DRUG-REFRACTORY DILATED CARDIOMYOPATHY TREATED WITH DDD PACING - EVALUATION OF THE SYMPATHOVAGAL BALANCE IN A LONG-TERM PERIOD

The aim of this study was to assess the long term efficacy of DDD paci ng mode in selected patients (pts) with idiopathic dilated cardiomyopa thy (IDCM) and drug refractory heart failure. The pts were evaluated a ccording to the long term alteration of the sympathovagal balance (SVB ). Pts with IDCM were considered eligible for DDD pacing if during tem porary VDD pacing a 15% or more increase in the resting cardiac output was demonstrated. From 29 pts studied, 20 pts (15M, 5F, 69+/-10 years ) were considered candidates for permanent DDD pacing (NYHA class: 3,5 +/- 0,3, Ejection fraction:27+/- 7%, Resting cardiac index (CI) 2,6+/- 0,4L/min). The ECG of the pts demonstrated LBBB in 13, RBBB in 4 and RBBB+LAH in 3, with a PR of 232+/- 28 ms and QRS of 138+/- 15ms. The p acemaker was programmed at 40-150 bpm, and AV delay 105+/- 20ms. We ev aluated the SVB in the pre and post-implant periods (3rd and 6th month ), using the hourly power spectral analysis (PSA) of heart rate variab ility during 24 hour Holter monitoring. As SVB we considered the ratio : low (0,04-0,15 Hz) to high frequency (0,15-0,40 Hz). We compared the SVB (LF/HF) during the day and night time for the pre and post implan t periods. Post pacing the NYHA class was significantly improved (2,9/- 0,2 and 2,7+/- 0,3 the 3rd and 6th month respectively). During the night time the LF/HF; decreased from 1.45+/- 0.2 in the pre-implant pe riod to 0.9+/- 0.09 (p<0.001) in the 3rd month. No further changes wer e observed in the 6th month (0.82+/- 0.05, p=NS) compared to the 3rd m onth. During the day time the LF/HF decreased from 1.5+/- 0.5 to 1.43/- 0.6 (p=NS) in the 3rd month and to 1.41+/- 0.09 in the 6th month (p =NS). Comparing the day and the night time, while in the pre-implant p eriod there was no significant difference (1.5+/- 0.5 vs 1.45+/- 0.2, p=NS), the difference became significant in the 3rd (1.43+/- 0.6 vs 0. 9+/- 0.09, p<0.001) and the 6th month (1.41+/- 0.09 vs 0.82+/- 0.05, p <0.001). In conclusion, DDD pacing with individualized AV delay as an adjunct therapy, could be a valuable method in selected pts with IDCM and drug refractory heart failure. DDD pacing improves the SVB in a lo ng term period. This improvement is attributed to sympathetic activity withdrawal and is more pronounced during night and less during day ti me.