Intervals
Results:
QT Interval: Basics
Key Points: Definition: The QT interval is measured from the onset of the QRS complex to the end of the T wave. It represents the total duration of ventricular depolarization…
Prolonged QT Interval: DDx
Key Points: What the QT Represents: The QT interval extends from the onset of the QRS to the end of the T wave and represents the total duration of ventricular…
Acquired Long QT Syndrome
Key Points: What It Is: Acquired Long QT Syndrome is delayed ventricular repolarization caused by an external or clinical factor, most commonly QT-prolonging medications, electrolyte abnormalities, or bradycardia. Why It…
Congenital Long QT Syndrome
Key Points: What It Is: Congenital Long QT Syndrome (LQTS) is an inherited cardiac channelopathy that delays ventricular repolarization and predisposes patients to torsades de pointes (TdP), ventricular fibrillation, syncope,…
Short QT Interval: DDx
Key Points: Short QT Interval: A QT interval is considered short when the corrected QT (QTc) interval is less than 350 ms. A short QT interval on the ECG can…
Short QT Syndrome
Key Points: Short QT Syndrome (SQTS) is a rare condition characterized by a shortened QT interval on the ECG, increasing the risk of atrial and ventricular arrhythmias, including sudden cardiac…
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….
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)….
Interval Interpretation
Key Points: Intervals are your ECG safety rails. Before you get seduced by ST segments and T waves, lock down PR, QRS, and QT/QTc. They frequently reveal the real danger…
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