Torsade de point

A cell may produce early afterdepolarizations that are depolarization during incomplete repolarization. This is possible if the action potential is considerably prolonged. This is the typical mechanism for elicitation of Torsade de Pointes arrhythmia, a typical complication of class III antiarrhythmics and many other drugs. 

Newly developed class III drugs comprise dofetilide, a specific Ik, blocker, and ibutilide, which blocks IKl and activates the slow iNa- Both drugs lack hemodynamic side effects. These drugs are scheduled for the treatment of atrial fibrillation and atrial flutter. As with class HI drugs, they can induce torsade de pointes arrhythmia. 

Intravenous administration of magnesium sulfate (1-5 g) is used for the termination of torsade de pointes arrhythmia. The underlying electrophysiological mechanism is not well understood. It includes changes of the current-voltage relationship of Iki and Ca2+ channel blockade. 

Torsade de pointes arrhythmia can be terminated by intravenous (not oral) administration of large doses of magnesium. 

Torsade de pointes is a life-threatening polymotphic ventricular tachycardia, which occurs in inherited long... 

In the Long QT Syndrome (LQTS), the repolarization phase of the cardiac muscle is delayed, rendering the heart vulnerable to an arrhythmia known as torsade de pointes. LQTS is associated with five genes encoding ion channels. LQTS type 3 (LQT3) results from mutations of Nav1.5, which cause persistent sodium cunent. In contrast, sodium channel mutations associated with Biugada syndrome reduce the expression level of cardiac sodium channels. 

Kornick CA, Kilborn MJ, San tiago-Palma J, et al QTc interval prolongation associated with intravenous methadone. Pain 103 499-506, 2003 Krantz MJ, Lewkowiez L, Hays H, et al Torsade de pointes associated with very-high-dose methadone. Ann Intern Med 137 501-304, 2002 Krantz MJ, Kutinsky IB, Robertson AD, et al Dose-related effects of methadone on QT prolongation in a series of patients with torsade de pointes. Pharmacotherapy 23 802-805, 2003... 

Titrate to increase heart rate (about 100 bpm) until torsades de pointes is suppressed... 

Sodium bicarbonate may be useful if torsades de pointes is because of quinidine... 

Compare and contrast the mechanisms of action of drugs used for the treatment of acute episodes of VT (including torsades de pointes), and describe options and indications for nonpharmacologic treatment of VT and VF. 

Design individualized drug therapy treatment plans for patients with (1) sinus bradycardia (2) AV nodal blockade (3) AF (4) PSVT (5) VPDs (6) VT (including torsades de pointes) and (7) VF. 

Drugs with the potential to cause QT interval prolongation and torsades de pointes should be avoided or used with extreme caution in patients with other risk factors for torsades de pointes. 

Sotalol Sinus bradycardia, AV block, fatigue, torsades de pointes... 

Torsades de pointes is a specific polymorphic VT that is associated with prolongation of the QT interval in the sinus beats that precede the arrhythmia.13... 

The incidence of torsades de pointes in the population at large is unknown. The incidence of torsades de pointes associated with specific drugs ranges from less than 1% to as high as 8% to 10%, depending on dose and plasma concentration of the drug and the presence of other risk factors for the arrhythmia. 

Torsades de pointes may be inherited or acquired. Patients with specific genetic mutations may have the inherited long QT syndrome, in which the QT interval is prolonged, and these patients are at risk for torsades de pointes. Acquired torsades de pointes maybe caused by numerous drugs (Table 6-13) the list of drugs that are known to cause torsades de pointes continues to expand. 

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