Pulmonary perfusion after endovascular stenting of pulmonary artery stenosis

Pulmonary artery stenosis is a well-known condition after surgical correction of tetralogy of Fallot. Endovascular stenting of the stenosis is a new technique for correction without surgical intervention. Objective evaluation of the procedure, however, is often hampered by moderate or severe pulmonary valve insufficiency. This disadvantage does not apply to 99mTc-macroaggregates of albumin (MAA) scintigraphy of the lungs. Moreover, quantification can be performed relatively easy.

Seven patients with surgically corrected tetralogy of Fallot (4 men, 3 women, mean age 15.7 yr, range 5-24 yr) were studied. The mean diameter decrement of a pulmonary artery was 69% +/- 8.7%. Before and after stenting, relative uptake in the left and right lung was assessed after injection of 37-55 MBq 99mTc-MAA. Three patients were studied twice after stenting.

In all patients, perfusion of the affected lung increased significantly: before 22.7% +/- 10.8%, after 38.6% +/- 12.3% (p < 0.0001). All patients claimed clinical improvement of their condition after stenting. The perfusion gain did not correlate with the prestenting diameter decrement or with the pressure gradient over the stenosis. Lung uptake in the patients studied twice after stenting was similar between the initial and poststenting study (< or = 2% difference).

Quantitative 99mTc-MAA lung imaging is a noninvasive technique without patient discomfort that objectively measures the effect of stenting pulmonary artery stenosis. The final outcome of stenting with regard to increment of pulmonary blood flow is not predicted by the severity of the stenosis or the pressure gradient over the stenosis.