Table 1 Open in new tab Inclusion and...

Inclusion criteria

Exclusion criteria

All cases

History

Symptomatic bradycardia
At least 1 syncope episode during the preceding 12 months or minimum of 2 pre-syncopal events during preceding 12 months

Use of negative chronotropic or dromotropic drugs
Typical history for vasovagal syncope

Laboratory assessment

Normal thyroid function tests

Thyroid function abnormality

If suspicion of obstructive sleep apnoea

Negative polysomnogram

Positive polysomnogram

Atropine response^a

Positive

Negative

Paroxysmal AVB cases

Baseline ECG

Normal PR interval or first-degree AVB

Prolonged ECG monitoring

PR prolongation before second- or third-degree AVB episode

Constant PR before second- or third-degree AVB episode

Decrease in sinus rate during or just prior to second- or third-degree AVB episode

Increase in sinus rate during second- or third-degree AVB episode

Resolution of AVB with an increase in sinus rate

Resolution of AVB with a constant sinus rate

Persistent AVB cases

Baseline ECG

Mobitz Type I second- or advanced-degree AVB

Mobitz Type II second degree

Atropine response^a

Positive

Negative

Electrophysiological study

Baseline H–V interval <55 ms

Baseline H–V interval ≥55 ms

Supra-Hisian AVB

Intra/infra-Hisian AVB by atrial pacing at rates at 150 bpm or less

Table 1

Inclusion and exclusion criteria

		Inclusion criteria	Exclusion criteria
All cases	History	Symptomatic bradycardia At least 1 syncope episode during the preceding 12 months or minimum of 2 pre-syncopal events during preceding 12 months	Use of negative chronotropic or dromotropic drugs Typical history for vasovagal syncope
	Laboratory assessment	Normal thyroid function tests	Thyroid function abnormality
	If suspicion of obstructive sleep apnoea	Negative polysomnogram	Positive polysomnogram
	Atropine response^a	Positive	Negative
Paroxysmal AVB cases	Baseline ECG	Normal PR interval or first-degree AVB
	Prolonged ECG monitoring	PR prolongation before second- or third-degree AVB episode	Constant PR before second- or third-degree AVB episode
		Decrease in sinus rate during or just prior to second- or third-degree AVB episode	Increase in sinus rate during second- or third-degree AVB episode
		Resolution of AVB with an increase in sinus rate	Resolution of AVB with a constant sinus rate
Persistent AVB cases	Baseline ECG	Mobitz Type I second- or advanced-degree AVB	Mobitz Type II second degree
	Atropine response^a	Positive	Negative
	Electrophysiological study	Baseline H–V interval <55 ms	Baseline H–V interval ≥55 ms
	Electrophysiological study	Supra-Hisian AVB	Intra/infra-Hisian AVB by atrial pacing at rates at 150 bpm or less

		Inclusion criteria	Exclusion criteria
All cases	History	Symptomatic bradycardia At least 1 syncope episode during the preceding 12 months or minimum of 2 pre-syncopal events during preceding 12 months	Use of negative chronotropic or dromotropic drugs Typical history for vasovagal syncope
	Laboratory assessment	Normal thyroid function tests	Thyroid function abnormality
	If suspicion of obstructive sleep apnoea	Negative polysomnogram	Positive polysomnogram
	Atropine response^a	Positive	Negative
Paroxysmal AVB cases	Baseline ECG	Normal PR interval or first-degree AVB
	Prolonged ECG monitoring	PR prolongation before second- or third-degree AVB episode	Constant PR before second- or third-degree AVB episode
		Decrease in sinus rate during or just prior to second- or third-degree AVB episode	Increase in sinus rate during second- or third-degree AVB episode
		Resolution of AVB with an increase in sinus rate	Resolution of AVB with a constant sinus rate
Persistent AVB cases	Baseline ECG	Mobitz Type I second- or advanced-degree AVB	Mobitz Type II second degree
	Atropine response^a	Positive	Negative
	Electrophysiological study	Baseline H–V interval <55 ms	Baseline H–V interval ≥55 ms
	Electrophysiological study	Supra-Hisian AVB	Intra/infra-Hisian AVB by atrial pacing at rates at 150 bpm or less

AVB, atrioventricular block; ECG, electrocardiogram.

^aSee text for details.