Basics & Fundamentals
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Brugada Syndrome (BrS)
Key Points: What It Is: Brugada syndrome is an inherited arrhythmogenic disorder associated with ventricular fibrillation (VF), polymorphic VT, and sudden cardiac death, often in patients without obvious structural heart…
Barcelona Criteria in Left Bundle Branch Block (LBBB): OMI Pattern
Key Points: The Barcelona Criteria are ECG criteria proposed to identify acute myocardial infarction in patients with LBBB. Core problem: LBBB causes expected secondary ST-T changes, so standard STEMI millimeter…
T Wave Alternans
Key Points: T wave alternans is beat-to-beat alternation in T wave amplitude, polarity, or morphology with otherwise stable P waves and QRS complexes. Visible T wave alternans is a warning…
Sinus Bradycardia
Key Points: Definition: Sinus bradycardia is a sinus rhythm with a rate <60 bpm. In clinical practice, a rate <50 bpm is often a more useful threshold because resting rates…
J Point: Basics
Key Points: The J point is the junction between the end of the QRS complex and the beginning of the ST segment. It is a location, not a separate waveform….
Post-Cardiac Arrest ECGs Hub
Key Points: The first post-ROSC ECG is essential but imperfect. Obtain it immediately, but interpret it in context. Global ischemia, defibrillation, acidosis, hypothermia, vasopressors, artifact, and severe metabolic derangements can…
Post-Arrest STEMI: Cath Lab Decisions
Key Points: Persistent ST elevation after ROSC remains a guideline-supported indication for emergency coronary angiography. The 2025 ACC/AHA/ACEP/NAEMSP/SCAI ACS guideline recommends emergency angiography for patients after cardiac arrest with suspected…
Post-Arrest No STEMI: When Cath Can Wait
Key Points: Stable post-arrest patients without ST elevation should not go to reflex immediate cath solely because cardiac arrest occurred. Randomized trials in OHCA patients without ST elevation have not…
Sinus Node Dysfunction (Sick Sinus Syndrome & Bradycardia-Tachycardia Syndrome)
Key Points: A spectrum, not a single rhythm: Sinus node dysfunction includes inappropriate sinus bradycardia, sinus pauses or arrest, SA exit block, chronotropic incompetence, and alternating atrial tachyarrhythmias with bradycardia….
Sinoatrial Exit Block
Key Points: Definition: Sinoatrial, or SA, exit block occurs when the sinus node generates an impulse that fails to conduct into the surrounding atrial tissue. The blocked impulse produces no…
Normal Cardiac Conduction
Key Points: Normal cardiac conduction begins in the SA node, travels through the atria to the AV node, then enters the His-Purkinje system to activate both ventricles rapidly and synchronously….
Right Bundle Branch Block (RBBB)
Key Points: RBBB delays right ventricular activation. The left ventricle depolarizes normally through the left bundle, while the right ventricle is activated late by slow myocardial spread. ECG hallmark: QRS…
Left Bundle Branch Block (LBBB)
Key Points: LBBB delays left ventricular activation. The RV activates first through the intact right bundle, then the impulse spreads slowly from right to left across the septum and LV…
QT Interval: Basics
Key Points: Definition: The QT interval is measured from the onset of the QRS complex to the end of the T wave. It represents the total duration of ventricular depolarization…
Junctional Tachycardia
Key Points: Junctional tachycardia is an uncommon supraventricular tachycardia arising from the AV junction, usually due to enhanced automaticity rather than reentry. It is usually a regular narrow-complex tachycardia, although…
Torsade de Pointes (TdP)
Key Points: Definition: Torsade de pointes is a specific form of polymorphic ventricular tachycardia (PMVT) occurring in the setting of prolonged ventricular repolarization/QT prolongation. ECG Pattern: TdP shows beat-to-beat variation…
Acquired Long QT Syndrome
Key Points: What It Is: Acquired Long QT Syndrome is delayed ventricular repolarization caused by an external or clinical factor, most commonly QT-prolonging medications, electrolyte abnormalities, or bradycardia. Why It…
Congenital Long QT Syndrome
Key Points: What It Is: Congenital Long QT Syndrome (LQTS) is an inherited cardiac channelopathy that delays ventricular repolarization and predisposes patients to torsades de pointes (TdP), ventricular fibrillation, syncope,…
Junctional Rhythms
Key Points: Junctional rhythms arise from the AV junction, usually the AV node or proximal His bundle, when the sinus node slows, fails, or impulses do not reach the ventricles…
Pediatric ECG: Basics
Key Points: Pediatric ECGs are not scaled-down adult ECGs. Right axis deviation, large R waves in V1, and T wave inversions in V1 to V3 are expected in healthy children….
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