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Published on: May 26, 2022
Catheter-based renal sympathetic denervation: chronic preclinical evidence for renal artery safety
Marian K Rippy1, Denise Zarins, Neil C Barman
1Rippy Pathology Solutions, Woodbury, MN, USA. marian.rippy@comcast.net
Insights
Renal sympathetic denervation using the Symplicity Catheter System showed no significant adverse effects in swine models. This preclinical study supports the vascular safety of the procedure for hypertension treatment.
Area of Science:
- Cardiovascular research
- Nephrology
- Interventional cardiology
Background:
- Renal sympathetic hyperactivity contributes to hypertension, a major global health concern.
- Renal sympathetic denervation (RSD) with the Symplicity Catheter System has demonstrated significant blood pressure reduction in clinical studies.
- Preclinical data is essential to validate the safety and healing response of RSD procedures.
Purpose of the Study:
- To assess the long-term vascular safety and healing response following therapeutic renal sympathetic denervation in a preclinical swine model.
- To characterize histological changes in renal arteries and nerves six months post-procedure.
Main Methods:
- Seven domestic swine underwent 32 radiofrequency ablations using the Symplicity Catheter System.
- Renal angiography was performed pre-procedure, immediately post-procedure, and at six months.
- Histological examination of renal vessels and organs utilized H&E and Movat pentachrome stains.
Main Results:
- Histology revealed nerve fibrosis and thickening of nerve sheaths, with mild renal artery wall fibrosis (10-25% media/adventitia).
- No significant smooth muscle hyperplasia, inflammation, renal artery stenosis, or thrombosis were observed.
- No gross or microscopic abnormalities were detected in the kidneys, surrounding tissues, or urinary bladder.
Conclusions:
- Renal denervation via the Symplicity Catheter System demonstrated excellent vascular safety in a swine model at six months.
- Histological findings showed localized nerve and mild arterial wall changes without clinically significant adverse events.
- These preclinical results align with the established safety profile of RSD in human clinical trials.
Background:
Renal sympathetic hyperactivity is associated with hypertension, a leading cause of mortality worldwide. Renal sympathetic denervation via the Symplicity Catheter System has been shown to decrease blood pressure by 33/11 mmHg by 6 months, with no radiofrequency (RF)-related adverse sequelae visible by CT/MR angiography or renal duplex ultrasound 6 months after the procedure. Here, we present preclinical work predating those clinical results. We performed therapeutic renal sympathetic denervation in a swine animal model to characterize the vascular safety and healing response 6 months after renal denervation therapy.
Methods:
In December 2007, seven domestic swine received a total of 32 radiofrequency ablations via the Symplicity Catheter System and were euthanatized 6 months later. Renal angiography was done before, immediately after, and 6 months after procedure. The renal vessels were examined histologically with H&E and Movat pentachrome stains to identify evidence of vascular and neural injury. The kidneys and urinary system were also examined for evidence of gross and microscopic abnormalities.
Results:
Renal nerve injury involved primarily nerve fibrosis, replacement of nerve fascicles with fibrous connective tissue, and thickening of the epineurium and perineurium. Renal arterial findings included fibrosis of 10-25% of the total media and underlying adventitia, with mild disruption of the external elastic lamina. No significant smooth muscle hyperplasia or inflammatory components were observed. There was no renal arterial stenosis or thrombosis observed by angiography or histology. No gross or microscopic device-related abnormalities were noted in the kidney, surrounding stroma, or urinary bladder.
Conclusions:
In a swine model, renal denervation via the Symplicity Catheter System resulted in no clinically significant adverse renal artery or renal findings 6 months after the procedure. This is corroborated by the vascular safety profile demonstrated in subsequent human clinical studies.
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