(A) Two-dimensional reformatted image. (B) Volume-rendered 3-dimensional image. The right lung has 4 pulmonary veins (asterisks), 3 of which form a confluence (C) as they drain into the left atrium (LA). Ao = aorta; LPA = left pulmonary artery; RPA = right pulmonary artery.

(A) Magnitude image showing the anatomy of the slice. The cross section of the right upper pulmonary vein (PV) is seen below the oblique section of the right pulmonary artery (RPA) and behind the superior vena cava (SVC). (B) A phase image obtained in systole shows the flow through the RPA in black and the flow through the right upper PV in white. (C) Time-velocity curves of the right pulmonary artery and right upper pulmonary vein. The pulmonary venous blood flow consists of systolic and diastolic (d) forward waves and a late diastolic reversed wave (a) on atrial contraction. The systolic wave consists of early (es) and late (ls) systolic peaks and is slightly higher than the diastolic wave. Ao = aorta; RA = right atrium.

(A) A contrast-enhanced 3-dimensional angiogram seen from posterior shows the anomalous connection of the right upper pulmonary vein (RUPV) to the superior vena cava (SVC). The small right lower pulmonary vein (RLPV) connects normally to the left atrium (LA). (B) Time-flow volume curves of the right upper and left upper pulmonary veins and right and left pulmonary arteries. The flow pattern of the right upper pulmonary vein is different from that of the left upper pulmonary vein. There is continuous flow without discernable systolic and diastolic waves in the anomalous right upper pulmonary vein. The right pulmonary artery shows a less resistant flow pattern with the systolic wave reaching its peak later and showing slower deceleration as compared with the left pulmonary artery. The blood flow ratio between the right and left lung is 56%:44%. The pulmonary-to-systemic blood flow ratio was 2.2, and the patient required surgical repair of the anomalous connection. Ao = aorta; RA = right atrium; RPA = right pulmonary artery.

Contrast-enhanced angiograms, reformatted in slanted coronal planes, show the scimitar vein draining most of the right lung to the inferior vena cava (IVC). (A) The scimitar vein shows severe stenosis as it connects to the IVC. Note the high signal intensity flow in the IVC. (B) A small right lower pulmonary vein (RLPV) and the left pulmonary veins (LUPV and LLPV) have normal connections to the left atrium (LA). The LUPV is stenosed. A small aberrant arterial branch arises from the abdominal descending aorta (Ao) to supply the posterior basal part of the right lower lobe. The right lung volume is smaller than the left lung volume. In this case, the right pulmonary artery (RPA) is not hypoplastic. LLPV = left lower pulmonary vein; LUPV = left upper pulmonary vein; PA = main pulmonary artery; RA = right atrium.

(A) Contrast-enhanced angiograms show severe stenosis of the left lower pulmonary vein (LLPV) and mild stenosis of the left upper pulmonary vein (LUPV). Both veins are slightly smaller than the right pulmonary veins (RUPV and RLPV). The left pulmonary artery (LPA) is smaller than the right pulmonary artery (RPA) due to diversion of blood flow to the right lung. (B) Time-velocity curves of the pulmonary veins and pulmonary arteries using phase-contrast imaging. The left pulmonary venous flow data were obtained from just upstream of the stenosis. The left pulmonary veins demonstrate reduced velocity and loss of phasic changes. The LPA has reduced systolic blood flow and a premature systolic peak. The blood flow ratio between the right and left lungs is 73%:27%. (C) Contrast-enhanced angiograms obtained 8 months after the surgical repair of the stenosis show residual tight stenosis of the LUPV and less severe narrowing of the LLPV. Both vessels are much smaller than the right pulmonary veins. The right and left pulmonary arteries remain discrepant in size. (D) Flow curves 8 months after surgery. Left lower pulmonary venous flow velocity is markedly reduced. Left pulmonary arterial systolic flow is further reduced, and there is reversed flow (shaded) in diastole. There is almost no net blood flow to the left lung. LA = left atrium; MPA = main pulmonary artery; RLPV = right lower pulmonary vein; RUPV = right upper pulmonary vein.

Contrast-enhanced magnetic resonance angiograms, reformatted in slanted coronal planes, reveal complete occlusion of the left upper (LUPV) and left lower (LLPV) pulmonary veins. (A) The left middle pulmonary vein (LMPV) has an unobstructed connection to the left atrium (LA). (B) Collateral channels (arrows) are seen between the peripheral branches of the unobstructed LMPV and the branches of the obstructed LUPVs and LLPVs. Ao = aorta; RA = right atrium; RLPV = right lower pulmonary vein; RPA = right pulmonary artery.

The unobstructed right upper pulmonary vein demonstrates the usual post-operative changes in flow pattern including a higher diastolic wave (d) than the early (es) and late (ls) systolic peaks. A reversed flow peak (asterisk) is seen in early systole as the mitral valve closes toward the stiff left atrium.

Contrast-enhanced angiograms show an unobstructed surgical anastomosis as well as the pulmonary arteries and veins. The right pulmonary artery (RPA) and vein are smaller than the vessels on the left side. The numbers in the figures represent flow volumes in liters per minute. There is net reversed flow in the left pulmonary artery (LPA). The amount of the systemic arterial collateral blood flow to each lung can be calculated by subtracting the pulmonary arterial blood flow volume from the pulmonary venous return. The right and left lungs receive systemic arterial collateral arterial flow of 0.2 and 0.6 l/min, respectively. Subsequent X-ray angiography confirmed florid systemic collateral circulation to the left lung and subtle collateral circulation to the right lung. SVC = superior vena cava. Reproduced with permission from Yoo et al. (30).