APPLICATION OF PULSED-DOPPLER TISSUE IMAGING IN PATIENTS WITH DUAL-CHAMBER PACING - THE IMPORTANCE OF CONDUCTION TIME AND AV DELAY ON REGIONAL LEFT-VENTRICULAR WALL DYNAMICS

Pulsed-Doppler tissue imaging (pDTI) is able to measure myocardial wal l velocities (systolic: S; early diastolic: E; late diastolic: A) and their timings. Relationships have been demonstrated between the preeje ction period and indexes of left ventricular systolic function. This s tudy was designed to examine with pDTI the effects of variations in at rioventricular delay (AVD) (100 ms, 150 ms, 200 ms) on myocardial dyna mics and on their timings at the basal interventricular septum (IVS) f rom an apical. approach and at the posterior wall (PW) from the parast ernal view. These data were compared with stroke volume measurements r ecorded from the left ventricular outflow tract. Seventeen patients wi th dual chamber pacemakers (7 because of complete heart block, 10 with sick sinus syndrome and first-degree AV block) were studied; full atr ial and ventricular capture was present at any AVD. These data were al so compared with those obtained in 10 age-matched healthy volunteers w ith comparable heart rates. Results: Optimal atrial contribution to le ft ventricular filling and, consequently, best systolic performance we re achieved when AVD was programmed such that a mean interval of 77 ms was allowed between the end of the A wave and the beginning of the S wave, similar to what was measured in the healthy control group by pDT I. Conclusion: The noninvasive measurement of timings of the cardiac c ycle by pDTI is helpful to determine the optimal AVD in individual pat ients.