Basics & Fundamentals
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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 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 ECG
Key Points: Clinical Context: A single normal 12-lead ECG in the emergent setting does not exclude life-threatening conditions such as occlusion MI, PE, tamponade, tension pneumothorax, or aortic dissection. Serial…
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…
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 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…
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