A 46-year-old man is admitted to the hospital for elective cholecystectomy. He is started on intravenous fluids and antibiotics. Just before he is to go to an operating room, the patient complains of a sudden onset of chest tightness and lightheadedness. His medical history is significant for anxiety, and he has had 2 previous visits to the emergency department for panic attacks. His blood pressure is 118/67 mm Hg. His electrocardiogram is shown in exhibit. Which of the following is the best initial step in treating this patient?

Question

A 46-year-old man is admitted to the hospital for elective cholecystectomy.  He is started on intravenous fluids and antibiotics.  Just before he is to go to an operating room, the patient complains of a sudden onset of chest tightness and lightheadedness.  His medical history is significant for anxiety, and he has had 2 previous visits to the emergency department for panic attacks.  His blood pressure is 118/67 mm Hg.  His electrocardiogram is shown in exhibit. Which of the following is the best initial step in treating this patient?

Quizplus · Accepted Answer

11ec25c8_d36b_3d2a_bc81_a9a81aa9a088_MD0003_00 The ECG shows a regular and narrow complex tachycardia (QRS duration < 120 ms) at a rate of approximately 160 beats per minute. This is consistent with a diagnosis of supraventricular tachycardia (SVT). SVT refers to any tachycardia originating above the His-bundle and includes sinus tachycardia, multifocal atrial tachycardia, atrial flutter, atrial fibrillation, atrioventricular (AV) nodal reentrant tachycardia (AVNRT), AV reentrant tachycardia (AVRT), and junctional tachycardia. Patients usually present with palpitations, although some may have dizziness, lightheadedness, shortness of breath, diaphoresis, chest pain, presyncope, or syncope. Paroxysmal supraventricular tachycardias (PSVTs) are SVTs with abrupt onset and offset; they include AVNRT, AVRT, atrial tachycardia, and junctional tachycardia. In patients who are hemodynamically stable, the next step in evaluation is to identify the type of SVT with the use of vagal maneuvers (eg, carotid sinus massage, Valsalva, eyeball pressure) or intravenous adenosine. Adenosine or vagal maneuvers temporarily slow conduction via the AV node and can aid in diagnosis by unmasking "hidden" P waves in patients with atrial flutter or atrial tachycardia. They can also cause a transient AV nodal block and terminate AV node-dependent arrhythmias, including AVNRT and orthodromic AVRT. (Choice B) Panic attacks typically cause sinus tachycardia, with normal P wave morphology and relationship with the QRS complex. In PSVT, P waves are usually "buried" within or are seen just after the QRS complex. Alprazolam is useful for patients with panic attacks or for reducing the anxiety associated with the episode of SVT. It is not useful for diagnosis or treatment of SVT. sinus tachycardia (Choices C and D) Amiodarone or lidocaine is often used in the treatment of hemodynamically stable patients with wide-QRS-complex tachycardia (ventricular tachycardia). Amiodarone is also used to treat atrial fibrillation. These drugs have no role in the management of PSVT. ventricular tachycardia (Choice E) Intravenous nitroglycerine is useful in patients with symptoms or signs of myocardial ischemia, acute pulmonary edema, and/or hypertensive urgency. This patient's ECG shows no signs of ischemia, and nitroglycerine would not be useful in this setting. Educational objective: Intravenous adenosine is useful in the initial diagnosis and management of patients with narrow-QRS-complex tachycardia. It slows the sinus rate, increases atrioventricular (AV) nodal conduction delay, or can cause a transient block in AV node conduction. Intravenous adenosine can be useful in identifying P waves to clarify diagnosis of atrial flutter or atrial tachycardia. It can also terminate paroxysmal supraventricular tachycardias by interrupting the AV nodal reentry circuit.

A 46-Year-Old Man Is Admitted to the Hospital for Elective