Total electrical alternans in a patient with tuberculous pericarditis.

Total electrical alternans is an uncommon electrocardiographic abnormality in which alternation in the direction and/or amplitude of all the components (P, QRS and T) of the tracing is present. The phenomenon is seen only in association with occasional cases of pericaditis with large effusion's. Knowledge of this fact may help in the often difficult differentiation between a pericardial effusion and cardiomyopathy. An illustrative case report is presented, with a résumé of the mechanisms postulated to explain total electrical alternans.