Failure to deliver a shock in a dual-chamber implantable cardioverter-defibrillator: A case report

Introduction: Inappropriate implantable cardioverter-defibrillator (ICD) therapies due to supraventricular tachyarrhythmia (SVT) are a common problem. The authors report this case to warn of a possible detection problem and subsequent failure of deliver appropriate therapy in patients with atrial fibrillation (AF) and a dual-chamber ICD using the PARAD+algorithm. To our knowledge this is the first reported case of failure to deliver a shock in a dual-chamber ICD due to the PARAD+ algorithm. Case report: The authors present a case of a 68-year-old Caucasian man with permanent AF and a dual-chamber Sorin Paradym ICD with the PARAD+algorithm, who presented an episode of sustained ventricular tachycardia (VT). The ICD did not store the event and did not delivery a therapy, although the heart rate curve was consistent with an episode of VT. No evidence of system dysfunction was found. Conclusion: Due to simultaneous occurrence of VT and AF rhythms and alternation in rhythm classification by the PARAD+ algorithm the number of cycles needed to diagnose VT was not achieved and no therapy was delivered. In patients with permanent or long-term persistent AF with a dual-chamber ICD using the PARAD+ algorithm, discrimination should be based only on the ventricular channel. In patients with paroxysmal or persistent recurrent AF the risk of not delivering VT therapy must be weighed against the risk of inappropriate therapy. (C) 2013 Sociedade Portuguesa de Cardiologia. Published by Elsevier Espana, S.L.U. All rights reserved.