Torsade de pointes ("twisting of the points") is a ventricular tachycardia with QRS complexes of changing amplitude that seem to "twist" around the isoelectric line. It is a re-entrant arrhythmia associated with malfunction of ion channels involved in myocyte repolarization. Certain drugs may result in prolongation of the QT interval and development of torsades, especially if certain clinical or electrocardiographic findings are present.


Risk factors for onset of torsade de pointes:

(1) female gender

(2) hypokalemia or hypomagnesemia

(3) diuretic use (independent of effect on serum electrolyte concentrations)

(4) high serum concentrations of drug prolonging the QT interval (except quinidine)

(5) bradycardia (especially if of recent onset)

(6) congestive heart failure

(7) myocardial hypertrophy

(8) congenital long QT syndrome

(9) possibly mitral valve prolapse syndrome

(10) possibly AIDS


ECG findings:

(11) prolonged QT interval in ECG prior to drug administration

(12) T wave lability in ECG prior to drug administration

(13) marked prolongation of QT interval in ECG after drug administration

(14) TU morphology (biphasic T waves)

(15) marked post-extrasystolic QTU changes


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