Scintigraphic diagnosis of a right to left shunt in end-stage lung disease

The presence of a right to left shunt influences the surgical approach to lung transplantation in patients with end-stage pulmonary disease. The purposes of this study included comparing contemporaneous lung scintigraphy with cardiac catheterization in the detection of intracardiac shunts in patients with end-stage lung disease and the point prevalence of right to left shunting was determined in patients with several different types of end-stage lung disease.

Hundred and twenty six patients with end-stage lung disease who were candidates for lung transplantation underwent perfusion images of the lungs with Tc-99m-labeled macro-aggregated albumin (MAA). Planar scans of the brain and the kidneys were performed contemporaneously. Statistical analyses included correlation ofthe clinical, laboratory and scintigraphic variables. Group means were compared with the students t-test (two-tailed P-value).

There were 21 patients with primary pulmonary hypertension (PPH), 72 with emphysematous lung disease (COPD), 22 with pulmonary fibrotic disease (PF) and 11 with congenital heart disease (CHD) leading to pulmonary hypertension. Only 13 patients (10.3%) were found to have a right to left shunt. Of these, 4 had PPH, 2 had PF, and 7 had CHD. No shunts were found in patients with emphysema. All the positive studies had abnormally increased activity in both the brain and the kidneys. However, there were 25 cases with renal activity and none of these patients had brain activity or clinical evidence of a shunt. Increased pulmonary artery pressure was associated with scintigraphic presence of a shunt. There were no cases of a right to left shunt with a mean pulmonary artery pressure less than 50 mm Hg. In the subset of patients with a pulmonary pressure greater than 50 mm Hg, approximately 40% of the patients had a right to a left shunt. There were no measurable differences in the spirometry results, right ventricular ejection fraction (RVEF) or left ventricular ejection fraction (LVEF) in the subgroup of patients with PPH and right to left shunt in comparison with patients with PPH but without a right to left shunt.

The findings indicate that images of the brain, but not the kidneys, are an effective way to diagnose extrapulmonary right to left shunts in patients with end-stage pulmonary disease. The problem of a right to left shunt is uncommon in patients with emphysematous lung disease and relatively common in patients with primary pulmonary hypertension.