First degree AV block natural history, complications and prognosis

First-degree atrioventricular block may be due to conduction delay in the atrium, atrioventricular node, and/or His-Purkinje system. The atrioventricular node is the site most commonly involved in adults. However, more than 1 site of conduction delay is often present. Isolated First-degree atrioventricular has few clinical consequences. There are no symptoms or signs associated with it. First-degree AV block rarely progresses to more severe form of conduction abnormalities. In the setting of neuromuscular diseases such as myotonic dystrophy 1 with conduction abnormalities in the heart, First-degree AV block may progress to complete heart block during variable period of time. Common complications associated with first-degree heart block may include increased risk of atrial fibrillation, increased risk of pacemaker implantation. Prognosis of First degree AV block is generally good. However, some studies showed worse prognosis with PR prolongation. Presence of First degree AV block is shown to be associated with a higher risk of cardiovascular and all-cause mortality as well as higher risk of heart failure, left ventricular dysfunction, and atrial fibrillation.

• First-degree atrioventricular block may be due to conduction delay in the atrium, atrioventricular node, and/or His-Purkinje system
• The atrioventricular node is the site most commonly involved in adults. However, more than 1 site of conduction delay is often present.
• Isolated first-degree atrioventricular has few clinical consequences. There are no symptoms or signs associated with it.
  • First-degree AV block rarely progresses to more severe form of conduction abnormalities, it is mostly a benign condition in healthy middle-aged men and is not correlated with coronary heart disease.^[1]
• In the setting of neuromuscular diseases such as myotonic dystrophy 1 with conduction abnormalities in the heart, First-degree AV block may progress to complete heart block during variable period of time.

Common complications associated with first-degree heart block may include the following: ^[2]

• Increased risk of atrial fibrillation
• Increased risk of Pacemaker implantation

  Individuals who have the First-degree block as part of a triad of First-degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block (known as trifascicular block) may be at an increased risk of progression to complete heart block.

• Prognosis of first degree AV block is generally good^[3]. However, some studies showed worse prognosis with PR prolongation.^[4]
• Presence of first degree AV block is shown to be associated with a higher risk of cardiovascular and all-cause mortality.^[5]

• In a 2016 meta-analysis, first degree AV block was found to be associated with higher mortality risk. It was also associated with a high risk of heart failure, left ventricular dysfunction, and atrial fibrillation. However, it was not associated with high risk of coronary artery disease, stroke, or myocardial infarction.^[6]

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