Changes in the optimal cardiac resynchronization therapy pacing configuration during physiologic stress

Some patients with ongoing heart failure symptoms after treatment with cardiac resynchronization therapy (CRT) demonstrate QRS prolongation during exercise. We investigated whether the optimal CRT pacing configuration changes during dobutamine stress.

Seven patients undergoing CRT implantation underwent invasive LV dP/dT_max measurement during CRT pacing in 10 configurations to determine the optimal baseline pacing configuration (OPC). Measurements were repeated during dobutamine infusion. Differences in mean LV dP/dT_max between pacing configurations were compared.

Baseline OPC differed from stress OPC in 6/7 patients. The mean (SD) LV dP/dT_max obtained during dobutamine infusion was 1140 (377) mmHg/s in AAI pacing, 1458 (448) mmHg/s in the baseline OPC, and 1656 (435) mmHg/s in the dobutamine OPC (p < 0.001 for differences). The mean increase in LV dP/dT_max obtained by changing from baseline OPC to dobutamine OPC during dobutamine infusion was 197 (338) mmHg/s (13%). The QRS duration, QRS morphology, QLV and QRV intervals did not change significantly during dobutamine infusion (all P > 0.05).

The optimal CRT pacing configuration changes during dobutamine infusion while LV and RV activation timing does not. Further studies investigating the usefulness of automated dynamic changes to CRT pacing configuration according to physiologic condition may be warranted.