PACING PARAMETERS CHANGES IN PATIENTS WITH IMPLANTED PACEMAKER IN DIFFERENT QRS COMPLEX DURATION CLASSES AT THE ANNUAL OBSERVATION STAGE

100 patients (46 ? women, 54 − men) 69 ± 7 years old with implanted pacemaker in three QRS complex duration classes (under 120, 120-149, 150 and more ms) were investigated in the early postoperative period, six months and a year of permanent pacing. Basic pacing rate, atrioventricular (AV) delay (stimulated and detected), ventricular threshold, ventricular lead impedance, percentage of ventricular pacing, percentage of atrial fibrillation/flutter time were measured. Basic pacing rate, stimulated and detected AV-delay, as well as the percentage of ventricular pacing were not associated with QRS complex duration classes and had not been changed in observation stages. Ventricular threshold, ventricular lead impedance and the percentage of atrial fibrillation/atrial flutter time in the annual monitoring stage were defined to QRS complex duration class. Ventricular threshold in the first six months of observation was not changed in any QRS complex duration classes and grew at an annual stage in class 3. The impedance of the ventricular lead in the first six months decreased in all classes, it was stabled at the year in classes 2 and 3 and was continued to decline in the class 1. Percentage of atrial fibrillation/flutter time was initially higher in class 3, and was decreased in six month observation stage, however, without reaching the values in classes 1 and 2.