[Quantitative assessments of regional myocardial perfusion by digital subtraction angiography]

Regional myocardial perfusion was evaluated by computerized washout analysis of digital subtraction angiography (DSA) images. Diatrizoate meglumine (76% Urografin), 2 to 3 ml, was manually injected into the left main coronary artery. For 26 patients with ischemic heart disease (IHD), 14 patients with cardiomyopathy, and eight patients with normal coronary angiograms, DSA images of myocardial perfusions were obtained in the right anterior oblique projection. These were digitized into an image-processing computer. Time-density curves were constructed in four segments of the left ventricle perfused by the left anterior descending coronary artery (LAD) and the contrast decay half-lives (T1/2) were calculated from the decay phases of the curves, using mono-exponential least square fits. The mean T1/2 was significantly longer in patients with 75% or more LAD narrowing than in those with normal coronary arteries. By contrast, patients with 50% or less LAD narrowing had T1/2 comparable to those with normal coronary arteries. In patients with IHD, there was a significant curvilinear relationship of T1/2 with percent stenosis of the LAD. This indicates that a decrease in regional myocardial flow develops rapidly in coronary stenosis of 70-80% or more. In patients with comparable coronary stenosis, T1/2 was significantly longer in the asynergic regions than in those with normal wall motion, but T1/2 was shorter in regions perfused by collateral vessels. These findings indicate that left ventricular contraction and collateral flow could contribute to regional myocardial perfusion. In addition, patients with hypertrophic and dilated cardiomyopathy had prolonged T1/2 despite normal coronary angiograms, suggesting abnormalities in intramural coronary arteries. Thus, T1/2 derived by computerized washout analysis of DSA myocardial image proved to be a useful index for quantitative evaluation of regional myocardial perfusion.