Pacing prescription for cardiac resynchronization therapy: When RV stimulation matters.

BACKGROUND

Cardiac resynchronization therapy (CRT) aims to correct delayed left ventricle (LV) activation resulting from left bundle branch block (LBBB). The source of LV activation delay resides in the septum and/or anterior LV. LV pacing, timed with intrinsic right bundle branch (RBB) conduction, may restore "physiological" biventricular activation. This is not assured because LV paced wavefronts themselves propagate unpredictably. Less studied are effects of right ventricle (RV) pacing on LV activation in heart failure (HF) patients with LBBB.

METHODS AND

RESULTS

In this case RV pacing pre-excited precisely the region left behind during LV pacing. Consequently, biventricular pacing produced confluent LV depolarization (the patient "responded" to this with reverse remodeling).

CONCLUSION

Successful electrical resynchronization requires best combination and timing of paced/intrinsic wavefront(s). This demands individualization. Sometimes, an RV paced wavefront may be valuable to resynchronization.