Acute hemodynamic effects of cardiac resynchronization therapy in patients with poor left ventricular function during cardiac surgery.

BACKGROUND: Cardiac resynchronization therapy improves systolic function in patients with heart failure and left ventricular (LV) dyssynchrony. However, the effect of biventricular (BiV) pacing on perioperative hemodynamics in cardiac surgery is not well known. We investigated the acute hemodynamic response using LVdP/dt(max) in patients with depressed LV function and conduction disturbances undergoing cardiac surgery.

METHODS: Patients with LV ejection fraction of < or =35%, QRS duration of >130 ms, and left bundle branch block undergoing aortocoronary bypass and valve surgery were included. Temporary atrial and left and right ventricular pacing wires were applied, and LVdP/dt(max) was measured with a high fidelity pressure wire in the left ventricle at the end of cardiopulmonary bypass. Responders had a > or =10% increase in LVdP/dt(max).

RESULTS: Eleven patients (age 63 +/- 11 years, eight males) with a LV ejection fraction 0.29 +/- 0.06% were included. Compared with right ventricular pacing (782 +/- 153 mmHg/sec), there was a significant improvement in the mean LVdP/dt(max) during simultaneous BiV pacing (849 +/- 174 mmHg/sec; p = 0.034) and sequential BiV pacing with the LV 40 ms advanced (880 +/- 157 mmHg/sec; p = 0.003). Improvement during LV pacing alone was not significant (811 +/- 141 mmHg/sec). Six patients were responders with simultaneous and nine with sequential BiV pacing. Only sequential BiV pacing had a significant improvement in LV systolic pressure (p = 0.02).

CONCLUSIONS: BiV pacing results in acute hemodynamic improvement of LV function during cardiac surgery. Optimization of the interventricular pacing interval contributes to the effect of the therapy.