Third degree AV block medical therapy: Difference between revisions
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==Medical Therapy== | ==Medical Therapy== | ||
Revision as of 19:32, 2 June 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Raviteja Guddeti, M.B.B.S. [3]
Medical Therapy
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[1]. A new third degree AV block is an emergency. Management is slightly different between unstable and stable patients.
Management of Unstable Patients
The most critical factor in determining the management of third-degree AV block patients is hemodynamic stability. Patients of third-degree AV block with hemodynamic instability should be urgently treated with atropine and temporary cardiac pacemaker.
- Atropine should be given urgently with an initial dose of 0.5 mg IV and can be repeated every three to five minutes with a total dose of 3 mg. Atropine is most effective if the AV block is due to abnormal conduction through the AV node. Atropine is not useful in wide complex bradyarrhythmias (block below the AV node). It is also not helpful in a denervated heart, like in patients who have undergone a cardiac transplant procedure. Treatment with atropine should be followed by transcutaneous pacing or a chronotropic agent.
- Hemodynamically unstable patients should be immediately provided with a temporary cardiac pacemaker. Transcutaneous pacing can be initiated more rapidly as compared to a transvenous pacemaker, which requires more expertise. However, a transvenous pacemaker is more durable and comfortable for the patient. Transcutaneous pacing should be used temporarily until temporary transvenous pacing can be provided.
- In patients presenting with hypotension and third-degree AV block, dopamine should be given as IV infusion, starting at a dose of 3mcg/kg/min and can be titrated up to 20 mcg/kg/min for stabilization of blood pressure and heart rate.
- In patients presenting with heart failure symptoms and left ventricular dysfunction associated with third-degree AV block, dobutamine is given via IV infusion, with a starting dose of 5 mcg/kg/minute and can be titrated up to 40 mcg/kg/minute if required.
After stabilizing the hemodynamically unstable patients, the approach to further management is the same as for initially stable patients.
Management of Stable Patients
Hemodynamically stable patients of third-degree heart block do not require urgent treatment with atropine and pacemaker. However, many ventricular escape rhythms have the potential to become unstable, so patients should be monitored on the telemetry floor or ICU.
While monitoring patients, management should be as fellows.
- Reversible causes of third-degree heart block should be evaluated before implantation of the permanent pacemaker. Such causes include myocardial ischemia, hyperkalemia, increased vagal tone, and medications that depress the conduction through the AV node.
- Patients of third-degree AV block due to acute myocardial infarction can be managed with revascularization and temporary cardiac pacing. Most of the patients improve after revascularization and do not require a permanent pacemaker.
- Patients with third-degree (complete) AV block felt to be medication-induced should be observed after removing offending medications. Most of the patients will improve and do not require a pacemaker.
- Patients with third-degree (complete) AV block because of hyperkalemia should receive therapy to reduce serum potassium levels. If third-degree AV block subsequently resolves, a permanent pacemaker is not usually needed
Most of the patients of third-degree AV block will require a permanent pacemaker if no reversible cause can be identified[2]. A Dual-chamber pacemaker is preferred to maintain AV synchrony in most patients due to the favorable hemodynamic benefits[3]. Implantable cardioverter-defibrillators should be considered in patients with complete AV block and significant left ventricle dysfunction.
Contraindicated medications
Third degree AV block(except in patients with a functioning artificial pacemaker) is considered an absolute contraindication to the use of the following medications:
- Adenosine
- Atenolol
- Betaxolol
- Bisoprolol
- Brimonidine tartrate and Timolol maleate
- Carteolol
- Diltiazem
- Disopyramide
- Dronedarone
- Flecainide
- Labetalol
- Metoprolol
- Mexiletine
- Nadolol
- Nebivolol
- Penbutolol
- Pindolol
- Procainamide
- Propranolol
- Quinidine gluconate
- Sotalol
- Timolol
- Verapamil
References
- ↑ Kusumoto FM, Schoenfeld MH, Barrett C, et al. 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 [published correction appears in J Am Coll Cardiol. 2019 Aug 20;74(7):1016-1018]. J Am Coll Cardiol. 2019;74(7):e51‐e156. doi:10.1016/j.jacc.2018.10.044
- ↑ Task force members. "2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA)". Eur Heart J. 34: 2281–2329.
- ↑ Brignole M, Auricchio A, Baron-Esquivias G, et al. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Eur Heart J. 2013;34(29):2281‐2329. doi:10.1093/eurheartj/eht150