A 54-year-old man is evaluated in the emergency department for a 2-hour history of palpitations. He reports no syncope, presyncope, chest pain, or shortness of breath, and has had no previous episodes of palpitations. Medical history is significant for nonischemic cardiomyopathy; ejection fraction was most recently measured at 38%. Medications are carvedilol and candesartan.

On physical examination, he is afebrile, blood pressure is 125/86 mm Hg, and pulse rate is 110/min. Cardiac evaluation reveals a regular rate and rhythm, although the intensity of the S₁ is variable. Cannon a waves are seen in the jugular venous pulsation.

The electrocardiogram is shown.

Which of the following is the most appropriate treatment?

The most appropriate treatment for this patient is amiodarone. The electrocardiogram (ECG) demonstrates a regular, monomorphic wide-complex tachycardia in a left bundle branch block pattern. The differential diagnosis is supraventricular tachycardia (SVT) with aberrancy, antidromic atrioventricular (AV) reciprocating tachycardia, and ventricular tachycardia (VT). In a patient with a wide-complex tachycardia with a history of coronary artery disease or cardiomyopathy, VT should be the assumed diagnosis. The presence of AV dissociation in this ECG (shown), as demonstrated by the arrows, confirms the diagnosis of VT. In addition, the patient has a variable S₁ as well as cannon a waves, which are caused by atrial contraction against a closed tricuspid valve, confirming AV dissociation. Hemodynamic stability does not rule out a diagnosis of VT.

The first-line treatment for a hemodynamically stable VT is an intravenous antiarrhythmic agent such as amiodarone. Procainamide and sotalol are also acceptable, and lidocaine can be used as a second-line agent.

Immediate cardioversion is not necessary because this patient does not have signs of instability. If an antiarrhythmic agent is not successful, an elective cardioversion with sedation can restore normal rhythm.

Adenosine may be given for a stable wide-complex rhythm to determine whether it is SVT or VT, but in this instance, the ECG and physical examination demonstrate VT.

The administration of verapamil or β-blockers is not indicated in patients with stable VT because these drugs can cause severe hemodynamic deterioration and lead to ventricular fibrillation and cardiac arrest.

This patient should be offered an implanted cardioverter-defibrillator for long-term sudden cardiac death prevention.

Key Point

• In a patient with a wide-complex tachycardia with a history of coronary artery disease or cardiomyopathy, ventricular tachycardia is the most likely diagnosis.