Perfusion defect patterns on thallium myocardial SPECT help discriminate proximal from distal left anterior descending artery stenosis

We investigated whether patterns of perfusion defects (PD) may help discern proximal from distal LAD stenosis. Study I: Among patients who underwent CAG and Tl SPECT within the same period, 90 patients with signficant single vessel LAD stenosis (< 50%) and a reversible PD were included. Study II (for validation): After study I, patterns of LAD defect in 156 patients were compared with CAG results. In study I, patterns were categorized as type I (n=20, PD on apex, apical anterior wall and septum), type II (n=25, apex and septum), type III (n=20, most of LAD territory), type IV (n=17, confined to apex), type V (n=4, mild anteroseptal PD) and others. Patients with type I and III had a higher proportion of proximal LAD stenosis (75% and 90%), while those with type II ad IV patterns were more likely to have mid stenosis (68% and 71%). Most (3/4) of type V had less severe proximal stenosis. In study II, the sensitivity and specificity of proximal types (I, III and V) were 66.7% and 95.3% (accuracy: 90.4%). Excluding patients with normal LAD perfusion, sensitivity was 85.7%. Specific defect patterns on myocardial SPECT can aid in differentiating proximal from mid LAD stenosis, whch would make it possible to avoid unnecessary invasive procedure