A 65-year-old man is brought to the emergency department by emergency medical services aft… — USMLE Step 2 CK

A 65-year-old man is brought to the emergency department by emergency medical services after collapsing at home. His wife reports that he had been complaining of palpitations and dizziness for the past several hours. He has a history of heart failure with reduced ejection fraction and atrial fibrillation, for which he takes carvedilol, sacubitril-valsartan, and amiodarone. Three days ago, he was evaluated at an urgent care clinic and prescribed oral ciprofloxacin for a suspected urinary tract infection. On arrival, the patient is minimally responsive. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $72/40\text{ mmHg}$ , pulse is $185\text{/min}$ , and respirations are $22\text{/min}$ . Cardiopulmonary examination reveals cold, clammy extremities and faint distal pulses. Continuous cardiac monitoring displays a rapid, irregular, wide-complex tachycardia with cyclic alterations in the QRS axis amplitude, appearing to twist around the isoelectric line. What is the most appropriate initial step in the management of this patient?

A
Intravenous magnesium sulfate
Unsynchronized electrical cardioversionAnswer
C
Intravenous amiodarone bolus
D
Synchronized electrical cardioversion
E
Intravenous furosemide and noninvasive positive-pressure ventilation

Answer

Unsynchronized electrical cardioversion

The correct answer is unsynchronized electrical cardioversion (defibrillation). This patient is presenting with hemodynamically unstable Torsades de Pointes (TdP), characterized by a polymorphic ventricular tachycardia with a cyclic shifting of the QRS axis. His instability is evidenced by profound hypotension (

72/40\text{ mmHg}

), altered mental status, and signs of poor peripheral perfusion (cold, clammy extremities). According to Advanced Cardiac Life Support (ACLS) guidelines, any patient with a tachyarrhythmia causing severe hemodynamic instability requires immediate electrical therapy. Because TdP has multiple rapidly varying QRS morphologies, a standard defibrillator cannot accurately track the R waves to synchronize the shock. Therefore, an unsynchronized high-energy shock (defibrillation) is the definitive and life-saving initial step.

Step-by-Step Solution

Identify the patient's hemodynamic status based on vital signs and physical examination.

The patient is hemodynamically unstable, evidenced by profound hypotension (

72/40\text{ mmHg}

), altered mental status (minimally responsive), and poor perfusion (cold, clammy extremities).

Hemodynamic stability dictates whether medical (pharmacologic) or electrical therapy is the primary intervention for tachyarrhythmias.

Interpret the continuous cardiac monitoring description.

The rhythm is Torsades de Pointes (TdP), a specific form of polymorphic ventricular tachycardia characterized by a continuously shifting QRS axis that twists around the isoelectric line.

Accurate rhythm identification is necessary to select the correct specific treatment algorithm.

Determine the underlying etiology of the arrhythmia.

The patient is taking amiodarone (which prolongs the QT interval) and was recently started on ciprofloxacin (which also prolongs the QT interval). This dangerous drug-drug interaction precipitated acquired Long QT Syndrome, leading to TdP.

Understanding the etiology prevents the administration of contraindicated medications (like further QT-prolonging agents).

Select the most appropriate initial step in management according to ACLS guidelines.

Unsynchronized electrical cardioversion (defibrillation).

For hemodynamically unstable TdP, immediate defibrillation is required because the polymorphic nature of the QRS complexes prevents reliable synchronization by the defibrillator.

Key Concept

Management of hemodynamically unstable polymorphic ventricular tachycardia (Torsades de Pointes)

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