The determination of myocardial perfusion parameters from coronary angiograms by analysing the passage of contrast media through the myocardium

Digital subtraction angiography allows to record the passage of contrast material through the myocardium as a time-intensity curve, the so-called densogram. Temporal changes of contrast material in a region of interest are described by a differential equation. The free parameters of this model equation are determined by a curve-fitting procedure. Four parameters of the model equation are expected to be connected with myocardial perfusion. We intended to verify this assumption by comparing changes in coronary blood flow (CBF) with changes of the different parameters. The angiograms of 9 patients without coronary artery disease were studied before and after intravenous application of dipyridamole. Changes in CBF were assessed by a videodensitometric method. Linear regressions between changes of CBF and the parameters of the differential equation show the following results: one parameter of the model equation--the ratio of regional blood flow and regional volume--remarkably underestimated CBF changes. This can be explained by an increase of regional blood volume after increased CBF due to dipyridamole. However, a close correlation was found between CBF changes and the remaining parameters. This study suggests that digital measurements from coronary angiograms using the presented model equation provide a means of assessing myocardial perfusion.