[Radionuclide study of left ventricular function and regional myocardial perfusion in patients with a DDD pacemaker]

In order to determine the influence of right ventricular artificial pacing on left ventricular function, particularly on diastolic specificity and regional myocardial perfusion, 99mTc multigated blood pool study and 201Tl myocardial SPECT at rest were performed on 12 patients with a DDD pacemaker implanted due to atrio-ventricular block at various degrees and on 7 normal adults without pacemaker as controls. Studies were performed on the pacing group during both ventricular pacing (VP) and atrio-ventricular sequential pacing (AVSP) at a rate of 80 beats/min. Although global left ventricular ejection fraction (LVEF) showed no significant differences between the control group (63.7 +/- 9.1%) and the pacing group, or between during AVSP (57.8 +/- 9.6%) and during VP (55.8 +/- 10.0%), global early diastolic peak filling rate (EDPFR) in the pacing group were significantly lower during AVSP (0.90 +/- 0.52 counts/second/end-diastolic counts) than during VP (1.55 +/- 0.52) (p less than 0.01), which were both found to be lower than those seen in control group (2.37 +/- 0.48 (p less than 0.01). Functional images disclosed regional prolongation of left ventricular ejection time (ET) in septal and apical areas of the left ventricle adjacent to the pacing site in 7 of the 12 patients (58.3%) during AVSP and in 3 of them (25%) during VP, and also revealed regional decrease in EDPFR in the similar areas in all of the patients during both modes, being more remarkable during AVSP than during VP. On 201Tl myocardial SPECT at rest, regional perfusion impairment was observed in septum, apex and the infero-posterior wall on the septal side adjacent to the pacing site in 8 of 10 patients (80%) during AVSP and in 6 of 9 patients (66.7%) during VP. These results suggest that a change in electrical conduction by right ventricular pacing may disturb regional myocardial relaxation, probably resulting in a regional impairment of myocardial perfusion.