Transthoracic cardiac ultrasonic stimulation induces a negative chronotropic effect

Abstract

The objective of this study is to investigate cardiac bioeffects resulting from ultrasonic stimulation using a specific set of acoustical parameters. Ten Sprague–Dawley rats were anesthetized and exposed to 1-MHz ultrasound pulses of 3-MPa peak rarefactional pressure and approximately 1% duty factor. The pulse repetition frequency started slightly above the heart rate and was decreased by 1 Hz every 10 s, for a total exposure duration of 30 s. The control group was composed of five rats. Two-way analysis of variance for repeated measures and Bonferroni post hoc tests were used to compare heart rate and ejection fraction, which was used as an index of myocardial contractility. It was demonstrated for the first time that transthoracic ultrasound has the potential to decrease the heart rate by ~20%. The negative chronotropic effect lasted for at least 15 min after ultrasound exposure and there was no apparent gross damage to the cardiac tissue.

The role of the duty factor in ultrasound-mediated cardiac stimulation

“…Because there were no signs of major problems to animals exposed to the pulsed sequence, 11 animals were allowed to recover.…”

“…A previous study 11 demonstrated that transthoracic ultrasound can promote a negative chronotropic effect without impairing cardiac pumping function and/or damaging cardiac tissue. 11 This effect was achieved using a specific sequence of 1-MHz ultrasonic bursts delivered transthoracically to the heart, progressively decreasing the PRF while maintaining the same DF.…”

“…11 This effect was achieved using a specific sequence of 1-MHz ultrasonic bursts delivered transthoracically to the heart, progressively decreasing the PRF while maintaining the same DF. The goal of this study is to investigate the DF role in cardiac pacing.…”

Ultrasound-induced heart rate decrease: role of the vagus nerve

“…Therapeutic effects of cardiac ultrasound have been examined through in vitro and in vivo studies [2]–[9]. In vitro cardiac tissue observations in frogs, guinea pigs, rats, dogs, and pigs included defibrillation [3], premature contraction of myocardium [7], [10]–[12], negative chronotropic effect [9], and positive inotropic/lusitropic effect [13].…”

“…Therapeutic effects of cardiac ultrasound have been examined through in vitro and in vivo studies [2]–[9]. In vitro cardiac tissue observations in frogs, guinea pigs, rats, dogs, and pigs included defibrillation [3], premature contraction of myocardium [7], [10]–[12], negative chronotropic effect [9], and positive inotropic/lusitropic effect [13]. In vivo observations of pulsed ultrasound (US) delivered to the animal heart caused a variety of effects such as intravascular bubbles [4], arrhythmias [5], changes in cardiac rhythm and aortic pressure [6], and cardiac pacing [8].…”