Electrical alternans can occur not only due to the classical mechanism of the heart swinging in pericardial effusion, but also due to tachycardia-related refractoriness, sympathetic overactivity, or myocardial damage.
Electrical alternans may arise from tachycardia, sympathetic activity, or cardiotoxicity; case reports leave open prospective validation.
Electrical alternans was observed in 6 cases with various underlying disorders.As for the mechanism of the development of this unusual electrocardiographic abnormality, the classical hypothesis that the heart swinged within the pericardial cavi y was assumed to be appropriate for only 2 cases with massive pericardial effusion and cardiac tamponade. An alternative explanation that the every alternate impulse met some region of the myocardium still normally refractory from previous activation because of tachycardia was thought to be more suitable for a case with otherwise normal heart. In this case, the electrical alternans developed during an episode of tachycardia caused by paroxysmal atrial flutter with 2 : 1 conduction. On the other hand, 2 cases with isolated T wave alternans, a 16-year-old female with pheochromocytoma and a 51-year-old female with subarachnoidal hemorrhage, raised a possibility of causal relationiship of increased circulating catecholamine and/or sympathetic overactivity with this rare form of electrical alternans.
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Murata et al. (1980) studied this question.
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