Electrocardiography, Dr. D. Penney



Table 11. SEQUENCE OF DEPOLARIZATION

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Process may be divided into 5 phases -

1) Atrial Depolarization - vector is toward apex; (+) 60 degrees; thus in most leads a (+) P wave.

  • AV Conduction System - isoelectric by remote electrodes; can record with intracardiac electrodes; PR segment.

    2) Septal Depolarization - LV --> RV; (+) 150 degrees; may produce a Q wave in some leads (eg. Lead I).

    3) Apical & Early LV Depolarization - (+) 60 degrees; R wave.

    4) Late LV Depolarization - moves from endocardium to epicardium; goes (-) to (+); vector (+) 60 degrees to final (-) 30 degrees; resultant R or S wave.

    5) LV Repolarization - moves from epicardium to endocardium; goes (+) to (-), making T wave upright; vector (+) 30 degrees; longer duration; T wave .
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