PVS

Anatomy

Pulmonary vein stenosis may occur as a primary disease (e.g. congenital PVS or associated with chronic lung disease of prematurity) or as a secondary phenomenon following repair of another disease (e.g. TAPVC repair). While the molecular mechanisms remain to be fully elucidated, it is thought that a process of neointimal proliferation begins at the LA-pulmonary vein junction and spreads distally (towards the hilum). It is possible that flow acceleration (due to anatomic factors) may stimulate a process leading to stenosis. As shown above, stenosis of the LPVs is often associated with compression against the aorta or LMSB, and the RPVs may be compressed by the RPA or RMSB.

Pathophysiology

Healthy lungs thrive with a low arterial and venous pressure. The effects of stenosis of pulmonary veins are several.
- The pulmonary venous pressure increases, increasing hydrostatic pressure within the alveolus –> increasing fluid transudation into the alveolus –> decreasing lung compliance –> increasing WOB.
- Alveolar fluid also leads to V/Q mismatching and intrapulmonary shunting, a cause of hypoxemia.
- Increased venous pressure increases total resistance to flow within a lung segment, decreasing regional flow. This can be quantified by lung perfusion scan. It is thought that this decreased flow may increase the rate of endothelial proliferation and (re)stenosis.
- Increased venous pressure, particularly in multiple lung segments, often leads to reactive pulmonary hypertension.

Treatment of PVS

Cardiac catheterization. Patients typically undergo cardiac catheterization when symptomatic (increased WOB, feeding intolerance, decreased saturations). Generally, an increasing frequency of catheterization indicates progressive or recurrent disease. The angiographic appearance (specifically diameter and length of the stenotic segment) and pressure gradients across them (PCWP to EDP gradient) provides prognostic information. Frequently, balloon angioplasty is performed to create an intimal tear and to acutely increase flow within an affected vein. Veins that are anatomically compressed or very stenotic may undergo stenting. Changes in RV or PA pressure are often indicative of improvement in physiology. Following catheterization for PVS, patients are at increased risk for stroke and other systemic emboli due to endothelial disruption of the pulmonary vein. Systemic anticoagulation is common. Some patients may benefit from mechanical ventilation (for lung recruitment), diuresis (remove lung water), and inotropic support (NE to augment subendocardial perfusion) and iNO (if pulmonary hypertension is severe).

Medication trial remains ongoing, including Bevacizumab (Avastin) and Imatinib Mesylate (Gleevec), which inhibit myoproliferation via VEGF and PDGF.

Sutureless repair is a procedure in which the stenotic pulmonary vein segments may be incised length-wise. In some cases, the veins themselves or the body of the LA may be augmented with homograft material. Because pericardium encases each individual pulmonary vein, the pericardium can be sewn directly to the LA proper to close the incision in the pulmonary vein, obviating the need for sutures (which may be pro-inflammatory) in the vein proper. Surgical pexy of impinging structures (e.g. aorta or bronchus) may also be performed.