Ventricular tachycardia (VT) in an electrocardiogram (ECG) refers to a fast, abnormal heart rhythm originating in the ventricles (lower chambers) of the heart. It's a serious arrhythmia defined by a heart rate exceeding 100 beats per minute with at least three consecutive abnormal heartbeats originating from the ventricles.
Understanding Ventricular Tachycardia (VT)
VT is characterized by rapid and irregular electrical activity in the ventricles, which can lead to inefficient pumping of blood and potentially life-threatening consequences. An ECG is a crucial tool used to diagnose and monitor VT.
Key Features of VT on an ECG:
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Wide QRS Complexes: The QRS complex represents ventricular depolarization (contraction). In VT, the QRS complexes are typically widened (usually > 0.12 seconds) due to the abnormal pathway of electrical activation within the ventricles.
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Rapid Heart Rate: VT is defined by a rapid ventricular rate, typically exceeding 100 beats per minute, and often much faster.
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Regular or Irregular Rhythm: While often regular, VT can sometimes present with an irregular rhythm.
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Dissociation of P Waves: P waves represent atrial depolarization (contraction). In VT, the P waves may be absent or dissociated from the QRS complexes, indicating that the atria and ventricles are beating independently.
Types of Ventricular Tachycardia:
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Monomorphic VT: All QRS complexes have the same morphology (shape) on the ECG, indicating that the arrhythmia originates from a single focus in the ventricles.
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Polymorphic VT: QRS complexes vary in morphology, suggesting multiple origins or changing pathways within the ventricles. Torsades de pointes is a specific type of polymorphic VT often associated with prolonged QT intervals.
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Non-Sustained VT (NSVT): Episodes of VT that last less than 30 seconds and terminate spontaneously.
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Sustained VT: VT that lasts longer than 30 seconds or requires intervention (e.g., cardioversion) to terminate.
Clinical Significance:
VT can be a sign of underlying heart disease (e.g., coronary artery disease, heart failure, cardiomyopathy). Sustained VT can degenerate into ventricular fibrillation (VF), a more dangerous arrhythmia that can lead to sudden cardiac arrest. Prompt diagnosis and treatment of VT are essential.
