SHORT ATRIOVENTRICULAR DELAY DUAL-CHAMBER PACING EARLY AFTER CORONARY-ARTERY BYPASS-GRAFTING IN PATIENTS WITH POOR LEFT-VENTRICULAR FUNCTION

Objective: To investigate the effect of short atrioventricular (AV) de lay dual-chamber pacing on mean arterial pressure (MAP) and stroke vol ume index (SVI) in patients with poor left ventricular (LV) function a fter cardiac surgery. Design: A prospective study. Setting: A universi ty hospital, single-center study. Participants: The study group consis ted of 20 patients aged 63 +/- 9 years with a left ventricular ejectio n fraction (LVEF) less than 30%. The control group consisted of 20 pat ients aged 61 +/- 10 years, with an LVEF greater than 50%.Intervention s: Immediately after routine coronary artery bypass grafting (CABG) th e AV delay was shortened from 160 to 40 milliseconds in atrial-paced ( DDD) mode and from 100 to 40 milliseconds in atrial-sensed ventricular stimulation (VDD) mode. MAP was on-line monitored and SVI was calcula ted by thermodilution. In one patient with an LVEF of 18% (case study) , transmitral flow velocity and LV isovolumetric relaxation time were assessed using Doppler echocardiography during VDD pacing at 40-, 80-, and 120-millisecond AV delay. Results: Short-AV delay DDD pacing decr eased MAP in the control group (84.3 +/- 9 v 75.7 +/- 9 mmHg; p < 0.05 ) and SVI in both groups (study group, 35.9 +/- 7 v 31.7 +/- 7 mL/m(2) ; control group, 35.3 +/- 6 v 31.0 +/- 6 mL/m(2); p < 0.05). Shortenin g the AV delay had no influence on MAP and SVI during VDD pacing. Duri ng the echocardiographic case study, AV delay shortening distinctly mo dified ventricular filling patterns. Optimal LV filling and transmitra l flow were achieved with an intermediate AV delay of 80 milliseconds. Conclusion: Dual-chamber pacing with nonphysiologic short AV delay fa iled to improve acute hemodynamics in patients with poor LV function a fter CABG. Short AV delay VDD pacing was superior to DDD pacing in bot h normal and impaired LV function. The use of Doppler echocardiography enabled optimization of the AV delay on the basis of LV filling patte rns. Copyright (C) 1998 by W.B. Saunders Company.