Background: Increased lung uptake of thallium 201 during myocardial perfusion scintigraphy is related to severe coronary artery disease (CAD), but a similar relationship for technetium 99m sestamibi has not been clearly established.
Methods and results: Resting and stress lung-heart ratios (LHR) were retrospectively determined in 96 patients who underwent Tc-99m sestamibi stress testing and coronary angiography within 4 months of each other. A semiquantitative CAD severity score (CADSS) was derived from the coronary angiogram. Left ventricular (LV) function was assessed in a subgroup of 42 subjects. CADSS of 24 or higher was associated with increased stress LHR compared with angiographically normal individuals (P =.009). Patients with severely impaired LV function also had a higher mean stress LHR than those with normal LV function (P =.01). Stress LHR was significantly greater than resting LHR in patients with coronary disease (0.32 +/- 0.07 vs 0.30 +/- 0.07; P =.003) and impaired LV function (0.35 +/- 0.08 vs 0.31 +/- 0.07; P <.02). CADSS correlated with stress, but not resting, LHR (P =.006), whereas the degree of LV dysfunction correlated with both resting (P =.046) and stress (P =.004) LHR. Left anterior descending (P =.017) and left main (P =.03) stenoses were independent predictors of increased stress LHR.
Conclusions: An increase in stress Tc-99m sestamibi lung uptake is a marker for severe CAD. Correlation of stress LHR, but not resting LHR, with CAD severity supports exercise-induced pulmonary congestion as the underlying mechanism.