Which clinical history findings are characteristic of first-degree atrioventricular (AV) block?

Updated: Jan 06, 2020
  • Author: Jamshid Alaeddini, MD, FACC, FHRS; Chief Editor: Jose M Dizon, MD  more...
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Patients with first-degree atrioventricular (AV) block are generally asymptomatic at rest. Markedly prolonged PR interval may reduce exercise tolerance in some patients with left ventricular systolic dysfunction. Syncope may result from transient high-degree AV block, especially in those with infranodal block and wide QRS complex.

Patients may have a history of past heart disease, including myocarditis or myocardial infarction (MI). Patients may be highly conditioned athletes with a high degree of vagal tone, or they may be on medications that slow conduction through the atrioventricular node (AVN).

A history of an infectious disease, such as Lyme disease, may be present. Asymptomatic first-degree heart block is part of the spectrum of presentation of Lyme carditis in children. Lyme carditis is most likely in children with Lyme disease who are older than 10 years of age, those with arthralgias, and those with cardiopulmonary symptoms. [14]

Borderline first-degree AV block in patients with long-standing systemic lupus erythematosus (SLE) may be a clue to more significant cardiac disease, resulting from the progression of SLE; these patients require careful screening for underlying myocardial disease. [24] Conduction disturbances may also be secondary to drugs used to treat SLE.

Patients who have undergone mitral valve replacement or mitral valve annuloplasty may have heart block postoperatively. [25]

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