Rapid Review·Cardiovascular
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HY Approach
T1Must knowApproach to Syncope
Focus on
Transient loss of consciousness from global cerebral hypoperfusion with quick, complete recovery. History, examination, orthostatic vitals and an ECG for everyone; then sort into reflex (prodrome and trigger — reassure), orthostatic (on standing — fix the cause), or cardiac (exertional, supine, no warning, abnormal ECG — admit and monitor). Separate it from seizure with the lateral tongue bite and the postictal state.
Key takeaways
What syncope is
Definition
a transient loss of consciousness from inadequate cerebral blood flow, usually about 10 seconds, with spontaneous complete recovery; it can cause a fall or a driving accident.Three families
reflex (vasovagal, situational, carotid sinus), orthostatic, and cardiac (arrhythmic or structural).Non-syncopal mimics
seizure, psychogenic pseudosyncope, hypoglycemia, drop attacks, and a mechanical fall with loss of consciousness from the head injury.| Mechanism | Clue pattern | Initial management | Page |
|---|---|---|---|
| Reflex | Trigger (standing, heat, pain, emotion, cough, micturition); prodrome of warmth, nausea, sweating, pallor; rapid recovery | Reassurance, fluid and salt, trigger avoidance, counterpressure maneuvers | Reflex Syncope |
| Orthostatic | On standing; volume loss, autonomic failure (diabetes, Parkinson), vasodilators, diuretics, alpha and beta blockers | Remove the cause, fluids, compression, midodrine or fludrocortisone | Orthostatic Hypotension |
| Cardiac, arrhythmic | Sudden, no prodrome or prodromal palpitations, supine or at rest; known heart disease, abnormal ECG, family history of sudden death | Admit and monitor; treat the rhythm; pacemaker or defibrillator | Ventricular Tachycardia, Atrioventricular Block, Sick Sinus Syndrome, Long QT Syndrome |
| Cardiac, structural | During exertion, with or without angina; systolic ejection murmur of outflow obstruction | Echocardiography; lesion-specific treatment | Aortic Stenosis, Hypertrophic Cardiomyopathy, Anomalous Aortic Origin of a Coronary Artery, pulmonary embolism, tamponade |
Evaluation and disposition
History and physical are key
position, activity, trigger, prodrome, duration, movements, tongue biting, incontinence, recovery, drugs, prior episodes, family history of sudden death; murmurs and neurologic findings on examination.Orthostatic vitals
a fall of 20 mm Hg systolic or 10 diastolic within 2 to 5 minutes of standing.Electrocardiogram (ECG) for all
then continuous monitoring or telemetry, because a transient arrhythmia (ventricular tachycardia, intermittent block) may not show on the first tracing.Labs and echo
routine labs; transthoracic echocardiography if a structural abnormality is suspected (murmur, abnormal ECG, heart disease, exertional syncope).Further tests by suspicion
ambulatory or implantable monitoring matched to how often it happens, exercise testing for exertional syncope after echo, tilt-table only when a reflex cause is unclear, carotid sinus massage over 40.Low risk (discharge)
a clear vasovagal story with no red flags.High risk (admit and monitor)
syncope during exercise, palpitations, or an abnormal ECG (ventricular tachycardia, sinus bradycardia, prolonged QT, heart block, bifascicular block).- Also structural heart disease, syncope while supine, no prodrome, and a family history of sudden death.
Recognizing arrhythmic syncope
No warning
usually underlying structural heart disease and no prodrome, unlike the aura and trigger of reflex syncope.- Syncope supine or sitting, at rest, without warning is arrhythmic until proven otherwise.
A scar points to ventricular tachycardia
ischemic scarring or a cardiomyopathy with a low ejection fraction.| Clue | Cause |
|---|---|
| No warning (other than palpitations); prior coronary disease, infarction, cardiomyopathy or low ejection fraction | Ventricular tachycardia |
| No warning; hypokalemia, hypomagnesemia, hypocalcemia; QT-prolonging drugs | Torsades de pointes (acquired long QT) |
| Family history of sudden death; long QT; triggers of exercise, startle or sleep | Congenital long QT syndrome |
| Preceding fatigue or dizziness; sinus pauses on ECG | Sick sinus syndrome |
| Bifascicular block or long PR; dropped QRS complexes | Advanced atrioventricular (AV) block (may be intermittent and absent on the day's ECG) |
General measures (reflex and orthostatic)
fluid 2 to 3 L/day and salt 6 to 9 g/day unless contraindicated; stop or reduce offending drugs (diuretics, antihypertensives); avoid or anticipate triggers; lie down when a short prodrome starts.Syncope vs its mimics
| Feature | Syncope | Seizure | Psychogenic pseudosyncope |
|---|---|---|---|
| Before | Prodrome of nausea and diaphoresis, or none; prolonged standing, stress, heat | Aura (smell, visual) or none; sleep loss, flashing lights, alcohol withdrawal | Unusual triggers and prodromes; frequent episodes, often witnessed |
| Position | Often standing (vasovagal); any position (cardiac) | Any, including sitting or sleeping | Any |
| Movements | Clonic jerks uncommon, only after loss of consciousness with prolonged hypoperfusion | Tonic-clonic, typically starting before or with loss of consciousness | Eyes closed |
| Tongue | Rare, frontal if present | Lateral bite: 96 percent specific, 33 percent sensitive | None |
| Incontinence | Less common, can occur | Common | Rare |
| Pulse and skin | Weak slow pulse, pallor, diaphoresis | Rapid strong pulse | Normal hemodynamics during the event |
| Recovery | Rapid (1 to 2 minutes), immediate return to baseline | Minutes to hours; postictal confusion or drowsiness | Prolonged (20 minutes or more); recalls events during the "unconsciousness"; detached affect; normal electroencephalogram (EEG) |
Hypoglycemia
a diabetic on antihyperglycemics with sweating and tremor, glucose under 70 (under 50 without diabetes), relieved by glucose.Drop attacks
sudden collapse without loss of consciousness (vertebrobasilar insufficiency, stroke, vestibular disease).A 67-year-old with a prior infarction and a low ejection fraction passes out while sitting watching television, with no warning. Is this low or high risk, and what is the likely cause?
High risk: admit and monitor. Syncope at rest without a prodrome in a patient with ischemic scar and a low ejection fraction points to ventricular tachycardia.
How it's tested
A 19-year-old faints after standing in a hot chapel, feeling warm and nauseated first, and recovers in a minute: vasovagal syncope — reassurance, fluids, counterpressure maneuvers; no imaging.
A 68-year-old with prior MI collapses while sitting, with no warning, and wakes within a minute: arrhythmic syncope until proven otherwise — admit for telemetry, echo, and probably an ICD if VT is found.
A 16-year-old collapses during a basketball game: exertional syncope — ECG and echocardiogram before returning to sport; HCM, AS, long QT and anomalous coronaries are on the list.
Witnessed collapse with a few jerks after falling, oriented within a minute, no tongue bite: convulsive syncope, not epilepsy — no antiseizure drugs.
Lightheaded when standing, on tamsulosin and furosemide, BP falls 30 mm Hg on standing: orthostatic syncope — adjust the drugs, hydrate.
Go deeper
Guidelines: 2017 ACC/AHA/HRS Syncope Guideline
Related Step 2 pages: Reflex Syncope, Orthostatic Hypotension, Exercise-Induced Postural Hypotension, Ventricular Tachycardia, Atrioventricular Block, Aortic Stenosis, Hypertrophic Cardiomyopathy, Cardiac Implantable Devices
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