AKT · Cardiovascular/Circulation & blood pressure

Syncope (vasovagal & cardiac)

Transient global cerebral hypoperfusion → brief loss of consciousness with spontaneous recovery

Overview

Transient loss of consciousness from global cerebral hypoperfusion, with rapid, complete spontaneous recovery. The central task is separating benign reflex (vasovagal) syncope from dangerous cardiac syncope (arrhythmia, structural disease), and from non-syncopal causes such as seizures. Red-flag features and an ECG drive risk stratification.

Recognise

Reflex (vasovagal): prodrome (nausea, sweating, pallor, tunnel vision), a clear trigger (standing, pain, emotion, micturition), rapid recovery
Cardiac: exertional or supine syncope, no/short prodrome, palpitations, known heart disease, family history of sudden death — high-risk
Brief myoclonic jerks can occur in syncope (convulsive syncope) — does not mean epilepsy

Red flags

Syncope on EXERTION, while supine, or with palpitations; abnormal ECG; family history of sudden death; structural heart disease → urgent cardiac assessment
New murmur (aortic stenosis/HCM) with syncope → investigate the structural cause

Differentials & how to tell them apart

Epileptic seizureaura, prolonged tonic-clonic activity, tongue-biting (lateral), post-ictal confusion — syncope recovers quickly

Orthostatic hypotensionon standing, with a documented postural BP drop

Cardiac arrhythmia / structural diseaseexertional/supine, abnormal ECG/echo — the dangerous group

Hypoglycaemialow glucose, autonomic/neuroglycopenic features, no rapid spontaneous recovery

Investigations

12-lead ECG in everyone (look for arrhythmia, long QT, Brugada, conduction disease, ischaemia, pre-excitation); lying/standing BP (orthostatic drop); bloods (anaemia, glucose); echo if structural disease suspected; ambulatory monitoring/tilt testing for recurrent unexplained episodes.

Management

Reflex syncope → education + counter-pressure manoeuvres; cardiac syncope → treat the cause

1Take a careful witness history, do a 12-lead ECG and lying/standing BP, and risk-stratify. Typical reflex (vasovagal) syncope → reassurance, trigger avoidance and physical counter-pressure manoeuvres.Gate: Exertional/supine syncope, palpitations, abnormal ECG, structural heart disease or a family history of sudden death → urgent cardiac assessment, NOT reassurance — this is the group at risk of sudden death.
2Investigate and treat the cardiac cause (pacing for conduction disease, ICD/ablation for ventricular arrhythmia, valve surgery for aortic stenosis); review and rationalise culprit drugs.

Reflex syncope: reassurance + education, avoid triggers, physical counter-pressure manoeuvres, good hydration/salt — no drug needed for typical vasovagal syncope

Treat the cardiac cause — pacemaker for bradyarrhythmia/AV block, ICD/ablation for ventricular arrhythmia, valve intervention for aortic stenosis

Review culprit drugs — antihypertensives, diuretics, QT-prolonging drugs

Key points

Prodrome + clear trigger + quick recovery = benign vasovagal syncope (education + counter-pressure manoeuvres). Syncope on EXERTION or lying down, with palpitations, an abnormal ECG or a family history of sudden death = cardiac syncope → urgent work-up. Always do an ECG.

Monitor & prognosis

Recurrence, ECG/ambulatory findings, response to treatment of the cause.

Reflex syncope is benign; cardiac syncope carries sudden-death risk until treated.

Source: NICE CG109 (transient loss of consciousness); ESC syncope