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Introduction: Our study was designed to analyze dynamic changes in autonomic tone before the onset of typical sustained atrioventricular nodal reentry tachycardia (AVNRT) in a large group of patients without structural heart disease. Materials and Methods: Twenty-four-hour Holter tapes from 42 consecutive patients (27 men and 15 women; aged 30 ± 21 years) with several episodes of sustained typical AVNRT were analyzed. The diagnosis was validated by transesophageal electrophysiological study. The time-domain calculated parameters were SDNN, SDANN, rMSSD, pNN50; the frequency-domain parameters were low-frequency power (LF, 0.04–0.15 Hz), high-frequency power (HF, 0.15–0.40 Hz), very low-frequency power (VLF, 0.008 to 0.04 Hz) and LF/HF. The mean values in the hour before the onset of sustained AVNRT were compared with the mean values of 2 hours before and 1 hour after the onset of sustained AVNRT. Results: The mean SDNN, rMSSD, pNN50, HF were significantly decreased during the hour preceding the onset of AVNRT, when compared to the mean values observed during the time periods selected. Instead, the LF values and LF/HF were increased before the onset of sustained AVNRT. No significant change in the VLF and atrial ectopic beats were observed. Conclusion: This study suggests that sustained typical AVNRT episodes are preceded by increase in adrenergic drive. Ann Noninvasive Electrocardiol 2010;15(1):49–55

Aim: We performed a two-year follow-up comparative study of long-term electrical parameters between the right atrial appendage (RAA) and Bachmann’s Bundle (BB) stimulation in myotonic dystrophy type 1 (MD1) patients. Methods: Twenty-five MD1 patients (18 men; age: 54 ± 13 years) with no difference in the electrical parameters between the RAA site and the BB region at implantation were randomized into two groups: in group I (13 patients; age: 52 ± 14 years; four women) the atrial lead was placed in the RAA and in group II (12 patients, age: 56 ± 12 years, three women) the lead was placed in the BB region. Measurements of electrical parameters were recorded at follow-up intervals of 6 weeks and then 12 and 24 months postimplant. Results: There was no statistically significant different in P-wave amplitude, pacing threshold, and impedance values between the two groups at 6 weeks. At 24 months follow-up, the intrinsic P-wave amplitude was 2.05 ± 1.45 mV in the RAA group versus 3.28 ± 1.09 mV in the BB group (P < 0.05); the pacing threshold was 1.85 ± 1.8 V in the RAA group versus 0.50 ± 0.39 V in the BB group (P = 0.03); there were no differences in the atrial impedance between the two groups during the follow-up period. Conclusions: In a direct two-year follow-up comparison between the RAA and BB atrial pacing sites, we showed a statistically significant increased pacing threshold and decreased intrinsic P-wave amplitude during RAA stimulation in MD1 patients. (PACE 2009; 32:1191–1196) Bachmann’s bundle, myotonic dystrophy, pacemaker, arrhythmias, heart block, fibrosis, sensing,pacing, impedance, atrial lead