Impact of different pacing modes on left ventricular function following cardiopulmonary bypass.

BACKGROUND: Patients with severely impaired left ventricular (LV) function often demonstrate prolonged inter- and intraventricular conduction. This prospective study investigates hemodynamic effects and outcomes of perioperative temporary biventricular pacing in patients with heart failure undergoing heart surgery.
METHODS: 80 consecutive cardiac surgery patients with a LV ejection fraction below 35 % received biventricular stimulation via temporary myocardial electrodes. Group 1 consisted of 40 patients with LV dilatation (mean LVEDD 65 +/- 5 mm), Group 2 of 40 patients with normal or slightly dilated LV (mean LVEDD 52 +/- 4 mm).
RESULTS: Hemodynamic parameters were measured immediately, 6 and 24 hours after operation. An increase of cardiac index (CI) and arterial blood pressure with biventricular pacing was observed in 27 patients (Group 1/67.5 %) versus 22 patients (Group 2/55 %) from 2.4 +/- 0.7 l/min/m2 to 3.5 +/- 0.5 l/min/m2 ( P < 0.01). This benefit persisted 6 and 24 hours postoperatively. The remaining patients already showed a higher cardiac index prior to pacing (3.7 +/- 0.9 l/min/m2). In Group 1, the duration of ventilation support and time in the intensive care unit of responding patients was shorter. QRS duration before surgery was not predictive for the response to biventricular pacing.
CONCLUSIONS: In the majority of patients with reduced LV function, temporary biventricular pacing improves CO and arterial blood pressure after surgery, especially when LV dilatation is present.