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Electrophysiological and mechanical effects of contrast media on isolated rat atria.

Cardiac complications caused by contrast media may occur during angiocardiography. The present study on spontaneously beating and electrically stimulated isolated rat atrial preparations investigated the direct effects on the myocardium of four different contrast media. A low-osmolar non-ionic compound, metrizamide, was compared with three ionic contrast media having different cation compositions: meglumine-Na-Ca metrizoate, meglumine-Na diatrizoate and meglumine iothalamate. The ionic contrast media at an organ bath concentration of 30 mg I.cm-3 produced a striking shortening of the effective refractory period. In addition, they reduced the spontaneous rate of contractions, prolonged sinus node recovery time and decreased excitability. Meglumine-Na diatrizoate and meglumine iothalamate induced great reductions in contractile force and "force-rate" product. Metrizamide influenced both the electrical and mechanical activities of the isolated rat atrial preparations to a smaller extent than the three ionic contrast media. The present study demonstrated direct arrhythmogenic and cardiodepressive effects of commonly used ionic contrast media. The low-osmolar non-ionic medium, metrizamide, appears to have lower cardiotoxicity than the ionic contrast media.