A 44-year-old man comes to the urgent care clinic due to palpitations. The current episode started 2 hours ago and feels like "fluttering in the chest." He has no chest pain, orthopnea, dizziness, syncope, or shortness of breath. The patient has had similar episodes in the past 6 months, but they usually last less than an hour and resolve spontaneously. He cannot identify any clear-cut precipitating factor for these episodes. He has a history of migraines and kidney stones. The patient does not use tobacco, alcohol, or illicit drugs. His family history is significant for liver cancer and renal failure. He works in an office and his lifestyle is mainly sedentary. On initial evaluation, he appears comfortable. Blood pressure is 124/82 mm Hg and pulse is 122/min. Oxygen saturation is 99% on room air. BMI is 31 kg/m². Cardiac auscultation reveals no murmurs. The patient's lungs are clear to auscultation and there is no peripheral edema. ECG shows atrial fibrillation with a rapid ventricular response. Complete blood count, basic metabolic panel, TSH level, and chest x-ray are normal. A transthoracic echocardiogram shows normal left ventricular size and function, mild enlargement of the left atrium, and no valvular abnormalities. The patient is given oral metoprolol and reports improvement of his symptoms after 2 hours. Repeat ECG shows normal sinus rhythm with a ventricular rate of 77/min at rest. There are no repolarization abnormalities and his QTc interval is 410 msec. In addition to oral metoprolol, which of the following is the most appropriate therapy for this patient?

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Explanation: 11ec2b69_be0c_4c6a_8f63_a9364d84442b_MD0005_00 This patient has new-onset atrial fibrillation (AF) that converted back to sinus rhythm while on metoprolol. Management of new-onset AF includes assessing for rate- versus rhythm-control strategy and preventing systemic embolization. Hemodynamically unstable patients require emergency cardioversion. Stable patients can receive medical therapy (eg, beta blockers, diltiazem, digoxin) to control the ventricular rate. Rate control with medical therapy can often convert AF back to sinus rhythm, as in this patient. Rhythm control for maintaining sinus rhythm should be considered in patients unable to achieve adequate rate control, with recurrent symptomatic episodes (eg, palpitations, lightheadedness, dyspnea, angina), or with heart failure symptoms in the setting of underlying left ventricular systolic dysfunction. Regardless of whether rate control or rhythm control is used, patients with AF should undergo a CHA₂DS₂-VASc score assessment to estimate thromboembolic risk. This patient's score is 0, placing him at low risk of thromboembolic complications. Therefore, he requires no additional therapy. Anticoagulation with warfarin or other anticoagulants (eg, dabigatran, rivaroxaban, apixaban) is recommended for those with a CHA₂DS₂-VASc score of >2 (Choice B). Therapy in patients with a score of 1 is often assessed on a case-by-case basis, taking into account clinical judgment and patient preference. CHA₂DS₂-VASc (Choice A) Amiodarone is used in some patients with symptomatic AF to maintain sinus rhythm. However, this patient has converted to sinus rhythm with metoprolol and does not need antiarrhythmic agents at this time. In addition, several clinical trials have found no significant difference in outcomes with a rate-control versus rhythm-control strategy. (Choice C) Digoxin is used as a rate-control agent in some patients with AF and rapid ventricular rate, especially those with low or borderline blood pressure or heart failure due to left ventricular systolic dysfunction. Digoxin also can be used as an adjunctive agent in patients who continue to have a rapid ventricular rate despite the use of beta blockers and calcium channel blockers. (Choice D) This patient is in sinus rhythm and is tolerating metoprolol well with symptomatic improvement. There is no indication to add diltiazem to his drug regimen. Educational objective: Patients with new-onset atrial fibrillation should undergo a CHA₂DS₂-VASc score assessment to estimate thromboembolic risk. Patients with a score of 0 are at the lowest risk of thromboembolic complications and are usually managed without anticoagulation. Patients with a score >2 should be managed with anticoagulant therapy (eg, warfarin, dabigatran, rivaroxaban, apixaban). References: Antithrombotic therapy for atrial fibrillation: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. (http://www.ncbi.nlm.nih.gov/pubmed/22315271)

A 44-Year-Old Man Comes to the Urgent Care Clinic Due