Basics & Fundamentals
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The Lewis Lead (Unmasking Atrial Activity)
Key Points: Purpose: The Lewis lead (modified S5 lead) is a modified ECG lead configuration designed to amplify atrial electrical activity, making P waves, flutter waves, and the relationship between…
The Bix Rule (Unmasking Atrial Flutter)
Key Points: Definition: The Bix rule is a bedside ECG clue suggesting that there may be twice as much atrial activity as is initially apparent. If an atrial deflection falls…
Monomorphic Ventricular Tachycardia (MMVT)
Key Points Definition: Monomorphic ventricular tachycardia is a ventricular rhythm with a wide QRS and a single, uniform QRS morphology throughout the run. Sustained VT: VT is sustained when it…
QRS Fragmentation (fQRS)
Key Points: Definition: Fragmented QRS (fQRS) refers to additional notches or deflections within the QRS complex, reflecting heterogeneous ventricular depolarization. In a narrow QRS, classic criteria include an additional R…
Arrhythmogenic Cardiomyopathy (ACM)
Key Points: Definition: Arrhythmogenic cardiomyopathy (ACM), historically called arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), is an inherited myocardial disease characterized by progressive myocardial injury and fibrous replacement, with or without fatty…
Atrial Septal Defect (ASD) & Crochetage Pattern
Key Points: ASD Overview: Atrial septal defects are congenital communications between the atria. Significant defects may remain unrecognized into adulthood, eventually causing right-sided volume overload, pulmonary hypertension, atrial arrhythmias, exercise…
Epsilon Waves
Key Points: Definition: Epsilon waves are reproducible, low-amplitude signals occurring between the end of the QRS complex and onset of the T wave, most often seen in the right precordial…
Hypokalemia
Key Points: Hypokalemia delays ventricular repolarization, producing progressive changes in the T-U complex before serious arrhythmias develop. ECG progression: T-wave flattening → mild ST depression → prominent U waves →…
Escape-Capture Bigeminy
Key Points: Definition: Escape-capture bigeminy is an uncommon rhythm in which escape beats alternate with conducted sinus capture beats, producing a repeating paired pattern. Mechanism: Sinus slowing, sinus pauses, or…
Hypermagnesemia
Key Points: Hypermagnesemia is uncommon and usually occurs when impaired renal magnesium clearance is combined with increased magnesium exposure, such as magnesium-containing laxatives, antacids, bowel preparations, or therapeutic magnesium administration….
Hypomagnesemia
Key Points: Hypomagnesemia is an important arrhythmogenic electrolyte abnormality. It can promote atrial and ventricular ectopy and increase susceptibility to ventricular arrhythmias, particularly when other repolarization abnormalities are present. ECG…
Hypocalcemia
Key Points: ECG hallmark: QT prolongation caused predominantly by ST-segment prolongation, usually with relatively preserved T-wave morphology. Arrhythmia risk: Severe hypocalcemia can predispose to ventricular arrhythmias, including torsades de pointes…
Persistent Juvenile T Wave Pattern
Key Points: Persistent juvenile T wave pattern is a benign normal variant that most often appears as shallow asymmetric T wave inversion in the right precordial leads, usually V1 to…
Slow Ventricular Tachycardia (VT)
Key Points: Definition: Slow VT refers to ventricular tachycardia occurring at an unusually low ventricular rate, often near or even below the conventional tachycardia threshold. There is no universally accepted…
S1Q3T3 Pattern
Key Points: Not a PE diagnosis: S1Q3T3 is classically associated with pulmonary embolism, but it is neither sensitive nor specific enough to diagnose or exclude PE. Think acute right heart…
ECG in Pulmonary Embolism (PE)
Key Points: The ECG cannot rule in or rule out PE: No single ECG finding is sufficiently sensitive or specific to diagnose or exclude acute pulmonary embolism. A Normal ECG…
Early Repolarization
Key Points: Definition: Early repolarization (ER) is a common ECG pattern characterized by J-point elevation, often with concave ST elevation and J-wave notching or slurring. Clinical importance: ER is one…
Atrial Fibrillation (AFib)
Key Points: Definition: Atrial fibrillation is a supraventricular arrhythmia characterized by disorganized atrial electrical activity, ineffective atrial contraction, and an irregular ventricular response. ECG diagnosis: Look for an irregularly irregular…
Atrial Flutter
Key Points: Atrial flutter is a supraventricular tachyarrhythmia caused by a macro-reentrant circuit, most commonly typical cavotricuspid isthmus-dependent flutter in the right atrium. The atrial rate is usually about 250-350…
Understanding ECG Artifacts
Key Points: Definition: ECG artifact is a noncardiac signal that distorts, obscures, or mimics the heart’s true electrical activity. Common sources: Patient movement or muscle activity, poor electrode contact, lead…
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