When are AV (atrioventricular) node blockers contraindicated?

AV Node Blockers: Contraindications and Drug Classes

What Are AV Node Blockers?

AV node blockers are medications that slow conduction through the atrioventricular node and include three main drug classes: beta-blockers, nondihydropyridine calcium channel antagonists (verapamil, diltiazem), and digoxin. 1

These agents work by prolonging the functional refractory period of the AV node, effectively controlling ventricular rate during atrial arrhythmias. 1

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Absolute Contraindications

Pre-Excited Atrial Fibrillation (Wolff-Parkinson-White Syndrome)

AV nodal blocking agents are absolutely contraindicated in patients with WPW syndrome and pre-excited atrial fibrillation because they can paradoxically accelerate ventricular response and precipitate ventricular fibrillation. 1

• Intravenous administration of beta-blockers, digoxin, adenosine, and nondihydropyridine calcium channel antagonists is classified as Class III: Harm in this population. 1
• These drugs facilitate antegrade conduction down the accessory pathway by blocking the AV node, resulting in extremely rapid ventricular rates, hypotension, or ventricular fibrillation. 1
• This contraindication applies to all patients with accessory bypass tracts (WPW, Lown-Ganong-Levine syndromes). 2
• The 2010 AHA guidelines explicitly state that AV nodal blocking drugs should not be used for pre-excited atrial fibrillation or flutter (Class III, LOE C). 1

Decompensated Heart Failure

Intravenous nondihydropyridine calcium channel antagonists and IV beta-blockers are contraindicated in patients with decompensated heart failure as they may exacerbate hemodynamic compromise. 1

• This is a Class III: Harm recommendation. 1
• Dronedarone is also contraindicated in this setting. 1
• In patients with overt congestion or hypotension, IV beta-blockers should be used with extreme caution even when pre-excitation is absent. 1

Severe Left Ventricular Dysfunction

Verapamil is contraindicated in patients with severe left ventricular dysfunction (ejection fraction <30%). 2

• The negative inotropic effects of calcium channel blockers can precipitate or worsen heart failure. 2
• Beta-blockers should also be avoided when combined with verapamil in patients with any degree of ventricular dysfunction due to additive negative inotropic effects. 2

Conduction System Disease

AV node blockers are contraindicated in the following conduction abnormalities (unless a functioning pacemaker is present): 2

• Sick sinus syndrome 2
• Second- or third-degree AV block 2
• Symptomatic bradycardia 1

Hypotension and Cardiogenic Shock

Verapamil and other AV nodal blockers are contraindicated when systolic blood pressure is less than 90 mmHg or in cardiogenic shock. 2

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Relative Contraindications and Cautions

Chronic Obstructive Pulmonary Disease

Beta-blockers should be used with caution in patients with obstructive pulmonary disease or asthma due to risk of bronchospasm. 1

• In these patients, nondihydropyridine calcium channel antagonists are the preferred AV nodal blocking agents (Class I, LOE C). 1

Heart Failure with Reduced Ejection Fraction (Acute Setting)

In the absence of pre-excitation, IV beta-blockers can be used to slow ventricular response in acute AF, but require caution in patients with heart failure with reduced ejection fraction (HFrEF). 1

• Digoxin or amiodarone are preferred alternatives for acute rate control in HFrEF (Class I, LOE B). 1

Hypertrophic Cardiomyopathy

Verapamil should be used cautiously in patients with hypertrophic cardiomyopathy, particularly those with severe left ventricular outflow obstruction. 2

• In clinical experience, pulmonary edema and severe hypotension occurred in patients with marked outflow obstruction and left ventricular dysfunction. 2

Drug Interactions

Avoid sequential administration of AV nodal blocking agents with longer half-lives (e.g., giving a beta-blocker after verapamil or vice versa) as profound bradycardia can develop. 1

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Clinical Pitfalls to Avoid

Atrial Flutter with Class IC Antiarrhythmics

When using class IC drugs (flecainide, propafenone) for atrial fibrillation, always co-administer AV nodal blocking agents to prevent 1:1 AV conduction during atrial flutter, which can cause dangerously rapid ventricular rates. 1

Paroxysmal AF in Elderly

Bradycardia and heart block may occur as unwanted effects of AV nodal blockers, particularly in elderly patients with paroxysmal AF. 1

Digoxin Monotherapy

Digoxin should not be used as the sole agent to control ventricular rate in paroxysmal AF (Class III recommendation). 1

• Digoxin is effective only for resting heart rate control and requires combination with beta-blockers or calcium channel antagonists for exercise rate control. 1