Study population
Between February 2017 and October 2019, we prospectively enrolled 13
patients in three hospital centers, with documented episodes of severe
functional bradyarrhythmias suggestive of vagal etiology (sinus
bradycardia and / or arrest, brady-tachy syndrome, transient AV block
and cardioinhibitory syncope). Functional bradyarrhythmias were
acknowledged after exclusion of reversible causes, such as negative
chronotropic drugs, ionic disorders, thyroid dysfunction, cardiac
ischemia, obstructive sleep apnea, intrinsic sinus or AV node disease
and in patients engaged in competitive sports, after deconditioning.
Intrinsic sinus and AV node disease were excluded after assessment of a
positive chronotropic response on 24-hour Holter monitoring and on
exercise treadmill test, with absence of exercise induced AV block and
when bradyarrhythmias were suggestive to occur in a vagal setting as
during sleep, post meals or prolonged standing. Patients with suspected
vagal syncope underwent tilt testing that exhibited syncope with
predominant cardioinhibitory response. An ECG was performed in all
patients and the HR and PQ interval was measured. Patients with abnormal
ECG apart from sinus bradycardia, first-degree or second-degree Mobitz
type I AV block or with abnormal transthoracic echocardiogram were
excluded.
Included patients were either symptomatic (syncope / pre-syncope related
to bradycardia) or had severe bradycardia with an indication for pacing
regardless of symptoms as outlined in the current European Society of
Cardiology Guidelines for the management of
bradyarrhythmias(10).