A study on premature ventricular contractions caused by ultrasound exposure with microbubbles using cultured cardiac myocytes

It has been shown that diagnostic ultrasound examination using a contrast agent can cause premature ventricular contractions (PVC). In this study, we investigated the usefulness of a new technique using cultured cardiac myocytes to study mechanisms of PVC production. Cardiac myocytes isolated from neonatal rats were cultured on a cover glass. Synchronized autonomous pulsation of myocytes started after incubation for one week. The cover glass was then attached to an observation chamber so that it was possible to observe changes in myocytes during exposure to ultrasound. In the experiments, cardiac myocytes were exposed to pulsed ultrasound with and without microbubbles. The peak negative pressure amplitudes were set at five steps (-0.28, -0.55, -0.73, -0.92 and -1.1 MPa), and threshold pressure to produce a PVC was recorded. The results showed that the presence of microbubbles attached to a cell reduces the threshold pressure for producing PVC, and it was concluded that our method is useful for studying the mechanisms of PVC production.