Effects of Heart Rate on the Pump Function and Electrophysiological Characteristics of the Heart in the Frog Rana temporaria

Natalya A. Kibler, PhD¹; Vladimir P. Nuzhny, PhD, ScD¹; Svetlana V. Achmetzhynova², Dmitry N. Shmakov¹

¹Institute of Physiology, Komi Science Center, Urals Branch of the RAS, ²Syktyvkar State University named after Pitirim Sorokin; Syktyvkar, Komi Republic, the Russian Federation

*Corresponding author: Natalya A. Kibler, PhD; Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Urals Branch of the RAS,Syktyvkar, Komi Republic, Russia. E-mail address: natanadya@mail.ru

Published: March 17, 2017.  doi: 10.21103/Article7(1)_OA5


The aim of the study was to investigate the electrical activity and contractility of the heart ventricle in frogs Rana temporaria (n=14) under different heart rates. The activation time (AT, as dV/dtmin during QRS complex), the repolarization time (RT, as dV/dtmax during ST-T wave), and the activation-recovery intervals (ARIs, as difference between RT and AT) were measured. The hemodynamic variables were determined with the Prucka MacLab 2000 system. Heart rate (HR) was changed by the use of right atrium pacing from 0.6 to 1.1Hz with step 0.1Hz. The increasing HR from 0.6 Hz to 1.1Hz led to the increased duration of ARIs on the ventral and dorsal fragments of ventricular epicardium as compared with initial sinus rhythm.  During the high HR, more prolonged ARIs were observed on the ventral side of the epicardium than on the dorsal surface (exclusion is supraventricular rhythm with rate of 1.1Hz). The repolarization dispersion of epicardium on the whole, as well as repolarization of both epicardial sides separately, decreased under the higher rate. Repolarization sequence depended on the activation sequence and the distribution of local repolarization durations only at supraventricular rhythm with a frequency of 1.1Hz. The indexes of pump function decreased under high HR.
Thus, the increased HR resulted in a decrease in the dispersion of repolarization and ARIs; the repolarization duration of ventricular epicardium at supraventricular rhythms was shortened as compared with sinus rhythm. During an increase in HR, repolarization sequence is formed in association with the level of ARI dispersion and changes of the repolarization duration.

ventricular pump function ● heart rate ● depolarization ● repolarization, activation-recovery intervals ● frog Rana temporaria

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International Journal of Biomedicine. 2017;7(1):46-50. © 2017 International Medical Research and Development Corporation. All rights reserved.