Changes in Evoked QT Intervals According to Variations in Atrioventricular Delay and Cardiac Function in Patients With Implanted QT-Driven DDDR Pacemakers

Abstract

In patients with implanted DDD pacemaker, cardiac output is maximal when atrioventricular (AV) delay is set to give the maximum QT interval (QTI). QTI is used as a sensor of a rate-responsive pacemaker and the evoked QTI (eQTI) is measured as the time duration from the ventricular pace-pulse and the T sense point, which is the steepest point of the intracardiac T wave. The relationship between the changes in eQTI according to AV delay variations and cardiac function was studied in 13 patients (74.2+/-9.3 [SD] years old) with an implanted QT-driven DDDR-pacemaker. A special software module was downloaded into the pacemaker memory and a personal computer equipped with the special software was connected to the programmer for eQTI date-logging. AV delay was set at 100, 120, 150, 180 and 210 ms. Delta eQTI was defined as maximal eQTI - minimal eQTI. The ejection fraction (EF) was measured by echocardiography. When the AV delay was prolonged, eQTI gradually increased and reached a peak, and then decreased. Delta eQTI in patients with reduced cardiac function (EF <40%) was significantly greater than that in normal cardiac function (EF >55%, 7.6+/-4.9 vs 2.7+/-9.8 ms, p<0.05). There was significant negative correlation between EF and delta eQTI (r=-0.63, p<0.05). The peak of changes in eQTI according to AV delay variations was steeper in patients with reduced cardiac function than in those with normal cardiac function. In conclusion, changes in eQTI according to AV delay variation are greater in patients with reduced cardiac function than in those with normal cardiac function, and the AV delay that gives the maximal eQTI can be easily determined in patients with reduced cardiac function.

Novel Method of Predicting the Optimal Atrioventricular Delay in Patients With Complete AV Block, Normal Left Ventricular Function and an Implanted DDD Pacemaker

“…[14][15][16][17] In the present study, we observed that the correlation between the amplitude of S1 and the length of the AV delay was represented as a cubic curve. Furthermore, the AV delay at the inflection point of this cubic curve showed a significant positive correlation with the optimal AV delay determined by echocardiography (R=0.925, P<0.005).…”

Rate-Responsive Cardiac Pacing: Technological Solutions and Their Applications

“…Under exercise or stress conditions, myocardial contractility increases in response to autonomic nervous system regulation, resulting in a change in the duration of the QT interval corresponding to the period of ventricular repolarization [ 70 , 71 , 72 ]. The atrioventricular interval, depending on the native atrioventricular conduction time or the programmed A-V interval settings on the pacemaker, is also closely related to the QT interval [ 73 , 74 , 75 , 76 ]. Recent studies describe the phenomenon of QT adaptation as an abrupt change in the rate or interruption of atrial and ventricular pacing; this is indicative of the complexity of the phenomenon and the existence of many potential factors (extrinsic, such as pacing, and intrinsic, such as pharmacotherapy of conduction dysfunctions, electrolyte disturbances, or short- or long-QT syndromes) that can affect this parameter [ 77 , 78 , 79 , 80 , 81 ].…”