Left ventricular pacing site and timing optimization during biventricular pacing using a multielectrode patch in pigs

Objectives: Biventricular pacing is important therapy for congestive heart failure, reversing left ventricular dysfunction in dilated cardiomyopathy. Although left ventricular lead location and right ventricular-left ventricular delay are believed to be critical in biventricular pacing, there is no established technique for optimizing pacing site and timing. Methods: After median sternotomy in 8 anesthetized pigs, an ultrasonic flow probe was placed on the ascending aorta to measure cardiac output, and pressure catheters were inserted into both ventricles. Temporary bipolar epicardial pacing leads were attached to the right atrium and anterior right ventricle. A patch with 5 bipolar electrodes was placed behind the left ventricle. A temporary bipolar lead was also placed on the left ventricular apex. Complete heart block was established by ethanol ablation. Right ventricular pressure overload was induced by snaring the pulmonary artery until right ventricular systolic pressure doubled. Dual-chamber mode biventricular pacing was instituted at 9 right ventricular-left ventricular delays, +80 ms to -80 ms in 20 ms increments, and 6 left ventricular sites. Data from the 54 combinations of these variables were acquired in a randomized fashion. Mixed model technology was used for statistical analysis. Results: Qualitatively, two unique site/timing pairs were optimal. Statistically, pacing the obtuse margin at a right ventricular-left ventricular delay of +60 ms (mean cardiac output = 1.80 L/min) and the inferolateral wall at a right ventricular-left ventricular delay of -20 ms (mean cardiac output = 1.79 L/min) was superior to all other site/timing combinations (mean cardiac output = 1.71 L/min; P = .006). Conclusions: Left ventricular pacing site and right ventricular-left ventricular delay can be optimized with a multielectrode patch and randomized data collection. This technique can be used further in clinical studies.