A 42-Year-Old Man With Seizures

Alfredo Musumeci, MD, PhD; Michele Alzetta, MD

Disclosures

March 13, 2017

Discussion

The cardiac rhythm strip (Figure 2) demonstrated torsade de pointes (French for "twisting of the points"), otherwise known as simply "torsades" or polymorphic ventricular tachycardia.

Figure 1.

Figure 2.

The initial ECG (Figure 1), which was obtained before the development of the torsades, revealed a prolonged QT interval (544 msec), with a QT interval corrected for the heart rate (QTc) of 647 msec. Moreover, notched T waves were noted in leads II, III, aVF, and V1-V6. A prolonged QT interval is often noted incidentally on an ECG in an asymptomatic patient; however, in a patient who presents with palpitations, presyncope, syncope, or cardiac arrest, the presence of a prolonged QT interval should raise particular concern for torsade de pointes.

QT prolongation can be either acquired or congenital. A thorough clinical history-taking and knowledge of the patient's current medications is very important for this differentiation. Congenital long QT syndrome (LQTS) is a disorder characterized by abnormal QT-interval prolongation on the ECG caused by cardiac myocyte ion channel gene mutations, with a propensity to ventricular tachyarrhythmias. Patients are typically young and may present with syncope or sudden death.[1,2]

Acquired QT interval prolongation may be drug-induced, or it may be caused by certain electrolyte derangements, such as hypomagnesemia, hypokalemia, and hypocalcemia. Many drugs have been implicated, including class 1A antiarrhythmic drugs such as quinidine and procainamide and class III antiarrhythmics such as amiodarone and sotalol. Others drugs that have been implicated include antihistamines (terfenadine, astemizole), macrolide antibiotics (erythromycin, clarithromycin, clindamycin), pentamidine, serotonin receptor antagonists (ketanserin), diuretics (indapamide), certain fluoroquinolone antibiotics, tricyclic antidepressants, antipsychotics (phenothiazines, haloperidol, mesoridazine, pimozide, thioridazine, ziprasidone), gastrointestinal motility enhancers (cisapride, domperidone), inotropes (amrinone, milrinone), toxins (organophosphates, arsenic), protease inhibitors, and methadone.[3,4,5,6,7,8,9,10]

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