Letter to the Editor
Contrast Agents for Selective Coronary Arteriography
TO THE EDITOR A recent publication in your journal by Shirey et al [l] accounts for the incidence of radiographic contrast-related side-effects and complications as they occurred in busy catheterization laboratories. The authors state in their concluding sentence that Vascoray, a mixture of sodium and meglumine salts of iothalamate in the ratio of 1 to 2, is suitable and safe for clinical use for angiographic studies of the heart and coronary artery circulation. Their concluding statement is unfortunate inasmuch as it not only implies an endorsement of Vascoray, but a tacitly made assumption that this compound might be equal to or even better in selective coronary arteriography than the other agent, Renografin 76.
Basic similarities between the two contrast agents, both representing tri-iodonate water soluble compounds at practically identical concentration (370 mg and 400 mg iodine/ml, respectively) explain the similar incidence of general side-effects. The agents differed, however, significantly in their content of free sodium ions, Vascoray containing more than twice the concentration (.41 mEq/ml) than Renografin 76 (0,159 mEq/ml). The importance of sodium concentration for cardiac sideeffects, in particular, the occurrence of ventricular fibrillation in conjunction with selective coronary artery injections, was first brought to attention by the work of Gensini and DiGiorgi in 1964 [2]. They concluded from their animal experiments that the higher the sodium content the greater the risk and, therefore, recommended the use of meglumine salt preparations. They failed to recognize at that time, however, that extreme depletion of sodium ions again increased the