Clinical Features

Asymptomatic (common): especially with first-degree and Mobitz type I blocks

• Irregular rhythms (e.g., Mobitz I): palpitations

• Clinical features of end-organ hypoperfusion (due to bradycardia) may be present, including: [9]

  • Fatigue

  • Exercise intolerance

  • Dyspnea

  • Dizziness

  • Syncope

Loss of atrioventricular synchrony (e.g., extreme 1° AV block or 3° AV block) :

• Feeling of pulsations in the neck or chest

• Cannon A waves: physical examination finding seen in AV dissociation (e.g., in third-degree heart block)

  • Caused by the atria and ventricles contracting simultaneously, which leads to blood being pushed against a closed tricuspid valve

  • The result is a retrograde pressure wave throughout the venous system that may appear as pulsations in the jugular vein.

• Symptoms of heart failure

• Stokes-Adams attacks

  • Sudden losses of consciousness that may occur with brief prodromal symptoms, e.g., dizziness, or without any warning, usually lasting a few seconds

  • Attacks are caused by ventricular asystole, most commonly due to third-degree heart block, especially idiopathic paroxysmal AV block.

• Cardiac arrest