The purpose of the study is to investigate the efficacy of the ROX coupler in treating patients with tilt test proven Neurally mediated syncope.

Neurally mediated syncope (NMS) is a debilitating condition, with no proven therapeutic measures. The ROX coupler is a device used to create an Iliac arterio-venous anastamosis which allows a shunt of 0.8 litres per minute. The haemodynamic changes following creation of an arterio-venous anastomosis at the iliac level leads to an increase in cardiac preload, reversing finding thought to induce NMS.

This a randomised controlled study to evaluate the effect of Iliac arterio-venous anastamosis in patients with neurally mediated syncope. The Head up tilt test is used as an objective measure to evaluate the effect of the arterio-venous anastamosis in patients with NMS. Participants with tilt test proven NMS will be eligible for the study ( if they satisfy all other eligibility criteria). Participants will be randomised to ROX coupler intervention or standard therapy. The primary outcome measure will be absence of loss consciousness on tilt table testing at 3 months post intervention.

Inclusion Criteria:

• Absence of transient loss of consciousness associated with reflex bradycardia or hypotension on tilt testing at 3 months following randomised intervention

Exclusion Criteria:

• Time to first episode of syncope after randomised intervention
• Number of syncopal episodes in the first 3 months after randomised intervention.
• Tilt table response at 6 months following randomised intervention i.e. 3 months after unblinding
• Number of syncopal episodes at 6 months after intervention i.e. 3 months after unblinding