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Five patients with impaired left ventricular function (LV) and implanted AV sequential pacemakers underwent serial radionuclide angiograms. The goal was a non-invasive evaluation of the rapid changes in left ventricular performance elicited by rate, pacing mode and AV interval manipulation. End diastolic volume, end systolic volume, stroke volume and cardiac output were increased by AV sequential pacing in comparison with ventricular pacing at 70 beats per minute. No significant change in ejection fraction and blood pressure were noted with changing AV sequential pacing rates at usual pacing rates. Our data suggest that a short AV interval (150 ms) improved LV performance more than a long AV interval (250 ms). A non-invasive technique to optimize left ventricular performance on an acute basis by varying heart rate, AV interval and pacing mode with the implanted AV sequential pacemaker is feasible and may be useful in selective clinical situations.

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