Basics & Fundamentals
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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…
Abnormal STAT ECG
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:…
Supraventricular Tachycardias (SVTs)
Key Points Definition: SVT refers to any tachyarrhythmia that originates above the ventricles (atria, AV node, or bundle of His). Most present as regular narrow-complex tachycardias, although aberrant conduction can…
Atrial Flutter 2:1 Conduction
Key Points Mechanism: Atrial flutter results from a macro re-entry circuit typically located within the right atrium, causing rapid and regular atrial activation (~300 bpm commonly). ECG Appearance: Classic “saw-tooth”…
Atrial Flutter
Key Points Definition: Atrial flutter is a common type of supraventricular tachycardia caused by a re-entry circuit within the right atrium. Atrial Rate: Typically around ~300 bpm, ranging from 240-360…
Second-Degree AV Block Type I (Mobitz I/Wenckebach)
Key Points: Definition: Progressive PR interval prolongation until one atrial impulse fails to conduct to the ventricles (P wave is non-conducted), after which the cycle repeats. Site of Block: Typically…
Second-Degree AV Block with 2:1 Conduction
Key Points: Definition: A form of second-degree AV block in which every other atrial impulse is blocked, producing a 2:1 atrioventricular conduction ratio. Typing Limitation: Differentiating between Mobitz I and…
Second-Degree AV Block Type II (Mobitz II)
Key Points Definition: Sudden failure of AV conduction after at least two consecutive conducted beats with identical PR intervals, followed by a single non‑conducted P wave. Sinus rate: P–P interval…
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…
Bifascicular Block
Key Points Definition: Conduction block in any two of the three fascicles: right bundle branch (RBB), left anterior fascicle (LAF), or left posterior fascicle (LPF). High-Risk OMI Pattern: New RBBB…
Bundle Branch Blocks
Key Point Types: The two main BBBs are Right Bundle Branch Block (RBBB) and Left Bundle Branch Block (LBBB). Impact on ECG: Both widen the QRS (>120 ms) and produce…
Dextrocardia
Key Points Dextrocardia is a congenital condition where the heart is located on the right side of the thorax. Situs inversus totalis refers to complete reversal of all thoracic and…
Interval Interpretation
Key Points: Intervals are your ECG safety rails. Before you get seduced by ST segments and T waves, lock down PR, QRS, and QT/QTc. They frequently reveal the real danger…
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