Background: Dual Chamber Implantable Cardioverter Defibrillator (ICD) in addition to providing hemodynamically improved bradycardia support can also reduce the incidence of inappropriate ventricular shocks owing to episodes of Supraventricular Tachycardia (SVT), with reported incidence of up to 41% of patients. An atrio-ventricular (AV) discrimination algorithm is needed in dual chamber implantable cardioverter-defibrillators (ICD) to avoid these inappropriate shocks. Methods: An AV discrimination algorithm, SMART DetectionTM, has been developed to differentiate between episodes of ventricular tachycardia (VT) and SVT. It relies on the concept that the chamber with the higher rate is the origin of the tachycardia. The ventricular rate stability criterion is also used to detect concurrent VT during an episode of SVT. Other parameters used in the discrimination algorithm are: atrial and ventricular rhythm multiplicity, P-R regularity, sudden onset. The SMART DetectionTM algorithm has been implemented in the Biotronik Phylax® AV dual chamber ICD. The original SMART DetectionTM has been improved recently with the addition of active detection in the case of 1:1 AV conduction. Results: 10 patients were implanted with Phylax® AV's at the Bakoulev Institute. Analyses of stored dual chamber intracardiac electrogram (IEGM) indicate that all episodes of VTs and Ventricular Fibrillations (VF) were terminated following appropriate therapies. No episode of Atrial Flutter (Afl) or Atrial Fibrillation (AF) was treated even though the majority of patients have a history of SVTs. In one patient, an episode of Sinus Tachycardia (ST) was inappropriately treated. Increasing the sudden onset criterion, which is used only in the case of stable 1:1 rhythms, was sufficient to prevent recurrence of inappropriate therapy. To avoid the necessity of setting the, not very reliable, sudden onset criterion an active detection procedure was developed. Isolated Premature Ventricular Stimuli were used to test the hypothesis of VT with retrograde atrial conduction in the 1:1 AV rate case. Results of acute tests of this active detection improvement are reported in this paper. Conclusion: The SMART DetectionTM algorithm, with is active detection improvement in the case of 1:1 AV rate, should prove to be an effective AV discrimination algorithm in dual chamber ICD which will offer freedom from unnecessary shocks in response to SVTs.
Tachycardia; Defibrillators; Tachycardia; Cardioversors; Algorithms
