Basics & Fundamentals
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QRS Axis 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…
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…
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 encounter new right axis deviation on an ECG, immediately consider the following life-threatening conditions: Acute Right Heart Strain or…
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…
Lead Misplacement
Key Points Proper lead placement is critical to avoid misdiagnoses that can lead to unnecessary interventions and patient harm. Misplaced precordial leads (V1-V6) can mimic ischemia and cause false MI…
Earliest Evidence of Occlusion MI
Key Points Dynamic Nature of ACS: Acute coronary syndromes (ACS) are complex and dynamic, with coronary arteries potentially undergoing reperfusion and reocclusion at any time. The ECG can provide real-time…
Computer Interpreted “Normal” ECGs
Key Points Do not fully trust computer interpretations of “normal” ECGs, they may miss significant abnormalities. Computer algorithms can miss early ischemic signs such as reciprocal changes in aVL and…
Abnormal STAT ECG
Key Points Clinical Context: Abnormal ECG findings in emergent settings must always be interpreted within the clinical context. Not all abnormalities represent life-threatening conditions, while several emergent conditions may present…
Early Reciprocal Changes
(OMI Pattern)
Key Points ACS Dynamics: ACS is complex and dynamic, with occluded arteries potentially reperfusing and reoccluding at any time. ECG Pattern Recognition: Mastering ECG pattern recognition in ACS is crucial…
Occlusion MI: STEMI Criteria & Beyond
Key Points A STAT ECG is the most critical first test in patients with suspected acute coronary syndrome (ACS). It allows for early identification of acute coronary occlusion myocardial infarction…
Hyperkalemia
Key Points ECG as a Frontline Diagnostic Tool: Hyperkalemia often reveals itself on the ECG before lab confirmation. Early recognition of characteristic changes can be life-saving, especially in critically ill…
Wide QRS Complex DDx
Key Points A QRS duration greater than 120 ms indicates abnormal ventricular depolarization. A wide QRS can signal conditions that range from benign to immediately life-threatening. Developing a focused differential…
Escape-Capture Bigeminy
Key Points Escape-capture bigeminy is a unique rhythm characterized by alternating escape beats and normally conducted sinus beats, resulting in a bigeminal (paired) rhythm pattern. It typically occurs in patients…
Modified Sgarbossa Criteria
Key Points Wide QRS Rhythms Can Mask OMI: Left bundle branch block (LBBB) and right ventricular (RV)-paced rhythms alter ventricular depolarization, producing expected secondary ST/T changes. However, acute occlusion MI…
Ventricular Escape Rhythms
Key Points Wide QRS Complex Rhythm: Ventricular escape rhythms (aka idioventricular rhythms) are characterized by a wide QRS duration (>120 ms), absent or dissociated P-waves, and a regular, slow ventricular…
Appropriate Discordance
Key Points Definition: Appropriate discordance is a normal repolarization pattern in which the ST segment and T wave are directed opposite to the main QRS vector. It reflects expected changes…
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