Timing of Surgery for TGA, Tetralogy of Fallot and TAPVR

In cyanotic congenital heart disease, surgical timing is measured in days and weeks. Transposition of the great arteries (TGA) with an intact septum is repaired before two weeks, and TGA with a ventricular septal defect (VSD) at four to eight weeks. Total anomalous pulmonary venous return (TAPVR) and truncus arteriosus need surgery at diagnosis. Tetralogy of Fallot is repaired at six to nine months, or at any age if symptomatic.

Cyanotic conditions are those that lower the oxygen content of the blood, so the baby can look blue. Dr. Aseem R. Srivastava, Chief – Pediatric CTVS & Chief – Adult CTVS, Artemis Hospitals, Gurugram, India, framed these conditions around one rule: the timing of surgery is always dictated by the natural history of the disease, the risk of death without treatment set against the risk of treatment. In this group the untreated natural history is so poor that the comparison almost always favours operating early, whatever the baby's weight. The underlying principle, and the timings for the acyanotic defects, are in the complete guide to the correct timing for congenital heart surgery.

Tetralogy of Fallot: single-stage repair at six to nine months

Tetralogy of Fallot is the prototype cyanotic heart disease of childhood, and Dr. Srivastava noted that doctors see it very frequently. It combines four features: a VSD, narrowing of the outflow from the right ventricle to the lungs (pulmonary stenosis), an aorta that overrides the VSD, and thickening of the right ventricle. Blood low in oxygen crosses the VSD into the aorta, so the child is blue.

The natural history

Untreated, about 25% of children with tetralogy die by the end of the first year and about 40% by three years. Waiting is therefore not recommended.

Timing of repair

Dr. Srivastava's practice follows the child's symptoms:

• Asymptomatic or mildly symptomatic children have a single-stage complete repair at around six to nine months of age.
• Symptomatic infants go for complete repair at any age or weight.

The survival curves he showed made the case. After repair there is an initial drop in survival, reflecting surgical mortality, after which the curve almost matches that of the normal population. Without treatment, survival is very poor. The risk-benefit ratio, in his words, is heavily in favour of early treatment. Indicative costs are on the tetralogy of Fallot repair cost page.

Tetralogy also behaves well when it presents late. Unlike shunt lesions, cyanotic conditions other than TGA usually remain operable in an older child, at a slightly higher risk.

TGA surgery timing: a race against the left ventricle

TGA with an intact ventricular septum needs an arterial switch before two weeks of age, and TGA with a VSD needs an arterial switch with VSD closure at four to eight weeks. In TGA the two great arteries are switched: the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. Blood returning from the body is pumped straight back to the body, and oxygenated blood from the lungs goes back to the lungs, so the babies are profoundly cyanotic. Dr. Srivastava described the two common variants separately, because their timing differs.

TGA with an intact ventricular septum

Without a VSD, the natural history is very poor:

• about 20% mortality by one week of age;
• about 80% mortality by around two months;
• only 4% of children alive at one year.

The cause of death is hypoxia. Treatment, by contrast, is straightforward and effective, with 95% survival at one year.

The operation is the arterial switch operation, in which the aorta and pulmonary artery are divided and reattached to the correct ventricles, and the coronary arteries are moved with the aorta. Dr. Srivastava's team operates before two weeks of age. Surgery can be delayed to four to six weeks, but no further, because the left ventricle, which has been pumping only to the low-pressure lungs, regresses. It becomes too weak to tolerate an arterial switch operation, and the team then has to devise ways to make it stronger first. In standard practice that means "retraining" the left ventricle, usually by placing a band on the pulmonary artery for a period before the switch, which adds an operation and risk. Indicative costs for the arterial switch and other complex neonatal repairs are on the paediatric congenital heart surgery cost page.

TGA with a VSD

With a VSD, children do a little better early on: about 90% survive the first month without treatment. The advantage is short-lived. By five months only about 40% are alive, and survival at one year is below 30 to 35%. The VSD exposes the lungs to high flow and pressure, pulmonary vascular resistance rises, and most children are inoperable by one year because of high pulmonary artery pressures. The cause of death here is heart failure.

