Background: The results of stem cell therapy after myocardial infarction (MI) have been conflicting. The effects of this therapy on ventricular arrhythmias and autonomic control of heart rate have not yet been established.

Aim: To assess the effects of bone marrow cell (BMC) transplantation on the occurrence of arrhythmias and heart rate variability (HRV) parameters in short-term observation after ST-elevation myocardial infarction (STEMI).

Methods: Sixty patients with STEMI who underwent primary PCI, were randomly assigned to two groups: Group 1 - 36 patients selected for active treatment (autologous BMC, intracoronary injection mean 7 days after STEMI), and Group 2 - 24 control patients not treated with BMC transplantation. In all patients the infarct-related artery was the left anterior descending, and the left ventricular ejection fraction was < 40%. Two Holter sessions were performed: at baseline (HM1), on average 6 days after MI, and another one (HM2), 1 month after BMC implantation. From these recordings the frequency of non-sustained ventricular tachycardia (nsVT) episodes and the parameters of HRV were calculated.

Results: Both groups were comparable with regard to demographic data, the presence of risk factors and electrocardiographic parameters. In HM2 examination the frequency of nsVT tended to be higher in Group 1 (25 vs. 12.5%, NS). The HRV analysis showed lower HF and significant SDNN increase in the BMC group. In controls all the HRV parameters increased. The increase in HF was significantly lower in the BMC group than in controls (22.4 vs. 89.2 ms(2), p $lt 0.011).

Conclusions: 1. During the first month after the intracoronary injection of BMC, non-significant increase of nsVT was observed. 2. The lack of significant increase in HF power after BMC infusion may be a sign of depressed parasympathetic tone.