Cardiothoracic Area Ratio Predicts Lethal Pulmonary Venous Obstruction in Patients with Single Ventricle and Total Anomalous Pulmonary Venous Connection

Fetal Doppler Echocardiographic Assessment Predicts Severe Postnatal Obstruction in Total Anomalous Pulmonary Venous Connection

BACKGROUND

Obstructed total anomalous pulmonary venous connection (TAPVC) is a form of critical congenital heart disease that usually requires urgent postnatal intervention. Knowing which patients have severe obstruction can aid delivery planning. The authors previously developed a novel quantitative metric of pulmonary venous flow, the pulmonary venous variability index (PVVI). The aim of this study was to test the hypothesis that fetal PVVI and vertical vein Doppler velocities are associated with severe pulmonary vein obstruction postnatally.

METHODS

A retrospective cohort study of neonates with prenatally diagnosed TAPVC was performed. Patients who underwent fetal echocardiography at the Children's Hospital of Philadelphia with Doppler interrogation of the vertical vein were included for analysis. Twenty-nine patients met criteria (21 with heterotaxy, 18 with supracardiac TAPVC). The latest gestation fetal echocardiogram was used. Severe pulmonary vein obstruction was defined as preoperative death or urgent surgery or catheter-based intervention (first day of life). Measurements of PVVI, defined as (maximum velocity - minimum velocity)/mean velocity, were made offline. Wilcoxon rank sum models were used to assess the associations of severe obstruction and PVVI and maximum, mean, and minimum velocities.

RESULTS

The mean gestational age at the latest fetal echocardiographic examination was 35 weeks (range, 30-39 weeks). Twelve of the 29 patients (41%) met criteria for severe pulmonary vein obstruction. Lower PVVI was associated with greater risk for severe pulmonary venous obstruction (P = .008). The maximum, mean, and minimum velocities in the vertical vein were all significantly associated with severe pulmonary venous obstruction (P = .03, P = .03, and P = .007, respectively). Qualitative assessment of obstruction was not significantly associated with the outcome. Interobserver reliability for all vertical vein Doppler metrics was high (intraclass correlation coefficient > 0.9).

CONCLUSIONS

Fetal PVVI and maximum, mean, and minimum velocities are associated with severe postnatal pulmonary vein obstruction in TAPVC. Accurate prediction of obstructed TAPVC could allow safer delivery planning. Further research with larger sample sizes is needed to identify the ideal cutoff values for these Doppler measures.

Radiological Cardiothoracic Ratio in Evidence-Based Medicine

The cardiothoracic ratio (CTR), expressing the relationship between the size of the heart and the transverse dimension of the chest measured on a chest PA radiograph, is a commonly used parameter in the assessment of cardiomegaly with a cut-off value of 0.5. A value of >0.5 should be interpreted as enlargement of the heart. The following review describes the current state of available knowledge in terms of contentious issues, limitations and useful aspects regarding the CTR. The review was carried out on the basis of an analysis of scientific articles available in the PubMed database, searched for using the following keywords: “CTR”, “cardiothoracic ratio”, “cardiopulmonary ratio”, “cardiopulmonary index”, and “heart-lung ratio”. According to the accumulated knowledge, the CTR can still be used as an important parameter that can be easily determined in establishing enlargement of the heart. However, an increased CTR does not directly relate to heart function. In the era following the development of diagnostic methods such as computed tomography, magnetic resonance imaging, and ultrasonography, CTR modifications based on these methods are used with varying clinical usefulness. It is important to consider the definition of the CTR and remember to base measurements on PA radiographs, as attempts to mark it in other projections face many limitations.