Premature ductal constriction is defined by significant narrowing of the patent ductus arteriosus (PDA) during pregnancy. It is rare before 27-28 weeks gestation. The physiology results in increased afterload on the right ventricle which can manifest as tricuspid regurgitation, right ventricular hypertrophy and right ventricular dysfunction. Should it be severe it can can Hydrops and even fetal demise. PDA constriction can be associated with maternal ingestion of extrinsic agents such as NSAIDS, herbal teas, sympathomimetics and high dose salicylates. The treatment involves elimination of potential extrinsic agent and close fetal monitoring. In some cases, induction of labor is indicated should there be evidence of worsening fetal distress and severe ductal constriction can result in intrauterine fetal demise.
Fetal Echocardiographic Findings:
1) High systolic and diastolic velocities in the PDA on spectral Doppler interrogation
Criteria for ductal constriction
Peak systolic velocity >1.4 meters/sec
Diastolic velocity > 35 cm/sec
Pulsatility index <1.9
2) Dilated right ventricle
3) Right ventricular dysfunction (elevated myocardial performance index)
4) Tricuspid and pulmonary regurgitation
Bader, Hornberger, Huhta. The Perinatal Cardiology Handbook.