The PR Interval | ECG Basics - MedSchool

Home » What Is The Pr Interval » The PR Interval | ECG Basics - MedSchool

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  4. The PR Interval
10/10 pages left today. Sign Up ECG Basics ECG Basics The PR Interval Bookmark ShareOn this page:Prolonged PR IntervalShort PR IntervalPR DepressionView Topic Outline

Overview

The PR interval is the time between atrial depolarisation and ventricular depolarisation. It is an indicator of atrioventricular conduction time, involving conduction from the atria, through the AV node and down the His-Purkinje system.

    • Normal Duration

    • 120-200ms (3-5mm)

  • Look For

  • The distance between the start of the P wave and the start of the R wave.

Prolonged PR Interval

Also known as first degree heart block; a prolonged PR interval suggests delayed conduction between the atria and the ventricles.

  • Look For

  • PR interval >200ms (5mm).
  • Prolonged PR Interval

  • Causes of First Degree AV Block

  • Intrinsic (AV Nodal)

  • Idiopathic degeneration
  • Myocardial infarction
  • Congenital - congenital heart disease, neonatal lupus
  • Infiltrative disease - sarcoidosis, amyloidosis, haemochromatosis
  • Cardiac procedures - valvular surgery, correction of congenital heart disease, catheter ablation
  • Systemic lupus erythematosus
  • Myocarditis

  • Extrinsic

  • Physiologic - sleep, athletes
  • Autonomic - carotid sinus massage, carotid sinus hypersensitivity
  • Drugs - beta blockers, calcium channel blockers, digoxin, adenosine, amiodarone
  • Hyperkalaemia
  • Hypothyroidism

Short PR Interval

  • Look For

  • PR interval

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