Fetal Surgery for Congenital Heart Disease Technique

Updated: Nov 05, 2019
  • Author: Anita J Moon-Grady, MD, FACC, FAAP, FASE; Chief Editor: Hanmin Lee, MD  more...
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Technique

Surgical Treatment of Congenital Heart Disease in the Fetus

Once adequate fetal anesthesia is achieved, another cardiac evaluation is performed before the procedure is started. In particular, the dimensions of the right or left outflow tract and valve anulus are determined in order to guide the choice of appropriate balloon catheter (usually to achieve a balloon diameter of 100-130% of the starting anulus diameter). [36, 69]

The ideal fetal position is one in which the projected needle course (see the images below) can be aligned with the long axis of the ventricle or across the two atria, depending on the indication for the procedure.

Percutaneous fetal balloon aortic valvuloplasty. N Percutaneous fetal balloon aortic valvuloplasty. Needle course is shown, with direct per-ventricular access to aortic valve.
Fetal aortic stenosis. Intraoperative image illust Fetal aortic stenosis. Intraoperative image illustrates needle trajectory that will afford access to left ventricle and aortic valve. Initial needle course must be precise; very little manipulation is possible once device has punctured left ventricle.

An 18- to 19-gauge needle is used to enter the uterus. The needle is introduced into the fetal heart through the uterus under continuous ultrasonographic (US) guidance and into the ventricle pointing toward the corresponding valve.

After ventricular puncture, the needle is positioned with the tip within the outflow tract below the valve. The trocar is removed, with care taken not to entrain air, and the wire with the preloaded and measured balloon catheter is inserted into the needle and advanced through the valve. For an atretic pulmonary valve, it may be necessary to perforate the valve with the needle before advancing the wire.

The balloon is positioned across the valve on the basis of previous measurements and appearance on US. When the position is confirmed, one or more inflations are accomplished before removal of the entire system from the fetus and uterus. Attempts to withdraw the balloon into the needle may result in shearing of the catheter and embolization of foreign material into the fetal circulation. (See the videos below.)

Sequence during fetal aortic valvuloplasty: step 1 of 4. Needle has been passed through maternal abdomen and uterus and is preparing to enter fetal chest.
Sequence during fetal aortic valvuloplasty: step 2 of 4. Needle puncturing left ventricle is aimed toward left ventricular outflow tract.
Sequence during fetal aortic valvuloplasty: step 3 of 4. Wire is advanced through needle, across aortic valve, and well into ascending aorta.
Sequence during fetal aortic valvuloplasty: step 4 of 4. Balloon is inflated, effectively dilating fetal aortic valve.
Echocardiography is done immediately after procedure in fetus with aortic stenosis. Note forward flow across valve and in transverse aortic arch, with moderate aortic insufficiency, demonstrating successful valvuloplasty.

For a restrictive or intact atrial septum, access is usually through the right atrium (see the image below), though it has also been obtained via a left posterior approach through the left atrium. After fetal positioning, the needle is advanced through the maternal abdomen and uterus, through the right lateral fetal chest wall, and directly into the right atrium (or left lateral posterior chest through the left atrium) and then across the thickened atrial septum.

Optimal fetal position and needle trajectory for a Optimal fetal position and needle trajectory for atrial septoplasty. Right atrium is punctured through fetal chest, and needle is advanced through atrial septum, which is thickened and bows tensely into right atrium.

The needle tip is directed toward either a left pulmonary vein (right atrial puncture) or the inferior vena cava (left atrial puncture) if the trajectory is correct, enabling advancement of the wire tip through the needle in such a manner that it may be secured in one of the left pulmonary (for right atrial entry) or inferior caval (for left atrial entry) veins, providing stability of the catheter-over-wire system during balloon catheter advancement.

Multiple balloon inflations for septoplasty or a single inflation for stent delivery are then accomplished before removal of the needle and catheter.

After removal of the needle, observation for several minutes is necessary to monitor for fetal bradycardia or hemopericardium. Fetal bradycardia should be aggressively treated with intracardiac epinephrine and other agents, which should be administered via a narrow-gauge needle with the assistance of a fetal anesthesiologist. Significant pericardial effusions should be expeditiously evacuated again via a transthoracic puncture.

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Complications

Maternal risks

Isolated maternal anesthetic risks, however small, are not entirely absent and depend on the mode of anesthetic used. [70] During an open surgical procedure involving general anesthesia, the risks include maternal cardiovascular compromise with respiratory distress and pulmonary edema. Because uterine manipulation may be necessary to achieve optimal fetal positioning similar to that involved with an external cephalic version, there is a risk of placental abruption and resultant maternal hemodynamic compromise.

After the procedure, there is a risk of preterm labor (10%), with a possible need for maternal hospital admission and monitoring. If labor ensues, there are the maternal pharmacologic implications of tocolysis. Premature rupture of membranes (2% risk) may lead to a uterine infection, for which maternal antibiotic therapy is required. Maternal risks, however, are low with the use of predominantly percutaneous techniques in the current era. [71]

Fetal risks

Needle puncture of the fetal heart and needle manipulation during the procedure often results in transient bradycardia (10-40% of cases). [33] Severe sustained fetal bradycardia and dysfunction have been noted, requiring intracardiac or intramuscular resuscitative medications. Occasionally, pericardiocentesis is necessary for hemopericardium impacting cardiac output. Intracardiac thrombus formation and loss of catheter tip have also been reported. [36, 18]  Balloon rupture and stent embolization have been reported for atrial septal procedures. [72]  Long-term effects of periprocedural events in fetuses have not been studied.

After the procedure, there is a higher incidence of fetal loss (10%) than for pregnancies continuing without invasive intervention. Generally, there is no change in the mode of delivery after cardiac surgery in utero, and delivery plans are made on the basis of the usual obstetric indications.

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