Summary:The opioid system plays a role in the regulation of the cardiovascular system. Endogenic as well as egzogenic administration of opioids influences the heart rhythm This work was undertaken in order to assess the influence of crossover activity of the heart opioid system on the heart conduction system in patients with various disturbances of rhythm having an efficient circulatory system and a normal 12-lead stationary ECG. Subjects were 20 patients (9 men and 11 women of mean age of 38.7 years) reporting sudden heart palpitations. They were subjected to invasive programmable electrophysiological studies (PES). Naloxone was administered intravenously to 10 patients. Pentazocine was administered in the same way. In the remaining 10 patients the order of drug administration was reversed. PES was done in the basic state and after the administration of each drug. Study results were subjected to stati\tical analysis with no-parameter Wilcoxon test assuming differences to be significant at p<0.05. Blocking of the opioid system resulted in signiticant lengthening of the \inontrial (SACT), intra-atrial (PA), and atrioventricular node (AH) conduction times, while no changes were induced in conduction in the His-Purkinje system (HV) and automation of the sinus node. Naloxone lengthened the atrial (ERPA) and atrioventricular node (ERPA AVN) effective refractory periods. Stimulation of the opioid sys- tem resulted in decreases of the following values: SACT, PA, AH, ERPA, ERPA AVN, while no effect was exerted on the SNRT, HV, ERPV. Neither drug influenced the QRS time, although naloxone lengthened QT, period significantly. Opioids did not influence the time of conduction in concealed extranodal atrioventricular pathways. Results of the studies suggest that the opioid system has a significant influence on electrophysiological properties of the proximal part of the heart conduction system-blocking the opioid system renders the conduction difticult, while stimulating favors it.

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