[Echocardiographic study for optimizing therapy with physiologic heart pacemakers--the relevance of mitral valve...

The hemodynamic effects of the AV-intervals 50, 150 and 250 ms were studied in 19 patients with VDD pacemakers and compared to VVI stimulation and 12 normal individuals. LV dimensions and systolic and diastolic time intervals were measured with echo-phonoapexcardiography. The amplitude of LV-contraction, LV enddiastolic diameter, PEP, LVET and PEP/LVET significantly improved with physiological pacing when compared to VVI-stimulation. The optimal AV-interval was 50 ms in 8 patients, 150 ms in 7 and 250 ms in 4. Mitral valve closure (128 +/- 13 ms) and PEP (193 +/- 19) were grossly delayed in comparison to normal individuals. With increasing AV-intervals PEP and the onset of rise in the apexcardiogram were not changed but mitral valve closure occurred earlier, being 128 +/- 13 ms at AV = 50, 82 +/- 36 ms at AV = 150 and 20 +/- 73 ms at AV = 250. Simultaneously LV-filling time normalized for cycle length decreased from 50 +/- 5% to 45 +/- 8% and 38 +/- 10% respectively. In the presence of early mitral valve closure there was a late mitral notch, which occurred 10 +/- 20 ms after the onset of rise of the apexcardiogram. Thus the onset of the isovolumic contraction period was defined. In patients with VDD pacemakers therefore, echocardiography allows measurements of LV function, of the late onset of systole, and of mitral valve closure, which depends on the previous PR-interval. These values need to be considered in programming the optimal AV-interval and cannot be derived from normal individuals.