Clinical electrocardiography . cardiac mechanism does not have sufficient time toadjust itself to the encumberance, and by mechanical interferencecontraction amplitude is diminished and rate accelerates progres-sively in the attempt to maintain volume flow. An electrocardio-gram of such a case would reveal a progressive tachycardia withdeflections of low amplitude. i56 CLINICAL ELECTROCARDIOGRAPHY Chronic effusions or those of gradual accumulation rarelyassume the proportions of those of sudden onset, and the heartmay be embarrassed but little. This is due to the fact that lesspressure is exer
Clinical electrocardiography . cardiac mechanism does not have sufficient time toadjust itself to the encumberance, and by mechanical interferencecontraction amplitude is diminished and rate accelerates progres-sively in the attempt to maintain volume flow. An electrocardio-gram of such a case would reveal a progressive tachycardia withdeflections of low amplitude. i56 CLINICAL ELECTROCARDIOGRAPHY Chronic effusions or those of gradual accumulation rarelyassume the proportions of those of sudden onset, and the heartmay be embarrassed but little. This is due to the fact that lesspressure is exerted by the effusion, and because of its gradualonset the heart is able to adjust its mechanism to the abnormalstatus. Electrocardiograms vary with the degree of myocardialdamage or fatigue that eixsts. Figure 136 is the electrocardiogramof a patient with chronic pericarditis with effusion. Note theaberrant QRS complexes in all derivations. The T wave in Deri-vation I is negative. Preponderance of the left ventricle is Fig. 137.—Electrocardiogram of a patient with early exophthalmic the rolling contour of the cycles and the increased amplitude of deflec-tions, especially of the T wave. Hyperthyroidism.—The effect of hyperthyroidism on the heartis twofold: (1) the effect of the thyroid active principle, thyroxin,on the myocardium, which is cellular, and (2) the increased cardiacwork accompanying the elevation of the basal metabolic rate. Electrocardiograms of patients with exophthalmic goiter () or with adenoma with hyperthyroidism are modified largelyby the degree of myocardial degeneration. Auricular fibrillationis a very frequent phenomenon, often disappearing after thyroid-ectomy when the basal metabolic rate attains normal. ELECTROCARDIOGRAPHIC STUDY OF HEART DISEASE 157 Myxedema.—Electrocardiograms of patients with myxedemausually reveal deflections of low amplitude, particularly of the Twave. Figure 138 is the electrocardiogram of a patie
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