A 17-year-old boy comes to the emergency department due to palpitations. He has had prior episodes of "chest fluttering" that were short-lived, but this episode is sustained. He is preparing for school examinations and has a high level of stress. The patient appears diaphoretic and uncomfortable on examination. Blood pressure is 110/75 mm Hg and pulse is 210/min. His pulse oxymetry shows 99% on room air. An ECG is immediately obtained and shows a narrow complex tachycardia. An intravenous bolus of medication is administered and results in abrupt cessation of the tachycardia. A follow-up ECG is shown in the exhibit. Which of the following is the most likely underlying cause of this patient's current condition?

Question

A 17-year-old boy comes to the emergency department due to palpitations.  He has had prior episodes of "chest fluttering" that were short-lived, but this episode is sustained.  He is preparing for school examinations and has a high level of stress.  The patient appears diaphoretic and uncomfortable on examination.  Blood pressure is 110/75 mm Hg and pulse is 210/min.  His pulse oxymetry shows 99% on room air.  An ECG is immediately obtained and shows a narrow complex tachycardia.  An intravenous bolus of medication is administered and results in abrupt cessation of the tachycardia.  A follow-up ECG is shown in the exhibit.  Which of the following is the most likely underlying cause of this patient's current condition?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d196_2e96_bc81_217fb2dac110_MD0003_00 The patient's clinical presentation is characteristic of Wolff-Parkinson-White (WPW) syndrome. Normally, electric impulses pass from the atria to the ventricles via the atrioventricular (AV) node. In WPW, there is an accessory pathway (bundle of Kent) that directly connects the atria to the ventricles, bypassing the AV node. Antegrade conduction through this pathway with resultant preexcitation of the ventricles produces characteristic ECG changes: Short PR interval, generally <0.12 seconds Slurred and broad upstroke of the QRS complex (delta wave) QRS interval widening (sometimes leading to a wide complex tachycardia [QRS >0.12 seconds]) with ST/T wave changes Most patients are asymptomatic; however, WPW can be associated with cardiac arrhythmias. If there is retrograde conduction from the ventricles to the atria, a re-entrant supraventricular tachycardia (SVT) may occur. ECG features of WPW will not be apparent during episodes of SVT, but the delta wave should be visible once the rhythm is slowed. Sudden death can occur if WPW is untreated. re-entrant supraventricular tachycardia (Choice B) Cocaine use can result in sinus tachycardia and chest pain and can also precipitate a myocardial infarction. However, cocaine does not cause delta waves on ECG. (Choice C) Dilated cardiomyopathy is associated with an increased risk of dysrhythmias but will not have the ECG findings seen with WPW. (Choice D) Hyperthyroidism would cause sinus tachycardia rather than SVT. (Choice E) Hypokalemia can lead to nonspecific ST segment changes (eg, ST segment depression, low T wave amplitude) and a prominent U wave on ECG. (Choice F) Long QT syndrome (LQTS) is characterized by prolongation of QT interval on ECG (QTc >450 msec in males or >470 msec in females). It can be congenital or acquired and is a marker for increased risk of sudden cardiac death due to torsades de pointes or polymorphic ventricular tachycardia. Long QT syndrome (LQTS) (Choice G) Rheumatic heart disease is associated with a progressive valvular disease, most commonly involving mitral and/or aortic valves. ECG findings of WPW pattern are not seen. Educational objective: Wolff-Parkinson-White (WPW) pattern refers to the characteristic ECG findings of a short PR interval (<120 msec), slurred initial upstroke of the QRS complex (delta wave), and widening of the QRS complex with ST/T wave changes. WPW is due to an accessory pathway that bypasses the atrioventricular node and directly connects the atria to the ventricles. References: WPW and preexcitation syndromes. (http://www.ncbi.nlm.nih.gov/pubmed/18368860)

A 17-Year-Old Boy Comes to the Emergency Department Due to Palpitations