Use of exercise thallium scintigraphy to assess extent of ischaemic myocardium in patients with left anterior descending artery disease.

In this study we attempted to examine the extent of jeopardised myocardium in patients with severe left anterior descending disease. The jeopardised myocardium was defined by the number of perfusion defects in the distribution of the left anterior descending artery depicted on exercise thallium201 images. One segment in each of the three projections was considered to represent the distribution of this vessel, that is the anterolateral segments in the anterior projection, the anteroseptal segment in the left anterior oblique projection, and the anterior segment in the lateral projection. We selected 45 patients with > 70 per cent diameter narrowing of the left anterior descending artery and abnormal exercise images in the distribution of this vessel. There were 17 patients with isolated left anterior descending artery disease and 28 patients with multivessel disease including the left anterior descending artery. Fifteen patients (33%) had one perfusion defect (four patients with isolated disease and 11 patients with multivessel disease); 17 patients (38%) had two perfusion defects (six with isolated disease and 11 with multivessel disease); and 13 patients (29%) had three perfusion defects (seven with isolated disease and six with multivessel disease). The anteroseptal segment was the most common segment to become ischaen.ic during exercise and was abnormal in 40 of the 45 patients (89%). The anterior segment in 27 patients (60%) was next, and the anterolateral segment in 20 patients (44%) the least common. The number of defects did not correlate with the site of disease of the left anterior descending artery (proximal vs. distal to the first septal and first diagonal branches); the degree of left anterior descending narrowing (70 to 99% vs. total occlusion); collaterals; left ventricular asynergy; the presence of isolated left anterior descending disease in contrast with multivessel disease. We conclude that variations in the extent ofperfusion abnormalities seen in patients with disease of the left anterior descending artery suggest that these patients do not constitute a homogeneous group. Future studies designed to study the effect of medical or surgical treatment in such patients may be more meaningful if the extent of jeopardised myocardium, as defined by exercise thallium-201 imaging, is incorporated as a variable in group comparison. Our results also suggest that the number of perfusion defects do not predict the site of the lesion of the left anterior descending artery in relation to its first septal and diagonal branches.