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health advisory Hospital Doctor Yu 2007-11-8 19:09:08

Answers:

No the T wave represents repolarization and is only altered by changes to the myocardium such as anoxia.

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The electrical activity forms a series of waves and complexes separated by regularly occurring intervals. These waves and complexes have been arbitrarily labeled as the P wave, the QRS complex, and the T wave. The P Wave is formed as the electrical impulse spreads across the atria (depolarization) and causes both atria to contract The QRS Complex is the deflection that is formed as the electrical impulse spreads from the Purkinje fibers to the ventricles (depolarization), causing both ventricles to contract. The T Wave is the wave formed after ventricles contract, which represents the ventricular resting period (repolarization). During the resting period the chambers fill with blood for the next contraction. Graph PaperThe graph paper moves through an ECG machine at a standard speed. This allows each vertical line to represent time. Each Small Box = 0.04 seconds and the Large Box = 0.20 seconds. Three-second time intervals are marked at the top of the ECG paper for your convience. The graph paper is usually started and stopped by a control button placed on the top or front of the monitor.

The T wave is the most labile wave in the ECG. T wave changes including low-amplitude T waves and abnormally inverted T waves may be the result of many cardiac and non-cardiac conditions. The normal T wave is usually in the same direction as the QRS except in the right precordial leads (see V2 below). Also, the normal T wave is asymmetric with the first half moving more slowly than the second half. In the normal ECG the T wave is always upright in leads I, II, V3-6, and always inverted in lead aVR. The other leads are variable depending on the direction of the QRS and the age of the patient.