Key result
Increasing heart rate via atrial pacing up to 60 bpm in rainbow trout and 44 bpm in frogs at low ambient temperatures significantly decreased myocardial contractility and deteriorated ventricular pumping function.
Why the study?
Does increasing heart rate via atrial pacing improve the pumping function of the heart ventricle in cold-blooded animals under low ambient temperature conditions?
Does increasing heart rate via atrial pacing improve the pumping function of the heart ventricle in cold-blooded animals under low ambient temperature conditions?
Increasing heart rate beyond physiological norms in cold-blooded animals at low temperatures deteriorates rather than improves ventricular pumping function.
Answers are grounded in this paper and cite their sources.
Challenges presumed benefit of higher rates for ventricular function in hypothermic ectotherms; leaves open translation to mammalian models.
This study investigated the effect of heart rate (HR) on the pumping function of the heart ventricle (HV) in rainbow trout Oncorhynchus mykiss acclimated to a temperature of 5-7C, and in adult frogs Rana temporaria at an ambient temperature of 10-12C. The dynamics of intracavitary ventricular pressure was recorded by transmural catheterization. HR was changed by atrial electrocardiostimulation. The increase in HR in rainbow trout resulted in a decrease in the maximal systolic ventricular pressure (MSVP), an increase of end-diastolic ventricular pressure (EDVP), and a reduction in the maximum rates of the rising and falling pressures. In the frog, MSVP and isovolumic parameters (dP/dt max and dP/d tmin ) also decreased as HR increased from 24 bpm to 42 bpm. The preload of the frog's HV did not change significantly, compared to the sinoatrial rhythm (SR). The maximum increase in the frequency of atrial stimulation up to 60 bpm in fish and up to 42 bpm in frogs resulted in a significant decrease in the myocardial contractility and deterioration of the pumping function of HV under low ambient temperature conditions.
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Киблер et al. (2020) studied Ventricular pumping function in cold-blooded animals (n=28). Atrial electrocardiostimulation (increased heart rate) vs. Sinoatrial rhythm was evaluated on Maximal systolic ventricular pressure (MSVP) and isovolumic parameters (p=<0.05). Increasing heart rate via atrial pacing up to 60 bpm in rainbow trout and 44 bpm in frogs at low ambient temperatures significantly decreased myocardial contractility and deteriorated ventricular pumping function.
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