Left ventricular sensing in cardiac resynchronization devices—opportunities and pitfalls for device programming

Clinical use of CRT-D devices with left ventricular sensing: Impact of the desynchronization-detection algorithm

The use of CRT-D devices with left ventricular (LV) sensing has created controversy about programming various parameters especially the left ventricular T wave protection (LVTP) designed to prevent the delivery of a pacing stimulus into the LV vulnerable period. Such devices are available from two manufacturers. This review focuses only on those provided by Biotronik. As the LVTP controls LV sensing, some investigators have advocated turning off the LVTP to prevent episodic desynchronization known a CRT pacing interrupt. However, LVTP off reduces but does not eliminate this type of desynchronization if triggering of an LV stimulus upon right ventricular sensing (RVs) is programmed on. Deactivation of the LVTP incurs loss of diagnostic data provided by CRT pacing interrupt itself. By choice, the occurrence of CRT pacing interrupt can be totally eliminated by appropriate programming of the LV upper rate interval, LVTP and triggering of an LV pacing event upon RVs. Various programmability options are available according to clinical circumstances. As a rule, clinical judgement must weigh the potential diagnostic benefit of preserving the LVTP capable of recording of episodic CRT pacing interrupt against the loss of diagnostic benefit when LVTP is programmed off (with or without triggering of an LV stimulus upon RVs).

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.

A review of specialized and automated features in implantable cardiac devices

Automated features available in cardiac implantable electronic devices continue to increase in number and complexity. These features are frequently confused with device malfunction and often result in unnecessary clinical attention. This review will serve as an update to some of the more commonly-encountered features discussed in terms of the behavior they exhibit.