Polymorphic ventricular arrhythmia

First, drug-induced lengthening of the QT interval has been associated with the occurrence of ventricular tachyarrhythmias, namely TdP, a polymorphous ventricular arrhythmia that may cause syncope and degenerate into ventricular fibrillation and sudden death although the incidence of TdP is a rare event (usually, less than 1 in 100 000) [32], even a low risk is not justified for drugs with uncertain benefits or drugs providing only symptomatic improvement of a mild disease. 

Bauce, B., Rampazzo, A., Basso, C., Bagattin, A., Daliento, L., Tiso, N., Turrini, P., Thiene, G., Danieli, G. A., and Nava, A. (2002). Screening for Ryanodine Receptor Type 2 Mutations in Families with Effort-Induced Polymorphic Ventricular Arrhythmias and Sudden Death Early Diagnosis of Asymptomatic Carriers. J Am Coll Cardiol 40(2) 341—9. 

Besides the class I-typical proarrhythmic risk class IA antiarrhythmics possess a marked proarrhythmic risk for the induction of torsade depointes arrhythmia (life-threatening polymorphic ventricular tachycardia observed with most action potential prolonging drugs). 

Finally, the ICH E14 guideline does not address the possible consequences of QT/ QTc shortening, which may be associated with significant arrhythmias [5,167]. Digitalis intoxication is a known example of drug-induced short QT syndrome associated with polymorphic ventricular tachycardia [ 168]. It should be acknowledged that this is an area of active research and no guidelines can be put forward at the moment. 

Magnesium sulfate may be effective in terminating refractory ventricular tachyarrhythmias, particularly polymorphic ventricular tachycardia. DigitaUs-induced arrhythmias are more likely in the presence of magnesium deficiency. Magnesium sulfate can be administered orally, intramuscularly, or, preferably, intravenously,... 

Unlabeled Uses Control of hemodynamicallystableventriculartachycardia, control of rapid ventricular rate due to accessory pathway conduction in preexcited atrial arrhythmias, conversion of atrial fibrillation to normal sinus rhythm, in cardiac arrest with persistent ventricular tachycardia or ventricular fibrillation, paroxysmal supraventricular tachycardia, polymorphic ventricular tachycardia or wide complex tachycardia of uncertain origin, prevention of postoperative atrial fibrillation... 

Adverse effects include SA block or arrest, high grade AV block, ventricular tachycardia, arrhythmia or ventricular asystole, polymorphic ventricular tachyarrhythmia, hypotension (particularly when given IV), cinchonism, tinnitus, loss of hearing, gastrointestinal upset, severe headache, diplopia, photophobia, etc. 

Ludomirsky, A., Klein, H.O., Sarelli, P., Becker, B., Hoffman, S., Taitelman, U., Barzilai, J., Lang, R., David, D., DiSegni, E., Kaplinsky, E. (1982). Q-T prolongation and polymorphous ( torsade de pointes ) ventricular arrhythmias associated with organophosphorus insecticide poisoning. Am. J. Cardiol. 49 1654-8. 

Ludomirsky A, Klein HO and Sarelli P (1982). Q-T Prolongations and polymorphous ( torsade de pointes ) ventricular arrhythmias associated with organophosphorus insecticide poisoning. Am J Cardiol, 49,1654-1658. 

Antiarrhythmic drugs that block potassium channels, such as sotalol and quinidine, can cause the polymorphic ventricular tachycardia known as torsades de pointes (see Chapter 34). The abnormal repolarization that leads to polymorphic ventricular tachycardia is potentiated by hypokalemia, and diuretics that produce potassium loss increase the risk of this drug-induced arrhythmia. 

Erythromycin can cause cardiac arrhythmias, including QT prolongation with polymorphic ventricular tachycardia. Most patients have had underlying cardiac disease, or the arrhythmias were seen in combination with other drugs ("see Chapter 34). 

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