Cyclic flow patterns in human coronary arteries

Biplane digital coronary angiograms, as routinely performed in angiography, are used to construct a three-dimensional model of the coronary arteries. This model is used to solve the fluid flow equations throughout the cardiac cycle. The spatial position of the centreline of the artery is determined in three dimensions by detecting the ridge line in the two images and using the rotation angles embedded in the DICOM format. Combining this with the arterial radii taken from the images allows a model of the surface of the artery to be built. This model is then discretised and a mesh constructed, both on its surface and within, which allows for a computational fluid dynamics package to solve the Navier-Stokes equations and provide detailed flow patterns, including wall shear stress. In a series of 4 patients the right coronary artery has been reconstructed throughout the cardiac cycle, and flows have been calculated for a typical pressure gradient at each step. The flow shows a wide variation of shear stresses with variations being due to both altered velocities as well as the altered configuration of the coronary due to systolic movement. The techniques of reconstruction appear robust, as can be shown by introduction of random noise in the model.