What is the prognosis of third-degree atrioventricular (AV) block?

Updated: Jul 05, 2018
  • Author: Akanksha Agrawal, MBBS; Chief Editor: Jeffrey N Rottman, MD  more...
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Patients with third-degree atrioventricular (AV) block (complete heart block) are frequently hemodynamically unstable; as a result, they may experience syncope, hypotension, cardiovascular collapse, or death. Other patients can be relatively asymptomatic and have minimal symptoms other than dizziness, weakness, or malaise.

Third-degree AV block may be an underlying condition in patients who present with sudden cardiac death. The cause of death may often be tachyarrhythmias precipitated by the secondary changes in ventricular repolarization (QT prolongation) due to the abrupt changes in rate.

Some patients may develop polymorphic ventricular tachycardia when significant bradycardia is present. This is related to prolongation of repolarization with extremely slow rates. This mechanism is also mostly responsible for death in these patients.

When treated with permanent pacing, the prognosis is excellent for patients with third-degree AV block. The complications related to pacemaker insertion are rare (< 1%). Ventricular arrhythmias from atropine or catecholamines may occur. Common complications include those related to line and/or transvenous pacemaker placement. These complications include arterial injury, hemothorax, pneumothorax, or cardiac tamponade.

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