Ventricular resynchronization by multisite pacing improves myocardial performance in the postoperative single-ventricle patient.

Background: Ventricular resynchronization with multisite pacing in heart failure patients results in acute improvement of myocardial performance, but the mechanism is unknown. Our goals were to determine whether multisite pacing results in acute improvement of myocardial performance in postoperative single-ventricle patients, and to elucidate the mechanism by assessing the synchronization of regional ventricular contraction during multisite pacing using real-time three-dimensional echocardiographic imaging.
Methods: Multisite pacing studies were performed in 26 single-ventricle patients (mean age, 28 months; range, 7 days to 11 years) undergoing some form of single-ventricle palliation (stage I Norwood, 4; aortopulmonary shunt, 1; cavopulmonary shunt, 9; Fontan, 8; Fontan revision, 3; valve replacement, 1). Electrocardiogram, blood pressure, mixed-venous oxygen saturation, and three-dimensional echocardiograms (n = 10) were recorded at baseline and during multisite pacing. Data were analyzed to obtain regional volume-time curves for 16 three-dimensional segments of the systemic ventricle. An index of asynchrony was calculated at baseline and during pacing as the standard deviation of all segmental volume-time curves from onset to end of ejection.
Results: With multisite pacing performed at a median postoperative day 2 (range, 0 to 9), QRS duration decreased in 24 of 26 patients (93.9 +/- 17.5 versus 71.7 +/- 10.8 ms; p < 0.001); systolic blood pressure increased in 25 of 26 patients (86.3 +/- 20.0 versus 93.8 +/- 20.2 mm Hg; p < 0.001); cardiac index increased in 21 of 22 patients (3.2 +/- 0.8 versus 3.7 +/- 1.0 L x min(-1) x m(-2); p < 0.001); and the index of asynchrony improved in 8 of 10 patients (10.3 +/- 4.8 versus 6.0 +/- 1.4; p < 0.04).
Conclusions: Multisite pacing improves cardiac performance after single-ventricle palliation. Real-time three-dimensional echocardiography demonstrated that multisite pacing improved the synchrony of ventricular contraction.