DC cardioversion is the best treatment for Atrial Fibrillation patients who are hemodynamically unstable !

A 76-year-old woman is evaluated in the emergency department for dizziness, shortness of breath, and palpitations that began acutely one hour ago. She has a history of hypertension and heart failure with preserved ejection fraction. Medications are hydrochlorothiazide, lisinopril, and aspirin.
On physical examination, she is afebrile, blood pressure is 80/60 mm Hg, pulse rate is 165/min, and respiration rate is 30/min. Oxygen saturation is 80% with 40% oxygen by face mask. Cardiac auscultation reveals an irregularly irregular rhythm, tachycardia, and some variability in S1 intensity. Crackles are heard bilaterally one-third up in the lower lung fields.

Electrocardiogram demonstrates atrial fibrillation with a rapid ventricular rate.
Q: Which of the following is the most appropriate acute treatment?
A. Adenosine
B. Amiodarone
C. Cardioversion
D. Diltiazem
E. Metoprolol

This patient with atrial fibrillation is hemodynamically unstable and should undergo immediate cardioversion. Hypotension and pulmonary edema in the setting of rapid atrial fibrillation requires DC cardioversion . In patients with heart failure with preserved systolic function, usually due to hypertension, the loss of the atrial “kick” with atrial fibrillation can sometimes lead to severe symptoms. The best treatment in this situation is immediate cardioversion to convert the patient to normal sinus rhythm. Although there is a risk of a thromboembolic event in patients who are  not anticoagulated, she is currently in extremis and is at risk of imminent demise if not aggressively treated. In addition, but in patients who  acutely became symptomatic, and while this is not proof that she developed atrial fibrillation very recently, her risk of thromboembolism is low if the atrial fibrillation developed within the previous 48 hours.

Adenosine can be useful for diagnosing a supraventricular tachycardia and can treat atrioventricular node-dependent tachycardias such as atrioventricular nodal reentrant tachycardia, but it is not useful in the treatment of atrial fibrillation.
Amiodarone can convert atrial fibrillation to normal sinus rhythm as well as provide rate control, but immediate treatment is needed and amiodarone may take several hours to work. Oral amiodarone may be a reasonable option for long-term atrial fibrillation prevention in this patient given the severity of her symptoms, especially if she has significant left ventricular hypertrophy.
Metoprolol or diltiazem would slow her heart rate; however, in patients who are  hypotensive and these medications could make their blood pressure lower. In addition, in patients who are  in active heart failure, and metoprolol or diltiazem could worsen the pulmonary edema.