DYNAMICITY OF THE VENTRICULAR REPOLARIZATION IN PACED PATIENTS WITH CONGESTIVE-HEART-FAILURE - INFLUENCE OF DIFFERENT PACING MODES

The QT interval dynamicity is related to the autonomous nervous system influence on the ventricular myocardium and it is associated to the s everity of structural heart disease. Aim of the study was to evaluate the dynamicity of ventricular repolarization in two different dimensio ns, space and time, in patients (pts) with congestive heart failure (C HF) during VVI and DDD pacing mode. We evaluated 28 pts (21M, 7F, 70+/ - 8 years) with CHF due to dilated (15 pts) or ischemic (13 pts) cardi omyopathy. All pts had a DDD pacemaker because of high degree AV block . All pts were evaluated during two periods of 24 hour duration, under DDD and VVI pacing mode at a lower heart rate of 75 bpm respectively. A 3 channel recorder, using the 3 plane Frank leads (XYZ) was connect ed to the pts. We considered as duration of ventricular repolarization , the interval between the ventricular spike and the T-wave apex (spik e-Ta). We measured the mean value of the spike-Ta interval (ms) for th e last 5 of a half minute of consecutive paced beats at the beginning of each hour separately, during VVI and DDD pacing mode. We compared t he mean value of spike-Ta interval during the day and night time perio d in VVI and DDD mode. The spike-Ta interval has a circadian behavior with higher values during the night and lower values during the day ti me. During the day time the spike-Ta interval was 321+/- 35 ms and 310 +/- 30 ms (p=NS) under DDD and VVI pacing mode respectively. During th e night time the spike-Ta interval was 378+/- 22 ms and 350+/- 17 ms ( p=0.016) under DDD and VVI pacing mode respectively. In conclusion, by evaluating the circadian dynamicity of the ventricular repolarization in paced pts with CHF, we found a less dynamic behavior during VVI th an DDD pacing mode.