Prevalence of high-risk thallium-201 scintigraphic findings in left main coronary artery stenosis: Comparison with patients with multiple- and single-vessel coronary artery disease

Abstract

To determine the prevalence of high-risk thallium-201 (TI-201) scintigraphic findings in patients with left main (LM) coronary artery disease (CAD), quantitative exercise TI-201 scintigrams were analyzed in 295 consecutive patients with angiographic (⩽ 50% stenosis) CAD, of which 43 (14%) had ⩽ 50% LM stenosis. A high-risk scintigram was defined as one that demonstrated (1) a LMCAD scintigraphic pattern (⩽ 25% homogeneous decrease in TI-201 activity in the middle and upper septal and posterolateral walls on the 45 ° left anterior oblique projection); (2) abnormal TI-201 uptake or washout in multiple vascular scan segments indicative of multivessel disease; and (3) increased lung TI-201 uptake on the initial anterior projection image. Of the 43 patients with LMCAD, 41 (95%) had an abnormal scintigram. Thirty-three (77%) had 1 or more high-risk scintigraphic findings, including 29 (67%) with a multivessel CAD scan pattern, of which 6 (14%) demonstrated a typical LMCAD pattern; and 18 (42%) with abnormal lung TI-201 uptake. The prevalence of a high-risk scintigram in patients with LMCAD was significantly greater than that in 53 patients with 3-vessel disease (58%) (p = 0.05), 99 patients with 2-vessel disease (60%) (p = 0.04) and 100 patients with 1-vessel disease (41%) (p < 0.0001).

In this study, a high-risk electrocardiographic stress test was defined as one that had at least 2 of the following characteristics: (1) ≥ 2.0 mm of ST depression (ST↓); (2) horizontal or downsloping (> 1.0 mm) ST↓ persisting for 5 minutes or longer after exercise; (3) appearance of ST↓ at 5 METs or less; and (4) a decrease in systolic blood pressure of 10 mm Hg or more during exercise. The prevalence of a high-risk stress test (58%) in the 43 patients with LMCAD was significantly lower than the prevalence of a high-risk scintigram (77%) (p = 0.05). The prevalence of a high-risk electrocardiographic stress test was significantly greater than that in the 53 patients with 3-vessel disease (32%) (p < 0.01), the 99 patients with 2-vessel disease (31%) (p = 0.003) and the 100 patients with 1-vessel disease (16%; p < 0.0001). The combination of the TI-201 scintigraphic and exercise electrocardiographic stress testing was no better than scintigraphy alone (86 vs 77%, p = 0.2), but did improve the overall detection rate of high-risk in LMCAD patients compared to exercise electrocardiographic testing alone (86 vs 58%, p = 0.04).

In conclusion, in patients with LMCAD of ⩽ 50% narrowing, a typical scintigraphic finding for LMCAD, is infrequently observed, but a markedly positive exercise stress test or a high-risk scintigram (predominantly showing a multivessel disease pattern) is seen in most patients (86%) with this angiographic finding.