A 28-year-old woman comes to the emergency department due to the abrupt onset of palpitations that started while she was watching television. She says, "I suddenly started to feel like my heart was racing." The patient describes mild lightheadedness but no chest pain, shortness of breath, or syncope. In the past, she has experienced similar episodes of palpitations that were nonsustained and terminated abruptly. The patient has never sought medical care for these episodes and cannot identify any provoking factor. She saw a physician for anxiety when she was a teenager but does not remember if she received any therapy. The patient has no other medical problems and takes no medications. She does not use tobacco, alcohol, or illicit drugs. She jogs 2-3 miles a day. The patient has no family history of coronary artery disease, cardiomyopathy, blood clots, or sudden cardiac death. She appears mildly uncomfortable but not in any respiratory distress. Temperature is 36.7 C (98 F), blood pressure is 100/60 mm Hg, pulse is 172/min, and respirations are 20/min. Urine pregnancy test is negative. ECG is shown in the exhibit. The patient receives antiarrhythmic therapy, and her pulse immediately decreases from 172/min to 68/min. The palpitations resolve, and she states that she feels "normal now." Cardiac examination reveals no murmurs or additional sounds. A 12-lead ECG is performed and is shown in the exhibit. Which of the following is the most likely diagnosis?

Question

A 28-year-old woman comes to the emergency department due to the abrupt onset of palpitations that started while she was watching television.  She says, "I suddenly started to feel like my heart was racing."  The patient describes mild lightheadedness but no chest pain, shortness of breath, or syncope.  In the past, she has experienced similar episodes of palpitations that were nonsustained and terminated abruptly.  The patient has never sought medical care for these episodes and cannot identify any provoking factor.  She saw a physician for anxiety when she was a teenager but does not remember if she received any therapy.  The patient has no other medical problems and takes no medications.  She does not use tobacco, alcohol, or illicit drugs.  She jogs 2-3 miles a day.  The patient has no family history of coronary artery disease, cardiomyopathy, blood clots, or sudden cardiac death.  She appears mildly uncomfortable but not in any respiratory distress.  Temperature is 36.7 C (98 F), blood pressure is 100/60 mm Hg, pulse is 172/min, and respirations are 20/min.  Urine pregnancy test is negative.  ECG is shown in the exhibit. The patient receives antiarrhythmic therapy, and her pulse immediately decreases from 172/min to 68/min.  The palpitations resolve, and she states that she feels "normal now."  Cardiac examination reveals no murmurs or additional sounds.  A 12-lead ECG is performed and is shown in the exhibit.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: This patient's ECG demonstrates a Wolff-Parkinson-White (WPW) pattern, which is commonly associated with the development of atrioventricular reentrant tachycardia (AVRT). WPW occurs due to an extranodal accessory conduction pathway that directly connects the atria and ventricles, bypassing the atrioventricular node. The classic ECG findings are short PR interval, slurred upstroke of the QRS complex (delta wave), and widening of the QRS complex. delta wave Not all patients with a WPW pattern on ECG become symptomatic; the finding of a WPW pattern combined with symptomatic tachyarrhythmia constitutes WPW syndrome. WPW pattern (Choice A) Electrolyte abnormalities can cause a variety of ECG abnormalities, including ST- and T-wave changes, intraventricular conduction delay, and atrial or ventricular arrhythmias. The triad of changes on this patient's ECG (ie, short PR interval, delta wave, and wide QRS complex) is classic for WPW syndrome. (Choice B) Patients with AVRT associated with an accessory pathway can have marked ST-segment depression during the tachycardia. This occurs even in young patients in the absence of coronary artery disease, and does not represent myocardial ischemia. (Choice C) Panic attacks can lead to rapid sinus tachycardia, but the tachycardia typically has gradual onset and recovers gradually with time. In contrast, AVRT associated with an accessory pathway has an abrupt onset and termination. (Choice D) A right bundle branch block causes wide QRS complexes but does not cause delta waves or short PR intervals. Furthermore, it would not explain this patient's paroxysmal supraventricular tachycardia. Educational objective: An accessory pathway can lead to a Wolff-Parkinson-White (WPW) pattern on ECG, characterized by a short PR interval, a delta wave at the beginning of the QRS complex, and widening of the QRS complex. Patients with a WPW pattern on ECG are at risk for developing symptomatic paroxysmal supraventricular tachycardia in the form of atrioventricular reentrant tachycardia, which constitutes WPW syndrome. References: WPW and preexcitation syndromes. (http://www.ncbi.nlm.nih.gov/pubmed/18368860)

A 28-Year-Old Woman Comes to the Emergency Department Due to the Abrupt