A 55-year-old man comes to the emergency department with palpitations that began earlier this morning. He was having tea when he suddenly started to experience fluttering in his chest. He tried walking around and taking deep breaths, but the feeling did not subside. The patient has previously felt his "'heart skipping a beat" but had never sustained palpitations as he did today. He has no lightheadedness, blurry vision, muscle weakness, chest pain, or shortness of breath. The patient has hypertension that is well controlled with valsartan and amlodipine. He does not use tobacco, alcohol, or illicit drugs. He has no drug allergies. His father had a stroke at age 65 and his mother has congestive heart failure. On initial evaluation, the patient appears anxious and in mild discomfort due to palpitations. Blood pressure is 140/80 mm Hg and respirations are 19/min. Jugular venous pressure is estimated at 2 cm H₂O. Cardiac auscultation reveals no murmurs. Lungs are clear to auscultation. The abdomen is soft, nontender, and non-distended. Neurologic examination shows no abnormalities. The patient is placed on a telemetry monitor, and a 12-lead ECG is performed. What is the most appropriate next step in management of this patient?

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Explanation: 11ec2b69_be0f_329b_8f63_09fed7eb1e52_MD0005_00 On a standard 10-second ECG tracing, the heart rate can be estimated by multiplying the number of QRS complexes by 6 (here, 23 x 6 = 138 beats/min). This patient's combination of a narrow QRS-complex tachycardia, absence of organized P waves, and irregularly irregular rhythm with varying R-R intervals (brackets) is consistent with atrial fibrillation (AF) with rapid ventricular response. Because rapid heart rate can lead to poor ventricular filling and low cardiac output, the next step in management of this patient is to control the ventricular response rate (goal <110 beats/min). This is usually achieved with the use of atrioventricular (AV) nodal blocking agents such as beta blockers (eg, metoprolol, atenolol) or nondihydropyridine calcium channel blockers (eg, diltiazem, verapamil). These drugs also have negative inotropic effects and so are contraindicated or must be used with extreme caution in patients with hypotension or decompensated heart failure.(Choice A) Adenosine is useful for the acute termination of certain paroxysmal supraventricular tachycardias (eg, AV nodal reentrant tachycardia). It has no role in management of patients with AF. (Choice B) Intravenous amiodarone can be used for chronic rhythm control in patients with AF. In addition, it has negative chronotropic effects and is occasionally used for rate control when first-line medications are ineffective or contraindicated. However, it is not recommended in initial management of this normotensive patient with new-onset AF with rapid ventricular response. (Choice C) Patients with new-onset AF should undergo thromboembolic risk stratification with CHA₂DS₂-VASc scores to identify those who would benefit from anticoagulation therapy. Clopidogrel alone is not recommended for reduction of thromboembolic risk in patients with AF. CHA₂DS₂-VASc scores anticoagulation therapy (Choice D) Digoxin is less effective for rate control than beta blockers or calcium channel blockers, and its effect can take several hours to become apparent. However, due to a positive inotropic effect, it is often used for rate control in AF patients with hypotension or concomitant systolic heart failure. Educational objective: Beta blockers or nondihydropyridine calcium channel blockers are the preferred first-line agents for ventricular rate control in patients with rapid atrial fibrillation. These drugs are contraindicated or should be used with caution in patients with decompensated heart failure, hypotension, or bradyarrhythmias. References: ß-Blockers and atrial fibrillation: hypertension and other medical conditions influencing their use. (http://www.ncbi.nlm.nih.gov/pubmed/24530215) Amiodarone versus diltiazem for rate control in critically ill patients with atrial tachyarrhythmias. (http://www.ncbi.nlm.nih.gov/pubmed/11395591)

A 55-Year-Old Man Comes to the Emergency Department with Palpitations