Third degree AV block medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Cafer Zorkun, M.D., Ph.D. [3] Raviteja Guddeti, M.B.B.S. [4] Soroush Seifirad, M.D.[5] Qasim Khurshid, M.B.B.S. [5]

Overview

The management of third-degree AV block depends on the severity of signs, symptoms, and the underlying cause. In symptomatic patients and with hemodynamic distress, pharmacological therapy should be initiated immediately to increase heart rate and cardiac output. Most of the patients who do not respond to pharmacologic therapy require a temporary pacemaker. After stabilizing the patients, assessment and treatment of potentially reversible causes should be done. Some patients without reversible cause or unidentified etiology require a permanent pacemaker.

Medical Therapy

Recommendations for Acute Management of Bradycardia Attributable to Atrioventricular Block

Symptomatic sinus bradycardia or atrioventricular block

❑ Atropine 0.5-1 mg IV (may be repeated every 3-5 min to a maximum dose of 3 mg) ❑ Dopamine 5 to 20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 min Dosages of >20 mcg/kg/min may lead to vasoconstriction or arrhythmias ❑ Isoproterenol 20-60 mcg IV bolus followed doses of 10-20 mcg, or infusion of 1-20 mcg/min based on heart rate response Monitoring of ischemic chest pain ❑ Epinephrine 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect

Second or third degree atrioventricular block associated acute inferior MI :

❑ Aminophylline 250-mg IV bolus

Calcium channel blocker overdose

❑ 10% calcium chloride 1-2 g IV every 10-20 min or an infusion of 0.2-0.4 mL/kg/h ❑ 10% calcium gluconate 3-6 g IV every 10-20 min or an infusion at 0.6-1.2 mL/kg/h

Betablocker or Calcium channel blocker overdose

❑ Glucagon 3-10 mg IV with infusion of 3-5 mg/h ❑ High dose insulin therapy IV bolus of 1 unit/kg followed by an infusion of 0.5 units/kg/h Checking potassium and glocagon level

Digoxin overdose

❑ Digoxin antibody fragment Every vial for 0.5 mg of digoxin, over 30 min, maybe repeated ❑ Dosage is dependent on the amount ingested or known digoxin concentration

Post heart transplant

❑ Aminophylline 6 mg/kg in 100-200 mL of IV fluid over 20-30 min ❑ Theophylline 300 mg IV, followed by oral dose of 5-10 mg/kg/d Therapeutic serum level 10-20 mcg/mL, posttransplant dosages average 450 mg±100 mg/d

Spinal cord injury

❑ Aminophylline 6 mg/kg in 100-200 mL of IVfluid over 20-30 min ❑ Theophylline Oral dose of 5-10 mg/kg/d titrated to effect Effective serum level 10-20 mcg/mL

The above table adopted from 2018 AHA/ACC/HRS Guideline

Class IIa

"1 Digoxin Fab antibody fragment is recommended in patients presented with digoxin toxicity resulting in symptomatic bradycardia or hemodynamic compromised. (Level of Evidence C)"

Class III

"2 Dialysis is not benefit in patients presented with bradycardia associated digoxin toxicity (Level of Evidence C)"

• Digoxin-specific antibody (Fab) is a monovalent immunoglobulin that rapidly binds to intravascular digoxin.
• Each vial of 40 mg of digoxin Fab binds 0.5 mg of digoxin and dosage is dependent on the estimated amount of ingested digoxin.
• Hyperkalemia or arrhythmias in the setting of digoxin serum levels of >2 mcg/L put the patients at increased risk of death.
• Signs and symptoms of toxicity can present at lower serum levels leading to sinus node dysfunction or atrioventricular block.

