Atropine for Complete Heart Block

Indications and Contraindications

The American College of Cardiology recommends against using atropine in complete heart block (third degree) at the infranodal level, especially with a wide complex escape rhythm, as it can paradoxically worsen bradycardia and precipitate ventricular asystole 1, 2
Atropine is contraindicated in Mobitz II second-degree or third-degree AV block with new wide QRS complex, as the block is likely at the infranodal level 2
The American Heart Association suggests that atropine may increase sinus rate without improving AV conduction, worsening the block 4

The initial dose of atropine is 0.5 mg IV, with repeat doses every 3-5 minutes as needed, according to the American College of Cardiology and Circulation guidelines 1, 2, 4
The maximum total dose is 3 mg (complete vagal block), although some guidelines suggest an alternative maximum dose of 2-2.5 mg 1, 2, 4

For symptomatic complete heart block that does not respond to atropine or when atropine is contraindicated, the American College of Cardiology recommends immediate transcutaneous pacing as a temporary measure 1, 2
Beta-adrenergic support with dopamine (5-20 mcg/kg/min IV) or epinephrine (2-10 mcg/min IV) may be used while preparing for transvenous pacing, according to Circulation guidelines 2

Atropine should be used with extreme caution in acute myocardial infarction, as the resulting tachycardia can increase ischemia and infarct extension, warns the American College of Cardiology 1, 4
Atropine should be avoided in heart transplant patients, as it can cause paradoxical slowing, according to Circulation guidelines 2