A 6-year-old boy with congenital deafness is brought to the emergency department after fainting. He was running in his backyard when he suddenly fell to the ground and lost consciousness. The patient regained consciousness quickly and without confusion. The event was not associated with convulsions, tongue biting, or urinary incontinence. He has never had an episode like this before. The patient is developmentally normal and takes no medications. He underwent bilateral cochlear implantation at age 2 for sensorineural hearing loss. The patient had a brother who died during a swim meet at age 14. Blood pressure is normal. Cardiac examination reveals a regular heart rate and no murmurs. The remainder of the physical examination is unremarkable. Serum chemistry is normal. ECG is shown in the exhibit. Which of the following is the most appropriate pharmacologic treatment for this patient?

Question

A 6-year-old boy with congenital deafness is brought to the emergency department after fainting.  He was running in his backyard when he suddenly fell to the ground and lost consciousness.  The patient regained consciousness quickly and without confusion.  The event was not associated with convulsions, tongue biting, or urinary incontinence.  He has never had an episode like this before.  The patient is developmentally normal and takes no medications.  He underwent bilateral cochlear implantation at age 2 for sensorineural hearing loss.  The patient had a brother who died during a swim meet at age 14.  Blood pressure is normal.  Cardiac examination reveals a regular heart rate and no murmurs.  The remainder of the physical examination is unremarkable.  Serum chemistry is normal.  ECG is shown in the exhibit.  Which of the following is the most appropriate pharmacologic treatment for this patient?

Quizplus · Accepted Answer

11ec25c8_d635_0b55_bc81_35a28127a490_MD0003_00 This patient likely has congenital long QT syndrome (LQTS). The disease results from genetically impaired function of the voltage-gated potassium channels that control the delayed rectifier potassium current and allow for repolarization of the cardiomyocyte action potential. LQTS can be inherited in autosomal dominant (ie, Romano-Ward syndrome) or autosomal recessive (ie, Jervell & Lange-Nielson syndrome) fashion, the latter of which is associated with sensorineural hearing loss and more severe cardiac manifestations. Delayed repolarization manifests as a prolonged QT interval (eg, >460 ms) on ECG (this patient's is approximately 520 ms), and predisposes to the development of torsade de pointes, a form of polymorphic ventricular tachycardia that can cause syncope or sudden cardiac death. These complications of congenital LQTS are most likely to occur during periods of rapid heart rate and high sympathetic activity (eg, exercise). Delayed repolarization 520 ms torsade de pointes Management of congenital LQTS involves avoidance of exacerbating factors (eg, hypomagnesemia, hypokalemia, QT-prolonging medications). In addition, beta blockers (class II antiarrhythmics) dampen sympathetic activity and shorten the QT interval at rapid heart rates to reduce the risk of syncope and death in patients with congenital LQTS; this benefit is most prominent with the nonselective beta blockers, propranolol and nadolol. Implantable cardioverter-defibrillator placement or left cardiac sympathetic denervation are also appropriate in some high-risk patients. (Choices A and C) Ethosuximide is first-line treatment for absence seizures and levetiracetam is commonly used for treatment of other generalized seizures; however, this patient's episode of loss of consciousness (LOC) is most consistent with syncope. With absence seizures, LOC is not accompanied by loss of body tone (ie, collapse). With other generalized seizures, LOC is usually accompanied by jerking movements, tongue-biting, urinary incontinence, and/or postictal confusion. (Choices B, E, and F) Class IA antiarrhythmics (eg, quinidine) and class III antiarrhythmics (eg, ibutilide, sotalol) are contraindicated in LQTS because these drugs inhibit the repolarizing voltage-gated potassium channels and exacerbate the disease. Despite the beta-blocking properties of sotalol, the drug must be avoided in LQTS due to inhibitory effects on potassium channels. Educational objective: Patients with congenital long QT syndrome are at risk for polymorphic ventricular tachycardia that leads to syncope or sudden cardiac death, especially during periods of rapid heart rate and high sympathetic activity. Beta blockers (eg, propranolol, nadolol) dampen sympathetic activity and shorten the QT interval at high heart rates to reduce the risk of these complications. References: The Jervell and Lange-Nielsen syndrome: natural history, molecular basis, and clinical outcome. (http://www.ncbi.nlm.nih.gov/pubmed/16461811) Effect of beta blockers on QT dynamics in patients with the long QT syndrome: measuring the benefit. (http://www.ncbi.nlm.nih.gov/pubmed/24833771) Management of Patients with Long QT Syndrome (http://www.ncbi.nlm.nih.gov/pubmed/27826330)

A 6-Year-Old Boy with Congenital Deafness Is Brought to the Emergency