Torsade de Pointes - Definition and Treatment
Torsades de Pointes is an uncommon variant of ventricular tachycardia that can be the result of lengthening the QT interval. Literally meaning the “twisting of points”, torsades refers to the repeating continuum of upward then downward pointing ventricular complexes.1 As the morphology of the QRS complex can vary with each beat, the outline on an EKG looks like a twisted ribbon.1 The underlying basis for rhythm disturbance is delay in phase III of the action potential, mediated by the potassium channels. This delay in depolarization allows for the emergence of re-entry points, called the “R-on-T” phenomenon. This vulnerable period in ventricular repolarization is a time when some, but not all, of the myocardial tissue is ready for the signal.2 The rhythm is usually self-terminating but may degenerate into ventricular fibrillation.
A mnemonic for the conditions that can potentially result in Torsades de Points is POINTES2:
Other medications (tricyclic antidepressants)
No known cause (idiopathic)
Type I anti-arrhythmics (quinidine, procainamide, dispyramide)
Syndrome of Prolonged QT (aka Long QT Syndrome)
It is important to accurately diagnose Torsades de Pointes, because failure to separate it from other forms of ventricular tachycardia can perpetuate the rhythm disturbances (using type 1A anti-arrhymthic agents to end classic ventricular tachycardia.)
Studies for a patient with Torsades de Pointes include laboratory potassium, magnesium, and calcium levels as well as continuous EKG monitoring. Because Torsades de Pointes is so unstable, it is very important to begin therapy immediately. Possible therapies include treating hypokalemia with magnesium sulfate, giving beta blockers, and pacing the heart to decrease the action potential duration.3 It is important to immediately withdraw all QT prolonging drugs, to limit recurrence. However, there is a 50% chance of recurrence even with therapy.3 The clinical course of these patients depends on their cardiac history, age, sex and genotype.4
- Dubin, D. Rapid Interpretation of EKG. Cover Publishing; 2000.
- Stead LG; Stead MS; Kaufman MS. First Aid for the Emergency Medicine Clerkship. New York, NY: McGraw-Hill Medical Publishing Division; 2002.
- “Torsades de points.” http://emedicine.medscape.com/
- Long QT syndrome and short QT syndrome. Prog Cardiovasc Dis. 2008 Nov-Dec;51(3):264-78.
Nelsson Becerra, MSIV
Howard University College of Medicine, Washington, DC
EMRA Medical Student Committee
EMRA Medical Student Council