Atrial fibrillation rate control

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Atrial fibrillation with rapid ventricular rate is a common finding in many hospitalized patients. The ventricular rate may be increased upto 150-170. It is essential to bring the ventricular rate down to less than 100 because a rapid ventricular response can cause hemodynamic instabilities and tachycardia mediated cardiomyopathies (heart failure). AF can cause disabling and annoying symptoms. Palpitations, angina, lassitude (weariness), and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF. This can significantly increase mortality and morbidity, which can be prevented by early and adequate treatment of the AF.

Rate control versus rhythm control

There are two ways to approach these symptoms: rate control and rhythm control.

• Rate control treatments seek to reduce the heart rate to normal, usually 60 to 100 beats per minute.
• Rhythm control seeks to restore the normal heart rhythm, called normal sinus rhythm.
• Studies suggest that rhythm control is mainly a concern in newly diagnosed AF, while rate control is more important in the chronic phase.
• Rate control with anticoagulation is as effective a treatment as rhythm control in long term mortality studies, the AFFIRM Trial.
• The AFFIRM study showed no difference in risk of stroke in patients who have converted to a normal rhythm with anti-arrhythmic treatment, compared to those who have only rate control.

Pharmacologic Rate control

Mechanism of action

• Rate control is achieved with medications that work by increasing the degree of block at the AV node, effectively decreasing the number of impulses that conduct to the ventricles. This can be accomplished with:

• Calcium channel blockers (i.e. diltiazem or verapamil) block the influx of calcium and reduce the upstroke of the action potential
• Beta blockers (preferably the "cardioselective" beta blockers such as metoprolol, atenolol, bisoprolol) slow conduction by decreasing sympathetic tone
• Cardiac glycosides (i.e. digoxin) are vagomimetics and slow conduction by increasing parasympathetic effects on the node
• Amiodarone has some AV node blocking effects, and can be used in individuals when other agents are contraindicated or ineffective (particularly due to hypotension).
• Adenosine slows conduction by increasing potassium conduction and decreasing calcium entry
• Carotid massage, Valsalva maneuver, and edrophonium though non-pharmacological methods are used sometimes. They slow conduction by increasing the parasympathetic tone on the AV node

Beta blockers

Acute beta blocker therapy

• Intravenous beta blocker like metoprolol, propranolol, and esmolol
• Useful when Atrial fibrillation is secondary to high adrenergic tone like in post operative situations

Metoprolol

• Dose 2.5-5 mg over 2 minutes
• Route - i/v
• Maximum dose 15 mg.
• Doses can be repeated over 5 minutes interval

Esmolol

• Short duration of action (10-20 min)
• Metabolized by RBC esterases
• Advantage - It can be used in conditions where patient's response and tolerance to beta blocker is uncertain for e.g bradycardia. In these situations its short half-life permits a therapeutic trial to check the patient's response. Based on that the patient are started on other long acting beta blockers.
• Doses
  • Infusion at rate of 50 µg/kg per min, with an increase in the rate of administration by 50 µg/kg per min every 30 minutes.
  • Some hospitals prefer starting with a bolus of 0.5 mg/kg over one minute, followed by infusion of 50 µg/kg per min. Monitor for four minutes. In case of inadequate response, another bolus is given followed by an infusion of 100 µg/kg per min. Wait for 4 minutes. In case of inadequate response a third bolus can be given followed by an infusion at 150 µg/kg per min rate. The maximum infusion that can be given is 200 µg/kg per min.

Chronic beta blocker therapy

• Oral beta blockers are preferred for treatment of chronic atrial fibrillation
• Commonly used agents are: Atenolol, Metoprolol, Timolol, Pindolol, Nadolol and labetalol.
• Atenolol is the preferred over other agents due to its long half life, once daily dose, and less CNS side effects
• Atenolol dose - 25 mg per day. Maximum dose permitted is 200 mg per day.
• Carvedilol has been found to be useful in patients with chronic heart failure due to systolic dysfunction.

Side effects of beta blocker therapy

• Congestive heart failure
• Hypotension
• AV block
• Bradycardia
• Bronchospasm

Calcium channel blocker

• Nondihydropyridine calcium channel blockers verapamil, and diltiazem (cardizem) are commonly used.

