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Ultrasound Med Biol. 2015 Feb;41(2):432-48. doi: 10.1016/j.ultrasmedbio.2014.09.009. Epub 2014 Dec 13.

Electrophysiological changes correlated with temperature increases induced by high-intensity focused ultrasound ablation.

Author information

1
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
2
Department of Biomedical Engineering, Washington University at Saint Louis, MO, USA.
3
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA. Electronic address: xdeng@umich.edu.

Abstract

To gain better understanding of the detailed mechanisms of high-intensity focused ultrasound (HIFU) ablation for cardiac arrhythmias, we investigated how the cellular electrophysiological (EP) changes were correlated with temperature increases and thermal dose (cumulative equivalent minutes [CEM43]) during HIFU application using Langendorff-perfused rabbit hearts. Employing voltage-sensitive dye di-4-ANEPPS, we measured the EP and temperature during HIFU using simultaneous optical mapping and infrared imaging. Both action potential amplitude (APA) and action potential duration at 50% repolarization (APD50) decreased with temperature increases, and APD50 was more thermally sensitive than APA. EP and tissue changes were irreversible when HIFU-induced temperature increased above 52.3 ± 1.4°C and log10(CEM43) above 2.16 ± 0.51 (n = 5), but were reversible when temperature was below 50.1 ± 0.8°C and log10(CEM43) below -0.9 ± 0.3 (n = 9). EP and temperature/thermal dose changes were spatially correlated with HIFU-induced tissue necrosis surrounded by a transition zone.

KEYWORDS:

Bioeffects; Cellular electrophysiology; High-intensity focused ultrasound; Infrared imaging; Langendorff-perfused rabbit hearts; Optical mapping

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