PR Segment: Cardiac Implications
PR interval (measured from the initial P wave to the beginning of the QRS complex) reflects the time needed for an electrical impulse to be transmitted from the sinus node to the ventricles, so it is an integration of informations about different sites of the conduction system of the heart. To find a PR interval out of normal limits is not always a benign condition as previously believed. PR prolongation may not only underlie a major conduction disturbance (as in case 2), but it has also been related to the risk of atrial fibrillation (as in case 1); furthermore it may reflect different electrophysiological abnormalities, including atrial enlargement. A short PR interval instead has been shown to be an AF predictor and is linked to higher incidence of ischemic heart disease (as in case 3).
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