Core
Results:
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….
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: Hypermagnesemia is usually seen in the setting of renal impairment or excessive magnesium exposure, including laxatives, antacids, bowel preps, or therapeutic magnesium infusion. The key ECG concern is…
Left Anterior Fascicular Block (LAFB)
Key Points: LAFB occurs when conduction through the left anterior fascicle is delayed or blocked. Ventricular activation travels preferentially down the left posterior fascicle, then spreads inferior-to-superior and rightward-to-leftward across…
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…
Hyperacute T Waves: OMI Pattern
Key Points: Complexity of ACS: Arteries can spontaneously reperfuse or re-occlude. Understanding early ECG patterns of early acute ischemia can help detect dynamic changes and prompt rapid interventions. ECG Pattern…
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…
Altered Mental Status Emergencies
Key Points: Always get a 12-lead ECG in altered or confused patients. The ECG is a great triage and risk stratification tool and can reveal reversible, life-threatening causes when history…
Metabolic Emergencies
Key Points: A Simple Yet Powerful Tool: With just a piece of paper and some ink, the ECG can be the earliest clue to life-threatening metabolic disease when labs are…
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…
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…
STEMI vs Artifact: DDx
Key Points: Not all ST elevation is ischemia. The most common mimics at the point of care are atrial activity riding on the ST segment, motion or lead artifact, early…
VT vs SVT with Aberrancy: DDx
Key Points ECG alone cannot reliably distinguish VT from SVT-aberrancy in many cases. Use ECG features to rule in VT, not to exclude it. Default: treat regular WCT as VT…
RV Outflow Tract Tachycardia (RVOT VT)
Key Points Idiopathic monomorphic VT arising from the right ventricular outflow tract. Most patients have no structural heart disease; catecholamine and cAMP-mediated triggers are common. Classic ECG pattern: LBBB morphology…
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