QT dispersion during DDD and VVI pacing

The purpose of the present study was to evaluate alterations in QT dispersi on (QTd) as a result of different pacing modes and programmed AV delay inte rvals. Material and Methods: We studied 60 patients (38M and 22F) with a mean age of 67.5+/-7.5 years in whom DDD pacemakers were implanted due to complete atrioventricular block. Coronary artery disease was diagnosed in 10 patients, arterial hypertensio n in 14, and coronary artery disease combined with arterial hypertension in 27 patients. The remaining patients served as controls. In all cases basic rate of the pacemaker was programmed at 70 bpm. ECG at rest showed all atr ial and ventricular complexes captured. AV delay was optimised based upon t he measurements of stroke volume (SV) by Doppler echocardiography. QT inter vals were measured from the 12-lead ECG at 50 mm/s paper speed. QTd was cal culated as the difference between maximal and minimal QT interval. It was m easured at optimal (DDDopt) and unoptimal (DDDn.opt) (with lowest SV) progr ammed AV intervals and then in VVI mode after 24 hours following reprogramm ing the pacemaker. Results: We found a negative correlation between SX and QTd (r = -0.65). In VVI mode SV was significantly lower than in DDDn.opt (mean 78.7 vs. 90.0 ml, p<0.00 1) and QTd was significantly greater (mean 74.3 vs. 69.2 ms, p<0.001). In C AD and AH patients the correlation of SV and QTd was stronger (r = -0.68 an d r = -0.54, respectively) as compared to the controls (r = -0.31). Conclusion: Programming different AV intervals and pacing modes significantly influence s QTd. QTd reflects the hemodynamic status of patients with pacemakers.