What are the red flags for syncope?

Historical Red Flags

The NSW ACI ECAT protocol identifies the following historical red flags:

• Age >65 years
• Structural or coronary heart disease
• Known abdominal aortic aneurysm (AAA)
• Syncope during exertion, while supine or sitting
• Palpitations prior to syncope
• Family history of sudden cardiac death
• Severe anaemia
• Known cardiac arrhythmia or cardiac history
• Sudden onset headache

The 2017 ACC/AHA/HRS guideline adds:

• Male sex
• Brief or absent prodrome (sudden loss of consciousness without warning)
• Low number of episodes (1 or 2, suggesting a new cardiac cause)
• Reduced ventricular function
• Family history of inheritable conditions or premature sudden cardiac death (<50 years of age)
• Known congenital heart disease

Clinical Red Flags (On Examination)

Per the NSW ACI protocol:

• Altered level of consciousness
• Confusion, agitation or irritability
• Persistent hypotension
• Cardiac arrhythmia or palpitations
• Chest pain
• Abdominal distension or rigidity
• Suspected AAA
• Head injury
• Suspected GI bleed (e.g. melaena)
• Suspected pulmonary embolism
• Suspected ectopic pregnancy

Additional features from the initial evaluation warranting concern include dyspnoea, persistent tachycardia, and abnormal ECG findings (ischaemia, conduction abnormalities, prolonged QTc, Brugada pattern, pre-excitation).

Low-Risk Features (Suggesting Non-Cardiac Cause)

For contrast, features suggesting a more benign aetiology include:

• Younger age
• No known cardiac disease
• Syncope only in the standing position
• Identifiable triggers (pain, emotional stress, prolonged standing, warm environment)
• Classic prodrome (nausea, diaphoresis, warmth, pallor)

Key Workup Points

• All patients should receive history, physical examination (including orthostatic BP), and a 12-lead ECG
• Routine neuroimaging has a low diagnostic yield and should not be ordered unless neurological signs/symptoms are present
• Patients with exertional syncope should have an exercise stress test