Mustard Operation for TGA - Options for RV failure

Dateline: 09/14/97

In last week's article, we took a look at the intermediate term complications of a Mustard Operation for TGA. In this article, I will discuss some of the options available in case of right ventricle failure which is a common sequela of the operation.

What options are available to the patient with right ventricular failure after a Mustard Operation ?

When RV failure is severe, and not well controlled medically, two main options are available:
Heart Transplantation (or Heart-Lung Transplantation, if pulmonary vascular disease is advanced)
Conversion to an Arterial Switch

Transplantation is an entirely different issue which I will discuss in future articles.

Since transplantation is a major, expensive and uncertain option in children, alternative approaches to avoid it are attractive. Dr.Roger Mee first conceived the idea of converting a failing Mustard to an Arterial Switch Operation (ASO).

As we discussed earlier, RV failure is rather common after correction for TGA with VSD, but it also occurs in 10% of TGA without VSD. The course of RV failure is unpredictable. While in some patients, dysfunction appears relatively stable or very slowly progressive, in others it may worsen rapidly.

Tricuspid valve replacement alone in this group of patients does not have very promising results.

The only feasible option is to convert the repair to an ASO. The problem then is that the left ventricle is too weak to take over the pumping action of a systemic ventricle, and pump blood to the entire body.

In order to overcome this, the correction is done in two stages. In the first stage, a band is placed around the pulmonary artery which narrows it. As the left ventricle is now forced to pump blood against a resistance, it has to work harder, and thus becomes stronger - Hypertrophied. This usually takes longer than in newborns, and the usual waiting period is 12 to 24 months.

Once tests show the left ventricle is strong enough to take over the systemic workload, the arterial switch operation is performed, with a simultaneous removal of the atrial baffle, and closure of the communication between the atria.

The tricky decision to make is WHEN to embark on this conversion. While no verifiable data exist, it is the opinion of experts that a banding of the pulmonary artery must be considered as soon as symptoms of right ventricle failure become severe enough to require medication. This way, there is enough time available to train the left ventricle to hypertrophy, and allow a arterial switch before the right ventricle failure becomes severe enough to compromise cardiac output. Another interesting, but experimental, attempt is also being made to stimulate earlier hypertrophy of the left ventricle using chemicals like orotic acid.

While the results of this technique are still uncertain, in Dr.Mee's first series of five patients who underwent banding, and a later conversion, one died soon after surgery, two had remarkable recoveries, one had only satisfactory outcome with failing LV function, and one died late after surgery due to a rhythm problem.