Pressure gradient, exercise thallium 201 scintigraphy, quantitative coronary cineangiography: in what sense are these measurements related?

In this study an attempt is made to assess the relationship between the pressure gradient measured during angioplasty, the angiographic severity of stenosis and the inducibility of regional perfusion defects during exercise Thallium-scintigraphy. As a first step it was decided to investigate the values and limitations of the transstenotic pressure gradient measured during PTCA by comparing the transstenotic gradient with the theoretical pressure drop calculated from fluid-mechanic equations. It has been shown that in canine femoral arteries the transstenotic gradient overestimated the 'true' gradient in a predictable manner, which is dependent on the ratio of the diameter of the angioplasty catheter to the stenosis diameter. In order to further characterize this relation in the coronary artery bed of humans, the transstenotic gradient was compared with the theoretical pressure drop calculated from fluid mechanic equations for steady flow of an incompressible fluid in rigid tubes. Therefore, the stenosis geometry was analyzed by quantitative coronary cine-angiography and the mean myocardial blood flow was measured by the thermodilution technique in a selected group of patients with proximal left anterior descending coronary artery disease. (Auth.)