Basics & Fundamentals
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Left Atrial Enlargement (LAE)
Key Points Definition: Left atrial enlargement (LAE) occurs when the left atrium dilates due to chronic pressure or volume overload. It commonly reflects underlying structural heart disease, particularly involving the…
Short QT Syndrome
Key Points Short QT Syndrome (SQTS) is a rare condition characterized by a shortened QT interval on the ECG, increasing the risk of atrial and ventricular arrhythmias, including sudden cardiac…
Slow Atrial Fibrillation
Key Points Definition: Atrial fibrillation with a slow ventricular response, usually < 60 bpm. ECG: Irregularly irregular rhythm, no discrete P waves, slow R-R intervals. Common causes: AV-nodal blockers (digoxin,…
Sinoatrial Exit Block
Key Points Definition: SA exit block occurs when the sinus node generates impulses that are blocked before they can activate the right atrium, leading to dropped P waves on the…
Unifasicular Block
Key Points Definition: Unifascicular block refers to conduction delay or interruption in a single fascicle of the ventricular conduction system: the right bundle branch (RBB), left anterior fascicle (LAF), or…
Pulmonary Embolism (PE)
Key Points ECG Findings in PE: No single ECG pattern is diagnostic of acute PE, and ECG findings are typically nonspecific. However, certain ECG patterns, especially those indicating right heart…
Persistent Juvenile T wave Pattern
Key Points Benign Variant: Persistent juvenile T waves (PJTW) represent a benign ECG finding and require no further evaluation in the absence of clinical symptoms or concerning findings. Typical Distribution:…
Left Posterior Fascicular Block (LPFB)
Key Points Anatomy of the Left Bundle Branch: The left bundle branch divides into two main fascicles: the left anterior fascicle (LAF) and the left posterior fascicle (LPF), both of…
Atrial Flutter with Variable Conduction
Key Points Mechanism: Typical atrial flutter arises from a large re-entry circuit in the right atrium. The atrial rate is usually near 300 beats per minute. ECG hallmark: Continuous “saw-tooth”…
QRS Voltage Basics
Key Points Definition: QRS voltage represents the amplitude (height) of the QRS complex on ECG, reflecting ventricular electrical activity during depolarization. High Voltage: Increased QRS voltage typically indicates ventricular hypertrophy—most…
Abnormal P Wave Axis DDx
Key Points Normal Sinus Rhythm: In a normal rhythm, the sinus node initiates atrial depolarization, resulting in a P wave with a normal axis: upright in lead II, inverted in…
Post-Cardiac Arrest ECGs
Key Points Coronary Occlusion After Shockable Arrest: ~30% of patients resuscitated from ventricular fibrillation (VF) arrest have an acute coronary occlusion and present with STEMI on ECG. Among patients without…
ECG Foundations
Key Points: Electrocardiography Defined: An ECG records the heart’s electrical activity in real time, offering a rapid window into rate, rhythm and conduction. The ECG measures changes in voltage between…
First-Degree AV Block
Key Points Definition: PR interval prolongation (>200 ms) without dropped QRS complexes (consistent 1:1 P:QRS conduction). Mechanism: Usually results from slowed conduction within the AV node or the His-Purkinje system,…
Flutter Waves (F waves)
Key Points Mechanism: Produced by a macro-reentrant circuit within the right atrium. Atrial Rate: Typically ~300 bpm (range 240–360 bpm). ECG Appearance: Characteristic saw-tooth baseline undulations without an isoelectric interval….
Electrical Alternans
Key Points Classically associated with pericardial tamponade but seen in fewer than 30% of confirmed cases. Combination of low-voltage QRS + sinus tachycardia strongly suggests pericardial effusion/tamponade. Always perform rapid…
Pericardial Effusion
Key Point Always consider pericardial effusion in any patient with new low-voltage QRS complexes combined with sinus tachycardia. Prompt bedside ultrasound (POCUS) prevents diagnostic delays and potentially catastrophic outcomes. Classic…
Acute Chest Pain DDx
Key Point In patients presenting with acute chest pain, rapidly identifying life-threatening conditions is essential. Use a systematic ECG approach alongside clinical context to evaluate for high-risk diagnoses that require…
QT Interval Basics
Key Points Definition: The QT interval is a measure of the time from the beginning of the QRS complex to the end of the T wave. It reflects the total…
Torsades de Pointes (TdP)
Key Points Definition: TdP is a specific subtype of polymorphic ventricular tachycardia associated with a prolonged QTc interval. It often presents with a “twisting” pattern on ECG but can be…
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