The pulmonary venous wedge pressure in pulmonary arterial hypertension

Pulmonary Venous Wedge Pressure Provides an Accurate Assessment of Pulmonary Artery Pressure in Children with a Bidirectional Glenn Shunt

PURPOSE

In circulations with pulsatile pulmonary artery flow the pulmonary venous wedge pressure (PVWp) has been validated as a good estimate of pulmonary artery pressure (PAp), when PAp is low. The purpose of this study was to validate PVWp estimates of PAp in the less-pulsatile pulmonary circulation of children after bidirectional Glenn shunts.

METHODS

A retrospective study was performed of 22 simultaneous measurements of PVWp and PAp made during 20 catheterizations in 19 children who had undergone bidirectional Glenn procedures. The PAp was measured directly from the branch PA ipsilateral to the side of the PVWp, or in the SVC. Pulmonary resistance (Rp) was calculated with both PAp and PVWp, to assess the impact of PAp estimates on Rp determinations.

RESULTS

Patients ranged in age from 5 months to 10.7 years. There were a variety of univentricular cardiac malformations in the study group. Two children had antegrade pulmonary blood flow in addition to a bidirectional Glenn shunt. The mean PAp ranged from 4 to 14 mmHg, while mean PVWp ranged from 3 to 15 mmHg. Mean PVWp never differed from mean PAp by more than 3 mmHg. There was a significant linear relation between mean PAp and PVWp: PAp = 0.86 (PVWp) + 2.0 (R2 = 0.89; P < 0.0001). PVWp provided a good approximation of PAp regardless of the presence (n = 2) or absence (n = 19) of antegrade pulmonary flow. There was a good linear correlation between the Rp calculated by both methods (RpPAp = 0.9 (RpVWp) + 0.5; R2 = 0.74; P < 0.0001).

CONCLUSION

The mean PVWp provides a close approximation of mean PAp in children with a bidirectional Glenn shunt and provides valuable hemodynamic information in cases where direct PAp measurements are unavailable.

The efficacy of using pulmonary vein wedge pressure for the estimation of pulmonary artery pressure in children with congenital heart disease

The objectives of this study were to assess the accuracy of pulmonary vein wedge pressure (PVWP) in estimating pulmonary artery pressure (PAP) in various types of congenital heart disease, including single-ventricle physiology. The systolic, diastolic, and mean values of both PAPs and PVWPs were measured in 30 patients (a total of 46 points). Pulmonary artery pressure ranged from 13 to 74 (34 +/- 15) mm Hg in systole, 5 to 25 (13 +/- 6) mm Hg in diastole, and 6 to 48 (18 +/- 10) mm Hg in mean. As a whole, good correlations between PAPs and PVWPs were observed (systole, r = 0.70; diastole, r = 0.85; mean, r = 0.82; P < 0.0001). However, with an increase in PAP, the discrepancy between PAPs and PVWPs increased. When the mean PVWP was more than 18 mm Hg, the mean PVWP in 14 of 24 (58%) underestimated the mean PAP by up to 22 mm Hg (mean difference, -1.7 +/- 5.8 mm Hg). On the other hand, all of the patients with mean PVWPs less than 18 mm Hg (n = 22) had mean PAPs less than 18 mm Hg (r = 0.86; PAP = 1.11 x PVWP - 1.41; P < 0.0001), and the mean difference was -0.2 +/- 1.8 mm Hg. The mean PVWP can accurately estimate the mean PAP in children with congenital heart disease who have a mean PVWP less than 18 mm Hg.

Estimation of pulmonary artery pressure from pulmonary vein wedge pressure

Correlations between pulmonary artery and pulmonary vein wedge pressures were investigated in 13 patients with atrial septal defect and 1 patient with Tetralogy of Fallot. Pulmonary vein wedge pressure wave form resembled that of pulmonary artery pressure, and the former lagged behind the latter by 70 to 110 msec (mean 88 +/- 14) as observed by the fluid-filled catheter system. Diastolic pulmonary artery and diastolic pulmonary vein wedge pressures were nearly identical. Although systolic and mean pulmonary artery pressures correlated well with respective pulmonary vein wedge pressures, there were discrepancies when systolic and mean pulmonary artery pressure exceeded 35 and 20 mm Hg, respectively. However, systolic and mean pulmonary artery pressures could be estimated by adding the difference between the diastolic pulmonary vein wedge pressure and the mean left atrial pressure to corresponding systolic or mean pulmonary artery pressure. In conclusion, pulmonary artery pressures can be estimated by measuring pulmonary vein wedge pressures and the mean left atrial pressure.

Lung biopsy with frozen section as a diagnostic aid in patients with congenital heart defects

In eight patients with congenital heart defects and equivocal preoperative hemodynamic data, lung biopsy with frozen section was performed and quantitative morphometric analysis carried out to help select a palliative or corrective surgical procedure. During catheterization it had been possible in only six of the eight patients to enter the pulmonary artery and obtain pressure measurements; four patients had moderate to severe elevation of pulmonary vascular resistance whereas the other two had only mild elevation of pulmonary arterial pressure, but they were being considered for a Fontan procedure. The lung biopsy tissue was taken inflated and fixed inflated in hot glutaraldehyde. From cryostat sections arterial concentration was assessed relative to alveolar concentration, and the degree of arterial muscularity was assessed by wall thickness and extension of muscle; the more advanced Health-Edwards arterial changes were also evaluated. On the basis of the morphologic assessment, six of the eight patients underwent corrective surgery and two underwent a palliative procedure. Postoperative hemodynamic data available in four of the patients who underwent corrective surgery revealed either a significant reduction in pulmonary vascular resistance or return to a normal level of pulmonary arterial pressure, whereas no change has occurred in the one patient studied who underwent a palliative procedure. Assessment of pulmonary arterial development and structure on lung biopsy with frozen section proved helpful in deciding between a palliative and corrective surgical procedure.