Evaluation of left ventricular performance by radionuclide ventriculography in patients with atrioventricular versus ventricular demand pacemakers.

In 55 patients with coronary artery disease (n = 37), cardiomyopathy (n = 12), or myocarditis (n = 6) and programmable ventricular or dual-chamber atrioventricular (AV) demand pacemakers, left ventricular (LV) performance was studied by gated radionuclide ventriculography during pacing (60 or 70 to 120 bpm). Twenty-three patients were followed over 4 to 6 months. In 16 patients the findings in ventricular (VVI) and dual-chamber AV (DDD) pacing were compared. In all patients end-diastolic volume (EDV) decreased and cardiac output increased when the pacing rate was changed from 60 or 70 to 120 bpm. For instance, in the patient group with VVI pacemakers, EDV decreased by 7.53% +/- 3.5% (p less than 0.01) and cardiac output increased by 53.5% +/- 19.4% (p less than 0.01). The results were independent of the underlying heart disease. After 4 to 6 months, a reduction of both cardiac output and ejection fraction was found in 6 of the 23 patients. As compared to VVI pacing, a significantly higher cardiac output (2% to 16%) was derived from DDD pacing. The results indicate the dependence of LV performance on the pacing rate and the benefit of DDD pacing. Since gated radionuclide ventriculography provides the means to determine the effect of different pacing modes on LV performance, an optimal pacing mode may be found for each individual.