Authors:
Andrew Fleischman, Christopher Vecchio, Youhan Sunny, Christopher R. Bawiec, Peter A. Lewin, J. Yasha Kresh, & Andrew R. Kohut
Summary:
Isolated neonatal rat ventricular cardiomyocytes were used to study the influence of ultrasound on the chronotropic response in a tissue culture model. The beat frequency of the cells, varying from 40-90 bpm, was measured based upon the translocation of the nuclear membrane captured by a high-speed camera. Ultrasound pulses (frequency = 2.5 MHz) were delivered at 300 ms intervals (3.33 Hz Pulse Repetition Frequency (PRF)), in turn corresponding to 200 pulses per minute. The intensity of acoustic energy and pulse duration were made variable, 0.02-0.87 W/cm2 and 1-5ms, respectively. In 57 of 99 trials, there was a noted average increase in beat frequency of 25% with 8 second exposures to ultrasonic pulses. Applied ultrasound energy with a spatial peak time average acoustic intensity (Ispta) of 0.02 W/cm2 and pulse duration of 1 ms effectively increased the contraction rate of cardiomyocytes (p < 0.05). Of the acoustic power tested, the lowest level of acoustic intensity and shortest pulse duration proved most effective at increasing the electrophysiological responsiveness and beat frequency of cardiomyocytes. Determining the optimal conditions for delivery of ultrasound will be essential to developing new models for understanding mechano-electrical coupling (MEC) and understanding novel non-electrical pacing modalities for clinical applications.
Source:
Journal of Applied Physiology; (04/09/15)