Fetal Intervention

Published on 07/06/2015 by admin

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32 Fetal Intervention

Rima S. Bader, Wayne Tworetzky

I. INTRODUCTION

This chapter is a brief summary of the current proposed indications for fetal cardiac intervention. For those who perform fetal echocardiography, this will serve as a guide for selecting patients for referral to a center that performs fetal interventions. The field of fetal cardiac intervention is in its infancy, and thus limited published data are available on patient selection for procedures and outcomes of fetal interventions.

II. RATIONALE FOR FETAL CARDIAC INTERVENTION

A. The cardiac defect

1. The cardiac defect can have a negative impact on postnatal survival (e.g., hypoplastic left heart syndrome [HLHS] with severely restrictive or intact atrial septum).

2. The defect significantly affects quality of life.

a. Single ventricle with Fontan circulation (aortic stenosis that evolves to HLHS with a single right ventricle [RV] as the systemic ventricle).

b. Pulmonary atresia with intact ventricular septum that can lead to hypoplastic right heart syndrome and single-ventricle circulation with a single morphologic left ventricle (LV) as the systemic ventricle.

3. It can lead to fetal demise, as could occur with the evolution of severe tricuspid or mitral insufficiency with progressive severe pulmonary or aortic outflow tract obstruction, respectively.

B. Intervention

1. There must be a feasible and effective fetal intervention procedure that is safe for both the mother and the fetus.

2. At this time, prenatal interventions should not be performed in cardiac defects that can undergo a complete anatomic and physiologic repair postnatally.

III. TREATMENT

A. Fetal aortic stenosis

1. Fetal intervention is currently only justifiable for a severe form of aortic stenosis that has a high likelihood of evolving into HLHS or in which heart failure has evolved as a result of the severe LV dysfunction and/or mitral insufficiency.

2. Mild or even moderate forms of fetal aortic stenosis do not usually result in LV hypoplasia or fetal heart failure. The fetus can undergo neonatal balloon aortic valvuloplasty (Figs. 32-1 and 32-2) with satisfactory results and long-term outcomes.

3. The postnatal outcomes for HLHS vary among institutions.

a. The best reported survival ranges from 80% to 90% for the first-stage Norwood surgery and 70% to 80% through the Fontan stage.

b. The long-term survival beyond 20 years of age is unknown.

c. In the context of progressive heart failure or fetal hydrops, the likelihood of survival if the fetus is not at a truly viable age and size for intervention is extremely low.

4. Fetal intervention can be justified if the intent is to prevent progression of severe aortic stenosis to HLHS or fetal hydrops.

a. We select patients we believe will have HLHS at birth but whose LV is still within the normal range at the time of diagnosis.

b. Fetal echocardiography shows features of fetal aortic stenosis with evolving HLHS.

    (1) Severe valvar aortic stenosis.
    (2) Initially dilated or globular LV.
    (3) Moderate to severe LV dysfunction.
    (4) Retrograde flow in the transverse aortic arch.
    (5) Left-to-right flow at the foramen ovale, or left-to-right bulging if the valve is intact.
    (6) Echogenic LV papillary muscles or endocardium.
    (7) Monophasic mitral valve inflow Doppler.
    (8) Minimum LV-to-RV diastolic length ratio of 80%.

c. Counseling.

    (1) Patients are counseled extensively about the surgical management and known short- and medium-term outcomes for HLHS. Long-term outcomes beyond 20 years are unknown.
    (2) Risk to the mother.
       (a) Procedures are performed under general anesthesia but could be performed under maternal sedation with additional fetal analgesia and paralysis.
       (b) Laparotomy may be used to improve fetal positioning, imaging, and access to the fetus.
       (c) Risks from the procedure.

         (i) Anesthesia.
         (ii) Premature labor.
         (iii) Rupture of membranes.
         (iv) Placental abruption.
         (v) Pregnancy loss.
         (vi) Wound infection.

    (3) Risk to the fetus.
       (a) Pleural and pericardial effusion, hemopericardium, hemothorax.
       (b) Bradycardia.
       (c) Intracardiac thrombus.
       (d) Balloon rupture with fragments left in the heart.
       (e) Fetal demise, early or late.
       (f) Premature birth.

d. Contraindications to fetal intervention.

    (1) Fetal.
       (a) Twin pregnancy, which is an additional risk to the mother and to the healthy twin.
       (b) Additional significant congenital anomalies (e.g., diaphragmatic hernia).
       (c) Serious chromosomal anomaly.
       (d) Gross fetal hydrops with impending fetal demise.
    (2) Maternal.
       (a) Anesthesia risk.
       (b) Serious medical conditions (e.g., thrombotic, bleeding, or hypertensive disorders).
       (c) Psychiatric illness or major social problems.

e. Fetal cardiac intervention team.

    (1) Maternal–fetal medicine and ultrasound specialists.
    (2) Fetal echocardiographer.
    (3) Interventional cardiologist.
    (4) Anesthesiologist for the mother and fetus.
    (5) Fetal surgeon.

f. Outcomes and follow-up after fetal intervention for aortic stenosis.

    (1) Technically successful.
       (a) The fetus is still at risk for fetal demise or prematurity.
       (b) Postnatally, the baby can have:

         (i) Biventricular circulation.
         (ii) HLHS spectrum.
         (iii) LV with borderline size and function.

    (2) Technically unsuccessful: The baby will most likely have HLHS at birth.
image

Fig. 32-1 Technique for fetal aortic valvuloplasty. Maternal anesthesia and uterine-relaxation medication are administered. The fetus is positioned and anesthetized. With ultrasound guidance, a coronary balloon is introduced percutaneously on a 0.014” wire through a 19-gauge needle.

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