ACCF/AHA/HRS 2011 Guidelines - Atrial Fibrillation - Treatment through Pharmacological Rate Control (DO NOT EDIT)

Class I

"1. Measurement of the heart rate at rest and control of the rate using pharmacological agents (either a beta blocker or non dihydropyridine calcium channel antagonist, in most cases) are recommended for patients with persistent or permanent AF. (Level of Evidence: B) "

"2. In the absence of preexcitation, intravenous administration of beta blockers (esmolol, metoprolol, or propranolol) or nondihydropyridine calcium channel antagonists (verapamil, diltiazem) is recommended to slow the ventricular response to AF in the acute setting, exercising caution in patients with hypotension or heart failure. (Level of Evidence: B) "

"3. Intravenous administration of digoxin or amiodarone is recommended to control the heart rate in patients with AF and heart failure who do not have an accessory pathway. (Level of Evidence: B) "

"4. In patients who experience symptoms related to AF during activity, the adequacy of heart rate control should be assessed during exercise, adjusting pharmacological treatment as necessary to keep the rate in the physiological range. (Level of Evidence: C) "

"5. Digoxin is effective following oral administration to control the heart rate at rest in patients with AF and is indicated for patients with heart failure, LV dysfunction, or for sedentary individuals. (Level of Evidence: C) "

Class III: Harm

"1. Digitalis should not be used as the sole agent to control the rate of ventricular response in patients with paroxysmal AF. (Level of Evidence: B)"

"2. Catheter ablation of the AV node should not be attempted without a prior trial of medication to control the ventricular rate in patients with AF. (Level of Evidence: C)"

"3. In patients with decompensated HF and AF, intravenous administration of a non dihydropyridine calcium channel antagonist may exacerbate hemodynamic compromise and is not recommended. (Level of Evidence: C)"

"4. Intravenous administration of digitalis glycosides or non dihydropyridine calcium channel antagonists to patients with AF and a pre-excitation syndrome may paradoxically accelerate the ventricular response and is not recommended. (Level of Evidence: C)"

Class III: No Benefit

"1. Treatment to achieve strict rate control of heart rate (<80 bpm at rest or <110 bpm during a 6-minute walk) is not beneficial compared to achieving a resting heart rate <110 bpm in patients with persistent AF who have stable ventricular function (LV ejection fraction >0.40) and no or acceptable symptoms related to the arrhythmia, though uncontrolled tachycardia may over time be associated with a reversible decline in ventricular performance. (Level of Evidence: B)"

Class IIa

"1. A combination of digoxin and either a beta blocker or non dihydropyridine calcium channel antagonist is reasonable to control the heart rate both at rest and during exercise in patients with AF. The choice of medication should be individualized and the dose modulated to avoid bradycardia. (Level of Evidence: B)"

"2. It is reasonable to use ablation of the AV node or accessory pathway to control heart rate when pharmacological therapy is insufficient or associated with side effects. (Level of Evidence: B)"

"3. Intravenous amiodarone can be useful to control the heart rate in patients with AF when other measures are unsuccessful or contraindicated. (Level of Evidence: C)"

"4. When electrical cardioversion is not necessary in patients with AF and an accessory pathway, intravenous procainamide or ibutilide is a reasonable alternative. (Level of Evidence: C)"

Class IIb

"1. When the ventricular rate cannot be adequately controlled both at rest and during exercise in patients with AF using a [beta blocker]], non dihydropyridine calcium channel antagonist, or digoxin, alone or in combination, oral amiodarone may be administered to control the heart rate. (Level of Evidence: C)"

"2. Intravenous procainamide, disopyramide, ibutilide, or amiodarone may be considered for hemodynamically stable patients with AF involving conduction over an accessory pathway. (Level of Evidence: B)"

"3. When the rate cannot be controlled with pharmacological agents or tachycardia-mediated cardiomyopathy is suspected, catheter-directed ablation of the AV node may be considered in patients with AF to control the heart rate. (Level of Evidence: C)"

Vote on and Suggest Revisions to the Current Guidelines

• The AF Living Guidelines: Vote on current recommendations and suggest revisions to the guidelines

Guideline Resources

• ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation

• 2011 ACCF/AHA/HRS Focused Updates Incorporated Into the ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation

References

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