Influence of peripheral intravenous contrast injection on the QRS complex in healthy men

The influence of acute plasma expansion induced by the administration of sodium containing hyperosmolar contrast medium on Frank lead electrocardiograms was investigated in 10 healthy male volunteers. The major electrocardiographic changes after injection of the contrast medium were a significant decrease in the amplitudes of Rx, Ry, and Qz and the maximal spatial QRS voltage, and a significant increase in the amplitude of Sx. The echocardiographic left ventricular end diastolic dimension tended to be larger after the injection, whereas no significant change occurred in the left ventricular systolic dimension. The electrocardiographic changes in this study were the opposite of those expected with the Brody effect. Although the precise mechanism underlying these findings is unclear, the increased intracardiac blood volume may have caused a decrease in the QRS voltage by a short circuiting effect. Alternatively if the activation in the left ventricle is assumed to be predominantly tangential the QRS voltage should have decreased with the Brody effect. The Brody effect may lead to an erroneous interpretation of electrocardiograms in certain clinical settings.