Basics & Fundamentals
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Paced Rhythms
Key Points Paced Rhythms Overview: Paced rhythms, whether from right ventricular (RV) pacemakers, left ventricular (LV) pacemakers, or dual-chamber pacemakers, produce specific ECG changes due to the altered sequence of…
Fascicular Blocks
Key Points Definition: Fascicular blocks refer to conduction delays or blockages in the left bundle branch fascicles, which can affect the QRS complex and T waves on the ECG. Types:…
Osborn Wave
Key Points What Are Osborne Waves? Osborne waves are positive deflections at the junction of the QRS complex and the ST segment, also known as the J point. While they…
Atrial Septal Defect (ASD) & Crochetage Pattern
Key Points ASD Overview: Atrial septal defects (ASDs) are often diagnosed and corrected in childhood, but even uncorrected, patients may do well into early adulthood. Symptoms typically develop by age…
Unifasicular Block
Key Points Trifascicular System: The ventricular Purkinje system is a trifascicular network that ensures rapid impulse conduction through the right and left ventricles, allowing for nearly simultaneous activation of both…
QRS Axis Basics
Key Points QRS Axis: The QRS axis represents the sum of all ventricular depolarization vectors and is primarily used to determine the electrical axis of the heart on an ECG….
Normal QRS Axis
Key Points Normal QRS Axis Range: Between -30° and +90°. Lead I: QRS complex is positive. Lead aVF: QRS complex is positive. KEY CLINICAL PEARLS: Correlate with Clinical Findings: Always…
Indeterminate Axis DDx
Key Points Axis is termed indeterminate when the QRS complexes are isoelectric (neither predoninately positive or negative) in lead I and aVF, hence making it not possible to determine the…
Left Axis Deviation Basics
Key Points Definition: Left Axis Deviation (LAD) occurs when the QRS axis on an ECG is shifted leftward, typically between -30° and -90°. Common Causes: LAD is often associated with…
Indeterminate QRS Axis Basics
Key Points Definition: An indeterminate QRS axis, also known as “no man’s land,” occurs when the QRS axis is between -90° and +180°. Indeterminate axis refers to situations where no…
Right Axis Deviation Basics
Key Points Definition: Right Axis Deviation (RAD) occurs when the QRS axis on an ECG is shifted rightward, typically between +90° and +180°. Common Causes: RAD is commonly associated with…
VT vs. SVT with Aberrancy
Key Points Basic Distinction: SVTs typically have narrow QRS complexes (<120 ms) but may present with wide complexes if aberrantly conducted (e.g., with existing bundle branch block). Clinical Importance: Differentiating…
History & Evolution of the “STAT ECG”
From Pioneering Beats to Lifesaving Measures: The Evolution of ECG in Clinical Medicine… In the ever-evolving landscape of emergency and acute care medicine, few tools have stood the test of…
Sinoatrial Nodal Reentry Tachycardia (SANRT)
Key Points Mechanism: SANRT is a rare type of paroxysmal supraventricular tachycardia (SVT) that operates through a similar mechanism as AV nodal reentry tachycardia (AVNRT), with the reentry loop occurring…
Junctional Tachycardia
Key Points Origin: Junctional tachycardia is a rare type of paroxysmal supraventricular tachycardia (SVT) that originates from the AV node or the bundle of His. Mechanism: The arrhythmia is caused…
Atrioventricular Nodal Reentry Tachycardia (AVNRT)
Key Points Definition: AVNRT is a type of paroxysmal supraventricular tachycardia (SVT) caused by a reentry circuit within or around the AV node, leading to a narrow complex regular rhythm….
Atrioventricular Reciprocating Tachycardia (AVRT)
Key Points Definition: AVRT is a type of supraventricular tachycardia (SVT) caused by a macroreentrant circuit that involves an accessory pathway in addition to the normal AV nodal pathway, allowing…
Inverted U waves
Key Points Normal U Waves: Small (< 0.5 mm) deflections following the T wave, usually in the same direction, best seen in leads V2-V3. Their amplitude is typically ~10% of…
Terminal QRS Distortion (OMI Pattern)
Key Points Early Repolarization (ER): A common ECG finding that can produce widespread ST-segment elevation, often mimicking STEMI or acute pericarditis. ST Segment Morphology: Convex and horizontal ST-segment morphology is…
Hypermagnesemia
Key Points ECG Red Flags: Flattened P waves, prolonged PR/QT, peaked T waves, risk of AV block or asystole. Neuromuscular Suppression: Hyporeflexia, progressing to muscle weakness, respiratory depression, and potential…
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