Is the isolated heart a relaxation-oscillator?

The heart is the main organ of the circulatory system. It is in charge of carrying out two essential functions for life: providing nutrients to all cells and collecting carbon dioxide in the periphery of the body for its subsequent gaseous exchange. The isolated heart preparation allows a definitive evaluation of cardiac contractile function directly on the heart without interactions with other tissues and organs present in the body. This study aimed to investigate whether cardiac contraction can be considered as a relaxation-oscillator. When stimulating in the early stages of the contractile cycle, the results show a decrease in the time of occurrence of the poststimulus event, while in intermediate stages, the time of occurrence increases. However, the stimulus has a more significant impact on the temporality and morphology of the second postdisturbance event, resulting in an incomplete or barely noticeable contraction.