Basics & Fundamentals
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Understanding ECG Artifacts
Key Points Artifacts = non-cardiac signals that distort or obscure true ECG. They come from the patient, leads/equipment, or the environment. Clues to artifact: lacks a physiologic pattern, varies beat-to-beat…
Ischemia & Infarction Interpretation
Key Points: The ECG is the fastest bedside tool for detecting acute coronary occlusion and dynamic ischemia, often before troponin changes and sometimes before classic symptoms. Acute coronary syndromes are…
Fascicular Ventricular Tachycardia (Idiopathic Left Fascicular VT)
Key Points Idiopathic reentrant VT arising within the left Purkinje system, most often the left posterior fascicle. Patients are usually young and lack structural heart disease. Signature ECG: RBBB-like morphology…
Atrial Septal Defect (ASD) & Crochetage Pattern
Key Points ASD Overview: Atrial septal defects are often detected and repaired in childhood, but uncorrected lesions may remain silent into early adulthood. Symptoms usually appear by age 30–40 and…
Irregularly Irregular Rhythm: Basics
Key Points: Definition: An irregularly irregular rhythm occurs when the R-R intervals or P-P intervals vary with no consistent pattern, making the rhythm unpredictable and abnormal. Clinical Significance: Identifying an…
Regularly Irregular Rhythm: Basics
Key Points: Definition: A regularly irregular rhythm occurs when the distance between R-R intervals or P-P intervals varies in a consistent, repeating pattern throughout the ECG tracing. Significance: Determining the…
Regular Rhythm: Basics
Key Points: Rhythm Regularity: Regular rhythm is characterized by equal distances between consecutive P waves (P-P intervals) and QRS complexes (R-R intervals). Verify rhythms with calipers—don’t trust the machine interpretation…
Heart Rate & Rhythm Interpretation
Key Points: Treat the patient, not just the number or rhythm. Start with a 10-second stability check. If the rhythm explains hypotension, shock, ischemic chest pain, altered mentation, or severe…
Sinus Arrhythmia
Key Points Definition: Phasic variation in sinus rate with respiration. P-P intervals shorten on inspiration and lengthen on expiration, producing a mild, patterned irregularity. Diagnostic threshold: Difference between the shortest…
Slow Ventricular Tachycardia (VT)
Key Points Definition: Slow ventricular tachycardia is defined as a wide complex tachycardia with a ventricular rate between 100–120 bpm. Distinction: Typical sustained VT usually exceeds 120 bpm. When encountering…
The Lewis Lead (Unmasking Atrial Activity)
Key Points: Purpose: The Lewis Lead (modified S5 lead) is a bedside ECG modification designed to enhance visualization of atrial activity. It is particularly useful for differentiating VT from SVT…
Multifocal Atrial Tachycardia (MAT)
Key Points Definition: Multifocal Atrial Tachycardia (MAT) is a rare type of irregularly irregular supraventricular tachycardia (SVT) characterized by the presence of at least three or more different P wave…
Terminal QRS Distortion: OMI Pattern
Key Points: What it is: In V2 or V3, there is no S wave (the R does not descend below the PQ baseline) and no J wave (no notch/slur at…
QRS Axis Interpretation: Basics
Key Points: Definition: The QRS axis reflects the net direction of ventricular depolarization and is expressed in degrees on the frontal plane. Why It Matters: Axis assessment is a fast,…
Extreme Axis Deviation: Basics
Key Points Definition: Extreme axis deviation (aka “Northwest Axis”) occurs when the QRS axis is between –90° and ±180°. ECG Clue: QRS negative in Lead I QRS negative in Lead…
Left Axis Deviation: Basics
Key Points Definition: LAD occurs when the QRS axis is between –30° and –90°. ECG Pattern: QRS positive in Lead I QRS negative in Lead aVF Clinical Use: LAD can…
Indeterminate QRS Axis: Basics
Key Points Definition: An indeterminate QRS axis (also called “no man’s land”) occurs when the frontal QRS vector lies between –90° and ±180°, but no dominant direction is evident. ECG…
Right Axis Deviation: Basics
Key Points Definition: Right Axis Deviation (RAD) occurs when the QRS axis is > +90°, typically up to +180°. ECG Criteria: Negative QRS in Lead I Positive QRS in Lead…
Right Axis Deviation: DDx
Top 3 Emergent Causes of New Rightward Axis Deviation: When you see new RAD in an adult, immediately consider life-threatening etiologies: Acute Right Heart Strain Pulmonary embolism until proven otherwise…
Normal QRS Axis
Key Points Normal Axis Range: –30° to +90° Lead I: QRS complex is positive Lead aVF: QRS complex is positive → This combination confirms a normal QRS axis Frontal plane…
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