Recommendations for Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block

Medical therapy (Class I, Level of Evidence B):

❑ In patients with transient or reversible causes of atrioventricular block including Lyme carditis or drug toxicity, medical therapy and transient pace maker insertion is recommended before making decision for implantation of PPM

PPM implantation ( Class IIa, Level of Evidence B) :

❑ In patients with symptomatic second-degree or third-degree atrioventricular block who are on chronic stable doses of medically necessary antiarrhythmic or beta-blocker therapy, PPM is recommended without further evaluation about drug washout or reversibility ❑ In patients with second-degree or third-degree atrioventricular block associated with cardiac sarcoidosis, PPM with defibrillation is recommended if life expectancy > 1 year, without further evaluation about reversibility

PPM implantation : (Class IIb, Level of Evidence C)

❑ In patients with symptomatic second-degree or third-degree atrioventricular block associated with thyroid function abnormalities but without clinical myxedema, PPM is recommended without further evaluation about reversibility

Abbreviations: PPM: Permanent pacemaker;

The above table adopted from 2018 AHA/ACC/HRS Guideline

Notes

• In the presence of new atrioventricular block, evaluation about reversible causes is recommended.
• Complete heart block is the most common manifestation of lyme carditis, commonly is reversible with appropriate antibiotic therapy.
• Atrioventricular block due to digoxin toxicity may be reversible after drug washout or using a neutralized antibody.
• Commonly, atrioventricular block due to overdose of antiarrhythmic drugs, calcium channel blocker or betablocker are reversible.
• Atrioventricular block in the setting of therapeutic dose of calcium channel blocker or betablocker, antiarrhythmic drugs class 1,3 in patients with heart failure or ischemic heart disease may be irreversible even after cessation of drugs and insertion of permanent pacemaker was needed in some cases.

• Before making decision for placement of permanent pacemakeker in atrioventricular block in the setting of cardiac sarcoidosis or hypothyroidism, medical therapy including hormone therapy for hypothyroidism and corticosteroid therapy for cardiac sarcoidosis is appropriate.

Recommendations for acute medical therapy for bradycardia associated atrioventricular block

Medical therapy (Class IIa, Level of Evidence C):

❑ Atropine is reasonable for patients with symptomatic bradycardia associated second-degree or third degree atrioventricular block at the atrioventricular nodal level

Medical therapy (Class IIb, Level of Evidence B):

❑ Beta adrenergic agonist such as isoproterenol, dopamine, dobutamine is recommended for symptomatic bradycardia associated second degree or third degree atrioventricular block with low likehood of ischemia

Medical therapy (Class IIb, Level of Evidence C):

❑ Aminophylline is recommended for symptomatic bradycardia associated second or third degree atrioventricular block in the setting of acute inferior MI

Comment

• Atropine is a parasympatholytic drug that increase atrioventricular nodal conduction and automaticity when atrioventricular block is at the atrioventricular nodal level or bradycardia is related to excess vagal tone.
• Dosage is 0.5- to 1.0-mg IV, may be repeated.
• Atropine may enhance atrioventricular conduction in the setting of inferior MI.
• For atrioventricular block at the level of His bundle or His-Purkinje, atropine may worsen atrioventricular conduction or compromise hemodynamic.
• Common adver effects of atropine include dry mouth, blurred vision, anhidrosis, urinary retention, and delirium , increased heart rate in the setting of MI.

• Beta-adrenergic agonists such as isoproterenol, dopamine, dobutamine, and epinephrine may have direct effect to increase atrioventricular nodal and, to a lesser degree, His-Purkinje conduction.
• The efficacy of dopamine was equal to transcutaneous pacing in 1 small randomized trial of patients with unstable bradycardia unresponsive to atropine.

• Common adverse effects of beta-adrenergic agonists may include ventricular arrhythmias , induction of coronary ischemia, particularly in the setting of acute MI.
• Isoproterenol because of the vasodilatory effects may exacerbate hypotension.
• Aminophylline is a nonselective adenosine receptor antagonist and phosphodiesterase inhibitor.
• Safety and efficacy of aminophylline for reversing bradycardia associated atrioventricular block in the setting of excess adnosine production in inferior MI was shown.
• There was no benefit for aminophylline in resuscitation for out-of-hospital brady-asystolic cardiac arrest based on a large randomized trial and a systematic review.