How can I differentiate between vasovagal syncope and other causes of transient loss of consciousness in a primary care setting?

To differentiate vasovagal syncope from other causes of transient loss of consciousness (TLoC) in primary care, focus on the clinical history and initial assessment.

• Vasovagal syncope diagnosis: Identify the presence of the 3 'P's: Posture (prolonged standing or episodes prevented by lying down), Provoking factors (such as pain or medical procedures), and Prodromal symptoms (like sweating or feeling warm/hot before TLoC). There should be no features suggesting an alternative diagnosis. Brief seizure-like activity can occur but does not necessarily indicate epilepsy ¹.
• Situational syncope: Consider if syncope is consistently provoked by straining during micturition, coughing, or swallowing, without other concerning features ¹.
• Postural hypotension: Suspect if history is typical and no alternative diagnosis is suggested; confirm with blood pressure measurements ¹.
• Epileptic seizures: Features strongly suggestive of epilepsy include bitten tongue (especially side), head-turning, no memory of abnormal behaviour, unusual posturing, prolonged limb-jerking, confusion after the event, and prodromal déjà vu or jamais vu. These features help differentiate epilepsy from vasovagal syncope ¹.
• Cardiac causes: Consider if syncope occurs during exertion, if there is a history or signs of heart failure, family history of sudden cardiac death under 40 years, new unexplained breathlessness, or a heart murmur. These require urgent referral and further cardiovascular assessment ¹.
• ECG and further tests: An ECG should be arranged within 3 days if vasovagal syncope or situational syncope is diagnosed. Tilt testing is not routinely recommended for vasovagal syncope diagnosis in primary care ¹.

Summary: Use detailed history focusing on posture, provoking factors, and prodromal symptoms to identify vasovagal syncope. Exclude features suggestive of cardiac causes, epilepsy, or postural hypotension. Use ECG and refer as appropriate for further assessment ¹.