QRS
Results:
Right Bundle Branch Block (RBBB)
Key Points: RBBB delays right ventricular activation. The left ventricle depolarizes normally through the left bundle, while the right ventricle is activated late by slow myocardial spread. ECG hallmark: QRS…
Left Bundle Branch Block (LBBB)
Key Points: LBBB delays left ventricular activation. The RV activates first through the intact right bundle, then the impulse spreads slowly from right to left across the septum and LV…
New RBBB + LAFB (Bifascicular Block) in ACS
Key Points: In a patient with ischemic symptoms, new RBBB + LAFB should raise concern for proximal LAD or septal ischemia until proven otherwise, especially if the patient has ongoing…
Wide QRS Complex: DDx
Key Points: A QRS duration greater than 120 ms reflects delayed or abnormal ventricular depolarization. A wide QRS may be chronic and benign in context, or it may be the…
Occlusion MI in Ventricular Paced Rhythms: STEMI Equivalent Pattern
Key Points: Ventricular paced rhythms can mask acute coronary occlusion. Pacing alters depolarization and produces expected secondary ST-T abnormalities, so standard STEMI criteria are unreliable. Appropriate discordance is expected in…
Ventricular Paced Rhythms
Key Points: Ventricular pacing changes depolarization and repolarization, so ST-T segments often look abnormal. In most paced rhythms, some discordant ST deviation is expected and should not be mistaken for…
Atrioventricular (AV) Block: Comprehensive Summary
Key Points: AV block refers specifically to delayed or failed conduction of impulses from the atria to the ventricles. AV block is classified by the ECG pattern of conduction: First-degree…
Occlusion MI in Left Bundle Branch Block (LBBB): STEMI Equivalent Pattern
Key Points: LBBB does not exclude acute coronary occlusion. LBBB produces abnormal depolarization and expected secondary ST-T changes, which can mask or mimic ischemia. Acute OMI can still be recognized…
Left Ventricular Hypertrophy (LVH)
Key Points: LVH reflects increased left ventricular muscle mass, usually from chronic pressure overload. Common causes include longstanding hypertension and aortic stenosis. ECG diagnosis is imperfect. Voltage criteria are specific…
Appropriate Discordance
Key Points: Appropriate discordance refers to the expected secondary ST segment and T wave pattern seen with abnormal ventricular depolarization, especially LBBB and ventricular-paced rhythm. The ST segment and T…
QRS Morphology and ST-T Interpretation: Basics
Key Points: Read the QRS before you read the ST segment or T wave. Ventricular depolarization shapes repolarization. Narrow QRS usually reflects normal His-Purkinje conduction. Wide QRS suggests abnormal ventricular…
ECG Foundations: Vectors, Leads, & Activation
Key Points: An ECG records voltage differences over time. The ECG tracing is a plot where the horizontal axis is time and the vertical axis is voltage. Leads are viewpoints….
Bidirectional Ventricular Tachycardia (BiVT)
Key Points: BiVT is a regular wide-complex tachycardia with strict beat-to-beat alternation of QRS axis and/or bundle-branch pattern (often an approximately 180° frontal-plane axis flip). In adults, assume digoxin toxicity…
Ventricular Tachycardia (VT): Core Overview
Key Points: VT is a ventricular-origin rhythm: ≥3 consecutive ventricular beats, QRS >120 ms, rate usually 120–250 bpm. Types include monomorphic VT, polymorphic VT, torsades (PMVT with long QT), ventricular…
Pulseless Ventricular Tachycardia (pVT) Arrest
Key Points: Defibrillation First, Minimal Pauses: pVT is rapidly fatal without immediate shocks and high‑quality CPR. Charge defibrillator during compressions and resume compressions immediately after each shock. pVT is a…
Ventricular Fibrillation (VF) Arrest
Key Points: Defibrillation First, Minimal Pauses: VF is rapidly fatal without immediate shocks and high‑quality CPR. Charge during compressions and resume compressions immediately after each shock. Chaotic Electrical Activity: VF…
Ventricular Flutter (V-Flutter)
Key Points: Definition: A malignant ventricular tachyarrhythmia with a regular, sine-wave–like waveform at ~250–350 bpm, no isoelectric baseline, and no discernible P/QRS/T distinction. Clinical importance: Rapidly degenerates into ventricular fibrillation…
Premature Complexes (PACs, PJCs, & PVCs) Overview
Key Points: Premature complexes are early depolarizations arising from the atrium, AV junction, or ventricle which interrupt the expected sinus rhythm. Rapid classification by origin: look for a P wave…
Premature Ventricular Complexes (PVCs)
Key Points PVCs are early ventricular depolarizations that produce a wide QRS with secondary ST-T changes and are usually followed by a full compensatory pause. No preceding P wave. A…
Accelerated Idioventricular Rhythm (AIVR)
Key Points: Definition: AIVR is a transient, usually benign ventricular rhythm often seen after reperfusion of an acute myocardial infarction (AMI), whether spontaneous or post-intervention (PCI or thrombolysis). Rate Differentiation:…
ECG Tags
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