The recommended operation is the arterial switch with VSD closure at four to eight weeks of life. TGA is also the exception Dr. Srivastava made when he said that cyanotic conditions usually remain operable in a child who arrives late.

TGA with VSD and pulmonary stenosis: Rastelli or Nikaidoh

In TGA with a VSD and pulmonary stenosis, oxygen saturation sets the timing: a thriving child with saturation above 75% can wait until about one year, while a child below 75% who is failing to thrive needs surgery at any age. A paediatric cardiologist from Ethiopia asked about the timing of surgery for TGA with a VSD and left ventricular outflow tract (LVOT) obstruction. Dr. Srivastava explained that these children essentially have pulmonary stenosis with a VSD. The obstruction limits blood flow to the lungs and so protects them from the high pressure that damages them in TGA with an unrestricted VSD.

The operations

These children go for either a Rastelli or a Nikaidoh operation. In the Rastelli operation, the surgeon builds a tunnel inside the heart that directs blood from the left ventricle through the VSD to the aorta, and places a conduit from the right ventricle to the pulmonary arteries. The Nikaidoh operation instead moves the aortic root back onto the left ventricle and also reconstructs the outflow to the lungs. Both need an implant to carry blood to the lungs.

The size of that implant drives the timing. The intent, Dr. Srivastava said, is to give the child the biggest implant possible, because the smaller the implant, the earlier the child comes back for an implant change.

Oxygen saturation decides when

The decision rests on the child's oxygen saturation:

• Saturation above 75% with a child who is growing and doing well: the child can wait and come for surgery at around one year of age, which allows a larger implant.
• Saturation below 75% with significant failure to thrive: the child should come for surgery at any age or weight.

This is the clearest example in the masterclass of how timing is a balance rather than a rule: waiting is right for a well-saturated, thriving child, and wrong for a blue one who is not growing.

TAPVR: no longer a "simple" condition

TAPVR needs surgery at diagnosis, whatever the child's age or weight. In total anomalous pulmonary venous return, the four pulmonary veins, which should carry oxygenated blood from the lungs to the left atrium, connect instead, either together or separately, to the right atrium or to one of the systemic veins that drain into it.

Dr. Srivastava singled this condition out for emphasis. When he was a resident in cardiac surgery, a child with TAPVR and a large atrial septal defect was considered to have a simple heart condition, and families were asked to wait about a year. Looking back, he said, these are not simple conditions, and there are many reasons these children die. About 50% die by three months of age, and survival to one year is below 20%.

With a mortality of about 80% by one year, surgical treatment is recommended at diagnosis, no matter what the age and no matter what the weight. In his words, the child goes for surgery exactly at diagnosis.

Truncus arteriosus: surgery in the newborn period

In truncus arteriosus there is a VSD and a single trunk artery leaving the heart, which gives rise to both the pulmonary arteries and the aorta. The lungs receive unrestricted flow at systemic pressure from birth.

Untreated mortality is high: only about 50% of babies survive the first month of life, and only about 30% survive beyond three months. Survival after surgery is reasonably good. As with TAPVR, the comparison is one-sided, and surgery is recommended exactly at diagnosis: if the child is a newborn, surgery is done in the newborn period.

Pulmonary atresia and single ventricle conditions

Dr. Srivastava placed pulmonary atresia and single ventricle conditions in the same group as TGA, TAPVR, coarctation and truncus: treatment starts at diagnosis. For these conditions the first step is often a palliative procedure to secure a reliable supply of blood to the lungs, followed by staged operations over the first years of life.

Early recognition is the bottleneck

None of these timings helps a baby who is diagnosed late. Several of the conditions in this article lower a newborn's oxygen saturation from the first days of life, and TGA in particular can be picked up with a pulse oximeter before the baby looks unwell. Dr. Srivastava's recommendation to referring doctors was to make oxygen saturation measurement routine at birth, at one month and at six months, and to refer any low reading for echocardiography early. His views on late presenters, operability and continued medical care are set out in the guide to timing congenital heart surgery, and the acyanotic defects, including VSD and AV canal defects, in ASD, VSD, AV canal, PDA and coarctation: the right age for surgery. The full question on TGA with LVOT obstruction is in the live discussion from this masterclass.