Related Subjects:
| Transient Loss of Consciousness
| Vasovagal Syncope
| Syncope
| Aortic Stenosis
| First Seizure
| Carotid Sinus Syncope
🤲 Vasovagal syncope (reflex syncope / “simple faint”) is a transient loss of consciousness (TLoC) caused by a reflex that triggers vasodilation ± bradycardia → a brief fall in arterial pressure → cerebral hypoperfusion.
🎯 OSCE focus: confirm the benign reflex pattern (trigger + prodrome + rapid recovery) while actively excluding dangerous cardiac causes.
✅ Definition (exam wording)
- 🧠 TLoC with rapid onset, short duration, and spontaneous complete recovery.
- 🫀 Vasovagal = reflex-mediated hypotension (vasodilation) and/or bradycardia causing transient cerebral hypoperfusion.
🧩 The “3 Ps” (high-yield history pattern)
- 🧍 Posture: prolonged standing; hot/crowded spaces; episodes often prevented by lying down.
- 🩹 Provoking factors: pain, emotion, needles/medical procedures, sight of blood.
- 🥵 Prodrome: sweating, warmth, nausea, light-headedness, “greying out”/blurred vision, ringing in ears.
🧠 Pathophysiology (why the patient faints)
- 🧍 Standing → venous pooling → ↓ preload (less venous return).
- ⚡ Early sympathetic compensation (↑ HR/contractility) is followed by a reflex “switch” → vagal activation + sympathetic withdrawal.
- ⬇️ Net effect: bradycardia + vasodilation → BP drop → brief cerebral hypoperfusion → syncope.
🩺 Clinical features (recognise vs seizure)
- ⏱️ LOC usually seconds to 1–2 minutes with rapid recovery (orientation returns quickly once supine).
- 🤢 Pallor, sweating, nausea, yawning, visual dimming are common.
- 🌀 Brief myoclonic jerks can occur (convulsive syncope), but the key discriminator is rapid return to baseline without a prolonged post-ictal phase.
🚩 Red flags (think cardiac / urgent assessment)
- 🏃 Syncope during exertion or while supine.
- 💥 No prodrome, sudden drop collapse, or significant injury without warning.
- 💓 Palpitations immediately before LOC; known structural heart disease.
- 😮💨 Chest pain, breathlessness, new murmur, family history of sudden cardiac death.
- 📉 Abnormal ECG (e.g., new conduction disease, long QT, ischaemia, Brugada pattern).
🔎 OSCE assessment
- 👂 History + witness: posture, trigger, prodrome, duration, colour change, movements, tongue bite, incontinence, recovery time, injuries.
- 💊 Medication review: antihypertensives/diuretics/vasodilators and other drugs that may worsen hypotension or prolong QT.
- 🩺 Examination: lying/standing BP, cardiovascular exam (murmur), hydration/volume status; focused neuro exam if indicated.
🧪 Investigations (NICE-style)
- 📈 12-lead ECG for all patients with TLoC (rule out arrhythmia/conduction disease).
- 🧍↕️ Lying + standing BP (exclude orthostatic hypotension).
- 🩸 Targeted bloods if suggested by history/exam:
- 🍬 Capillary glucose (especially if diabetic/altered).
- 🩸 FBC (anaemia), U&E (electrolytes/renal), pregnancy test where appropriate.
- 🧲 Carotid sinus massage (specialist setting; typically >40 years with compatible history; avoid if recent TIA/stroke or significant carotid disease).
- 🧪 Tilt-table testing for recurrent/unexplained episodes where diagnosis remains uncertain after initial assessment.
- 🛰️ Ambulatory monitoring / implantable loop recorder if unexplained TLoC and arrhythmia is still suspected (especially no prodrome or abnormal ECG).
💊 Management (stepwise, OSCE-ready)
- 🧠 Explain + reassure: a benign reflex is common; recognising prodrome reduces recurrence and injury.
- 💧 Hydration + salt optimisation: encourage fluid intake; consider salt increase if appropriate (use caution in HF/CKD).
- 🧍 Avoid triggers: heat, dehydration, prolonged standing; moderate alcohol; consider smaller meals if post-prandial symptoms.
- 🦵 Counter-pressure manoeuvres at prodrome (raise venous return/BP):
- ✊ Handgrip, arm tensing
- 🦵 Leg crossing with muscle tensing
- 🧎 Squatting (if safe)
- 🛏️ Immediate self-management: lie flat, elevate legs, loosen clothing, cool environment.
- 💊 Recurrent troublesome syncope (specialist): selected patients may benefit from midodrine or fludrocortisone after excluding cardiac causes and optimising conservative measures; pacing is reserved for a small subgroup with documented cardioinhibitory syncope/asystole.
🧠 Differentials (quick discrimination)
- ⚡ Seizure: prolonged post-event confusion, lateral tongue bite, cyanosis, longer LOC, muscle aches afterwards.
- 🧍↕️ Orthostatic hypotension: triggered by standing; confirmed on lying/standing BP; often meds/dehydration/autonomic failure.
- 💓 Arrhythmia: sudden LOC without prodrome, palpitations, abnormal ECG, structural heart disease.
- 🫀 Structural cardiac: exertional syncope (aortic stenosis, HCM), chest pain, murmur.
🎭 OSCE mini-script (30–45 seconds)
- 🗣️ “This sounds most consistent with vasovagal syncope because there was a typical trigger, a clear prodrome, and rapid recovery. I would still exclude high-risk causes by doing a 12-lead ECG, lying/standing BP, and targeted blood tests if indicated.”
- 🗣️ “Management is reassurance, hydration, avoiding triggers, and teaching counter-pressure manoeuvres. If episodes are recurrent or atypical, I’d arrange specialist assessment and consider tilt testing or rhythm monitoring.”
🚗 Driving (UK)
- 🧾 Driving advice depends on Group 1 vs Group 2, recurrence, and whether episodes are explained/treated. Use the latest DVLA “Assessing fitness to drive” standards and document advice given.
📚 References (UK + core)
