Basics & Fundamentals

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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…

Premature Atrial Complexes (PACs)

Key Points PACs are early atrial depolarizations from an ectopic focus that create a premature P wave with a different morphology and axis than the sinus P wave, usually followed…

Atrial Fibrillation (AFib)

Key Points Prevalence: The most common sustained cardiac arrhythmia, particularly prevalent among elderly individuals, associated with increased stroke, heart failure, and mortality risks. Mechanism: Caused by chaotic, multiple reentry circuits…

Post-Cardiac Arrest ECGs

Key Points Early post-ROSC ECGs often mislead. Within the first 8–10 minutes, transient global ischemia and catecholamines can exaggerate ST changes. Plan a repeat at 10–15 minutes before making cath…

Premature Junctional Complexes (PJCs)

Key Points PJCs are premature impulses from ectopic foci in or near the AV junction. ECG hallmark is a narrow premature beat with an absent or retrograde P wave. Retrograde…

J Point Basics

Key Points The J point is the junction where QRS ends and the ST segment begins. It is a location, not a waveform. ST deviation is judged at the J…

Blocked Premature Atrial Complexes (PACs)

Key Points Definition: early ectopic atrial beats that do not conduct to the ventricles. You see a premature P wave with no following QRS and a pause that is usually…

J Wave Basics

Key Points Definitions: The J point is the QRS–ST junction (a location). A J wave is an added deflection at or just after that point (notch or slur).  Why it…

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…

Osborn (J) Wave

Key Points An Osborn wave is a notch or slur at the J point that becomes more prominent as core temperature falls. Most visible in inferolateral and precordial leads; can…

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…

Spontaneous Coronary Artery Dissection (SCAD)

Key Points SCAD Definition: A spontaneous, non-atherosclerotic tear in the coronary artery wall, often affecting young, otherwise low-risk women (including peripartum patients). SCAD presents similarly to ACS and is an…

Non-Thrombotic Causes of Acute Coronary Syndrome (ACS)

Key Points ACS ≠ Always Thrombosis: While most ACS is due to plaque rupture with thrombus formation, several important non-thrombotic causes can produce identical ECG changes, troponin elevation, and symptoms….

ECG Lead Misplacement

Key Points Lead misplacement is common and can mimic ischemia, MI, conduction blocks, and arrhythmias. Always verify placement when ECG and clinical picture do not match. V1 and V2 placed…

Proper 12-Lead ECG Electrode Placement

Key Points A diagnostic 12‑lead ECG is only as good as your electrode placement. Misplacement can mimic MI, BBB, or poor R‑wave progression and trigger unnecessary workups. A standard 12‑lead…

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:…

STEMI Mimics

Key Points Context Matters: ECGs must be interpreted in the clinical setting. Chest pain, shock, or ACS risk factors increase pretest probability of STEMI/OMI, while atypical presentations lower it. Prevalence:…

Atrioventricular Nodal Reentry Tachycardia (AVNRT)

Key Points AVNRT is a paroxysmal, regular, usually narrow-complex SVT caused by a reentry circuit within or adjacent to the AV node. Dual-pathway physiology is typical. Bedside hallmark is a…

Atrioventricular Reciprocating Tachycardia (AVRT)

Key Points AVRT is a macroreentrant SVT that uses both the AV node and an accessory pathway. Orthodromic AVRT conducts down the AV node and up the pathway and is…

Atrial Fibrillation with RVR

Key Points Most Common Sustained Arrhythmia: Atrial Fibrillation (AFib) is the most frequently encountered sustained arrhythmia in clinical practice, particularly among the elderly population. Misdiagnosis Risk: AFib is commonly misdiagnosed…

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