THRESHOLDS FOR PREMATURE CONTRACTIONS IN MURINE HEARTS EXPOSED TO PULSED ULTRASOUND

A single pulse of high intensity ultrasound can produce either a prema ture ventricular contraction or a reduction in the aortic pressure in frog hearts, The objective of this study was to determine whether simi lar ultrasound exposures can produce premature contractions in the mam malian heart. The cardiac activity of murine hearts in vivo was monito red noninvasively using electrocardiography and plethysmography, Each ultrasound exposure was a single pulse of ultrasound, several millisec onds in duration, delivered to the murine heart during diastole, The t hreshold for producing a premature contraction with a 5-ms ultrasound pulse at 1.2 MHz was similar to 2 MPa peak positive pressure, The occu rrence of premature contractions decreased as the duration of the ultr asound pulse decreased. These results found with the mammalian heart a re similar to those reported earlier for the frog heart, No damage to cardiac tissue was observed grossly, although significant hemorrhage o ccurred to adjacent lung tissue. (C) 1997 World Federation for Ultraso und in Medicine and Biology.