocol.