First-degree heart block is a type of atrioventricular (AV)

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First degree heart block

First-degree heart block is a type of atrioventricular (AV) conduction abnormality characterized by a delay in the conduction of electrical impulses from the atria to the ventricles. In first-degree heart block, every electrical impulse originating in the sinoatrial (SA) node, the heart’s natural pacemaker, is transmitted to the ventricles, but with a delay.

Key features of first-degree heart block include:

  1. Prolonged PR Interval: The PR interval, which represents the time it takes for the electrical impulse to travel from the atria to the ventricles, is prolonged. Specifically, the PR interval is greater than 0.20 seconds (200 milliseconds) in adults.
  2. Normal QRS Complex: The QRS complex, which represents ventricular depolarization (contraction), is typically normal in duration and morphology.

First-degree heart block is often asymptomatic and does not typically require specific treatment. It may be a normal variant in some individuals, particularly in athletes or those with a well-conditioned cardiovascular system. However, in some cases, first-degree heart block can be associated with underlying heart disease or certain medications.

Causes and risk factors for first-degree heart block may include:

  1. Age-Related Degenerative Changes: Fibrosis or degenerative changes in the electrical conduction system of the heart, which can occur with aging, may contribute to first-degree heart block.
  2. Medications: Certain medications, such as beta-blockers, calcium channel blockers, and antiarrhythmic drugs, can slow conduction through the AV node and lead to first-degree heart block.
  3. Acute Myocardial Infarction: First-degree heart block can occur as a result of acute myocardial infarction (heart attack), particularly involving the inferior wall of the heart.
  4. Inflammatory or Infiltrative Conditions: Conditions such as myocarditis (inflammation of the heart muscle) or infiltrative disorders affecting the conduction system may cause first-degree heart block.
  5. Electrolyte Imbalances: Abnormal levels of electrolytes, such as potassium or calcium, can affect the conduction system and contribute to heart block.

While first-degree heart block itself may not be clinically significant, it is important to evaluate and monitor individuals with this condition, particularly if symptoms develop or if there are underlying risk factors for progression to more advanced forms of heart block. Treatment is typically directed at addressing underlying causes or managing symptoms, if present. Close follow-up with a healthcare provider or cardiologist may be recommended for individuals with first-degree heart block.