Third degree AV block medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Associate Editor(s)-in-Chief: Sara Zand, M.D. Cafer Zorkun, M.D., Ph.D.  Raviteja Guddeti, M.B.B.S.  Soroush Seifirad, M.D. Qasim Khurshid, M.B.B.S. 
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.
|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)
❑ 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|
|Betablocker or Calcium channel blocker overdose|
❑ Glucagon 3-10 mg IV with infusion of 3-5 mg/h
❑ Digoxin antibody fragment
❑ 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
|Spinal cord injury|
|The above table adopted from 2018 AHA/ACC/HRS Guideline|
|"1 Digoxin Fab antibody fragment is recommended in patients presented with digoxin toxicity resulting in symptomatic bradycardia or hemodynamic compromised. (Level of Evidence C)"|
|"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
|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
PPM: Permanent pacemaker;
|The above table adopted from 2018 AHA/ACC/HRS Guideline|
- 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):|
|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):|
- 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.
- Kusumoto, Fred M.; Schoenfeld, Mark H.; Barrett, Coletta; Edgerton, James R.; Ellenbogen, Kenneth A.; Gold, Michael R.; Goldschlager, Nora F.; Hamilton, Robert M.; Joglar, José A.; Kim, Robert J.; Lee, Richard; Marine, Joseph E.; McLeod, Christopher J.; Oken, Keith R.; Patton, Kristen K.; Pellegrini, Cara N.; Selzman, Kimberly A.; Thompson, Annemarie; Varosy, Paul D. (2019). "2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society". Circulation. 140 (8). doi:10.1161/CIR.0000000000000628. ISSN 0009-7322.
- Chan BS, Buckley NA (2014). "Digoxin-specific antibody fragments in the treatment of digoxin toxicity". Clin Toxicol (Phila). 52 (8): 824–36. doi:10.3109/15563650.2014.943907. PMID 25089630.
- Forrester, J. D.; Mead, P. (2014). "Third-Degree Heart Block Associated With Lyme Carditis: Review of Published Cases". Clinical Infectious Diseases. 59 (7): 996–1000. doi:10.1093/cid/ciu411. ISSN 1058-4838.
- Antman, E M; Wenger, T L; Butler, V P; Haber, E; Smith, T W (1990). "Treatment of 150 cases of life-threatening digitalis intoxication with digoxin-specific Fab antibody fragments. Final report of a multicenter study". Circulation. 81 (6): 1744–1752. doi:10.1161/01.CIR.81.6.1744. ISSN 0009-7322.
- Kennebäck, Göran; Tabrizi, Fariborz; Lindell, Peter; Nordlander, Rolf (2007). "High-degree atrioventricular block during anti-arrhythmic drug treatment: use of a pacemaker with a bradycardia-detection algorithm to study the time course after drug withdrawal". EP Europace. 9 (3): 186–191. doi:10.1093/europace/eul185. ISSN 1532-2092.
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- Kandolin R, Lehtonen J, Kupari M (June 2011). "Cardiac sarcoidosis and giant cell myocarditis as causes of atrioventricular block in young and middle-aged adults". Circ Arrhythm Electrophysiol. 4 (3): 303–9. doi:10.1161/CIRCEP.110.959254. PMID 21427276.
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- Hatle L, Rokseth R (July 1971). "Conservative treatment of AV block in acute myocardial infarction. Results in 105 consecutive patients". Br Heart J. 33 (4): 595–600. doi:10.1136/hrt.33.4.595. PMC 487219. PMID 5557475.
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|pmc=value (help). PMID 17933452.
- Hurley KF, Magee K, Green R (November 2015). "Aminophylline for bradyasystolic cardiac arrest in adults". Cochrane Database Syst Rev (11): CD006781. doi:10.1002/14651858.CD006781.pub3. PMID 26593309.