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In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200ms in duration. If a Q wave is measured by EKG, the PR interval is sometimes termed the PQ interval. ==Interpretation== Variations in the PR interval can be associated with certain medical conditions: * Duration * * A long PR interval (of over 200 ms) may indicate a first degree heart block. Prolongation can be associated with hypokalemia, acute rheumatic fever, 〔http://www.utmb.edu/pedi_ed/core/cardiology/page_40.htm〕 or carditis associated with Lyme disease. * * A short PR interval (of less than 120ms) may be associated with Wolff–Parkinson–White syndrome, Lown–Ganong–Levine syndrome, or Junctional rhythms, although it often is a harmless, normal variant seen on EKG. * * A variable PR interval may indicate other types of heart block. * PR segment depression may indicate atrial injury or pericarditis. * Variable morphologies of P waves in a single EKG lead is suggestive of an ectopic pacemaker rhythm such as wandering pacemaker or multifocal atrial tachycardia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「PR interval」の詳細全文を読む スポンサード リンク
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