Elimination of variable vasomotor tone in studies with repeated quantitative coronary angiography

Summary In quantitative coronary angiographic studies, unintentional changes of coronary vasomotor tone may have a significant influence on the coronary artery diameters, thereby increasing the variability in the measurements. To obtain objective data on these measurement variabilities, two protocols were designed to assess the influences of ionic and nonionic radiographic contrast media on the mean diameters of angiographically normal coronary arteries. The vessel sizes were determined with the CAAS using automated edge detection techniques. In 21 patients (study no. I), coronary angiograms were taken in identical angiographic projections before (control), and immediately following several (at average 7) subsequent diagnostic dye injections administered over a period of about 7 min. The ionic contrast agent diatrizoate 76% induced a coronary dilation of 19 ± 7% (mean ± s.d., p<0.001; n=10); the nonionic agent iopromide 370 increased the coronary artery diameters by only 6 ± 4% (p<0.01; n=11). In another 11 patients (study no. II) coronary angiograms were obtained using the nonionic contrast medium iopamidol 300 at 5, 8, 10 and 11 min after the control acquisition; this protocol was repeated in the same patients with diatrizoate 76%. With iopamidol, coronary diameter changes were not significant at any time; with diatrizoate, however, coronary dilation was measured at 10 min (2 ± 2%; p<0.01) and at 11 min (10 ± 3%; p<0.001).In a third study it was tested, whether standardization of coronary vasomotor tone (e.g. in coronary angiographic follow-up studies) is possible by the induction of a reproducible maximum coronary dilation with nitrocompounds. In 12 patients, the mean diameters of angiographically normal coronary segments were analyzed before and at various times after i.v. administration (over 4 min) of 0.025 mg SIN-1/kg bodyweight. Coronary dilation was maximal at 10 or 15 min after the onset of the SIN-1-infusion (29 ± 5%; p<0.001). 0.8 mg nitroglycerin given s.l. at 15 min did not further dilate the coronary arteries (28 ± 7%). One hour after SIN-1, coronary dilation still amounted to an average of 24 ± 8% (p<0.001) and became maximal again, when 0.8 mg nitroglycerin was again administered sublingually (28 ± 8%; p<0.001).In conclusion, short-term variability of coronary vasomotor tone induced by ionic radiographic contrast media can be eliminated by the use of nonionic contrast agents and observation of injection intervals of at least 2 min. In quantitative coronary angiographic follow-up studies, as well as during acute interventions (e.g. PTCA), identical baseline vasomotor tone can be achieved by induction of the maximal coronary dilation using nitrocompounds.Dedicated to Prof. Paul R. Lichtlen on the occasion of his 60st birthday.