Enhanced hepatic uptake of thallium-201 in patients with severe narrowing of the right coronary artery

To assess the hepatic uptake of thallium-201 after exercise treadmill testing and to investigate whether hepatic uptake of thallium-201 may be a useful marker of right coronary artery (RCA) disease, 43 patients were studied: 17 with RCA disease (9 with 1-vessel disease, 8 with multivessel disease including the RCA), 8 with left coronary system disease alone, and 18 with a low probability (< 5%) of coronary disease. All subjects were studied with symptom-limited exercise and redistribution thallium-201 single-photon emission computed tomographic (SPECT) scintigraphy. Two indexes of hepatic uptake were derived: a liver-to-heart ratio after stress, and a stress-to-rest hepatic ratio. The low-probability group had a liver/heart ratio of 0.48 ± 0.02. In the group with RCA disease alone, liver/heart ratio was 1.29 ± 0.20 (p < 0.005 vs low-probability group). Patients with multivessel coronary artery disease involving the RCA had a ratio of 1.19 ± 0.16 (p < 0.005 vs low-probability group), and patients with only left coronary system disease had a liver/heart ratio of 0.87 ± 0.15 (p < 0.05 vs low-probability group). The stress/rest ratio of the low-probability group was 0.83 ± 0.04. Patients with RCA disease alone had a stress/rest ratio of 1.49 ± 0.25 (p < 0.05 vs low-probability group), and patients with multivessel disease involving the RCA had a stress/rest ratio of 1.16 ± 0.08 (p < 0.005 vs low-probability group). For detecting RCA disease with the liver/heart ratio, the area under the receiver-operating characteristic curve was 0.91 for all patients with RCA disease; for the stress/rest ratio, the area was 0.88. Four of the 17 patients with RCA disease had no inferior wall defect identified on SPECT images: all 4 had a liver/heart ratio and 3 a stress/rest ratio >2 SDs above the mean of the low-probability group; there was no significant difference in either ratio between those with and without inferior stress perfusion defects in patients with RCA disease. Thus, significant RCA disease is strongly associated with increased hepatic thallium-201 uptake during exercise, which is possibly related to inducible ischemic right ventricular dysfunction. These indexes have excellent ability to discriminate between the presence and absence of RCA disease.