The contrast media iohexol causes vasoconstriction of the proximal left anterior descending coronary artery: implications for appropriate stent sizing.

The effect of the contrast agent iohexol on reference vessel size in patients with proximal left anterior descending disease is unknown. Quantitative coronary angiography and intravascular ultrasound were performed in 15 patients with atherosclerotic disease of the proximal left anterior descending. Mean proximal reference vessel diameter was 2.95 +/- 0.59 mm with quantitative coronary angiography and 4.65 +/- 0.66 mm with intravascular ultrasound (P < .05). Intracoronary injection of iohexol resulted in a significant decrease in intravascular ultrasound-measured proximal reference vessel diameter from 4.65 +/- 0.66 mm to 4.47 +/- 0.68 mm (P = .002). Vasoconstrictive response to iohexol in the proximal reference vessel ranged from -0.04 mm to 0.5 mm with a mean of 0.18 +/- 0.16 mm. This study shows that iohexol can cause significant vasoconstriction of the proximal reference vessel in patients with severe disease involving the proximal left anterior descending.