Subclavian Ansae Stimulation in AF (SAS-AF)
Condition: Atrial Fibrillation
MeSH terms: Atrial Fibrillation
Study type: Interventional

Summary: 
      Atrial Fibrillation (AF) is a common heart rhythm condition that affects over 3% of the total
      population. AF can lead to serious health problems such as heart failure or stroke and can
      also cause troublesome symptoms in some people. Although many advances have been made, there
      remains a pressing need to improvement treatment of AF.

      It is increasingly recognised that the brain and nerves can influence the electrical activity
      of the heart.

      Therefore, this research involves studying a new nerve target (Subclavian ansae) that is
      connected to the heart and can be a potential target for future treatment of AF. This nerve
      lies around an area close to an artery that runs to participant's left arm called left
      subclavian artery which can be approached via leg (key hole). The investigators aim to
      conduct this study in patients who have been referred for first time AF ablation.
    

Detailed description: 
      Atrial Fibrillation (AF) is a common and significant medical problem that affects
      approximately 3% of the population. There is increasing recognition of the importance of
      interactions between the heart and the autonomic nervous system (ANS) in the pathophysiology
      of arrhythmias. The role of ANS in the onset and maintenance of AF is thought to be related
      to autonomic imbalance. Several studies have experimented the use of autonomic modification
      in AF and identified potential targets for therapy ( for example: ganglionic plexi ablation,
      renal denervation, stellate ganglion block, and low level vagal nerve stimulation). However,
      some targets like stellate ganglion block/sympathectomy will have off-target side-effects.
      Easily accessible, minimally invasive, and selective targets for neuromodulation are of great
      interest for development of novel therapy in the management of AF.

      The subclavian ansae was first described in 1864 by Vieussens and is a nerve cord that forms
      a loop inferiorly around the subclavian artery and connects the inferior cervical ganglion
      and middle cervical ganglia.According to literature cardiac-related preganglionic fibers
      arising from the thoracic cord traverse up the paravertebral chain through the T1-T2 region,
      some making synaptic contact with postganglionic neurons in the stellate with others
      projecting through the subclavian ansae to more distal intrathoracic ganglia (middle
      cervical, mediastinal, and intrinsic). As such the ansa subclavia and the T1-T2 region of the
      paravertebral chain are critical nexus points for sympathetic nerve traffic to and afferent
      projections of the heart. Based on structure and function consideration, both sites are
      potential targets for cardiac neuromodulation.

      Preclinical studies have showed that stimulation of the subclavian ansae produces
      reproducible increases in cardiac rate, contractility and conduction velocity. Denervation of
      the subclavian ansae followed by stellate ganglion stimulation results in no change in
      cardiac indices confirming the nodal intervention point for cardiac sympathetic traffic. Due
      to the close anatomical proximity, stimulation of subclavian ansae should be possible via the
      subclavian artery which is accessible by percutaneous approach.

      Hypothesis:

      The investigators intend to introduce a percutaneous approach for identification and
      stimulation of subclavian ansae (sympathetic nerves) which exclusively innervate the heart
      and therefore stimulation will result in in changes in human cardiac haemodynamic and
      electrophysiological parameters.

      Primary objective:

      The primary objective of the study is to determine the human cardiac haemodynamics and
      electrophysiological response to left subclavian ansae stimulation (SAS) in patients with AF.

      Secondary objective:

      To determine appropriate stimulation parameters to selectively target subclavian ansae via
      percutaneous transarterial approach and to confirm safety of the procedure.

      Patients referred by Electrophysiologist for catheter ablation of paroxysmal AF (PAF) will be
      recruited. Participants will undergo consenting for the procedure and their involvement in
      the research study. The procedure will be performed under general anaesthesia. A stimulation
      wire will be passed into the left subclavian artery via the femoral arterial access. Further
      wires will be passed (via venous access) to the left top chamber of the heart which will then
      be used for 3D guided AF ablation after stimulation protocol. Study measurements will be
      gathered before and after the stimulation subclavian ansae. This will be followed by AF
      ablation (pulmonary vein isolation) and direct current cardioversion (DCCV) [if required] as
      standard care.
    

Intervention name(s): Selective left subclavian ansae stimulation
Intervention type(s): Other
Intervention description(s): Percutaneous, transarterial approach for target stimulation
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Atrial Fibrillation; Subclavian ansae stimulation