A 44-year-old woman comes to the emergency department with sudden onset of weakness and dizziness. The patient does not have any chest pain but feels her heart pounding in her chest. She is otherwise healthy and does not have any other medical problems. Her maternal uncle died suddenly at age 42. Blood pressure is 110/60 mm Hg and pulse is 170/min. Lungs are clear to auscultation and cardiac examination is normal. Her electrocardiogram (ECG) is shown in this Exhibit. Which of the following is the best initial treatment for this patient's condition?

Question

A 44-year-old woman comes to the emergency department with sudden onset of weakness and dizziness.  The patient does not have any chest pain but feels her heart pounding in her chest.  She is otherwise healthy and does not have any other medical problems.  Her maternal uncle died suddenly at age 42.  Blood pressure is 110/60 mm Hg and pulse is 170/min.  Lungs are clear to auscultation and cardiac examination is normal.  Her electrocardiogram (ECG) is shown in this Exhibit.  Which of the following is the best initial treatment for this patient's condition?

Quizplus · Accepted Answer

Explanation: 11ec2b69_be64_56b8_8f63_bded74740d54_MD0005_00 This patient's electrocardiogram (ECG) shows a regular and narrow QRS complex tachycardia consistent with paroxysmal supraventricular tachycardia (PSVT). Patients with SVT typically present with palpitations, but some may have dizziness, lightheadedness, shortness of breath, diaphoresis, chest pain, presyncope, or syncope. narrow QRS complex tachycardia It is often difficult to distinguish between various types of SVT, which include sinus tachycardia, atrioventricular nodal reentrant tachycardia (AVNRT), AV reentrant tachycardia (AVRT), atrial fibrillation, and atrial flutter. In hemodynamically stable patients, the next step in evaluation is to identify the type of SVT with the use of intravenous (IV) adenosine or vagal maneuvers (carotid sinus massage or Valsalva). Adenosine or vagal maneuvers temporarily slow conduction through the AV node and can aid in diagnosis by unmasking the "hidden" P waves on the surface ECG. They can also cause a transient AV nodal block and terminate AV node-dependent arrhythmias, including AVNRT and orthodromic AVRT. (Choice B) Patients with persistent tachyarrhythmia (narrow or wide complex) causing hemodynamic instability (hypotension, altered mental status) should be managed with immediate synchronized direct-current cardioversion. However, this patient is hemodynamically stable and does not require cardioversion. (Choice C) Esmolol is an ultra-short acting beta-blocker that is used for rate control in patients with rapid atrial flutter or fibrillation. It is not indicated in patients with PSVT. (Choice D) Ibutilide is a class III antiarrhythmic drug and is approved for the pharmacologic cardioversion of atrial fibrillation and atrial flutter. It has no role in the management of patients with PSVT. (Choice E) Lidocaine is a class IB antiarrhythmic that is used to treat ventricular arrhythmias. It is often used in the treatment of hemodynamically stable patients with wide QRS complex tachycardia but is not recommended for narrow-complex SVT. Educational objective: Patients with regular, narrow complex tachycardia should be initially managed with vagal maneuvers (eg, carotid sinus massage) and/or intravenous adenosine. Patients with persistent tachyarrhythmia (narrow or wide complex) causing hemodynamic instability should be managed with immediate synchronized direct-current cardioversion. References: Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. (http://www.ncbi.nlm.nih.gov/pubmed/20956224)

A 44-Year-Old Woman Comes to the Emergency Department with Sudden