Third degree AV block natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2] Raviteja Guddeti, M.B.B.S. [3] ; Aditya Ganti M.B.B.S. [4]

The majority of the patients with complete heart block do not recover spontaneously. Untreated complete heart block is associated with high morbidity and mortality. Patients with complete heart blocks are prone to decreased perfusion related to symptomatic bradycardia and decreased cardiac output. Common Complications of third-degree AV block include sudden cardiac death due to asystole, syncope, and musculoskeletal injuries secondary to fall after syncope. The prognosis of the third-degree heart block is most likely dependent on the patient‘s underlying disease burden and severity of the clinical presentation on arrival. Patients treated with permanent pacemakers have an excellent prognosis.

• Spontaneous recovery from third-degree heart block is very rare.
• The estimated overall mortality of non-paced patients with isolated AV block is 8%–16% in infants and 4%–8% in children and adults.^[1][2]
• If left untreated, third-degree heart block is associated with high mortality which appears to occur as a consequence of the complications of prematurity and bradycardia owing to the delayed initiation of pacing therapy.

• Patients with complete heart block are susceptible to hypotension related to decreased cardiac output and bradycardia.^[3]
• Patients with hemodynamic instability may be unable to protect their airway due to altered mental status leading to an aspiration that has high morbidity and mortality.
• Complications related to pace maker implantation include malposition or dislodgement of a pacemaker leads and cardiac perforation.

• Common complications of third degree AV block include:
  • Sudden cardiac death due to asystole
  • Syncope
  • Musculoskeletal injuries secondary to fall after syncope.
  • Cardiovascular collapse
  • Hypotension
  • Stokes-Adams syndrome
  • Ventricular tachycardia^[4][5]
  • Ventricular fibrillation
  • Worsening of heart failure
  • Worsening of angina
  • Death

• The prognosis of third degree heart block is most likely dependent on the patient‘s underlying disease burden and severity of the clinical presentation on arrival.^[6]
• Complete heart block is sometimes reversible in settings such as acute MI by restoring coronary perfusion and in conditions such as Lymes disease by treatment with antibiotics.^[7]
• Patients treated with permanent pacemaker have an excellent prognosis.
• Patients with complete heart block due to acute myocardial infarction are at a greater risk for sudden cardiac death.

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