Ventricular Epicardial Lead Placement for Resynchronization by Determination of Paced Depolarization Intervals: Technique and Rationale

Abstract

Cardiac resynchronization therapy has been shown to be an effective treatment to improve functional status and prolong survival among patients with advanced congestive heart failure. However, as many as 30% of patients do not respond. Nonresponse may be due to suboptimal left ventricular lead placement. Studies have indicated that leads placed in the midlateral left ventricle (LV) wall usually result in improved dP/dT and increased pulse pressure, compared with other locations. When the surgeon is placing the leads thoracoscopically, however, in a chest with multiple adhesions, anatomic landmarks can be obscured. It is desirable to have an objective physiologic method to determine optimal lead placement. The optimal LV pacing site may be best determined by locating the site with the latest depolarization. A pacing lead attached to a pulse analyzer was introduced through a thoracoscopic port and used as a mapping electrode to electrically map exposed areas of the left ventricle. The right ventricular pacing lead was also attached to the pulse analyzer and the interval between the right ventricular pulse and the LV depolarization (paced depolarization interval) was measured in 19 patients undergoing thoracoscopic LV lead placement. A site with a paced depolarization interval less than 110 ms was not accepted. Electrical mapping was possible in 19 of 29 consecutive patients in whom it was attempted. The most frequent reason for not mapping was the presence of extensive scarring. In 7 of 19 patients (36.8%) mapped, the site that would have been chosen by anatomic landmarks was not the site with the longest paced depolarization interval, and thus the lead placement was altered. The site with the longest paced depolarization interval is only selected 63.2% of the time when utilizing anatomic landmarks for placement. Nonresponse may be due to suboptimal LV lead placement. Measurement of paced depolarization intervals provides a physiologic method of determining optimal LV lead placement.