Rate Control in Atrial Fibrillation
A 68-year-old woman with persistent atrial fibrillation and moderate persistent asthma attends with palpitations and breathlessness on climbing one flight of stairs. Heart rate is 132 beats/min and irregularly irregular, with no wheeze at rest. An electrocardiogram confirms atrial fibrillation with no pre-excitation, and echocardiography shows a left ventricular ejection fraction of 58 per cent. Thyroid function and electrolytes are normal. What is the most appropriate rate-control agent?
- A.Oral flecainide
- B.Oral bisoprolol
- C.Oral amiodarone
- D.Oral diltiazemCorrect
Explanation
Beta-blockers are the usual first-line agents for rate control in atrial fibrillation, but in a patient with moderate persistent asthma a non-dihydropyridine calcium channel blocker is preferred because beta-blockade risks bronchospasm. Diltiazem and verapamil slow atrioventricular nodal conduction and are effective rate-control drugs, and diltiazem is generally better tolerated haemodynamically than verapamil. The essential caveat is that non-dihydropyridine calcium channel blockers are contraindicated in heart failure with reduced ejection fraction because of their negative inotropic effect; this patient's ejection fraction is preserved at 58 per cent, so diltiazem is safe. In a patient with reduced ejection fraction the choice would be a beta-blocker, with digoxin added or used alone when a beta-blocker is contraindicated or when the patient is sedentary or hypotensive, remembering that digoxin controls rate at rest but poorly during exertion and is renally cleared. Amiodarone is a rhythm-control drug used for rate control only as a last resort because of thyroid, pulmonary, hepatic, ocular and dermatological toxicity with long-term use. Flecainide is a class Ic antiarrhythmic used for cardioversion and rhythm maintenance in structurally normal hearts; it does not control ventricular rate and can dangerously accelerate conduction if atrial fibrillation organises into flutter unless a nodal blocker is co-administered. Anticoagulation is guided separately by the CHA2DS2-VASc score and is independent of the rate versus rhythm decision.
Why each option
- A.
- Flecainide does not slow the ventricular rate and may accelerate conduction if the rhythm organises to atrial flutter.
- B.
- Beta-blockers are usually first line but risk bronchospasm in moderate persistent asthma, making them a poor choice here.
- C.
- Amiodarone is a rhythm-control agent used for rate control only as a last resort because of its substantial multi-organ toxicity.
- D.
- Correct. A non-dihydropyridine calcium channel blocker is the rate-control agent of choice when a beta-blocker is contraindicated by asthma and ejection fraction is preserved.
Reference: 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation
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