Interatrial conduction time from electrograms of cardiac resynchronization therapy devices with left ventricular sensing

Background: The interatrial conduction time (IACT) is relevant for atrioventricular delay optimization in cardiac resynchronization therapy (CRT) devices. However, this information cannot be easily used as it requires invasive measurements. We tested whether electrical activation of left atrium (LA) could be detected in CRT devices with left ventricular (LV) sensing and used to estimate IACT. Methods: The presence of LA activation on LV channel was evaluated in consecutive patients implanted with CRT and quadripolar LV leads whose sensing was temporarily set in the most proximal polarity (Ring LV4-housing). Estimates of IACT during sinus rhythm and atrial pacing were measured and compared with the values obtained with invasive catheterization of coronary sinus. Results: Among six patients (50% female; mean age 73.3 ± 4.9 years) included in the analysis, four (66%) had a visible LA signal on the LV channel. The mean IACT measured with device electrograms was 71 ± 8 ms and 133 ± 15 ms during sinus rhythm and atrial pacing, respectively. These values were equivalent to the measurements obtained during invasive catheterization. Both patients without evidence of LA activation had an LV lead with a short total interelectrodes distance (46 mm) resulting in a significant anatomical distance between Ring LV4 and LA. Conclusions: In CRT devices with left ventricular sensing, LA signal could be detected and used to estimate IACT especially if long-spaced electrodes are used.