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.