Torsades de pointes overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Torsade de pointes in French means "Twisting of the Points". It is characterized by a polymorphic ventricular tachycardia and can occur in the congenital long QT syndromes, electrolyte abnormalities (hypomagnesemia, hypokalemia), usage of certain drugs like antiarrhythmic (quinidine), nonsedating antihistamines (terfenadine); antibiotics (erythromycin) and neuroleptics (thioridazine). Torsade de pointes is characterized by constantly changing rhythm amplitude. The changing rhythm amplitudes 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. Torsade de pointes is typically initiated by a short-long-short interval. A ventricle 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). An understanding of the patho-physiology has led to development of treatment modalities like pacing, isoproterenol and drugs like magnesium and beta blockers. 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. Also, a more rare form of short coupled Torsade de pointes has been observed.[1]
References
- ↑ Leenhardt A, Glaser E, Burguera M, Nuernberg M, Maison-Blanche P, and Coumel P. Short-coupled variant of torsade de pointes. A new electrocardiographic entity in the spectrum of idiopathic ventricular tachyarrhythmias. Circulation 1994 Jan; 89(1) 206-15. PMID 8281648