Medication Summary
Long-term medical therapy is not indicated in atrioventricular (AV) block. As noted earlier, permanent pacing is the therapy of choice in symptomatic AV block with bradycardia.
Anticholinergic Agents
Class Summary
The goal of administering anticholinergic agents is to improve conduction through the atrioventricular node (AVN) by reducing vagal tone via muscarinic receptor blockade. This is only effective if the site of block is within the AVN. For patients with suspected infranodal block, this therapy is ineffective and may make the level of the block worse if it is in the His bundle or below.
Atropine IV/IM (Atropair, Atropisol)
Atropine increases AV conduction by reducing vagal tone via muscarinic receptor blockade; this may improve AV conduction if the block is in the AV node but atropine is ineffective in infranodal block and may worsen the block. An insufficient dose may cause paradoxical slowing of the heart rate.
Beta1/Beta2 Adrenergic Agonists
Isoproterenol (Isuprel)
Isoproterenol binds and stimulates beta-receptors of the heart, smooth and skeletal muscle, vasculature, and alimentary tract. It has positive inotropic and chronotropic actions.
Vasopressors, Alpha/Beta Agonists
Class Summary
For hemodynamically unstable patients with AV block, intravenous dopamine or dobutamine should be started to improve chronotropic and inotropic cardiac function.
Dopamine (Intropin)
Intravenous dopamine infusion typically begins at a dose of 3 mcg/kg/minute and can be titrated up to 20 mcg/kg/minute for heart rate and blood pressure augmentation.
Dobutamine
Intravenous dobutamine infusion typically begins at a dose of 5 mcg/kg/minute and can be titrated up to 20 mcg/kg/minute.
-
Atrioventricular Block. This rhythm strip shows first-degree atrioventricular block with a PR interval of 0.360 sec. Note the fixed prolonged PR interval.
-
Atrioventricular Block. First-degree atrioventricular block. PR interval is constant and is 0.280 sec.
-
Atrioventricular Block. Second-degree Mobitz type I atrioventricular block. Note the prolongation of the PR interval preceding the dropped beat and the shortened PR interval following the dropped beat.
-
Atrioventricular Block. Second-degree atrioventricular block, Mobitz type I (Wenckebach). Note the prolongation of the PR interval preceding the dropped beat and the shortened PR interval following the dropped beat.
-
Atrioventricular Block. Second-degree Mobitz II atrioventricular block. Note the fixed PR interval, but after the third beat, an atrial impulse fails to conduct to the ventricle. Courtesy of Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Second_degree_heart_block.png).
-
Atrioventricular Block. Second-degree atrioventricular block, Mobitz type II. A constant PR interval in conducted beats is present. Intraventricular conduction delay is also present.
-
Atrioventricular Block. A constant PP interval and normal PR interval in conducted beats is present. This progresses to 2:1 atrioventricular (AV) block. A 2:1 AV block can be present with conduction delay in the AV node or His-Purkinje system, but it is more likely to be in the AV node for all patients (with a greater chance of AV block in the His-Purkinje system if there is a bundle branch block). Review extended monitoring strips because Mobitz I or Mobitz II may be present at other times, and this might help to determine the level of the block.
-
Atrioventricular Block. High-degree atrioventricular block is demonstrated with a 4:1 atrial-to-ventricular conduction ratio. Note the P wave prior to the QRS conducts whereas the others do not. Courtesy of Life in the Fast Lane (https://lifeinthefastlane.com/ecg-library/basics/high-grade-block/), Edward J Burns, MD, Sydney, Australia.
-
Atrioventricular Block. This rhythm strip shows third-degree atrioventricular block (complete heart block). The atrial rate is faster than the ventricular rate, and no association exists between the atrial and ventricular activity. Courtesy of Life in the Fast Lane (https://lifeinthefastlane.com/ecg-library/basics/complete-heart-block/), Edward J Burns, MD, Sydney, Australia.
-
Atrioventricular Block. Third-degree atrioventricular block (complete heart block). The atrial rate is faster than the ventricular rate, and no association exists between the atrial and ventricular activity.
