Assessment of the severity of coronary artery stenosis by the ratio of theregional washout rate determined by adenosine triphosphate stress Tl-201SPECT

Background, Adenosine triphosphate stress thallium-201 single-photon emissi on computed tomography (ATP SPECT) is useful for diagnosis of coronary arte ry disease, but its usefulness for evaluating the severity of coronary arte ry stenosis has not been established. Methods and Results. We performed region-of-interest analysis of short-axis images obtained by ATP SPECT in 31 patients with single-vessel disease (>5 0% stenosis of the luminal diameter). We selected the lowest and highest wa shout rates (WR) among the anterior, lateral, and inferior WRs and calculat ed the ratio of the lowest WR to the highest WR (WR ratio = 0.925 +/- 0.027 in 14 control subjects). ATP SPECT showed positive results in 29 (94%) of 31 patients. The severity of coronary artery stenosis was inversely correla ted with the WR ratio (r = -0.703, P < .0001). The sensitivity and specific ity of a WR ratio less than or equal to 0.660 for the diagnosis of severe c oronary stenosis (greater than or equal to 80% stenosis) were 83% and 80%, respectively. Conclusions. Results suggest that ATP SPECT may be useful for assessment of the severity of coronary artery stenosis in patients with single-vessel di sease.