In a 60‑year‑old patient with atrial fibrillation requiring ventricular‑rate control, which medication is most appropriate?

Ventricular Rate Control in Atrial Fibrillation

Direct Answer

For a 60-year-old patient with atrial fibrillation requiring ventricular rate control, either metoprolol (C) or diltiazem (A) are the most appropriate first-line choices, with metoprolol preferred if the patient has coronary disease or post-MI status, and diltiazem preferred if the patient has chronic obstructive pulmonary disease. 1

First-Line Agent Selection

Beta-blockers (metoprolol) and non-dihydropyridine calcium channel blockers (diltiazem) are Class I recommendations for rate control in persistent or permanent AF. 1 The 2011 ACC/AHA/HRS guidelines explicitly state that measurement and control of heart rate using "either a beta blocker or nondihydropyridine calcium channel antagonist, in most cases" is the standard approach. 1

Why Metoprolol or Diltiazem Are Superior:

• Both agents control heart rate effectively at rest AND during exercise, which is critical for quality of life and preventing tachycardia-induced cardiomyopathy. 1
• Efficacy is approximately 80% in clinical trials for pharmacological rate control with these agents. 1
• Beta-blockers achieved rate control targets in 70% of patients in the AFFIRM study, compared to 54% with calcium channel blockers. 1
• Diltiazem and verapamil are the only agents associated with improved quality of life and exercise tolerance. 1

Why NOT Digoxin (B)

Digoxin should NOT be used as the sole agent for rate control in AF—this is a Class III recommendation (meaning "do not do this"). 1 The guidelines are unequivocal on this point:

• Digoxin is ineffective during exercise and states of high sympathetic tone, which commonly precipitate paroxysmal AF. 1, 2
• Onset of action is delayed by at least 60 minutes with peak effect at 6 hours, making it inadequate for acute rate control. 1
• Digoxin only controls resting heart rate, not exercise heart rate, severely limiting functional capacity. 1
• The 2003 AAFP/ACP guideline explicitly states: "Digoxin is only effective for rate control at rest and therefore should only be used as a second-line agent." 1

Limited Role for Digoxin:

Digoxin may be reasonable as an add-on agent (not monotherapy) in specific circumstances: 1, 2

• Patients with concomitant heart failure where it provides inotropic support 2, 3
• Physically inactive elderly patients (≥80 years) where other agents are contraindicated 3
• As combination therapy with beta-blockers or calcium channel blockers when monotherapy fails 1

Why NOT Lisinopril (D)

Lisinopril is an ACE inhibitor with no direct effect on AV nodal conduction and does not control ventricular rate in AF. This is not a rate-control agent and is therefore incorrect for this indication.

Clinical Algorithm for Agent Selection

Step 1: Assess Cardiac Function and Comorbidities

If heart failure with reduced ejection fraction (HFrEF) is present:

• Choose metoprolol or carvedilol (beta-blockers should be initiated cautiously in HF). 1, 4
• Avoid diltiazem/verapamil as they can exacerbate hemodynamic compromise due to negative inotropic effects (Class III recommendation). 1

If normal left ventricular function:

• Either metoprolol or diltiazem are appropriate first choices. 4

If chronic obstructive pulmonary disease or asthma:

• Choose diltiazem or verapamil (avoid beta-blockers). 1, 5

If coronary artery disease, post-MI, or hyperthyroidism:

• Choose metoprolol or another beta-blocker. 6, 5

Step 2: Verify Rate Control Adequacy

Target heart rate should be <100 bpm at rest, with mean ventricular rate around 80 bpm and 90-115 bpm on moderate exertion. 4 This must be verified by:

• 24-hour Holter monitoring, OR
• Submaximal stress test 4

Step 3: If Monotherapy Fails

Add a second agent from a different class (e.g., combine beta-blocker with digoxin, or calcium channel blocker with digoxin). 1 The combination is reasonable to control rate both at rest and during exercise (Class IIa recommendation). 1

Critical Pitfalls to Avoid

• Never use digoxin as monotherapy for paroxysmal AF—it is contraindicated (Class III). 1
• Never use diltiazem or verapamil in decompensated heart failure—this may precipitate hemodynamic collapse (Class III). 1
• Never use digoxin, diltiazem, or verapamil in Wolff-Parkinson-White syndrome with AF—these can paradoxically accelerate ventricular response and cause ventricular fibrillation (Class III). 1, 2, 5
• Avoid excessive rate reduction that limits exercise tolerance—this worsens quality of life. 4

Dosing Considerations

For metoprolol: 25-100 mg twice daily orally (or 50-400 mg daily of extended-release formulation). 1

For diltiazem: 120-360 mg daily in divided doses or extended-release formulation. 1

Both agents can be initiated intravenously for acute rate control if needed, with metoprolol 2.5-5 mg IV bolus and diltiazem 0.25 mg/kg IV bolus. 1