[Effect of propranolol on the cardiac rhythm variability and the cardiac cycle phase structure in healthy volunteers].

In an acute pharmacological test in 13 healthy volunteers (24 +/- 4) years old effects were studied of propranolol, 40 mg/50 kg body mass, on the sympathovagal regulation and phase patterns of the cardiac cycle. The study was made with the aid of the computer electrocardiograph "Cardiolab 2000" at the height of the propranolol effect by standard methods. The state of the sympathovagal regulation was assessed by the heart's rhythm variability technique with respect to the spectrum lowfrequency and highfrequency ranges powers. There have been measured duration of the P-wave, PQ-interval, QRS-complex, QT-interval to analyze phase patterns of the cardiac cycle. One-dose intake of propranolol has been shown to optimize the sympathovagal balance by boosting the influence of that portion of the autonomic nervous system, whose baseline activity has been shown to be slight. Optimization of the sympathovagal balance was accompanied by general enhancement of the level of neurohumoral regulation. Effect of propranolol on the phase patterns of the cardiac cycle was invariant from the baseline state and from subsequent changes in the sympathovagal balance.