Differential effects of Renografin-76 on the ischemic and nonischemic myocardium

The effects of intracoronary diatrizoate meglumine and diatrizoate sodium (Renografin-76) on regional contraction were examined in the normal coronary circulation and during partial (50 percent) coronary occlusion in 11 dogs using strain and length gauges. Intracoronary injections of Renografin-76 (1.5 cc) (1,690 mosM/liter; 0.19 mEq Na/ml), equiosmolar dextrose solution and 0.19 mEq Na⁺/ml saline solution were made randomly. Renografin-76 caused a decrease in preejection tension to 87.4 ± 4.3 percent (p < 0.025), total tension to 74.6 ± 3.3 percent (p < 0.01) and ejection tension to 11.9 ± 12.6 percent (p < 0.001) of control value. Segment length increased to 106.7 ± 7.3 percent of control value. These changes lasted only 12 ± 2 (range 5 to 20) seconds (mean ± standard error of the mean). During partial coronary occlusion and after injection of Renografin-76, preejection tension decreased from 91.7 ± 6.3 to 53.8 ± 3.9 percent (p < 0.01), total tension from 89.9 ± 5.0 to 59.7 ± 3.5 percent (p < 0.01) and ejection tension from 22.8 ± 8.1 to 17.8 ± 10.9 percent, whereas segment length increased from 112.7 ± 3.7 to 130.7 ± 4.6 percent (p < 0.01) of control value. In contrast to findings in the normal coronary circulation, tension and length changes lasted 54 ± 16 (range 15 to 180) seconds (p < 0.05). The hyperemic response during normal coronary circulation was completely abolished during partial coronary occlusion. Prior administration of nitroglycerin did not shorten the duration of the myocardial depressant effects of Renografin. Injections of equiosmolar dextrose or saline solution produced qualitatively similar but quantitatively less marked changes. Thus, intracoronary Renografin-76 has an accentuated and prolonged depressant effect on the ischemic as compared with the normally perfused myocardium; this effect is not solely due to its hyperosmolarity or sodium concentration.