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The sensitiveness of the electrocardiograph to various stimuli and the consequent variation in tracings taken from the same person make it an important instrument in the study of myocardial function. Important also is the determination of normal variations under the stress of these stimuli. Changes in the ventricular complexes during attacks of angina have long been recognized. Similarly well known is the demonstration in latent coronary disease of characteristic electrocardiographic deviation after exercise. But2it has been pointed out also that inversion of the T wave may occur with such functional disorders as neurocirculatory asthenia and thyrotoxicosis.3It has been shown that excessive tobacco smoking can produce depression or inversion of the T wave.4Alkalosis and acidosis, the former produced by the simple procedure of hyperventilation with deep breathing, affect the amplitude of the T wave.5Anoxemia may flatten the T wave and depress the ST
William H. Barrow (1943) studied this question.
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