Basics & Fundamentals
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Atrial Tachycardia
Key Points: Definition: Atrial tachycardia is a supraventricular arrhythmia characterized by rapid atrial depolarizations from one or more ectopic foci outside the SA node. Atrial Rate: > 100 bpm, typically…
Trifascicular Block
Key Points Definition: Trifascicular block describes ECG evidence of impaired conduction across all three fascicles: right bundle branch (RBB), left anterior fascicle (LAF), and left posterior fascicle (LPF). Common Usage:…
Pseudo-Wellens Waves
Key Points Wellens Syndrome: A critical condition resulting from severe stenosis of the left anterior descending (LAD) coronary artery, characterized by specific ECG patterns known as Wellens waves. This is…
Sinus Bradycardia
Key Points Definition: Sinus bradycardia is a rhythm originating from the sinoatrial (SA) node with a rate < 60 bpm. Physiological Occurrence: Common in young, healthy adults, athletes, and during…
Sinus Node Dysfunction (Sick Sinus / Brady–Tachy Syndrome)
Key Points Spectrum, not one rhythm: Look for sinus brady, pauses, arrest, alternating atrial tachyarrhythmias (AF, flutter, ATach). Symptoms matter: Syncope, presyncope, fatigue usually come from cerebral/systemic hypoperfusion, especially after…
Wellens Waves
Key Points Significance: Wellens waves are T wave abnormalities (either biphasic or deeply inverted) in the mid-precordial leads (V2-V3, +/-V4-6) that are highly specific for critical obstruction of the left…
Right Atrial Enlargement (RAE)
Key Points Definition: Right atrial enlargement (RAE) is an increase in the size of the right atrium, typically resulting from chronic pressure or volume overload, commonly related to cardiac or…
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:…
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 Early post-ROSC ECGs often mislead. Within the first 8–10 minutes, transient global ischemia and catecholamines can exaggerate ST changes. Plan a repeat at 10–15 minutes before making cath…
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,…
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