Core
Results:
JT Interval: Basics
Key Points: The JT interval isolates ventricular repolarization by removing QRS duration from the QT. JT = QT − QRS. It is most useful when the QRS is wide, where…
PR Interval: Basics
Key Points: Definition: PR interval runs from P-wave onset to the first ventricular deflection (start of QRS). It reflects atrial depolarization plus conduction through the AV node and His-Purkinje system….
RR Interval: Basics
Key Points: The RR interval is the time between consecutive R waves. It is the most practical way to assess rate and regularity. RR is the backbone of rhythm interpretation:…
Waveforms, Segments, & Intervals: Basics
Key Points: Every ECG tracing is built from waveforms (deflections), segments (baseline portions between waveforms), and intervals (time that include waveforms plus segments). Waveforms describe electrical events (depolarization or repolarization)….
STAT ECG 101: The Acute Care ECG Workflow
Key Points: The ECG is the fastest bedside test for rhythm, conduction, ischemia, and tox-metabolic disease. It only saves lives when interpreted systematically and acted on. In acute care, the…
Prolonged QT Interval: DDx
Key Points: The QT interval reflects the time it takes for total ventricular depolarization and repolarization (Q wave onset to T wave end). QT prolongation increases the risk of torsades…
Hypocalcemia
Key Points: Prolonged QTc is the hallmark ECG change in hypocalcemia, driven mainly by ST-segment prolongation with relatively normal T-wave shape. Hypocalcemia can increase arrhythmia risk, including TdP, but TdP…
STEMI in the Presence of Baseline ECG Abnormalities
Key Points: Baseline ECG abnormalities do not protect patients from occlusion MI. They increase miss rates because they distort the ST segment and T waves. The core question is not…
Lateral and High-Lateral STEMI: Criteria, Localization, and Pitfalls
Key Points: Lateral and high-lateral STEMI often present with subtle ST elevation and are commonly missed or labeled as nonspecific ST-T changes. Small-appearing ECG changes may represent true coronary occlusion…
Inferior STEMI: Criteria, RV Involvement, and Pitfalls
Key Points: Inferior STEMI is the most common STEMI subtype and is frequently complicated by right ventricular and posterior involvement. Inferior occlusion may present with classic ST elevation, subtle ischemic…
Anterior STEMI: Criteria, Localization, and Pitfalls
Key Points: Anterior STEMI represents large myocardial territory at risk and carries the highest mortality among STEMI subtypes. Early recognition and reperfusion are critical. LAD occlusion may present with classic…
Posterior STEMI: Criteria & Pitfalls
Key Points: High risk of missed diagnosis. Isolated posterior occlusion MI is frequently missed because ST elevation is absent on the standard 12-lead ECG. Instead, posterior infarction most often presents…
STEMI vs Early Repolarization: DDx
Key Points: Early repolarization (ER) is a common, benign ECG pattern that most often appears in young, healthy patients. It can closely resemble acute anterior STEMI, creating a high-risk diagnostic…
STEMI vs LV Aneurysm: DDx
Key Points: LV aneurysm pattern is a post MI scar pattern with persistent ST elevation in the prior infarct territory, usually with pathologic Q waves and a stable, non evolving…
ST Elevation in aVR with Diffuse ST Segment Depression: OMI Pattern
Key Points: Pattern, not a STEMI equivalent. ST elevation in aVR (≥1 mm), often with ST elevation in V1 and diffuse ST depression (≥1 mm in ≥6 leads), represents high-risk…
STEMI Mimics: DDx
Key Points: ST elevation is a pattern, not a diagnosis. STEMI represents one cause of ST elevation and requires correlation with ECG morphology, distribution, evolution, and clinical context. Most ED…
Hyperkalemia Emergencies
Key Points: Severe Hyperkalemia Mimics Several Life-Threatening Conditions: Severe hyperkalemia is one of the most dangerous ECG mimics in emergency medicine. It can resemble unstable bradyarrhythmias, VT, STEMI, and pacemaker…
STEMI vs Severe Hyperkalemia: DDx
Key Points: Severe hyperkalemia is a true ECG chameleon. It can produce ST elevation, wide QRS complexes, axis shifts, and conduction blocks that closely mimic STEMI or ventricular tachycardia. New…
STEMI vs Acute Pericarditis: DDx
Key Points: Start by looking for STEMI, not pericarditis. The safest workflow is to actively search for occlusion MI features first, then use pericarditis features as supportive evidence. Reciprocal ST…
Traditional STEMI Criteria (Millimetric Thresholds)
Key Points: STAT ECG is the first decision point in ACS. The primary purpose of the initial ECG is to identify patients who meet traditional STEMI criteria and require immediate…
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