Step 2 CK · Internal Medicine · Cardiology

Syncope & Cardiac Risk Assessment

Name: Syncope & Cardiac Risk Assessment
Creator: Veli Bakalov, MD

Fainting from the benign to the deadly — plus who is fit for the OR

Cardiology·Cardiac Evaluation & Diagnostics·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

Study materialsNo account needed

Card deckActive-recall cards · quick checks · quiz

High-yield

Syncope has three buckets: reflex/vasovagal (most common, triggered, with prodrome, benign), orthostatic, and cardiac (most dangerous).
Orthostatic hypotension = systolic fall ≥20 or diastolic fall ≥10 mmHg within 3 minutes of standing; think volume loss, diuretics, α-blockers, vasodilators, or autonomic failure (diabetes, Parkinson disease).
Red flags for cardiac syncope: exertional or supine onset, no prodrome, preceding palpitations, structural heart disease, abnormal ECG, family history of sudden death.
Exertional syncope = aortic stenosis or hypertrophic cardiomyopathy until proven otherwise; get an echocardiogram.
Every syncope patient gets an ECG; add echo, Holter or loop recorder, or tilt-table by suspicion; neuroimaging and EEG are low-yield without focal signs or seizure features.
Long QT (QTc > 450 ms men, > 470 ms women; > 500 ms high risk) causes torsades: Romano-Ward is autosomal dominant, Jervell-Lange-Nielsen is autosomal recessive with deafness.
Acquired long QT: sotalol and class IA drugs, macrolides, fluoroquinolones, haloperidol, ondansetron, methadone, low K/Mg/Ca; acute torsades gets IV magnesium; congenital LQTS gets β-blockers (ICD if high risk).
Preop: emergency surgery proceeds; active cardiac conditions delay elective surgery; ≥4 METs (a flight of stairs) proceeds without testing; stress-test only if it would change management.
RCRI: high-risk surgery, ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, creatinine > 2; continue chronic β-blockers and statins but never start a high-dose β-blocker on the day of surgery (POISE).

Syncope: three mechanisms

Definition. Syncope is a transient loss of consciousness from global cerebral hypoperfusion, with spontaneous, complete recovery. Every case falls into one of three buckets: reflex (neurocardiogenic), orthostatic, or cardiac. Cardiac syncope is the one that kills.

Types of syncope

Feature	Reflex (vasovagal)	Orthostatic	Cardiac
Setting	Pain, fear, sight of blood, prolonged standing, heat	On standing up	Exertion, while supine, or with no trigger at all
Warning	Prodrome: nausea, warmth, diaphoresis, tunnel vision	Lightheadedness on rising	Sudden, no prodrome; palpitations just before
Causes	Vagal surge with vasodilation and bradycardia	Volume depletion; diuretics, α-blockers, vasodilators; autonomic failure (diabetes, Parkinson disease)	Arrhythmic: brady- or tachyarrhythmia, long QT, WPW, Brugada. Structural: aortic stenosis, HCM, PE, tamponade
Prognosis	Benign; most common type	Depends on cause; falls in the elderly	Most dangerous; risk of sudden death

Reflex syncope. Vasovagal syncope is the most common cause overall and recovers quickly once the patient is supine. Situational syncope (cough, micturition, defecation) and carotid sinus hypersensitivity (shaving, a tight collar, turning the head) belong to the same reflex family. Management is reassurance, hydration, avoiding triggers, and physical counterpressure maneuvers at the first symptoms; tilt-table testing is reserved for recurrent or unclear cases.

Orthostatic hypotension is a fall in systolic BP of ≥20 mmHg or diastolic BP of ≥10 mmHg within 3 minutes of standing, confirmed with orthostatic vital signs. Polypharmacy in older adults is a frequent culprit. Stop offending drugs and restore volume; compression stockings, fludrocortisone, or midodrine help neurogenic cases.

Exertional syncope signals a fixed outflow obstruction, aortic stenosis or hypertrophic cardiomyopathy, until proven otherwise, so get an echocardiogram. A murmur that grows louder with Valsalva points to HCM.

Red flags and workup

Red flags for cardiac syncope. Any of these mandates a cardiac workup and often admission:

Onset during exertion or while supine
No prodrome, or palpitations just before the event
Known structural heart disease
An abnormal ECG
Family history of sudden death

ECG for everyoneLook for long QT, delta wave (WPW), Brugada pattern, AV block, and LVH.
Orthostatic vital signsA drop of ≥20 systolic or ≥10 diastolic within 3 minutes of standing.
EchocardiogramFor suspected structural disease: murmur, exertional syncope, heart failure.
Ambulatory monitoringHolter for frequent symptoms; event monitor or implantable loop recorder for infrequent ones.
Tilt-table testFor recurrent, unexplained reflex syncope.

What not to order. Neuroimaging and EEG are low-yield without focal neurologic signs or features of seizure. A seizure is suggested by lateral tongue-biting, prolonged postictal confusion, and sustained tonic-clonic activity, whereas brief jerks with rapid recovery are common in plain syncope.

Long QT syndrome

>450 msprolonged QTc in men

>470 msprolonged QTc in women

>500 mshigh risk of torsades

Why it matters. A prolonged QT interval predisposes to torsades de pointes, a polymorphic VT that causes syncope and sudden death.

Congenital vs acquired long QT

Form	Features	Management
Romano-Ward	Autosomal dominant; normal hearing	β-blocker, avoid triggers and QT-prolonging drugs; ICD if high risk
Jervell-Lange-Nielsen	Autosomal recessive; sensorineural deafness	Same approach; typically higher risk
Acquired	Drugs; hypokalemia, hypomagnesemia, hypocalcemia	Stop the drug and correct electrolytes

Drugs that stretch the QT. Antiarrhythmics (sotalol, class IA agents), macrolides, fluoroquinolones, antipsychotics (haloperidol), ondansetron, and methadone. Risk multiplies when several are combined or when potassium, magnesium, or calcium is low.

Acute torsades: give IV magnesium, stop the offending drugs, and correct electrolytes. Defibrillate if the patient is unstable.

Preoperative cardiac risk assessment

Emergency surgery?Proceed without delay.
Active cardiac condition?Unstable angina, recent MI, decompensated heart failure, severe valvular disease (especially severe aortic stenosis), or significant arrhythmia: delay elective surgery and optimize first.
Estimate riskRevised Cardiac Risk Index plus the type of surgery.
Functional capacity ≥4 METs?Climbing a flight of stairs or walking uphill without symptoms: proceed with no further cardiac testing.
Under 4 METs or unknown, with risk factorsStress testing only if the result would change management.

Revised Cardiac Risk Index (RCRI). One point each for high-risk surgery (intraperitoneal, intrathoracic, or suprainguinal vascular), ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, and creatinine >2 mg/dL. Zero or one predictor means low risk; more predictors mean progressively higher risk of major cardiac events. Combine the score with functional capacity.

Perioperative medications. Continue β-blockers and statins in patients already taking them. Do not start a high-dose β-blocker on the day of surgery: in the POISE trial, perioperative metoprolol reduced MIs but increased strokes, hypotension, and total deaths. Coronary revascularization before noncardiac surgery is done only when it would be indicated anyway.