[1][2] The procedure uses balloons to open pulmonary arteries that have been narrowed or blocked by webs, bands and fibrous tissue[2] and therefore restores blood flow to the lungs, reduces shortness of breath, and improves exercise tolerance.

[3][5] PTE is an established treatment for CTEPH but is only performed at a few specialist centres, requires surgical competence and intermittent total circulatory arrest under deep hypothermia.

[8] A local anesthetic and moderate sedation are used but a general anaesthetic is not required, hence the person remains awake throughout the procedure.

[9] This increases the size of the lumen of the arteries, thus opening them and allowing the blood flow to be restored.

[9] The pulmonary arteries have thinner walls than the blood vessels of the heart and therefore injury by rupture or dissection caused by over-dilatation of the balloon or piercing pulmonary arteries by the tip of the guide wire, resulting in haemorrhage, are risks.

[10] Since 2012, reports of the effect of BPA has mainly come from the National Hospital Organization Okayama Medical Center in Japan[9] where the procedure was refined and where smaller balloons were used.