Influence of echocardiographic and radiographic characteristics on atrial sensing amplitude in patients with Linox Smart S DX defibrillation leads.

Background: Single-lead for implantable cardioverter-defibrillator (ICD) with floating atrial sensing dipole is a new diagnostic tool with the potential advantage in terms of arrhythmia discrimination. We sought to determine whether right heart size and dipole position influence atrial sensing. Methods: Atrial sensing (AS) amplitude was measured during implantation (PP, periprocedural), predischarge (IHFU, in-hospital follow-up) and 3–6 months after the procedure (AFU, ambulatory follow-up). Results were related to atrial dipole position in the right atrium (RA) on the basis of chest X-ray examination as well as right heart dimensions at echocardiography. Results: Twenty-four patients were included into final analysis. In 14 (58.3%) patients, sensing dipole was located in regions 1 and 2 of the RA. AS amplitude was greater in regions 1 and 2 when com¬pared to other locations (3.15 vs. 1.2 mV, p = 0.045, 7.53 vs. 3.8 mV, p < 0.001 and 5.63 vs. 2.44 mV, p = 0.017 for PP measurements, IHFU and AFU, respectively). There was a significant negative correlation between AS-PP and short RA dimension (RADs) (r = –0.56, p = 0.02), AS-IHFU and RA area (RAA) (r = –0.45, p < 0.05), AS-AFU and long RA dimension (RADl) (r = –0.46; p = 0.02), AS-AFU and RADs (r = –0,48, p = 0.02), and AS-AFU and RAA (and r = –0.52, p < 0.01). There was no relationship between AS and other right heart dimensions. Conclusions: Larger RA size and low sensing dipole location were associated with lower AS amplitude in single-lead dual chamber ICD.