A 24-year-old male with antiphospholipid syndrome (APS) had taken warfarin for 2 years. Two months ago, after he had stopped taking warfarin, he presented with acute dyspnea. He was admitted to our hospital for evaluation and treatment.

At admission, contrast-enhanced computed tomography (CT) image (Somatom Definition; Siemens Healthcare, Erlangen, Germany) showed occlusive embolism in segmental-subsegmental arteries of right segment 5 (S5) and lower lobe (Figure 1A, arrows). Lung perfusion blood volume (PBV) images showed a perfusion defect only in right S5, corresponding to occlusive pulmonary embolism. However, perfusion defect was not found in the right lower lobe (Figure 1B). The dilated bronchial artery suggested that a systemic collateral supply had developed (Figure 1C, arrows). Lung perfusion single-photon emission computed tomography (SPECT)/CT images showed that perfusion defects were found in the right S5 and lower lobe (Figure 1D, arrows).

Figure 1.

A previous report showed that perfusion defects on acute pulmonary embolism corresponded to lung PBV and lung perfusion SPECT (1). Usually, perfusion defects in chronic thromboembolic pulmonary hypertension also correspond to lung PBV and lung perfusion SPECT (2). However, in some cases, there is a discrepancy between them because of the systemic collateral supply (3, 4). Lung perfusion SPECT depicts only pulmonary artery perfusion, but lung PBV depicts both pulmonary artery perfusion and systemic collateral supply. In our case, the discrepancy between lung PVB and lung perfusion SPECT images might have been caused by the presence of systemic collateral supply via dilated bronchial artery.