| Background: Arrhythmias are known as one of the leading causes ofdisable and death. Nowadays, it is estimated about7,000,000peopleworld-wide died from arrhythmias every year. Clinically, catheter ablationhas been investigated and proved to be an important strategy for cardiacarrhythmia treatment and over1,000,000cases of catheter ablation catheterablations are performed globally each year. However, catheter procedure isassociated with certain complications and limitations. Therefore, it isimperative to explore non-invasive, yet safe and efficient strategies formyocardial ablation.Purpose: To explore the feasibility of non-invasive atrioventricularjunction ablation using HIFU after improvement of the ultrasound transmission.Methods:18healthy mongrel canines of either sex were used in thestudy. Acoustic coupling was improved by degreasing, degassing andestablishing artificial pleural effusion in ultrasound path in all animals. Thetarget of HIFU was set at right side of the central fibrous body between thecuspis medialis and interventricular septum guided by echocardiography.After successful ablation, the last8animals received short-term pacing totest any recovery of ECG. The sample tissues of the target region and theultrasound path were obtained for macroscopical and histologicalexamination.Results: A clear cardiac2-demension ultrasound image can beobtained by producing artificial pleural effusion. Complete atrioventricularblock (AVB) was achieved in all21canines using400W×22.3±10.6s HFIUenergy. The duration of the ablation procedure was under average7minutes.The ablation lesion with a clear margin at the top part of interventricularseptum was observed grossly and necrosis of the conduction fiber was alsoconfirmed histologically. After2hours cardiac pacing in the8canines whichhad achieved complete artioventricular block, not any recovery ofatrioventricular conduction was observed on the ECG. In addition, only mildhemorrhagic injury in the inferior lobe of left lung was found in1animal, noother complications associated with the procedures were observed.Conclusion: Our results had demonstrated the feasibility of non-invasive atrioventricular junction ablation using HIFU. Furthermore,our findings indicate that the transthoracic HIFU for blocking cardiacconduction is safe and efficient, which may lent itself as an importantmethod for different types of ablation within the thoracic cavity independentof X-ray and catheter intervention. Background: Arrhythmias are known as one of the leading causes ofdisable and death. Clinically, catheter ablation using radio-frequency energyhas been investigated and proved to be an important strategy for cardiacarrhythmia treatment. However, catheter procedure is associated with certaincomplications and limitations. Our previous results had demonstrated thatnon-invasive atrioventricular junction ablation using HIFU is feasible afterproducing artificial pleural effusion. However, the previous study onlyevaluated the short-term efficacy and safety of blocking cardiac electricalconduction using HIFU.Methods:3healthy mongrel canines of either sex were used in thestudy. A pacemaker and a right ventricular electrode were implanted in3canines under the guidance of X-ray in the2weeks prior to receive ablation.Acoustic coupling was improved by degreasing, degassing and establishingartificial pleural effusion in ultrasound path in all canines. The target of HIFU was set at right side of the central fibrous body between the cuspismedialis and interventricular septum guided by echocardiography. Aftersuccessful ablation, the3animals were fed for3months for evaluating themid-term efficacy and safety of atrioventricular ablation using HIFU. Atendpoint, the sample tissues of the target region were obtained for gross,histological and immuno-histochemical examination.Results: A pacemaker was implanted in all the3canines. Afterproducing artificial pleural effusion a clear cardiac2-demension ultrasoundimage can be obtained. Complete atrioventricular block was achieved in all3canines using400W×24.0±6.0s HIFU energy.3months after theprocedure, the3animals still kept a complete AVB. Small fibrosis of thetarget region with intact endothelium was observed grossly. Thehomogenous and red-stained hyaline degeneration of ablation lesion wasalso confirmed histologically. No complications associated with theprocedures were observed. In addition, there was not any damage of thepacing electrode observed.Conclusion: Our results had demonstrated the mid-term efficacy andsafety of non-invasive atrioventricular junction ablation using HIFU. Andour findings further indicated that the transthoracic HIFU for blockingcardiac conduction was safe and efficient, which may lend itself as animportant component of the techniques for arrhythmia therapy independentof X-ray and catheter intervention.
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