Mechanical effect of contrast injection on coronary artery diameter during angiography

The authors performed an angiographic study in six healthy anaesthetized pigs to investigate possible mechanical effects of contrast injection on coronary artery pressure and diameter during the period of image acquisition. Angiograms were acquired at 30 f/sec for repeated injections of 8 ml of contrast material by hand and with a power injector at rates of 2, 4, and 6 ml/sec. A 1.5 F micro-tip pressure transducer was used to measure intracoronary pressure at 1, 2, and 4 cm downstream from the injection site for each injection rate. The results show a progressive increase in intracoronary pressure with increasing rate of injection (p<0.005), ranging from 3 to 117 mmHg. Corresponding diameters were distended by 0.02 to 0.6 mm (p<0.05) during the injection, as evaluated by quantitative coronary angiography (QCA). These mechanical effects were related to the mean coronary pressure prior to injection (p<0.02) in a manner consistent with the nonlinear compliance of the arterial wall. The authors conclude that coronary dimensions obtained from QCA critically depend on the mode of contrast injection, which may represent a previously unrecognized source of error in the analysis and interpretation of clinical angiographic studies