Axis
Results:
Left Posterior Fascicular Block (LPFB)
Key Points Mechanism: Block in the left posterior fascicle → LV activates mainly via the left anterior fascicle, spreading superior-to-inferior toward the inferior/posterior LV. ECG signature: Right axis deviation (RAD)…
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…
Right Axis Deviation + ST Elevation: DDx
Key Points RAD combined with ST-segment elevation (STE) is an uncommon but high-risk finding. While STE often suggests acute coronary occlusion, this pattern rarely reflects classic STEMI. Several non-ischemic conditions…
Extreme Axis Deviation: DDx
Key Points Definition: Extreme axis deviation is present when the QRS axis lies between –90° and ±180°. This is sometimes referred to as the “northwest axis.” ECG Pattern: QRS is…
Indeterminate Axis: DDx
Key Points An indeterminate axis, sometimes referred to as an “extreme” or “undetermined” axis, is suspected when the QRS complexes are isoelectric or nearly biphasic in both Lead I and…
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…
Left Axis Deviation: DDx
Key Points Definition: Left axis deviation (LAD) is defined as a QRS axis between –30° and –90°. ECG Clue: QRS complex is positive in Lead I and negative in Lead…
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…
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…
ECG Foundations: Waveforms, Intervals, Conduction, and Leads
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…
Sodium Channel Blocker Toxicity
Key Points Recognizing the Danger: Sodium channel blocker toxicity can present with a variety of ECG changes that are critical to recognize, especially in patients with altered mental status or…
Navigating a Very Abnormal QRS Axis with a Stepwise Approach
A 44-year-old woman presents to the emergency department with vague complaints about shortness of breath. The following ECG is obtained at triage and brought to you for interpretation:
ECG Basics and Fundamentals: Limb Lead Reversal
A 82-year-old woman presents to the ED “not feeling well”. She reports malaise, mild dyspnea, but denies any pain. Vital signs are normal. The following ECG is obtained on arrival…
ECG Basics and Fundamentals: right axis deviation differential and ST segment elevation in rightward leads
A 48-year-old woman presents to the ED with chest pain and near syncope. The following ECG is obtained:
ECG Basics & Fundamentals: a 5 step approach to ECG interpretation and how to think of differential diagnoses
HPI: A 70-year-old man presents with generalized malaise. He has a history of ESRD and has missed dialysis this week. The following ECG is obtained: Case ECG Before watching…
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