Fetal Coarctation

From a manuscript by our group - written by student Sam Amar: "Coarctation of the aorta (CoA) is a form of congenital heart disease that involves the narrowing of the aortic arch lumen, usually at the level of the aortic isthmus. It represents 5 to 8% of congenital heart defects, which means it is a relatively common disease. If unrecognized and untreated in the post-natal setting, this lesion can lead to cardiovascular collapse and organ damage. Therefore, early detection and treatment of CoA is essential for the health of the affected neonates. CoA is challenging to accurately detect in the prenatal setting because of the patency of the ductus arteriosus (DA) and because only 10% of the combined fetal cardiac output passes through the isthmus during fetal life. The DA is a fetal vascular structure that usually connects to the aortic isthmus. The DA obscures the aorta’s anatomy on fetal echocardiography, challenging the direct observation of the aortic arch narrowing during fetal life and of the posterior shelf commonly identified after ductal constriction. As such, fetal cardiology has traditionally relied on indirect prenatal markers such as: 

• ventricular size discrepancy

• persistent left superior vena cava (SVC), 

• small left-sided structures,

• small aortic arch size. 

Because of its limited detection, there is a high false-positive rate for the antenatal suspicion of CoA by fetal echocardiography. As such, numerous newborns who are suspected to have a CoA in the antenatal period will not develop true significant obstruction. The false-positive rate is highest towards the end of pregnancy, when ventricular size discrepancy can be present even in normal fetuses. However, prenatal suspicion still warrants post-natal monitoring and admission to a critical care unit, such as a neonatal intensive care unit (NICU) or a cardiac intensive care unit."

More on post-natal Coarctation here.

Articles on fetal coarctation: here and here.

Further, when facing ventricular asymmetry, one may contemplate a differential diagnosis of various conditions: 

• LV "smaller" than RV: fetal coarctation, hypoplastic LV (HLHS, obstructive lesion to the LV), unbalanced AVSD, large RV secondary to tricuspid insufficiency, large RV secondary to TAPVD, large RV secondary to ductal constriction. 

• RV "smaller" than LV: RV obstructive lesion (RV hypoplasia, such as in PAIVS), tricuspid atresia with hypoplastic RV, double inlet left ventricle (RV hypoplasia), Aortic stenosis (enlarged LV), Mitral insufficiency (enlarged LV). 

Slides prepared by student Sam Amar on measurements in suspicion of Fetal Coarctation:

Image provided by Dr Wadi Mawad - Pediatric Cardiology at the Montreal Children's Hospital 

Neonatal Guidance in anticipation of fetal coarctation

This is to be adapted to your clinical practice and realities. This is a draft of the overall plan that I (G. Altit) provide in my fetal consultations for a concern of fetal coarctation. This has to be adapted on the individual patient and in collaborations with cardiology and maternal-fetal medicine. It must also be individualize to your practice. Here for reference: 

For the baby:

• Delivery can be done vaginally at term unless other obstetrical concerns arise.

• At birth, presence of the neonatal resuscitation team.

• Birth must occur in an expert perinatal centre with expertise in fetal cardiology such as the Montreal Children's Hospital. 

• No current contraindications for vaginal delivery and delayed cord clamping based on the congenital heart defect concern.

• Depending on degree of concern by the fetal cardiology, the baby may can be given 20 minutes with mother if stable before admission to NICU (especially if significant coarctation concern is unlikely and admission based on RV/LV dyscrepancy, as well as absence of other significant associated CHD).

Admission to the NICU – Hypoplastic Arch:

• Follow the admission of congenital heart defect protocol (see in the Congenital Heart Defect section), including NIRS monitoring (local Montreal Children's Hospital practice).

• Following birth, baby will be admitted for cardiorespiratory monitoring. Pre and post-saturation (a differential of saturation may indicate a closing PDA with right to left shunt by the closing ductus). Monitor blood pressure in the Right Upper limb (pre-ductal) and one of the lower limbs as per CHD protocol. A gradient of systolic blood pressure 10 mmHg or more is of concern. Monitor urine output as a marker of end-organ perfusion, pH and lactate.

• This baby will be kept NPO. Babies with a Left sided obstruction (ie: CoA) are at increased risk of necrotizing enterocolitis, Please install peripheral intravenous line and provide D10 at TFI 60-65 mL/kg/min. Await cardiology first assessment to initiate trophic feeds (20 mL/kg/day of breast/human milk).

• Cardiology consult in the post-natal life with assessment in the first hours (or earlier if clinical instability).

• Consideration for initiation of immediate PGE infusion depends on the assessment by the fetal cardiologist on the degree of suspicion for a significant coarctation. However, PGE should be initiated if a clinical concern of coarctation – decrease femoral pulses, differential pressure from Right upper to lower limps. If started, PGE to be started at 0.02 mcg/kg/min.

  • If PGE initiated - install central umbilical venous line (double-lumen) and umbilical arterial line for hemodynamic monitoring and blood sampling. 

  • At UAL placement, send arterial blood gaz, cross-match.

  • If Coarctation confirmed: At 24 hours of life, do: baseline bilirubin, Triglycerides, phosphate, magnesium, creatinine, urea, liver enzymes. These are the baseline end-organ evaluations that we locally send as well as our regular TPN evaluations.

  • If UVL placed - initiate Starter TPN and SMOF (1g/kg/day)

  • If Coarctation confirmed: Obtain consent for PICC line (double-lumen), transfusion consent, pasteurized human milk consent and admission consent (for all admissions).

• Blood gaz on admission and follow q4-6 hours for first 48 hours depending on clinical evolution: evaluate for presence of metabolic acidosis, high lactate, hypocalcemia (could be present in the context of Di George)

• Some of these infants may have concomitant small for gestational age status: Follow blood glucose q3hours x 3 until ensuring no hypoglycemia on a reliable source of intravenous dextrose infusion. If SGA status, also need an evaluation for urine CMV PCR and CBC (rule out thrombocytopenia and abnormal leukocytes).

• Consider CBC with first bilirubin check at 24 hours of life. Rule out lymphopenia (Di George)

• Evaluate for thymus presence on fetal echocardiography, post-natal echocardiography or chest radiography if performed. 

• If coarctation requiring intervention confirmed, involve genetics and complement dysmorphological examination with abdominal and head ultrasound (unless a head MRI is requested by the cardiac team). 

• Send placenta for analysis in pathology

• If coarctation confirmed, will need to have involvement of occupational therapy, physiotherapy, neonata follow-up, music therapy, lactation therapy and social service for benefits from EnCoeur Foundation (in Quebec Only).