Basics & Fundamentals
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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…
Heart Rhythm: Basics
Key Points: Don’t trust the ECG machines automated interpretation. Confirm the rhythm yourself. Start with the ventricles (R–R pattern), then the atria (P waves), then the AV relationship (PR behavior/P:QRS)….
Heart Rate: Basics
Key Points: Never accept the machine’s rate blindly. Confirm it yourself as ECG computer interpretations are frequently inaccurate. Verify paper speed and gain first (default 25 mm/s, 10 mm/mV). Name…
Normal STAT ECGs
Key Points: Clinical Context: A single normal 12-lead ECG in the emergent setting does not exclude all life-threatening conditions such as early occlusion MI/ACS, PE, tamponade, or aortic catastrophe. Do…
Computer Interpreted “Normal” ECGs
Key Points: Do not trust a computer read of “normal” without your own review. Computer interpretation is especially unreliable for subtle or early ischemia, including hyperacute T waves, minimal ST…
Abnormal STAT ECGs
Key Points: Clinical Context: Abnormal ECGs must be interpreted within the patient’s presentation. Not all abnormalities are life-threatening, and high-risk conditions can still appear subtle or even “normal.” Serial Monitoring:…
Pacemaker Syndrome
Key Points: Pacemaker syndrome is a hemodynamic problem caused by loss of proper atrioventricular (AV) synchrony. Most commonly occurs with ventricular pacing that produces retrograde atrial activation, but can also…
Right Atrial Enlargement (RAE)
Key Points: RAE reflects increased right atrial size or pressure load and is usually a marker of underlying pulmonary or right-sided cardiac disease. The classic ECG clue is a tall,…
Left Atrial Enlargement (LAE)
Key Points: LAE reflects delayed and prolonged left atrial depolarization, usually from chronically elevated left atrial pressure or volume. Classic ECG clues are a broad, often notched P wave in…
Ventricular Paced Rhythms
Key Points: Ventricular pacing changes depolarization and repolarization, so ST-T segments often look abnormal. In most paced rhythms, some discordant ST deviation is expected and should not be mistaken for…
ECG Basics & Fundamentals Hub
Key Points: This hub organizes ECG basics and fundamentals into three complementary “start here” pathways: ECG definitions and measurement, how ECGs work and are generated, and the acute care STAT…
Atrioventricular (AV) Block: Comprehensive Summary
Key Points: AV block refers specifically to delayed or failed conduction of impulses from the atria to the ventricles. AV block is classified by the ECG pattern of conduction: First-degree…
Electrical Alternans
Key Points: Electrical alternans is a beat-to-beat alternation in QRS amplitude, axis, or both. It is classically associated with a large pericardial effusion and may support concern for tamponade, but…
Pericardial Effusion
Key Points: Pericardial effusion is the accumulation of fluid in the pericardial sac. ECG may provide clues, but it is not sensitive enough to exclude effusion. Important ECG clues include…
Left Ventricular Hypertrophy (LVH)
Key Points: LVH reflects increased left ventricular muscle mass, usually from chronic pressure overload. Common causes include longstanding hypertension and aortic stenosis. ECG diagnosis is imperfect. Voltage criteria are specific…
Modified Sgarbossa Criteria: STEMI Equivalent Pattern
Key Points: LBBB and ventricular-paced rhythms can hide acute coronary occlusion because abnormal depolarization creates expected secondary ST-T changes. Occlusion MI can still be recognized when those ST changes are…
Persistent Juvenile T Wave Pattern
Key Points: Persistent juvenile T wave pattern is a benign normal variant that most often appears as shallow asymmetric T wave inversion in the right precordial leads, usually V1 to…
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”…
Isorhythmic AV Dissociation
Key Points: Isorhythmic AV dissociation is a form of AV dissociation in which the sinus rate and junctional or ventricular escape rate are nearly identical, making the P waves and…
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