Absence of additional improvement in outcome of patients receiving cardiac resynchronization therapy paced at the most delayed left ventricular region.

Background: The choice of the optimal left ventricular (LV) pacing site remains an issue in patients requiring cardiac resynchronization therapy (CRT).

Aim: This prospective study compared the outcome of patients paced at the most delayed LV region with that of patients paced at any other LV site.

Methods: Forty-four patients with severe heart failure underwent three-dimensional (3D) echocardiography before implantation and 3 days after implantation of a CRT device, to determine the most delayed LV region during spontaneous rhythm and during right ventricular pacing. The patients were divided subsequently into four groups: group 1 (n=19), LV lead placed at the most delayed echocardiographic site in spontaneous rhythm; group 2 (n=25), LV lead placed at any other site; group 3 (n=21), LV lead placed at the most delayed echocardiographic site during right ventricular pacing; group 4 (n=23), LV lead placed at any other site.

Results: No significant differences were observed between the four groups before implantation. After 6 months of CRT, no significant differences were observed between groups 1 and 2 or between groups 3 and 4 in terms of change in New York Heart Association functional class, Minnesota living with heart failure questionnaire, 6-minute walk test, peak exercise oxygen consumption, 3D ventricular dyssynchrony and 3D LV ejection fraction.

Conclusion: Implantation of the LV lead in the most delayed region of the left ventricle determined by 3D echocardiography did not result in additional improvement in symptoms or LV function.