The index of pulmonary vascular disease in children with congenital heart disease: relationship to clinical and haemodynamic findings

A novel mouse model of high flow-induced pulmonary hypertension-surgically induced by right pulmonary artery ligation

BACKGROUND

This study sought to establish a new model of high-flow pulmonary hypertension (PH) in mice. This model may be useful for studies seeking to reduce the pulmonary vascular resistance and delay the development of PH caused by congenital heart disease.

MATERIALS AND METHODS

The right pulmonary artery was ligated via a right posterolateral thoracotomy. Pulmonary hemodynamics was evaluated by right heart catheterization immediately after ligation and at 2, 4, 8, and 12 wk postoperatively. The right ventricle (RV) and the left ventricle (LV) with septum (S) were weighed to calculate the RV/(LV + S) ratio as an index of right ventricular hypertrophy. Morphologic changes in the left lungs were analyzed, and percentages of muscularized pulmonary vessels were assessed by hematoxylin and eosin, elastica van Gieson and alpha-smooth muscle actin staining. All the study data were compared with data from a model of PH generated by hypoxic stimulation.

RESULTS

A pulmonary hypertensive state was successfully induced by 2 wk after surgery. However, the morphologic analysis demonstrated that pulmonary vascular muscularization, as evaluated using right ventricular systolic pressure and RV/(LV + S), was not significantly increased until 4 wk postoperatively. When mice from the new model and the hypoxic model were compared, no significant differences were observed in any of the evaluated indices.

CONCLUSIONS

High-flow PH can be induced within 4 wk after ligation of the right pulmonary artery, which is easily performed in mice. Such mice can be used as a model of high-flow PH.

Pulmonary vascular changes in piglets with increased pulmonary blood flow and pressure

In this model of pulmonary vascular disease, high pulmonary blood flow was created by an anastomosis between the left subclavian artery and the main pulmonary artery [Blalock-Taussig (BT) shunt] in 4-week-old piglets (n = 6). Additional ligation of the left pulmonary artery (LPA) was used to increase pulmonary artery pressure (n = 6). Seven piglets were sham-operated. After 3 months, mean pulmonary artery pressure was higher in animals with BT shunt and LPA ligation (22 +/- 5; mean+/-SD) compared to sham-operated animals (15 +/- 2). In addition, thickening of the medial coat (20.1 +/- 2.8% versus 13.6 +/- 3.1% wall thickness) and increased immunostaining for vascular endothelial growth factor A (VEGF-A) were observed. Relative gene expression for endothelin-converting enzyme-1 (ECE-1) mRNA was 1.8 times higher, and VEGF-A mRNA was 2.5 times higher in pigs with BT shunt and LPA ligation compared with sham-operated animals. VEGF receptor-1 and VEGF receptor-2 mRNA was lower in shunted animals and in animals with additional ligation of LPA. Upregulation of ECE-1 and VEGF-A, as well as changes in VEGFR expression in the pulmonary hypertensive lung, may contribute to pulmonary vascular changes.

Two-Stage Procedure for Pulmonary Vascular Obstructive Disease in Down Syndrome With Congenital Heart Disease

BACKGROUND

Down syndrome patients are characterized by early progression of pulmonary vascular obstructive disease because of insufficient thickness of the pulmonary arterial media. For those with congenital heart disease (CHD) associated with pulmonary hypertension (PH), a 2-stage procedure of pulmonary artery banding (PAB) and then intracardiac repair (ICR) in early infancy is performed to prevent such pulmonary vascular diseases in early infancy.

METHODS AND RESULTS

The subjects were 16 patients with Down syndrome who underwent lung biopsy during PAB and ICR. PAB was planned to be performed in early infancy and ICR approximately 1 year later. Efficacy of the 2-stage procedure was retrospectively examined with reference to pulmonary vascular disease and pulmonary diseases. The index of pulmonary vascular disease at PAB fulfilled the indication for ICR, and it was significantly lower at ICR than at PAB (p=0.0469); furthermore, PAB prevented progression of pulmonary diseases.

CONCLUSIONS

The results of the lung biopsies support the safety of the 2-stage procedure and show that it is effective for Down syndrome patients with CHD and PH.

Misalignment of pulmonary vessels with alveolar capillary dysplasia: association with atrioventricular septal defect and quadricuspid pulmonary valve

Misalignment of pulmonary vessels (MPV) with alveolar capillary dysplasia (ACD) is a complex congenital vascular abnormality in newborn infants. This condition is often associated with persistent pulmonary hypertension, which leads to severe respiratory distress and finally to the death of the newborn. Here, two cases of MPV with ACD are reported that were associated with atrioventricular septal defects. Both cases showed a combination of a large atrial septal defect and a smaller subvalvular ventricular septal defect. In one newborn, the cardiac malformation was accompanied by a quadricuspid pulmonary valve. These cases emphasize the importance of considering MPV with ACD a possible cause for pulmonary hypertension in the newborn, especially when a concomitant atrioventricular septal defect could represent an alternative explanation for the pulmonary hypertension.