Diminution of QRS complexes caused by anasarca after an acute myocardial infarction: A case report and a discussion of the plausible underlying pathophysiological mechanisms

We describe the case of an 81-year-old man with an acute anterior myocardial infarction (MI), complicated by anoxic encephalopathy, respiratory, and acute renal failure, who developed gradually marked reduction in the QRS complexes of his electrocardiogram (ECG) in the process of gaining 44 pounds, due to anasarca. Such ECG pattern has been recently associated with marked peripheral edema in the context of critical illness of varying etiologies. Our patient did not have a pericardial effusion, and his gradually increasing weight values correlated strongly with the corresponding sums of the amplitudes of the QRS complexes of the 12-lead ECGs (r = .92, P = .0029). The mechanism of this ECG phenomenon is attributed to a reduction of the overall transfer impedance of the conducting volume surrounding the heart, which leads to an attenuation of the potentials recorded on the body surface, due to a shunting effect of the edematous subcutaneous connective tissues. This reduction of the composite transfer impedance of the conducting medium is being mediated by the low resistivity of the water of the retained anasarca fluid.