Management of Third-Degree Heart Block
Permanent pacemaker implantation is the definitive treatment for patients with third-degree atrioventricular block regardless of symptoms, as this condition poses significant mortality risk. 1
Initial Assessment and Stabilization
- Assess for signs of hemodynamic compromise including syncope, dyspnea, chest pain, hypotension, or altered mental status 1
- Establish IV access, provide supplemental oxygen if hypoxemic, and initiate continuous cardiac monitoring 1
- For symptomatic patients with hemodynamic compromise, immediate intervention is required 2
Acute Medical Therapy
- For patients with third-degree AV block at the AV nodal level with symptoms or hemodynamic compromise, atropine (0.5-1.0 mg IV every 3-5 minutes, maximum 3 mg) is reasonable to improve AV conduction and increase ventricular rate 2, 1
- Atropine works by inhibiting vagal activity, which may improve conduction through the AV node, but is often ineffective in infranodal blocks 3
- For patients with persistent symptoms despite atropine, beta-adrenergic agonists such as isoproterenol, dopamine, dobutamine, or epinephrine may be considered to increase ventricular rate 2, 1
- In the setting of acute inferior myocardial infarction with third-degree AV block, intravenous aminophylline may be considered to improve AV conduction 2
Temporary Pacing
- For patients with third-degree AV block associated with symptoms or hemodynamic compromise refractory to medical therapy, temporary transvenous pacing is reasonable 2, 1
- Transcutaneous pacing may be considered as a bridge until temporary transvenous or permanent pacemaker is placed 2, 4
- For patients requiring prolonged temporary transvenous pacing, an externalized permanent active fixation lead is preferable over a standard passive fixation temporary pacing lead 2
Definitive Management
- Permanent pacemaker implantation is indicated for all patients with acquired third-degree AV block regardless of symptom status 1, 4
- This recommendation is particularly strong for patients with:
Management of Potentially Reversible Causes
- Evaluate for potentially reversible causes including acute myocardial infarction, drug effects, electrolyte abnormalities, or Lyme carditis 1
- In patients with symptomatic AV block attributable to a known reversible cause that does not resolve despite treatment, permanent pacing is recommended 2
- For patients with third-degree AV block due to drug toxicity, electrolyte abnormalities, or other reversible causes, medical therapy and supportive care, including temporary pacing if necessary, should be provided before determining need for permanent pacing 2
- For patients with confirmed Lyme disease causing third-degree AV block, parenteral antibiotics (ceftriaxone) should be initiated immediately 1, 5
Special Considerations
- In patients with third-degree AV block associated with cardiac sarcoidosis, permanent pacing with additional defibrillator capability (if needed and meaningful survival >1 year is expected) is reasonable without further observation for reversibility 2
- Patients with third-degree AV block associated with thyroid function abnormalities but without clinical myxedema may be considered for permanent pacing without further observation for reversibility 2
- Patients on chronic stable doses of medically necessary antiarrhythmic or beta-blocker therapy who develop third-degree AV block may reasonably proceed to permanent pacing without further observation for drug washout or reversibility 2
- Patients with ischemic third-degree AV block tend to be younger and have lower ejection fractions compared to those with non-ischemic causes 6
Prognosis and Follow-up
- After permanent pacemaker implantation, patients should be followed regularly to ensure proper device function 1
- Underlying causes (ischemia, infiltrative disease, etc.) should be addressed to improve long-term outcomes 1
- The prognosis varies based on the underlying cause, with non-ischemic causes generally having better outcomes than ischemic causes 6