Basics & Fundamentals
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Left Anterior Fascicular Block (LAFB)
Key Points Mechanism: Block in the left anterior fascicle → ventricular activation proceeds down the left posterior fascicle, then spreads inferior-to-superior and right-to-left across the LV. ECG signature: Left axis…
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)…
Left Ventricular Hypertrophy (LVH)
Key Points Pathophysiology: Chronic pressure overload thickens the LV wall. Expect prolonged depolarization vectors and delayed repolarization that produce characteristic ECG voltage and ST-T changes. ECG signature: High precordial voltages,…
PR Segment: Basics
Key Points Definition: The PR segment is the flat line from the end of the P wave to the beginning of the QRS. It reflects conduction through the AV node,…
TP Segment: Basics
Key Points Definition: The TP segment is the isoelectric interval from the end of the T wave to the start of the P wave. It reflects electrical diastole when the…
U Wave: Basics
Key Points Definition and origin: The U wave is a small deflection following the T wave, best seen in V2–V3. It likely reflects late ventricular repolarization or Purkinje repolarization. Normal…
T Wave: Basics
Key Points Definition: The T wave reflects ventricular repolarization. Measure amplitude from baseline to peak and identify the end of T to help define the QT interval. Normal appearance: Upright…
S Wave: Basics
Key Points Definition and measurement: The S wave is the first negative deflection after the R wave within the QRS. Measure depth in mm from baseline to nadir; width contributes…
Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)
Key Points Rare, inherited ventricular arrhythmia triggered by adrenergic stress during exertion or emotion. Classically presents in children or adolescents with syncope or cardiac arrest despite a normal resting ECG…
Artifact vs Ventricular Rhythms: DDx
Key Points Artifact is a common source of misdiagnosis for serious arrhythmias such as polymorphic ventricular tachycardia (PVT), torsades de pointes, or ventricular fibrillation (VF). Always correlate the ECG findings…
Isoelectric Segment of the ECG
Key Points The reference for ST-segment shift is the J point relative to an isoelectric baseline. The two candidates for that baseline are the TP segment and the PR segment….
Monomorphic Ventricular Tachycardia
Key Points Monomorphic ventricular tachycardia (MMVT) is the most common sustained VT. It shows a single, uniform QRS morphology throughout. Classified as sustained if lasting > 30 seconds or associated…
Inverted U Waves
Key Points Definition: A negative deflection after the T wave (a true U wave) that is ≥0.5 mm deep in a lead where the T wave is upright. Why it…
Atrioventricular Blocks (AVB): Comprehensive Summary
Key Points: AV block specifically reflects delayed or failed impulse conduction from atria to ventricles. Classification of blocks depend on the location of conduction delay or block within the cardiac…
Hypokalemia
Key Points: Hypokalemia slows ventricular repolarization and alters the T–U complex before it triggers arrhythmias. Progressive pattern: T-wave flattening → prominent U waves → T–U fusion with apparent QT prolongation;…
Understanding ECG Artifacts
Key Points Artifacts = non-cardiac signals that distort or obscure true ECG. They come from the patient, leads/equipment, or the environment. Clues to artifact: lacks a physiologic pattern, varies beat-to-beat…
Ischemia & Infarction Interpretation
Key Points: The ECG is the fastest bedside tool for detecting acute coronary occlusion and dynamic ischemia, often before troponin changes and sometimes before classic symptoms. Acute coronary syndromes are…
Fascicular Ventricular Tachycardia (Idiopathic Left Fascicular VT)
Key Points Idiopathic reentrant VT arising within the left Purkinje system, most often the left posterior fascicle. Patients are usually young and lack structural heart disease. Signature ECG: RBBB-like morphology…
Isorhythmic AV Dissociation
Key Points Definition: A type of AV dissociation in which sinus and escape rates are nearly identical, so P waves and QRS complexes appear to “track” each other while remaining unrelated….
Atrial Septal Defect (ASD) & Crochetage Pattern
Key Points ASD Overview: Atrial septal defects are often detected and repaired in childhood, but uncorrected lesions may remain silent into early adulthood. Symptoms usually appear by age 30–40 and…
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