What is the role of coronary artery disease in the etiology 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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Coronary artery disease is a factor. First-degree AV block occurs in fewer than 15% of patients with acute MI admitted to coronary care units. His bundle electrocardiographic studies have shown that, in most of these patients, the AVN is the site of conduction block.

AV block is more common in the setting of inferior MI. In the Thrombolysis in Myocardial Infarction (TIMI) II study, high-degree (second- or third-degree) AV block occurred in 6.3% of patients at the time of presentation and in 5.7% in the first 24 hours after thrombolytic therapy. [5]

Patients with AV block at the time of presentation had a higher in-hospital mortality than patients without AV block; however, the 2 groups had similar mortalities during the following year. [5] Patients who developed AV block after thrombolytic therapy had higher mortalities both in hospital and during the following year than patients without AV block. The right coronary artery was more often the site of infarction in patients with heart block than in those without heart block.

Patients with AV block are believed to have larger infarct size. However, the prevalence of multivessel disease is not higher in patients with AV block.

In a systematic review and meta-analysis comprising 14 studies undertaken between 1972 and 2011, with 400,750 participants, Kwok et al found evidence that prolonged PR interval is associated with adverse cardiovascular outcomes and mortality. [6] In their meta-analysis, data from observational studies suggested a possible association between prolonged PR interval and significant increases in atrial fibrillation, heart failure, and mortality. [6]

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