Discussion
In patients with PA, VSD and SPCAs several strategies are reported during the last 30 years indicating the challenging management [2, 13-16]. In 1989 we choose to follow one strategy for all consecutive patients and have sticked to this protocol since then. This allows to present after 30 years our long term results showing that 81% of the patients surviving after unifocalization are suitable for biventricular correction with a conduit between RVOT and the unifocalized pulmonary artery system. We consider this an adequate success rate in the complete and unselected cohort of these complex patients also compared to other series and strategies [2, 14, 17-21]. The use of a central aorto-pulmonary shunt to promote growth in diminutive pulmonary arteries is still subject of several studies [15, 22]. In a preliminary report of our first six cases we concluded that central shunts did not preclude the need for unifocalization with no significant growth of the pulmonary arteries [23].
Over the years of working with the staged approach several aspects evolved. We reduced the diameter of the MBT shunts during our experience. We learned to avoid as much tissue of the SPCAs as possible. Closure of unnecessary collateral arteries and intrapulmonary anastomoses are two factors to prevent later problems with stenosis or dilatation. Nevertheless these problems do occur due to the histological characteristics of the collateral arteries [10]. During follow up several dilatation and stenting procedures may be necessary and in some cases adequate relieve of stenosis cannot be maintained at the long term.
After our initial experience with central shunts with disappointing results with regard to growth and increase of the pulmonary artery size [23] we use these procedure for diminutive pulmonary arteries to promote outgrowth as mentioned by other authors [24, 25]. In our opinion rehabilitation of the pulmonary artery as promoted by several authors [15, 26, 27] may be useful, but still does not preclude further unifocalization in most of our cases.
During long term follow up allograft degeneration and replacement occurred as expected. An explanation for this could be that these allografts are placed in a more extra-anatomic position and in patients with a younger mean age at correction. Also elevated right ventricular pressures, probably due to an abnormal pulmonary vascular bed, can contribute to this degeneration process [28].
Considering the complex patient group we realize that there life expectancy is below normal, but we lack long term data comparable with other with right-sided allograft placement i.e. tetralogy of Fallot [29].
A limitation of this study is the relatively small group of patients. However we treated all cases consecutively and without selection during a long period of time with the same strategy by the same team. Because of these numbers we did not perform sub analysis for example for patients operated later on after our learning curve.
In conclusion staged repair of PA, VSD and SPCAs offers an adequate solution for most patients with a high correction rate and low operative mortality. Surgical or catheter interventions are necessary during follow up for pulmonary artery stenosis and allograft degeneration. Long term survival seems to be diminished.
We continue to follow these patients to achieve more data on long term outcome. The function of the right ventricle is a point of concern Echocardiography and cardiac MRI showed moderate and severe dilatation of the right ventricle (75%) and impairment of the function in 25% of the patients. Additional genetic abnormalities, in particular 22q11 deletion seems to be risk factor for adverse outcome[30].
Another limitation is the retrospective collection of data which resulting in incomplete data on exercise testing and quality of life studies. We are also looking forward to compare our long term results to those of other strategies, to make better comparison between different methods for this challenging patient group.