Echocardiographic study of the optimal atrioventricular delay at rest and during exercise in recipients of cardiac resynchronization therapy systems

BackgroundIt is unclear whether, in recipients of cardiac resynchronization therapy (CRT) systems, the optimal AV delay should be the same, shorter, or longer during exercise than at rest.ObjectiveThis study sought to examine the effects of atrioventricular (AV) delay optimization at rest and during exercise in 50 recipients of CRT systems.MethodsWe measured left ventricular (LV) outflow tract velocity time integral (OT-VTI) and LV filling time (FT) echocardiographically, at rest and during exercise to 60% of the maximal predicted heart rate, with the sensed AV delay set at 40, 70, 100, 120, 150, and 200 ms. The measurements made at rest versus those made during exercise, and among the several programmed AV delays, were compared.ResultsThe optimal AV delay based on LVOT-VTI was shorter during exercise than at rest in 37%, unchanged in 37%, and longer in 26% of patients. The optimal AV delay based on LVFT was shorter during exercise than at rest in 27%, unchanged in 23%, and longer in 50% of patients. Optimization of the AV delay during exercise increased LVFT and LVOT-VTI significantly (P < .05) compared with (1) any other arbitrarily chosen AV delay, (2) the optimal AV delay at rest, (3) an AV delay systematically shortened from rest to exercise.ConclusionOptimization of the AV delay had a positive effect on echocardiographic indices of LV function. The systematic shortening of the AV delay during exercise is not recommended because, in a high proportion of patients, the optimal AV delay was longer during exercise than at rest.