First worldwide clinical experience with a new dual chamber implantable cardioverter defibrillator - Advantages and complications

Aims The need for physiological pacing and for improving the ability to dis criminate atrial from ventricular tachyarrhythmias has prompted the develop ment of dual chamber implantable cardioverter/defibrillators (ICDs). Methods Fifty-two patients were implanted with a newly developed dual-chamb er ICD providing rate-responsive physiological pacing (Ventak AV II DR). Th e device possesses two new arrhythmia detection algorithms ('atrial fibrill ation rate threshold' and 'ventricular to atrial rate relationship') in add ition to commonly used features such as 'onset' and 'stability'. During imp lantation, the atrial and ventricular lead impedances and pacing thresholds were determined together with the defibrillation threshold. Prior to disch arge. attempts were made to induce both atrial and ventricular tachyarrhyth mias in order to test those new detection criteria, All patients were follo wed for at least 3 months. Results The device was successfully implanted in all 52 patients. Placement of the atrial lead was successful in 50/52 patients (96%: P-wave 3.2 +/- 1 .4mV; impedance 576 +/- 123 Omega; atrial pacing threshold 1.2 +/- 0.9 V). Prior to discharge, 32 episodes of atrial fibrillation (AF) alone, 38 episo des of AF with ventricular fibrillation and 10 episodes of AF with monomorp hic ventricular tachycardia were induced in 33/50 patients (66%) and all we re appropriately classified by the detection algorithm. During the 3 months follow-up, 12 patients (23%) had appropriate and successful therapies for ventricular arrhythmias, while four patients (8%) experienced inappropriate ICD therapies. Although all these episodes were detected correctly as supr aventricular arrhythmias by the device, therapy was delivered because of in correct or incomplete programming. In all cases reprogramming of the device resolved the problem. Conclusion Implantation of dual chamber ICDs is feasible and appears to imp rove discrimination of supraventricular from ventricular tachyarrhythmias. In addition, patients with tachyarrhythmias and concomitant bradyarrhythmia s may benefit from simultaneous physiological pacing. However, implantation and follow-up of such patients should be performed at experienced centres since both surgical handling and programming of these devices is more diffi cult and complex than conventional ICDs.