Atrioventricular delay programming in cardiac resynchronization therapy devices: fixed or adaptive? A randomized...

Cardiac resynchronization therapy devices are routinely programmed on fixed atrioventricular delays (AVD) under resting conditions based on echocardiographic techniques. Whether this AVD also ensures optimal exercise hemodynamics, is unclear.

In order to compare fixed-AVD with rate-adaptive AVD, 100 patients with cardiac resynchronization therapy systems and sinus rhythm were randomized to fixed-AVD or adaptive-AVD. The patients then underwent bicycle ergometry with noninvasive hemodynamic monitoring. At rest and at peak exercise, stroke volume, cardiac output, and cardiac index were determined using "electrical velocimetry."

There were no significant differences in clinical characteristics and baseline hemodynamic parameters between fixed or adaptive AVD. In patients randomized to adaptive AVD, a trend towards higher stroke volume, cardiac output, and cardiac index at peak exercise was encountered.

Based on the trend towards better exercise hemodynamics demonstrated by this pilot study, a randomized follow-up study with clinical end points appears to be justified to clarify this issue.