ECG Findings in Syncope

Overview

This lecture reviews the essential ECG findings in patients presenting with syncope, focusing on life-threatening cardiac causes and specific patterns that should never be missed.

Syncope Evaluation Basics

• Most syncope workups do not require routine labs unless history or exam suggests a specific need.
• The only test that should be routinely performed on all syncope patients is an ECG.
• Good history and physical examination should direct any further workup.

Key ECG Findings to Identify in Syncope

• Always look for evidence of cardiac ischemia and arrhythmias (including AV blocks).
• Additional critical ECG patterns include hypertrophic cardiomyopathy, Brugada syndrome, Wolff-Parkinson-White (WPW) syndrome, and prolonged QT interval.

Hypertrophic Cardiomyopathy (HCM)

• Look for high voltage QRS complexes and deep, narrow "dagger-like" Q waves in lateral leads (I, aVL, V5, V6).
• Q waves are not wide enough to indicate infarction; commonly misread as old MI.
• Send for Doppler echocardiogram if suspected, and advise no exertion; consider beta blockers until cardiology evaluation.

Brugada Syndrome

• Look for incomplete right bundle branch block pattern with coved or straight ST elevation and inverted T wave in V1/V2.
• The "coved" ST segment elevation is most concerning.
• Brugada can lead to polymorphic VT or sudden death, often triggered during rest or sleep.
• Most reliably managed by electrophysiologists, not general cardiologists.
• Confirm diagnosis with sodium channel blocker challenge in EP lab; treat with AICD if positive.

Wolff-Parkinson-White (WPW) Syndrome

• Classic triad: short PR interval, wide QRS, and delta wave (slurred upstroke in QRS).
• Delta wave may not be present in all leads; always check PR interval first.
• WPW with atrial fibrillation: irregularly irregular rhythm with changing QRS morphology (some narrow, some wide complexes).
• Avoid AV nodal blockers (adenosine, calcium channel blockers, beta blockers, digoxin, amiodarone); use procainamide or cardioversion instead.

Prolonged QT Syndrome

• QTC > 500 ms increases risk for torsades de pointes and sudden cardiac death.
• Causes include hypokalemia, hypomagnesemia, hypocalcemia, and QT-prolonging drugs.
• Patients may present after syncope, seizure, or with predisposing risk factors.
• Always check electrolytes and medication lists; avoid QT-prolonging agents.

Key Terms & Definitions

• Syncope — Sudden, temporary loss of consciousness with spontaneous recovery.
• ECG (Electrocardiogram) — A test recording the heart's electrical activity.
• Hypertrophic Cardiomyopathy — Genetic condition causing thickened heart muscle.
• Q Waves — Downward deflection on ECG; deep/narrow Q waves suggest HCM.
• Brugada Syndrome — Genetic sodium channel defect causing distinctive ST elevation in V1/V2.
• WPW Syndrome — Pre-excitation due to accessory pathway, resulting in short PR, delta waves.
• Delta Wave — Slurred upstroke on QRS indicating early ventricular activation.
• Prolonged QT — Extended QT interval; risk factor for torsades de pointes.

Action Items / Next Steps

• Perform an ECG on every patient presenting with syncope.
• Be alert for and document critical ECG patterns: HCM, Brugada, WPW, and prolonged QT.
• Refer suspected HCM or Brugada cases urgently to cardiology/electrophysiology.
• Avoid AV node blockers in WPW with AFib; use alternatives per protocol.
• Review medication and electrolyte causes in prolonged QT and manage accordingly.