Transthoracic Ultrasound Improves Cardiac Function in Mice.

Abstract

Cardiac dysfunction is a severe complication that is associated with an increased risk of mortality in multiple diseases. Cardioprotection solution that has been researched is the electrical stimulation of the vagus nerve to exert cardio protection. This method has been shown to reduce the systemic inflammatory response and maintain the immune homeostasis of the heart. However, the invasive procedure of electrode implantation poses a risk of nerve or fiber damage. Here, we propose transthoracic ultrasound stimulation (US) of the vagus nerve to alleviate cardiac dysfunction caused by lipopolysaccharide (LPS). We developed a noninvasive transthoracic US system and exposed anesthetized mice to ultrasound protocol or sham stimulation 24 h after LPS treatment. Results showed that daily heart targeting US for 4 days significantly increased left ventricular systolic function ( p = 0.01) and improved ejection fraction ( p = 0.03) and shortening fraction ( p = 0.04). Furthermore, US significantly reduced inflammation cytokines, including IL-6 ( p = 0.03) and IL- 1β ( p = 0.04). In addition, cervical vagotomy abrogated the effect of US, suggesting the involvement of the vagus nerve's anti-inflammatory effect. Finally, the same ultrasound treatment but for a longer period (14 days) also significantly increased cardiac function in naturally aged mice. Collectively, these findings suggest the potential of transthoracic US as a possible novel noninvasive approach in the context of cardiac dysfunction with reduced systolic function and provide new targets for rehabilitation of peripheral organ function.