Age-related propofol effects on electrophysiological properties of isolated hearts

We compared the direct effects of propofol on the conduction system of neonatal (< 7 days) and adult (> 3 mo) rabbit hearts using intracardiac recording/ stimulation in Langendorff-perfusion and autonomic blockade. At a low concentration (3 microM), propofol caused a slight but significant lengthening of the atrio-ventricular (AV) conduction interval of the adult hearts, but not of neonatal hearts. At a higher concentration (10 microM and above), propofol significantly prolonged the AV conduction interval in a frequency-dependent manner in both neonates and adults. The AV Wenckebach cycle length was also lengthened, with the change more significant in the adults. However, with concentrations of propofol up to 100 microM, the neonatal hearts frequently (9 of 13 experiments) progressed to complete AV block, which was not observed in the adults. Conduction through the atrial tissue (SA interval) and the His-Purkinje system (HV interval), as well as the spontaneous heart rate, were all slowed by propofol at 30 microM or above. However, the lengthening of SA interval was more pronounced in the neonates, and only in the neonate was the atrial refractory period prolonged by propofol at 10 microM and above. We conclude that 3 microM propofol produces no significant direct effects on the neonatal cardiac electrophysiological properties, although AV conduction of the adult heart may be suppressed at this concentration of propofol. At higher concentrations, age-related propofol effects were demonstrated in the AV node and the atrial tissue.