Long-Term Stability and Clinical Utility of Amplified Atrial Electrograms in a Single-Lead ICD System with Floating Atrial Electrodes.

BACKGROUND: Available atrial electrograms in implantable cardioverter defibrillators (ICDs) improve arrhythmia diagnosis, allow monitoring for atrial fibrillation, and may reduce the risk of inappropriate therapies. A recently introduced ICD system using a single-lead with floating atrial electrodes provides diagnostic capability of a dual-chamber system without placing an additional lead. Data on long-term clinical performance of this system are limited. METHODS: We retrospectively analyzed data from 35 consecutive patients implanted with Biotronik VR-T DX devices and LinoxSmart DX leads. (Biotronik, SE & Co., Berlin, Germany) RESULTS: Of 35 patients (77% male, age 52 ± 11.28 years), 32 were followed for a mean of 432 ± 197 days (range 56-765). During implantation, average preamplified and amplified sinus P-wave amplitudes were 2.61 ± 1.39 mV (range 0.9-6.8 mV) and 8.7 ± 4.51 mV (range 1.4-18 mV), respectively. Despite statistically significant variations, the amplified P-wave amplitude measurements (calculated mean values over 3 months) remained within a clinically acceptable range during follow-up (5.4-8.7 mV). R-wave amplitude and ventricular pacing threshold measurements were stable over time. A total of 13 stored arrhythmia events (three ventricular tachycardia, eight supraventricular tachycardia, two atrial fibrillation) were reviewed. All of them showed readily interpretable atrial electrograms. Eight out of 10 (80%) supraventricular events were correctly classified by the device. Three patients received inappropriate ICD therapies. CONCLUSION: The single-lead ICD system using a floating atrial dipole provides reliable recording of atrial signals during sinus rhythm and arrhythmias. Our data suggest that the system may offer diagnostic advantages of a dual-chamber device without potential risks of an additional atrial lead.