Pulmonary vein stenosis
There has been increasing recognition of acquired pulmonary vein stenosis (PVS) in extremely premature newborns. This entity seems to be developing at variable age, but as late as 6 months of corrected age. The entity may be related to inflammatory fibrosis and seems to be markedly affecting the osteum of the pulmonary veins. This may lead to post-capillary pulmonary hypertension, although many of these infants may also have a contribution of pulmonary arterial hypertension (pre-capillary) superimposed on the phenotype. These infants may have significant pulmonary hypertension and right ventricular failure. There has been some reports associating this entity with other inflammatory or vascular diseases of the newborn, such as necrotizing enterocolitis or retinopathy of prematurity. Pulmonary vein stenosis is often suspected by echcocardiography when there is a monophasic Doppler flow profile with a mean gradient of more than 4 mmHg. Echocardiography has many limitations. PVS may not be detected because of poor acoustic windows (often these infants have severe pulmonary phenotype rendering the scanning quite challenging). Further, some infants have also concomitant tracheostomy (or other apparatus for respiratory support), making it challenging to obtain a crab view. Infants with complete osteum atresia may be missed, since PVS is often detected when there is residual accelerated flow through the narrowed osteum. Echocardiography may not appreciate the extent of the pulmonary venous disease, since there may be long-segment involvement. The presence of pulmonary venous disease at the osteum may only be the hallmark of a more profound proximal venous disease. Acceleration of flow may also be "flow-driven", but the loss of the biphasic or triphasic venous pattern may be a clue indicating that there is a stenosis. Echocardiography is practical since it allows for concomitant evaluation of the right ventricular function and presence of shunt. Nonetheless, one should always pay attention to the pulmonary veins when evaluating extremely premature newborns, even if their normal connection has been objectified in the past. Especially when suspecting high pulmonary pressures, there should be an exhaustive evaluation of the pulmonary veins and the left sided structures (mitral valve, aortic valve, left ventricular performance and pulmonary venous drainage). Some centres advocate for computed tomography, magnetic resonance imaging and/or cardiac catheterization angiography in these infants. The management is controversial and many strategies have been described: pulmonary vasodilators to redistribute the blood flow to unaltered areas of pulmonary venous drainage, cath-based procedures (balloon, stent), surgical suture-less repair, immunomodulation, lung transplant. These cases should be managed by an experienced pulmonary hypertension team. Some interesting references are provided below. Here are clips that exemplify pulmonary venous stenosis in the context of prematurity.
B-mode / Colour-Profile of the pulmonary veins and Doppler
PDA profile indicating some bidirectional shunt, mostly right to left - suprasystemic pulmonary pressures
A4C showing RV hypertrophy but preserved RV function (TDI showcasing systolic velocities)
TR jet with incomplete curve outlining that the sPAP is estimated at (at least) 117 mmHg
PSAX with a sweep outlining some bowing of the septum in systole
Inter-atrial shunt is mostly left to right (some right to left intermittent) indicating relatively preserved RV diastolic function.