Post-cardiopulmonary bypass biventricular pacing improves hemodynamics but without clearly defined predictors of response. Based on preclinical studies and prior observations, it was suspected that diastolic dysfunction or pulmonary hypertension is predictive of hemodynamic benefit.
Patients who underwent bypass with pre-operative ejection fraction ≤40% and QRS duration ≥100 ms or double-valve surgery were enrolled. At 3 time points between separation from bypass and postoperative day 1, pacing delays were varied to optimize hemodynamics.
Cardiac output and arterial pressure were measured under no pacing, atrial pacing, and biventricular pacing. Preoperative echocardiograms and pulmonary artery catheterizations were reviewed, and measures of both systolic and diastolic function were compared to hemodynamic response. Early after separation, improvement in cardiac output was positively correlated with pulmonary vascular resistance (R 2 = 0.97, p < 0.001), ventricle wall thickness (R 2 = 0.72, p = 0.002)), and E/e′, a measure of abnormal diastolic ventricular filling velocity (R 2 = 0.56, p = 0.04). Similar trends were seen with mean arterial pressure. QRS duration and ejection fraction did not correlate significantly with improvements in hemodynamics.