[Optimal x-ray contrast media for ambulatory coronary angiography from the microcirculatory point of view]

Side effects must be expected in 7 to 8% of cases, even when non-ionic radiocontrast agents are used. Contrast agent-induced microcirculatory disturbances constitute one potential cause under discussion. These disturbances may be caused by either the hyperviscosity or the hyperosmolality of the contrast agents. Within the framework of 3 comparative studies, the influence of viscosity and/or osmolality in intraarterial bolus injections on downstream microcirculation was tested in patients with coronary heart disease. Blood flow in the nailfold capillaries was recorded by intravital videomicroscopy and evaluated off-line, before and after randomized injection of 20 ml of each different radiocontrast agent into the Arteria auxillaries ipsilateral. Injection of 20 ml of a radiographic contrast agent into the Arteria auxillaries with a viscosity of 9.9 mPas and an osmolality of 770 mOsmol/kg H2O (Iopromid with 370 mg iodine/ml) results in a significant reduction in mean erythrocyte velocity in the ipsilateral nailfold capillaries from 0.76 +/- 0.27 to 0.39 +/- 0.31 mm/s after 30 s (p = 0.0001), corresponding to a reduction of 51.3%, whereas electrolyte solution shows no influence. With one exception, all patients reacted with a pronounced reduction in perfusion following injection of the radiocontrast agent, 3 patients showed an extreme reaction with flow cessation in the capillaries, in 1 case lasting up to 2 minutes. Following injection of 20 ml of Iodixanol with 270 mg iodine/ml (5.8 mPas, 290 mOsmol/kg H2O) a significant reduction of mean erythrocyte velocity of 60.8% was recorded from 0.44 +/- 0.27 mm/s to 0.17 +/- 0.09 mm/s only 10 s after the injection (p = 0.0001) lasting to the end of the observation period (6 minutes). Following injection of 20 ml of low-viscosity Iopentol with 150 mg iodine/ml and comparable osmolality (1.7 mPas, 340 mOsmol/kg H2O) no change in erythrocyte velocity was recorded (p = 0.151). Following injection of 2 high-viscosity radiocontrast agents of varying osmolality, mean erythrocyte velocity is reduced significantly in the first 30 s, after which period the erythrocyte velocity gradually increases (ANOVA repeated measures, category "time": p < 0.0001). The time curve for the 2 radiocontrast agents do not, however, differ (ANOVA, category "agents x time": p = 0.9890). Perfusion of the nailfold capillaries depends significantly on the viscosity, but not the osmolality, of the radiocontrast agent injected in coronary heart disease patients. From a microcirculatory point of view, it would therefore make sense to use low-viscosity radiocontrast agents in outpatients to exclude the existing risk of an induced myocardial microcirculatory disturbance.