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Introduction: In patients (pts) with heart failure (HF) qualified to cardiac resynchronization therapy (CRT), the left ventricular pacing (LV) is an alternative treatment method to biventricular pacing (BiV). The aim of the study was to compare the influence of LV vs BiV pacing on the spectral indexes of HRV in patients with HF. Material and methods: 17 pts (mean age 60+11years) with nonischemic cardiomyopathy, HF (NYHA III) , QRS duration >120ms and EF<35% were studied after implantation of CRT device. The 5-minute ECG recording were performed during BiV and LV pacing. The power spectral density within two frequency bands: 0,04-0,15 Hz (LF) and 0,15-0,4 Hz (HF) was computed by autoregression method and the ratio of LF/HF was calculated. Results: Patients according to LH/LF during BiV were divided into 2 groups: 1st - consisted of 8 pts with LF/HF>1 and 2nd of 9 pts with LF/HF<1. In 1st group LV vs. BiV pacing did not cause significant modification of HRV measures. In 2nd group LV pacing not impact on HF too, however provoked non significant rise of LF (65+60 vs 107+120 ms2, p=0,09) and significant increase of LF/HF (0,7+0,1 vs 1,13+0,7 ms2, p<0,05). Among these 9 pts, in 3 pts, an considerable elevation of LF/HF was observed. Conclusion: In some patients with HF and predominance of parasympathetic activity during BiV pacing, a switch to LV pacing provokes a modification of sympatho-vagal balance to predominance of sympathetic tone. (Clin Exp Med Lett 2009; 50(1)29-31)

Keywords: Spectral analysis, heart rate variability