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.
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. 
Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: This patient is experiencing paroxysmal supraventricular tachycardia (PSVT), a classification that includes several types of supraventricular tachycardia with abrupt onset and offset and regular ventricular response. These arrhythmias usually result from asecondary conduction pathway that allows abnormal cycling of cardiac conduction and formation of a reentrant circuit. The most common type is atrioventricular nodal reentrant tachycardia (AVNRT), resulting from a secondary conduction pathway within the atrioventricular node and usually affecting young and healthy patients. Atrioventricular reentrant tachycardia (AVRT) is the second most common type, resulting from an accessory pathway outside the atrioventricular node. Patients with PSVT typically have intermittent, abrupt-onset palpitations accompanied by a sensation of a rapid heartbeat. Some may experience dyspnea, lightheadedness, chest pain, or (rarely) syncope. ECG demonstrates a narrow-complex tachycardia with regular R-R intervals; P waves are usually inverted (due to retrograde atrial conduction) and often buried within the QRS complex, but are sometimes visible (eg, after the QRS complex). In hemodynamically stable patients, vagal maneuvers (eg, Valsalva) can be performed or adenosine administered to slow the atrioventricular node and allow for easier identification of the arrhythmia on cardiac monitoring; however, hemodynamically unstable patients should undergo urgent synchronized cardioversion. Cardiac ablation of the secondary conduction pathway is the definitive treatment of choice. ECG (Choices A and B) Atrial fibrillation and atrial flutter are not included in the classification of PSVT. Atrial fibrillation is characterized by an irregularly irregular rhythm and absent P waves. Atrial flutter typically demonstrates "flutter waves" in a sawtooth pattern with a ventricular rate of approximately 150/min, 100/min, or 75/min due to 2:1, 3:1, or 4:1 atrial-to-ventricular conduction, respectively; the rhythm may be regular or irregular. Atrial fibrillation Atrial flutter (Choice C) Multifocal atrial tachycardia is typically seen in patients with underlying pulmonary disease (eg, chronic obstructive pulmonary disease) and is characterized by an irregular, narrow complex tachycardia with variable P-wave morphology. Multifocal atrial tachycardia (Choice E) Sinus tachycardia has narrow QRS complexes, each one preceded by a normal P wave. The onset is usually gradual rather than abrupt. Sinus tachycardia Educational objective: Paroxysmal supraventricular tachycardia is a classification that includes several supraventricular tachycardias with regular ventricular response (eg, atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia). Patients typically have intermittent episodes of abrupt-onset palpitations and a sensation of a racing heartbeat, and ECG demonstrates a narrow-complex tachycardia with regular R-R intervals; inverted P waves are often buried within the QRS complex but are sometimes visible. References: Clinical practice. Evaluation and initial treatment of supraventricular tachycardia. (http://www.ncbi.nlm.nih.gov/pubmed/23050527)

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