Abnormal ductus venosus streaming toward the right heart offers a new and plausible explanation for left heart hypoplasia in human fetuses with left diaphragmatic hernia

Aims: Underdevelopment of left heart structures is common in fetuses with left diaphragmatic hernia. This finding has been explained with external compression of the left heart by herniated organs and/or low pulmonary venous return from the hypoplastic lungs. As right or left heart underdevelopment is usually no feature in right diaphragmatic hernias, we refuted the previously proposed explanations for left heart hypoplasia and searched for an alternative cause. Since in normal fetuses the major fraction of left heart filling is provided by the ductus venosus, our study focused in particular on ductus venosus streaming patterns.

Patients & Methods: We prospectively studied 22 fetuses with left diaphragmatic hernias between 19+6 and 38+6 weeks of gestation employing multimodal echocardiography. Thirteen of the fetuses had significantly smaller left than right cardiovascular structures, whereas in the remaining nine fetuses the proportions of both ventricles and great arteries appeared normal. Based on our hypothesis that abnormal streaming patterns of the ductus venosus might result in underfilling of the left heart in fetuses with left diaphragmatic hernia we examined ductus venosus blood flow.

Results: All 13 fetuses with decreased left heart dimensions had abnormal streaming of ductus venosus blood flow toward the right side of the heart. All 9 fetuses in whom cardiac proportions appeared normal exhibited a normal connection of the ductus venosus to the heart.

Conclusions: Abnormal ductus venosus streaming toward the right heart offers a new and very plausible explanation for the common association of left heart hypoplasia and left diaphragmatic hernia. The pathoanatomical basis of the abnormal flow findings in this condition is provided by the dystortion of the normal spatial arrangements of the inferior caval vein, ductus venosus and floor of the heart from intrathoracic herniation of abdominal organs and rightward displacement of the heart.

congenital heart disease - diaphragmatic hernia - ductus venosus - fetus - left heart hypoplasia