Basics & Fundamentals
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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…
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…
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…
ECG Findings in Tension Pneumothorax
Key Points Tension pneumothorax is a clinical diagnosis—ECG changes are nonspecific but can provide supportive evidence in the right context. Electrical changes are primarily due to mechanical effects of air…
Acute Chest Pain DDx
Key Points In patients presenting with acute chest pain, identifying life-threatening conditions is essential. Use a systematic ECG approach alongside clinical context to evaluate for high-risk diagnoses that require immediate…
ECG Findings in Aortic Dissection
Key Points Aortic dissection or aneurysm can produce ischemic‑appearing ECGs due to coronary malperfusion, most often right coronary involvement causing inferior changes. Pseudo‑infarction patterns, ST‑deviation, and conduction blocks can occur…
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…
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