Optimal atrio-ventricular delay setting determined by QT interval measurement in patients with dual-chamber pacemakers

Objective To apprasie the optimum atrioventricular delay (AVD) determined by QT interval measurement in patients with implanted DDD pacemakers.Methods Nineteen patients with implanted DDD pacemakers for complete A-V block [aged (66.79±15.52) years] were studied. Cardiac output (CO), Left ventricular ejection fraction (LVEF), left ventricular end-systolic diameter (LVESd) and left ventricular end-diastolic diameter(LVEDd) in different AVDs were measured by colored doppler echocardiography as well as the QT interval by synchronous twelve leads ECGs. The atrial pacing rate was set at 75 bpm and the AVD was prolonged to 240 ms by 30 ms stepwise starting from 90 ms. Results QT intervals changed with the cardiac function at different AVDs. At the maximum CO[(6.50±1.54) L/min], the AVD was (163.30±30.41) ms and the QT interval (463.30±27.83) ms. At the maximum QT interval [(473.33±25.00) ms], CO and AVD were (6.29±1.75) L/min and (158.80±13.64) ms' respectively. There were no significant differences between the “optimum AVD” at which the CO was maximal and the AVD at which the QT interval was the longest [(163.30±30.41) ms vs (158.80±13.64) ms, P0.05], and there were no significant differences in cardiac function parameters at the maximum QT interval and at the “optimal AVD” [CO:(6.29±1.75) L/min vs (6.50±1.54) L/min, P0.05; LVEF:(65.89±10.80)% vs (67.04 ±11.19)%;P0.05]; There was a significant positive correlation between QT interval and CO (r=0.70, P0.05).Conclusion QT interval changed with cardiac function at different AVDs, the optimal AVD setting can be determined by QT interval measurement.