Heart rate power spectral analysis in patients before and 6 weeks after coronary artery bypass grafting.

Decreased cardiac vagal activity is a known risk factor in coronary artery disease. The aim of our study was to determine the effect of coronary artery bypass grafting (CABG) on heart rate variability (HRV) before and 6 weeks after CABG. The study group consisted of 34 patients (4 women, 30 men, mean age 56 +/- 9 years). ECGs were recorded in 10 minutes periods in both supine and standing position with controlled breathing rate (0.25Hz). The analysis of HRV power spectrum was done by means of fast Fourier transformation. The total spectral power (TPS), power in very low frequency band (VLF: < 0.05 Hz), low frequency band (LF:0.05-0.15Hz), high frequency band (HF:0.15-0.5Hz), LF/HF ratio and percentage fraction of total power in these frequency bands (%VLF, %LF, %HF) were analysed. Significant attenuation of all spectral components of HRV were found during orthostatic load before CABG (p < 0.05). TPS, VLF, LF, %HF decreased in standing position to about half of their level in supine position, HF decreased to as little as one fourth, while LF/HF ratio and %LF increased significantly (p < 0.05). After the CABG these changes were not significant. We have found significant increase of HF (p < 0.05) and %HF (p < 0.01) in standing position after the CABG. The results suggest that CABG causes an improvement in cardiac vagal activity especially in standing position.

Bioavailability of isosorbide dinitrate from an oral therapeutic system and from tablet Sorbonit Prolongatum 20,0 in human volunteers.

The bioavailability of isosorbide dinitrate from an oral therapeutic system (OTS) and from tablet Sorbonit Prolongatum 20,0 mg in 6 volunteers employing a crossover method was studied. Concentrations of isosorbide dinitrate (1),2-mononitrate (2) and 5-mononitrate (3) are plotted as mean concentrations for all volunteers. As evident, the concentration-time curves are similar after administration of both OTS and tablet Sorbonit Prolongatum. Concentration of the nitrates in the serum is close to the maximum level starting 2 h after the drugs were administered. Such concentration is nearly constant for 7 h in the case of nonmetabolized 1 and for 9 h for its metabolites. 24 h after administration metabolites 2 and 3 were found in the serum of 5 subjects. Based on the experimental data, we calculated the areas under curves (AUC). The observed differences in AUC appeared statistically insignificant at the 95% confidence level for the two preparations studied in the case both 1 and its metabolites.