Arrhythmic syncope: From diagnosis to management

Table 1 Main cardiac causes of syncope

Cardiac syncope
Arrhythmic causes	Bradyarrhythmia	Sick sinus syndrome/sinus node disfunction
		Atrioventricular block
	Tachyarrhythmia	Supraventricular tachycardia (AVNRT, AVRT, AT, fast AF, etc.)
		Ventricular arrhythmias	Related to structural heart disease
			Channelopathies and inherited arrhythmia syndromes
Non-arrhythmic causes	Mechanical causes	Valvulopathies (aortic stenosis, mitral stenosis, etc.)
		HCM
		Atrial myxoma
		Pulmonary emboli
		Tamponade
		Severe pulmonary hypertension
Acute coronary syndrome

AVNRT: Atrioventricular nodal re-entrant tachycardia; AVRT: Atrioventricular re-entrant tachycardia; HCM: Hypertrophic cardiomyopathy; AF: Atrial fibrillation; AT: Atrial tachycardia.

Table 2 Main advantages, limitations, and indications of the most commonly used devices for electrocardiogram cardiac monitoring in patients with syncope

	Advantages	Disadvantages	Main indications
24-hr holter	Continuous recording: 12 leads with good correlation with surface ECG; low economic cost per study	Discomfort for the patient; artifacts; maximum recording of 24-48 h (low diagnostic yield); high economic cost per diagnosis	Very frequent (daily) symptoms; in-hospital monitoring (if ECG-telemetry not available)
Skin patches	Continuous recording of 7-14 d; good tolerability for patients	Single-use and greater economic cost; only one lead1; low diagnostic yield	Frequent (weekly) symptoms
External loop recorders	Loop recording (includes beginning and end of arrhythmic event); monitoring for 4 wk; low economic cost per study	Patient discomfort; requires education from healthcare professional on how to correctly place the electrodes; relatively low diagnostic yield	Frequent (weekly-monthly) symptoms
Implantable loop recorders	Loop recording; up to 3-yr monitoring (good diagnostic yield); patient does not have to do anything; remote monitoring	Invasiveness and associated complications (infection, bleeding, etc.); individual economic cost; single lead	Infrequent symptoms; most useful in syncope

¹There are devices with more leads.

ECG: Electrocardiogram.

Table 3 High-risk features suggesting cardiac syncope

High-risk features
Past medical history
Previous myocardial infarction
Previous cardiovascular condition (i.e., BrS, hypertrophic cardiomyopathy, Long QT syndrome, etc.)
Syncopal event
Syncope during exertion or in supine position
Syncope associated with chest pain, palpitations, breathless, or abdominal pain
Physical examination
Signs of heart failure
Cardiac murmur suggesting specific condition (i.e., aortic stenosis)
Signs of shock
Electrocardiogram
Conduction disturbance (AV block, bundle branch block)
Pathological Q waves
Long QT interval
Pre-excitation syndrome
Negative T waves

BrS: Brugada syndrome; AV: Atrio-ventricular.