Arrhythmogenic and cardiodepressive effects of contrast media on isolated rat atria.

The cardiotoxicity of four radiopaque contrast media were studied on spontaneously beating isolated rat atria in order to compare the low-osmolar non-ionic medium, metrizamide, with three other contrast media having different cation compositions. The addition of the ionic contrast media to concentrations of 28 and 84 mg I/ml induced atrial arrhythmias in the following order of potency: meglumine iothalamate greater than meglumine--Na--Ca metrizoate greater than meglumine--Na diatrizoate. No arrhythmias were observed after the addition of metrizamide. Metrizamide had only slight effects on the rate and amplitude of the atrial contractions, and hence the work index was almost unaffected. The highest concentration of the three ionic contrast media had very significant cardiodepressive effects. Meglumine iothalamate had the most severe influence on the spontaneous rate of the contractions, while meglumine--Na diatrizoate induced the greatest initial reduction in the amplitude of the contractions and the work index. The present study indicates that the low-osmolar non-ionic medium, metrizamide, is better tolerated by the myocardium than the ionic contrast media.