Basics & Fundamentals
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Epsilon Waves
Key Points Definition: Small, low-amplitude positive deflections at the terminal QRS or very early ST segment, caused by delayed right ventricular activation through diseased myocardium. Association: Highly specific for arrhythmogenic…
Fascicular Blocks
Key Points Definition: Delay/block within the left bundle’s fascicles—left anterior (LAF) or left posterior (LPF)—alters ventricular activation and the QRS axis. Types: LAFB (common) → left axis deviation; LPFB (rare)…
J Point Basics
Key Points Definition: The J point is the junction where the QRS complex ends and the ST segment begins. It is a location, not a waveform. Clinical importance: J point…
J Wave Basics
Key Points Definition: A J wave (Osborn wave) is a distinct hump or slur at the end of the QRS at or just after the J point. The J point…
ST Segment Basics
Key Points Definition: The ST segment runs from the J point (end of QRS) to the start of the T wave, the interval between ventricular depolarization and repolarization. Normal: Usually…
Right Ventricular Hypertrophy (RVH)
Key Points Definition: Chronic pressure/volume overload → thickened RV (pulm HTN, congenital lesions, pulmonary disease). ECG signature: Rightward axis, dominant R in V1, deep S in V5–V6, with possible right-sided…
Q Wave Basics
Key Points Definition and Measurement: A Q wave is the first negative deflection of the QRS. Measure width in ms from the onset below baseline to its return to baseline;…
QRS Complex Basics
Key Points Definition and measurement: The QRS complex is ventricular depolarization, measured from the earliest ventricular deflection (Q or R) to the latest S return to baseline in any lead….
QT Interval Basics
Key Points Definition: QT = onset of QRS → end of T; reflects total ventricular depolarization + repolarization. Rate correction (QTc): Use corrected QT interval, because QT shortens with faster…
R Wave Basics
Key Points Definition: The R wave is the first positive deflection of the QRS complex, reflecting early ventricular depolarization, predominantly of the left ventricle. Normal progression: Precordial R amplitude increases…
Hypermagnesemia
Key Points ECG red flags: Bradycardia, PR/QRS/QT prolongation, flattened P, peaked T, → AV block/asystole at higher levels. Neuromuscular: Hyporeflexia → weakness → respiratory depression → coma. Immediate countermeasure (severe/symptomatic):…
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 Interval Basics
Key Points Definition: The PR interval runs from P-wave onset to the first ventricular deflection (Q or R). It reflects atrial depolarization plus AV node–His–Purkinje conduction delay. Normal range: 120–200…
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,…
Preexcitation Syndromes
Key Points Terminology: WPW pattern = ECG evidence of pre-excitation without symptoms. WPW syndrome = pattern plus symptomatic tachyarrhythmia (e.g., AVRT, pre-excited AF). Mechanism: An atrioventricular accessory pathway (e.g., Kent;…
Waveforms, Segments, & Intervals
Key Points ECGs display voltage changes across the cardiac cycle, captured as waveforms, segments, and intervals. Waveforms represent depolarization or repolarization events. Segments are baseline connections between waveforms, usually representing…
Ventricular Flutter
Key Points Definition: A malignant ventricular tachyarrhythmia with a regular, sine-wave–like waveform at ~250–350 bpm, with no isoelectric baseline and no clear P/QRS/T distinction. Why it matters: Rapidly degenerates to…
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…
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