ACUTE EFFECTS OF INTRAOPERATIVE MULTISITE VENTRICULAR PACING ON LEFT-VENTRICULAR FUNCTION AND ACTIVATION CONTRACTION SEQUENCE IN PATIENTS WITH DEPRESSED VENTRICULAR-FUNCTION/

Multisite Pacing Effect on LV Function. Introduction: We hypothesized that simultaneous right and left ventricular apical pacing would resul t in improvement in left ventricular function due to improved coordina tion of segmental ventricular contraction. Structural changes in ventr icular muscle present in dilated cardiomyopathy compromise ventricular excitation and mechanical contraction. Methods and Results: Eleven pa tients with depressed left ventricular function having cardiac surgery underwent epicardial multisite pacing with continuous transesophageal echocardiographic imaging. Quantitative measurement of percent fracti onal area change was performed, and segmental changes in contraction s equence resulting from simultaneous right and left ventricular pacing were assessed by application of phase analysis to recorded transesopha geal images. There was no statistically significant difference between the paced QRS duration achieved with simultaneous right and left vent ricular apical pacing and the native QRS duration (139 +/- 39 msec vs 106 +/- 18 msec, P = NS), but all other paced modes resulted in longer QRS durations. Percent fractional area change improved with simultane ous right and left ventricular apical pacing but not,vith other paced modes (41.5 +/- 11.9 vs 34.3 +/- 9.7, P < 0.01). Phase analysis demons trated a resequencing of segmental left ventricular activation/contrac tion when compared to baseline ventricular activation. Conclusion: Sim ultaneous right and left ventricular apical pacing results in acute im provements in global ventricular performance in patients with depresse d ventricular function. Improvements may result from pacing-induced gl obal coordination through recruitment of left and right ventricular ap ical and septal segments critical to effective ventricular contraction .