Basics & Fundamentals
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Escape-Capture Bigeminy
Key Points: Definition: Escape-capture bigeminy is an uncommon rhythm in which escape beats alternate with conducted sinus capture beats, producing a repeating paired pattern. Mechanism: Sinus slowing, sinus pauses, or…
S1Q3T3 Pattern
Key Points: Not a PE diagnosis: S1Q3T3 is classically associated with pulmonary embolism, but it is neither sensitive nor specific enough to diagnose or exclude PE. Think acute right heart…
ECG in Pulmonary Embolism (PE)
Key Points: The ECG cannot rule in or rule out PE: No single ECG finding is sufficiently sensitive or specific to diagnose or exclude acute pulmonary embolism. A Normal ECG…
Atrial Fibrillation (AFib)
Key Points: Definition: Atrial fibrillation is a supraventricular arrhythmia characterized by disorganized atrial electrical activity, ineffective atrial contraction, and an irregular ventricular response. ECG diagnosis: Look for an irregularly irregular…
Understanding ECG Artifacts
Key Points: Definition: ECG artifact is a noncardiac signal that distorts, obscures, or mimics the heart’s true electrical activity. Common sources: Patient movement or muscle activity, poor electrode contact, lead…
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…
The Bix Rule (Unmasking Atrial Flutter)
Key Points: The Bix Rule is a bedside ECG clue for atrial flutter with 2:1 conduction. If an apparent “P wave” sits exactly halfway between 2 QRS complexes in a…
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…
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…
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…
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