Myocardial Toxicity of Contrast Agents Used in Angiography

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Abstract
Although reports on the general, neurological, and renal toxicity of the more widely used triiodinated compounds for cardiovascular contrast studies are not infrequent (1, 19, 20), relatively little (3, 8, 15, 16, 18, 21) has been published regarding their specific myocardial toxicity, especially with reference to the ever-growing application of selective injection technics. Our increasing interest in these methods (6, 13), particularly in coronary arteriography (10, 12), and the reportedly frequent occurrence of inadvertent intra-myocardial injection (14, 23) induced us to undertake an experimental investigation of the myocardial toxicity of commonly used radiopaque agents. We proposed to select the contrast medium combining the advantages of satisfactory opacity with the lowest possible degree of myocardial toxicity. With this goal in mind, we developed the concept and standardized the technic of occlusion retrograde coronary venous injection, a previously unreported method affording the opportunity of conducting a study under controlled conditions. Materials and Methods The substances tested were as follows: I. Physiologic fluids (a) Fresh, heparinized dog blood (b) Physiologic saline solution (c) 5 per cent dextrose II. Contrast agent (see Table I) Seventy large dogs were used for this investigation, their weight ranging between 18 and 24 kg., with an average of 20 kg. All dogs were anesthetized with intravenous Pentothal and received tubocurarine (20 mg. and 0.3 mg. per kilogram, respectively); they were intubated, and respiration was maintained with a Harvard apparatus pump. The Lead II of the electrocardiogram and the aortic pressure were continuously monitored and recorded. Forty animals had a fourth left intercostal space thoracotomy. The pericardium was opened and the great cardiac vein was isolated. The vein was tied around an indwelling catheter by way of a silk snare between the left marginal and the anterior interventricular branches. In 10 of the thoracotomized animals, the left coronary artery was also intubated by the Sones' catheterization technic (26). In 30 dogs the chest was not opened; in 15 of these a catheter was wedged in either the anterior or the posterior interventricular vein, or the great cardiac vein was occluded with a special balloon catheter. A Sones' catheter was introduced into the left coronary artery of the remaining 15 dogs. In the majority of the animals the Cordis automatic syringe was employed. All the substances to be injected were prewarmed to a temperature of 37° C. In all cases of coronary venous injection the delivery of the contrast agent was so adjusted as to produce a temporary myocardial infiltration lasting not more than two minutes (Fig. 1, A and B).