| ObjectiveHypertension has effected more than 25% adults global wide, resistant hypertension is up to 20%-30%. The definition of resistant hypertension is:using three types of antihypertensive drugs simultaneously still cannot reach the target blood pressure or using 4 types of antihypertensive drugs can barely keep the ideal blood pressure, which medications in this case, are hardly effective. Renal denervation has come up as an invasive operation aside to medication treatment for resistant hypertension since 1935. For its aggressive surgery methods, the damage of the operation is severe and the complications is unknown, even though after renal denervation, the blood pressure had decreased, this method was still not recommended. Up till 2009, Krum reported a multicenter-clinic trial of catheter-based renal sympathetic denervation which known as Symplicity HTN-1 has shown: in 45 cases, during 1,3,6,9 and 12 months post-operate office blood pressure had decreased 14/10,21/10,22/11,24/11 and 27/17 mmHg. Due to this study, renal denervation has once become one of the major non-drug treatment for resistant hypertension, which is a fast growing field which is under hot discussion nowadays. After HTN-2 and HTN-3, currently the mainstream approach in clinical trials is catheter-based subcutaneous renal denervation, which is technically simple to perform, by ablate the nerve tissue from inside of the renal artery by gradually spirals towards the farther end of renal artery in 6 ablation points by 0°,60°,120°,180°,240°,300°of the intersecting surface. Although, this operation suffers a comparatively high post-op complication rate owing to its invasive nature.High-intensity focused ultrasound (HIFU) can transfer ultrasonic into heat energy which can ablate and damage the tissues, this technique is widely used in Oncology operations, for example, resection of tumor by ablation and denervation for cancerous pain in the terminal stage. HIFU’s technique features is noninvasive operative pathways, for its minimal damage to the tissues and areas through the surgery pathway. This study choose to use noninvasive high-intensity focused ultrasound (HIFU) to perform the procedure from outside the body to ablate the renal sympathetic nerve and evaluate the safety and validity of the operation afterwards in order to provide fundamental pre-clinical research data for future use.MethodsPigs were randomly divided into three groups (control group,280W×2s ablation group and 320Wx2s ablation group). We used color Doppler flow imaging system as guidance to locate the target renal arteries, and performed bilateral renal sympathetic denervation (each treating area was treated repeatedly by 10 times with the interval of 3mm under the ablation power of 280W×2s and 320W×2s) using high-intensity focused ultrasound (HIFU). All the animals’blood pressure, plasma norepinephrine level and renal function were measured before and after the operation and on day7, day28 post-op. The pigs was euthanatized on day 28 and the histopathological changes were examined. ResultsAfter renal sympathetic denervation, all animals’vital signs were normal. The systolic blood pressure was reduced by average of 7 mmHg in the 280W×2s ablation group (P = 0.12), and the systolic blood pressure of 320W×2s group was declined by average of 15mmHg (P< 0.01). Postoperative plasma norepinephrine levels in both ablation groups have declined. Renal function had no obvious change post-operatively. The pathological results showed the renal sympathetic nerve was damaged in different degrees, while the blood vessel walls remained undamaged. No significant postoperative complications were found.ConclusionUnder the guidance of color Doppler flow imaging, peripheral noninvasive High-intensity focused ultrasound can be used for renal sympathetic denervation under the guidance of color Doppler flow image. Norepinephrine has dropped and blood pressure has decreased under the ablation power of 320W×2s. This animal model indicates HIFU can induce renal denervation. Further studies of this method are desirable to investigate the potential of HIFU as an hoice for patients not suitable for catheter-based renal sympathicolysis. |
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