A 28-year-old woman is evaluated after a brief episode of syncope in the shopping mall. The patient walked into an overcrowded store where she felt hot and nauseated before passing out. She also had some palpitations. Her past medical history is significant for 2 prior episodes of syncope and a recent urinary tract infection. Electrocardiogram (ECG) is shown in this exhibit.
Which of the following medications should be avoided in this patient?

Question

A 28-year-old woman is evaluated after a brief episode of syncope in the shopping mall.  The patient walked into an overcrowded store where she felt hot and nauseated before passing out.  She also had some palpitations.  Her past medical history is significant for 2 prior episodes of syncope and a recent urinary tract infection.  Electrocardiogram (ECG) is shown in this exhibit. 
Which of the following medications should be avoided in this patient?

Quizplus · Accepted Answer

11ec193a_9771_fcc3_853d_7d0d0b5d41ec_MD0002_00 This patient's baseline electrocardiogram shows prolonged QT interval. QT interval varies inversely with the heart rate and may be "corrected" using Bazett's formula: electrocardiogram Corrected QT interval (QTc) = (QT interval) / ? (RR interval) A QTc >450 msec in male patients and >470 msec in female patients is considered a prolonged QT interval. Long QT syndrome (LQTS) can be congenital or acquired and is associated with an increased risk of torsades de pointes (TdP), a form of polymorphic ventricular tachycardia. Episodes of TdP may terminate spontaneously, occur in rapid succession, or deteriorate to ventricular fibrillation. Patients with LQTS may be asymptomatic or can present with palpitations, presyncope or syncope, seizures, or sudden cardiac arrest. Electrolyte abnormalities (eg, hypomagnesemia, hypokalemia) and drug therapy (eg, fluoroquinolones, antipsychotics) are the 2 most common causes of acquired LQTS. As a general rule, implicated drugs (eg, levofloxacin) should not be initiated if the baseline QTc >450 msec. If the QTc becomes >500 msec during therapy, the drug dose should be reduced or discontinued. (Choices A and B) Penicillins and cephalosporins are not associated with any significant risk of prolonged QT interval or TdP. (Choice D) Class IB antiarrhythmic drugs (lidocaine and phenytoin) are occasionally used for acute management of TdP. (Choice E) Beta-blockers (atenolol, metoprolol, or propranolol) are recommended as a first-line therapy in both symptomatic and asymptomatic patients with congenital LQTS to reduce the risk of sudden cardiac death. Educational objective: Prolonged QTc interval can be congenital or acquired, and increases risk of torsades de pointes, a form of polymorphic ventricular tachycardia. Electrolyte abnormalities (eg, hypomagnesemia, hypokalemia) and certain drugs (eg, fluoroquinolones, antipsychotics) are the most common causes of acquired long QT syndrome. __________ References: Mechanisms, risk factors, and management of acquired long QT syndrome: a comprehensive review. (http://www.ncbi.nlm.nih.gov/pubmed/22593664)

A 28-Year-Old Woman Is Evaluated After a Brief Episode of Syncope