ASSESSMENT OF THE OPTIMAL ATRIOVENTRICULA R DELAY IN DUAL-CHAMBER PACING BY IMPEDANCE PLETHYSMOGRAPHY - CORRELATIONS WITH DOPPLER STUDY OF LEFT-VENTRICULAR FILLING

The stroke volume (SV) was measured by the change in the impedance in thirteen patients with dual chamber pacemakers at different atrioventr icular delay (AVD) intervals : 31 to 219 ms or 75 to 220 ms. The mitra l inflow was also recorded by Doppler echocardiography at each AVD wit h measurement of the duration of mitral flow (MFD) and the velocity ti me integral (VTI). All thirteen patients were studied in the DDD mode ; in addition, 5 patients were studied in the atrial sensing ventricul ar stimulation VDD mode. The SV measurement by impedance plethysmograp hy was reproducible with an average variability of 3.5 % : the optimal AVD was determined by this method in 11 patients with DDD and 4 patie nts with VDD pacing: in 3 patients (2 in DDD and 1 in VDD mode) 2 opti mal AVD were obtained. The optimal AVD was 123 +/- 31 ms (63 to 156 ms ) in DDD mode and 91 +/- 17 ms (63 to 110 ms) in VDD mode. The analysi s of left ventricular filling showed that changes in AVD led to simila r changes in mitral VTI. The MFD increased as the AVD was shortened to a constant value at the optimal AVD. In all patients, the optimal AVD was obtained when the MFD became maximal and constant. Measurement of MFD is a simple and rapid means of assessing optimal AVD at rest in p atients with dual chamber pacing systems.