Torsades de pointes pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Torsades de pointes is defined as the presence of polymorphic ventricular tachycardia with a prolonged QT segment on EKG. It is characterized by a constantly changing rhythm amplitude which comes from the ventricular depolarizing waves constantly shifting its axis. The underlying mechanism is thought to be triggered activity arising as a consequence of early after-depolarizations. During Torsade de pointes the ventricles depolarize in a circular fashion resulting in QRS complexes with a continuously turning heart axis around the baseline (hence the name Torsade de Pointes).
Pathophysiology
Torsade de pointes is characterized by constantly changing rhythm amplitude. 'Torsade de pointes' in French means "Twisting of the Points". The changing rhythm amplitudes comes from the ventricular depolarizing waves constantly shifting its axis. It is usually caused by hypomagnesemia, hypokalemia, and malnourished alcoholics. Although Torsades de Pointes (TdP) is a rare ventricular arrhythmia, it can degenerate into ventricular fibrillation, leading to death without rapid medical intervention. TdP is associated with long QT syndrome, a condition whereby prolonged QT intervals are visible on the ECG.
Torsade de pointes is typically initiated by a short-long-short interval. A ventricular extrasystole (first beat: short) is followed by a compensatory pause. The following beat (second beat: long) has a longer QT interval. If the next beat follows shortly thereafter, there is a good chance that this third beat falls within the QT interval, resulting in the R on T phenomenon and subsequent Torsade de pointes. During Torsade de pointes the ventricles depolarize in a circular fashion resulting in QRS complexes with a continuously turning heart axis around the baseline (hence the name Torsade de Pointes).
Video: Torsade de pointes
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