Congenital transposition of the great arteries (TGA) is one of the most common serious congenital heart defects. In TGA, the pulmonary circulation and the systemic circulation run in parallel. As a result, the body and its organs are not adequately supplied with oxygen.

Until the 1970s, most children born with this condition died as a result. Today, the heart defect can be corrected so well that more over 90 percent of patients reach adulthood.

As a recent study confirms, this is also true when TGA is accompanied by a ventricular septal defect (VSD) and a narrowing of the left ventricular outflow tract (LVOTO).

"We refer to this triple constellation as a complex TGA," explains study leader Professor Fabian Kari from the European Children's Heart Center in Munich. Complex does not mean difficult, says the pediatric heart surgeon: "It simply means that there are other organ changes as well. A TGA without a VSD can be even more difficult. A VSD often gives newborns a better chance of survival because it ensures that more oxygen-rich blood can reach the circulatory system."

Challenging Combination

However, a complex TGA poses special technical challenges for cardiac surgery. Several corrective steps are required to ensure that the body and all its organs are adequately supplied with oxygen and nutrients:

"Either we have to redirect the deoxygenated blood so that it can be enriched with oxygen, or we have to switch the arteries to the anatomical correct position, as is common practice today. The goal of both surgical methods is, that the pulmonary and systemic circulations work "in series" again. The VSD is closed with a patch of pericardium or synthetic material. And the constriction in the outflow tract of the left ventricle has to be removed," explains Professor Fabian Kari.

All this can be done very well today. "We see the improvement immediately after the surgery, even in the intensive care unit. The little patients really blossom.”

When the Hole is Too Far Away

Surgical procedures have become much more sophisticated since the 1970s. But none of the procedures is trivial. "Every heart is different and every complex TGA has its own anatomy," says Professor Fabian Kari.

For example, the exact location of the VSD plays an important role. It can be located either directly under the aorta (subaortic) or under the pulmonary artery (subpulmonary) or in the middle under both great vessels (double-committed).

"It is unfavorable if the hole is too far away from the two large arteries and therefore does not create the ideal short-circuit connection. In technical terms, this is known as a "non-committed" VSD. This is very rare, but it requires special surgical management and appropriate pediatric cardiology support," says Professor Fabian Kari.

Which Procedure is Best and When?

But what happens in the long term after a successful initial correction? This is a question that concerns the heart surgeon and his colleagues. "We still know too little about the long-term results of our work," says Professor Fabian Kari. Various problems that can arise are known, including with the Rastelli procedure.

"The procedure is the gold standard for complex TGA. A tunnel is created in the left ventricle to connect it to the aortic valve and the ascending aorta," he explains. But there is a catch: "If the VSD is too far away, we need a longer and more complex tunnel. This is associated with an increased risk of a renewed narrowing of the left ventricular outflow tract. In the long run, it could also lead to leaks in the baffle used to "tunnel".

Long-term Study Provides Important Clues

As part of a long-term study, Professor Fabian Kari and his research team have, for the first time, investigated the outcome of the different surgical procedures for complex TGA with such a non-committed VSD after twenty years.

The aim was to find out which procedure has the best long-term results and whether there is a particularly favourable time for correction.

Data from the National Registry for Congenital Heart Defects were used over a 20-year period to determine survival, reoperation rates, and reinterventions for new LVOTO, recurrent VSD, or complications due to a leaky baffle.

Medical Data from 14 Heart Centers

The medical data to study the course of disease in TGA associated with non-committed VSD and LVOTO were obtained from 47 patients treated between 1984 and 2020 at one of 14 different German heart centers: Berlin, Dusseldorf, Erlangen, Freiburg, Hamburg, Hanover, Homburg, Kiel, Leipzig, Lübeck, Munich, Rostock, Sankt Augustin (near Bonn), and Tübingen.

Nine patients (19 percent) had their first corrective surgery as newborns, 21 (45 percent) as infants, and 17 (36 percent) as toddlers.

Encouraging Results With a Small Caveat

"Irrespective of the time of the operation and the surgical procedure, the twenty-year survival rate was encouragingly high at over 90 percent," summarizes Professor Fabian Kari. He cautions, however, that minimal bias cannot be ruled out: "Fortunately, this rarely happens nowadays: It is only when a child dies that many parents are understandably reluctant to continue participating in the registry. It is therefore conceivable that some of the data on deaths did not reach us."

Rastelli Surgery Often Requires Repeat Surgeries

The overall analysis of the three factors survival rate, reoperation rate, and follow-up operation rate also showed hardly any significant differences between the arterial switch operation, the Rastelli operation, and the atrial reversal operation (according to Senning or Mustard). "Measured by the endpoint consisting of all three factors, all procedures performed satisfactorily in the long-term follow-up," says Professor Fabian Kari.

However, most patients cannot avoid repeated surgery. This was also demonstrated by the results of this study. Only around one-third of the patients with non-commited VSD (30 percent) remained free of repeat procedures at the end of the twenty-year observation period. "Reoperations were slightly more frequent with the Rastelli procedure, mainly due to recurrent VSDs, LVOTO, or a leaking baffle," explains Professor Fabian Kari.

Excellent Long-Term Results with Neonatal Arterial Switch Surgery

In contrast, the results of arterial switch surgery, which is increasingly performed in newborns, are excellent. However, "the anatomy and location of cardiac malformations do not always allow for arterial switch surgery. The Rastelli procedure also produces solid results in non-committed VSDs.

Since this procedure can only be performed between the ages of six and twelve months when the circulation is "balanced," the time until surgery must be bridged with palliative treatment to ensure that sufficient oxygenated blood is transported throughout the body. We have seen that this bridging has no negative effect on the long-term outcome," says Professor Fabian Kari.

Atrial switch surgery, on the other hand, should only be used if nothing else is possible for medical and anatomical reasons. "It carries significant risks of complications, as the right ventricle is not designed to maintain the entire body’s circulation in the long term."

Registry-Based Research is Essential

For more than two decades, the National Registry for Congenital Heart Defects has been continuously collecting the data and samples required for such multi-center, long-term studies. The samples are collected from heart centers, clinics, and doctors' offices throughout Germany following patient's consent.

"The diversity of a TGA alone makes this necessary. Registry-based research is essential. In the case of congenital heart defects, we are talking about numerous different diagnoses with a large variance. This raises many pressing questions about optimal treatment, even in the long term," says Professor Fabian Kari.

Research like this is already helping to improve medical care. This ultimately leads to a better quality of life for patients and their families and reduces the risk of premature death from the consequences of a congenital heart disease.