Cardiovascular applications of therapeutic ultrasound

Abstract

Ultrasound (US) has gained widespread use in diagnostic cardiovascular applications. At amplitudes and frequencies typical of diagnostic use, its biomechanical effects on tissue are largely negligible. However, these parameters can be altered to harness US's thermal and non-thermal effects for therapeutic indications. High-intensity focused ultrasound (HIFU) and extracorporeal shock wave therapy (ECWT) are two therapeutic US modalities which have been investigated for treating cardiac arrhythmias and ischemic heart disease, respectively. Here, we review the biomechanical effects of HIFU and ECWT, their potential therapeutic mechanisms, and pre-clinical and clinical studies demonstrating their efficacy and safety limitations. Furthermore, we discuss other potential clinical applications of therapeutic US and areas in which future research is needed.

Figures

Fig. 1

Schematic and ex vivo microscopy images of non-thermal vascular effects of therapeutic ultrasound. Top row demonstrates microstreaming (a), jetting (b, c), bubble expansion/compression (d, e). Bottom row images demonstrate interaction of lipid-coated perfluoropropane ultrasound contrast bubbles with capillary walls (injected with Green India Ink for contrast) in ex vivo rat mesentery, during HIFU treatment, under 40× high-speed microscopy [9, 10]

Fig. 2

Comparison of ECWT (a) and HIFU (b) waveforms. Note the continuous HIFU waveform with a dedicated frequency, compared with the higher pressure/amplitude, single waveform of ECWT

Fig. 3

HIFU-BC (balloon catheter) developed by ProRhythm (Ronkonkoma, NY, USA) for circumferential pulmonary vein isolation