TLD uses a
radiofrequency
ablation
catheter to
disrupt the
pulmonary
connections
of the vagus
nerve with
a minimally-
invasive
technique
cholinergic receptors. Intravenous atropine
administration would therefore cause systemic
disruption of parasympathetic pathways,
including those supplied by the pulmonary
trunks of the vagus nerve. Both nocturnal and
daytime PEF significantly improved after
atropine. Whilst the nocturnal fall in PEF was not
completely abolished, it was certainly diminished.
The proposed mechanism was speculative, but it
was suggested that the normal circadian effects
of the vagus nerve are exaggerated by
hypersensitisation of airway muscarinic receptors
by inflammatory mediators. 8 Therefore blocking
the actions of the nerve (pharmacologically or
physically) could help to limit nocturnal airflow
obstruction, a phenomenon which causes
symptoms in many asthma patients.
History of vagal section
TLD is not the first procedure proposed for
asthma that involves section of airway nerves.
In 1923, the German surgeon Professor Hermann
Kümmell reported the first surgical intervention
on the nerve supply to the lungs for asthma. 9
He actually performed a unilateral cervical
sympathectomy in the belief that some vagal
fibres enter the lung via the sympathetic trunk.
It was subsequently postulated that the
sympathetic trunk is the afferent part of a reflex
arc, of which the efferent component is the
bronchoconstriction-inducing parasympathetic
vagal fibres. 3 Kümmell’s report documented
immediate relief of asthma after the surgery.
This led to the uptake of similar procedures in
other centres. In 1929, Phillips and Scott
8
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published a review of cases of operations to the
pulmonary nerves. They found over 300 cases had
been performed since 1923, but only 29 had been
reported in sufficient detail and had undergone at
least 6 months follow-up. Of these, 8 (28%) were
‘cured,’ 5 (17%) were ‘improved,’ and 16 (55%)
were ‘unimproved.’ 10 Most of these procedures
involved intervention to the sympathetic trunk,
with few vagotomy procedures.
Vagal section for asthma underwent something
of a revival in the 1950s. Blades et al carried out
procedures that involved destruction of the
pulmonary plexus around the main bronchus,
as well as division of the vagus nerve below the
level of the recurrent laryngeal nerve. Of the
38 patients treated, 22 saw a resolution or
improvement in their asthma, though 7 patients
died. 11 Dimitrov-Skokodi et al performed 19 cases
of vagotomy and sympathectomy. They reported
asthma attacks ceased altogether in ten patients
and were reduced in seven. There were also
improvements in mucosal oedema, sputum
volume and eosinophilia, radiographic
‘emphysema,’ bronchographic bronchospasm and
forced vital capacity. 12 Rienhoff and Gay described
bilateral pulmonary plexus resection in 11
patients. Results were very similar to Dimitrov-
Skokodi’s results, with a reduction in the severity
and frequency of asthma attacks, reduced sputum
volume, and resolution of radiographic
‘emphysema.’ 13 Given the period these reports
were published in, the assessment of outcomes
are mostly subjective with little objective
physiological data. It was also prior to the onset
of randomised controlled trials, with the reports