Optimally Timed Rate-adaptive Atrioventricular Delay in AV Sequential Pacing

Abstract

Background and Objectives:The impetus for the spectacular advances in pacemaker technology has been a shift in the aims of pacemaker therapy from ensuring survival of patients with conduction defects to optimizing hemodynamic function. Now, optimization of the system through rate adaptive AV sequential pacing and adjusting the appropriate time of the AV interval is the main goal. At lower levels of exercise, the relative importance of an appropriately timed atrial contraction in maintaining optimal cardiac output is now well established in patients with normal and abnormal ventricular function. The purpose of this study is to define the optimal AV delay patterns in AV sequential pacing in association with heart rate changes. Materials and Methods:Eleven patients who had been treated with dual chamber pacemakers under the diagnosis of complete heart block or sick sinus syndrome were included. During the study, the pacemaker was programmed to the atrial triggered ventricular pacing mode. The heart rates were increased from 50 beats/minute to 80 beats/min by 5 beats/minute's interval. At each heart rate, the AV delay was programmed to 100, 125, 150, 175, 200 ms and the time velocity integral was measured by a continuous wave Doppler echocardiography. Results:When the heart rate changes were not considered, time velocity integral was the greatest with an AV delay of 150 ms (p<0.0001). There were no significant differences between AV delays regarding the time velocity integrals in rate responsive optimal fixed AV delay. The average r-value of linear regressions for optimal AV delay was -0.54. Individually programmed AV delay showed that the optimal AV delays were at 125 ms in two cases, 150 ms in five cases, 175 ms in three cases, and 200 ms in one case. The most unfavorable AV delays were at 100 ms in four cases, 150 ms in one case, 175 ms in two cases, and 200 ms in three cases. The r-values of linear regression for individualized optimal AV delay showed very wide range (-2.5-0.89). Conclusion:The optimal AV delay within the range of 50-80 bpm of heart rates is 150 ms. The average r-value of linear regression for optimal AV delay was -0.54. However there were wide variations in optimal AV delay individually, we should consider a patient-specific AV delay algorithm. (Korean Circulation J 2000;30(3):310-317)