Increased lung uptake of thallium-201 during exercise myocardial imaging: Clinical,hemodynamic and angiographic implications in patients with coronary artery disease

To determine the clinical significance of increased thallium-201 activity in the lung immediately after exercise stress, the thallium-201 scans in 227 patients undergoing cardiac catheterization were reviewed. Thallium lung activity on the Initial anterior view images were graded qualitatively as follows: 0 (none) in 175 patients (77 percent); 1+ (moderate—increased activity in the lungs but less intense than that in left ventricular myocardium) in 37 patients (16 percent); and 2+ (severe—activity equal to or greater in intensity than left ventricular myocardlal activity) in 15 patients (7 percent). Increased (1+ or 2+) lung activity was related to (1) a greater number of myocardial segmental thallium defects (probability [p] < 0.05); and (2) increased severity and extent of coronary artery disease (p < 0.05). In addition, 2+ lung thallium activity was associated with: (1) a greater prevalence of prior myocardial infarctions (p < 0.01); and (2) a lower angiographic ejection fraction at rest (p < 0.05). To determine the hemodynamic changes associated with increased lung uptake of thallium-201, supine stress thallium imaging was performed during cardiac catheterization in 12 additional patients. Of these, the five patients with increased lung activity on thallium scanning had a mean pulmonary capillary wedge pressure that increased with exercise from 12 ± 1 (mean ± 1 standard deviation) to 24 ± 3 mm Hg (p < 0.05); cardiac index did not increase with stress. In contrast, seven patients without increased lung thallium activity demonstrated an increase in mean cardiac index (p < 0.05) without an associated rise in pulmonary capillary wedge pressure (at rest = 10 ± 3 mm Hg; during stress = 12 ± 2 mm Hg). In conclusion, increased pulmonary uptake during exercise thallium-201 imaging suggests the development of exercise-induced left ventricular dysfunction. Evaluation of lung activity should be added to the routine interpretation of exercise thallium-201 myocardial imaging studies.