Management of Heart Block with Beta-Adrenergic Agonists

First-Line Treatment Approach

The American College of Cardiology recommends atropine as the initial pharmacological intervention for symptomatic bradycardia due to heart block, with a dose of 0.5-1 mg IV, repeated every 3-5 minutes as needed up to a maximum total dose of 1.5-3 mg 1, 2
Atropine is reasonable for second-degree or third-degree AV block believed to be at the AV nodal level when associated with symptoms or hemodynamic compromise, as recommended by the American College of Cardiology 1, 3

The American College of Cardiology suggests considering beta-adrenergic agonists like isoproterenol only after atropine has failed to improve AV conduction and ventricular rate, with a critical prerequisite of low likelihood for coronary ischemia 1, 3, 4
Isoproterenol increases myocardial oxygen demand and decreases coronary perfusion, thus it should be used with caution, as noted by the American College of Cardiology 5

The standard dosing for isoproterenol is 1-20 mcg/min IV infusion, titrated to hemodynamic response, as recommended by the American College of Cardiology 4, 5
Alternative bolus dosing is 20-60 mcg IV bolus followed by 10-20 mcg increments based on heart rate response, according to the American College of Cardiology 4

Dopamine may be preferable to isoproterenol, with a dose of 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 minutes, as suggested by the American College of Cardiology 4, 5
Epinephrine is another alternative, with a dose of 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV, titrated to desired effect, as recommended by the American College of Cardiology 3, 4, 5

The American College of Cardiology states that active myocardial ischemia or high likelihood of coronary disease is an absolute contraindication to beta-agonist use in heart block 1, 5
Isoproterenol should be avoided when coronary ischemia is a concern due to its paradoxical reduction in coronary perfusion, as noted by the American College of Cardiology 5

The American College of Cardiology recommends temporary transvenous pacing for second-degree or third-degree AV block with symptoms or hemodynamic compromise refractory to medical therapy 1, 3
Transcutaneous pacing may be considered as a bridge until transvenous or permanent pacemaker placement, as suggested by the American College of Cardiology 1, 3

In acute inferior myocardial infarction with heart block, intravenous aminophylline may be considered instead of beta-agonists to avoid increased myocardial oxygen demand, as recommended by the American College of Cardiology 1, 4, 3
Patients with transient or reversible causes of AV block should receive medical therapy and supportive care, including temporary transvenous pacing if necessary, before determining the need for permanent pacing, as noted by the American College of Cardiology 1, 3