Pulmonary artery denervation using catheter-based ultrasonic energy

Aims: Pulmonary arterial hypertension is a devastating disease characterised by pulmonary vascular remodelling and right heart failure. Radio-frequency pulmonary artery denervation (PDN) has improved pulmonary haemodynamics in preclinical and early clinical studies; however, denervation depth is limited. High-frequency non-focused ultrasound can deliver energy to the vessel adventitia, sparing the intima and media. We therefore aimed to investigate the feasibility, safety and efficacy of ultrasound PDN. Methods and results: Histological examination demonstrated that innervation of human pulmonary arteries is predominantly sympathetic (71%), with >40% of nerves at a depth of >4 mm. Finite element analysis of ultrasound energy distribution and ex vivo studies demonstrated generation of temperatures >47ºC to a depth of 10 mm. In domestic swine, PDN reduced mean pulmonary artery pressure induced by thromboxane A2 in comparison to sham. No adverse events were observed up to 95 days. Histological examination identified structural and immunohistological changes of nerves in PDN-treated animals, with sparing of the intima and media and reduced tyrosine hydroxylase staining 95 days post procedure, indicating persistent alteration of the structure of sympathetic nerves. Conclusions: Ultrasound PDN is safe and effective in the preclinical setting, with energy delivery to a depth that would permit targeting sympathetic nerves in humans.