Septal Ablation Induced by Transthoracic High-Intensity Focused Ultrasound in Canines

doi:10.1016/j.echo.2013.06.020

Journal of the American Society of Echocardiography

Volume 26, Issue 10, October 2013, Pages 1228-1234

https://doi.org/10.1016/j.echo.2013.06.020 Get rights and content

Background

High-intensity focused ultrasound (HIFU) can achieve accurate and focused deep tissue ablation through an extracorporeal emission. Cardiac ablation using HIFU applied transthoracically must overcome potential interference from intervening thoracic structures. The aim of this study was to explore the efficacy and safety of septal ablation that was induced using transthoracic HIFU.

Methods

Twenty-one canines were pretreated to improve acoustic transmission. Single ablations were induced by targeting transthoracic HIFU with acoustic power of 400 W for 3 sec at the middle and basal septum in eight canines. Extended ablations were performed to create larger lesions at the basal septum in eight more canines. The three-dimensional morphology of a basal septum lesion induced by a single ablation was analyzed. The temperature at the ablative targets was measured in the other five canines.

Results

The cardiomyocytes in the lesions underwent necrosis with a clear boundary. The three-dimensional morphology of the lesions appeared approximately as ellipsoids with a flatter endocardial side. The peak temperature at a power of 400 W for 3 sec was 93.27 ± 2.54°C, and it remained >50°C for nearly 10 sec. No procedure-related complications were observed.

Conclusions

Ultrasound-guided transthoracic HIFU has the potential to safely create small dot or large mass lesions in the septum without a thoracotomy or a catheter.

Section snippets

HIFU Apparatus for Transthoracic Septal Ablation

The model JC200 HIFU tumor therapeutic system (Chongqing Haifu Technology Co. Ltd., Chongqing, China) was used. This system includes the following components: an ultrasound therapeutic transducer, an ultrasound imaging unit, a degassed water circulation unit, a motion unit, an operator console, and an ultrasound signal generator (Figure 1). The therapeutic transducer has a diameter of 22 cm, a focal length of 148 mm, and an operating frequency of 1.03 MHz. The acoustic focal region is an

Overall Procedural Considerations

Each dog received an artificial hydrothorax without obvious complications. No vital sign disturbances were observed. The artificial hydrothorax successfully improved the ultrasound transmission (Figure 4). All of the canines, except five from group C, underwent HIFU-induced ablation and were maintained with normal respiratory rhythm, appetite, and activity level. The canines in group C were sacrificed because of the tamponade caused by retrieving the optic fiber after the temperature

Discussion

Our results demonstrated that cardiac septal ablation could be achieved and extended using transthoracic ultrasound-guided HIFU in canines. The lesions displayed full coagulation necrosis with a clear boundary that distinguished the surrounding normal tissue. In addition, no significant injuries were observed in the surrounding tissues near the target or along the acoustic path.

Conclusions

Ultrasound-guided transthoracic HIFU has the potential to safely create small dot or large mass lesions in the septum without a thoracotomy or a catheter. These findings suggest that transthoracic HIFU may be developed as an alternative noninvasive, nonradiation strategy for intramyocardial ablation.

Acknowledgments

We thank Professor Shunhe Wang from the Department of Pathology at Chongqing Medical University for advice on the histologic analysis. We thank Dr. Rong Jiang from the Department of Histology and Embryology at Chongqing Medical University for technical support for the tissue preparations and histologic analysis.

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: This work was supported in part by research grants from the National Natural Science Foundation of China (30527001 and 30830040), the National Key Basic Research Program of China (973 Program, 2011CB707902), and the Foundation for Key Scientific and Technical Research of Chongqing, China (CSTC2005AA5008-5 and CSTC2009AB5003). Zhibiao Wang is a shareholder in Chongqing Haifu and a professor in the Department of Biomedical Engineering of Chongqing Medical University, Chongqing, China.

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Pre-Clinical InvestigationSeptal Ablation Induced by Transthoracic High-Intensity Focused Ultrasound in Canines

Background

Methods

Results

Conclusions

Section snippets

HIFU Apparatus for Transthoracic Septal Ablation

Overall Procedural Considerations

Discussion

Conclusions

Acknowledgments

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J Am Soc Echocardiogr

J Am Soc Echocardiogr

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Am Heart J

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High-intensity focused ultrasound in the treatment of solid tumours

Nat Rev Cancer

Primary bone malignancy: effective treatment with high-intensity focused ultrasound ablation

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Pre-Clinical Investigation
Septal Ablation Induced by Transthoracic High-Intensity Focused Ultrasound in Canines