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Changes in pulmonary artery size before and after total cavopulmonary connection
  1. Z SLAVIK,
  2. R FRANKLIN
  1. Paediatric Surgical Unit,
  2. Harefield Hospital,
  3. Harefield, Middlesex UB9 6JH, UK

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    Sir,—We read with interest the paper of Buheitelet al dealing with the important topic of pulmonary artery size in children before and after total cavopulmonary connection.1 We congratulate the authors on their contribution to the ongoing discussion about the fate of pulmonary arteries following various forms of right heart bypass operation.2 3 However, there are several issues related to the paper that were not clear.

    In our opinion the authors do not provide enough information about the surgical techniques used in the treatment of the patients either at primary palliation or during the so called total cavopulmonary connection. We particularly miss data related to the type of systemic–pulmonary arterial shunt preceding the total cavopulmonary connection, the extent of surgical reconstruction of the central pulmonary arteries, or the use of atrial baffle fenestration. It is not clear whether the total cavopulmonary connection was done as a primary right heart bypass operation or as a completion of previous hemi-Fontan or bidirectional superior cavopulmonary anastomosis. We believe that this information is crucial if the results of this study are to be compared with other published series.4 5

    The authors studied two distinctly different groups of patients, which deserve closer analysis. The first, much younger group of patients (group I; mean age 1.5 month) had severely hypoplastic pulmonary arteries (Z score of the right and left pulmonary arteries −6.0 and −9.6, respectively) at the time of their first cardiac catheterisation. One can only assume that these patients had very low pulmonary blood flow and that they went on to have some form of initial palliation to augment pulmonary blood flow. This provided sufficient pulmonary blood flow to enhance pulmonary arterial growth to reach normal values (mean Z score 0.5 and −0.5 for the right and left pulmonary artery) although remaining below the volume of systemic blood flow. These patients underwent a total cavopulmonary connection within a mean interval of 3.34 years from the time of their first cardiac catheterisation, at the relatively young mean age of 3.46 years. This operation was followed by relatively poor pulmonary arterial growth (change of mean Z score −2.9 and −4.4 for the right and left pulmonary arteries).

    The second, older group of patients (group II; mean age 10 months) had mildly underdeveloped pulmonary arteries at the time of their first cardiac catheterisation. One is left to speculate as to the proportions of this group who had either well balanced or increased pulmonary blood flow at first assessment, and how many received initial palliation to restrict pulmonary blood flow. Subsequent assessment demonstrated pulmonary blood flow in excess of systemic blood flow and pronounced enlargement of both pulmonary arteries (mean Z score > 8.0) over a much longer period of time (mean 7.3 years) leading to the total cavopulmonary connection. The ensuing reduction of high pulmonary blood flow to more physiological levels after this definitive procedure led to an encouraging return of the size of both pulmonary arteries to close to normal values (mean Z score 2.2 and −0.7 for the right and left pulmonary arteries).

    These are certainly interesting findings, which to a certain extent support our previous conclusions6 that candidates for any Fontan-type operation will initially fall into a group with hypoplastic pulmonary arteries or a group with adequate or even larger than normal pulmonary arteries at initial assessment. This division is in most cases matched by the volume of pulmonary blood flow. The aim of subsequent palliative procedures will be different in these groups of patients. Promotion of growth of originally hypoplastic pulmonary arteries is mandatory; however, the paper of Buheitelet al appears to imply that an early total cavopulmonary connection will give a suboptimal result in terms of pulmonary arterial growth. In patients with larger than normal pulmonary arteries, the role of an early total cavopulmonary connection is not clear. The relevance of these data to clinical outcome is also far from clear and is not addressed in this paper. We support the conclusion of the authors that more information about the long term development of pulmonary arteries following Fontan-type operations is required. We look forward to the next report on their patients’ pulmonary arterial growth. However, the lack of correlation between the size of pulmonary arteries and pulmonary arteriolar resistance or clinical findings may question the value of central pulmonary arterial measurement for the long term outcome of patients after total cavopulmonary connection.

    References

    This letter was shown to the authors, who reply as follows:

    We thank Drs Slavik and Franklin for their interesting comments on our study. To answer the questions raised in their comment we provide some additional information.

    We agree that possible candidates for a later Fontan-type operation can be divided initially into patients with diminished pulmonary blood flow and rather small pulmonary arteries, and patients with adequate or increased pulmonary blood flow and normal or even larger than normal pulmonary arteries. As we did not perform complete haemodynamic studies in all children at the time of initial cardiac catheterisation (especially in children with duct dependent pulmonary circulation), we were unable to provide information about Qp/Qs in all our children in the neonatal period or in early infancy. We decided not to include this incomplete information in our study and rather preferred to divide our patients into two groups based on the findings of the complete haemodynamic assessment before the total cavopulmonary connection.

    In group I (patients with Qp/Qs ⩽ 1) nine of 16 children had one, four of 16 had two, and only three of 16 children had no palliative procedure before the creation of the total cavopulmonary connection. The palliative procedures included 11 systemic–pulmonary artery shunt procedures (using Goretex prostheses), three bidirectional cavopulmonary shunt procedures, two atrial septectomies, and only one pulmonary banding. Among children of group II (Qp/Qs > 1 before total cavopulmonary connection) 10 of 16 patients had one, three of 16 had two, and three of 16 had no palliative procedure. These palliative procedures included eight systemic–pulmonary artery shunts, one atrial septectomy, and seven pulmonary bandings.

    The total cavopulmonary connection was performed using an intra-atrial tunnel without fenestration in all patients. Together with the total cavopulmonary connection, patch enlargement of a central pulmonary artery stenosis had to be performed in both groups with an equal frequency and therefore should have no major influence on our results (four children of group I and three children of group II). In 29 of 32 patients the total cavopulmonary connection was performed as a primary right heart bypass operation, in three of 32 (all group I) it was done as a completion following a bidirectional Glenn procedure.

    Our study aimed to give a description of the behaviour of pulmonary arterial size following total cavopulmonary connection. We emphasise that the decrease in pulmonary artery size found during medium term follow up should not be interpreted as a lack of pulmonary artery growth. As we pointed out in our paper, there was turbulent flow in the central pulmonary arteries in almost all our patients before total cavopulmonary connection (with the exception of the three children who underwent a prior bidirectional Glenn anastomosis). The abolition of turbulent blood flow in the central pulmonary arteries could well explain their reduction in size following total cavopulmonary connection. We certainly did not want to imply that an early total cavopulmonary connection will give a suboptimal result in terms of pulmonary arterial growth, and we have expressed this explicitly in our discussion.

    We agree completely with Drs Slavik and Franklin that presently the clinical relevance of these changes in pulmonary artery size after a Fontan-type repair remains unclear, as all our patients are in good clinical condition. Nevertheless, the growth of the central pulmonary arteries might have serious consequences on the long term outcome following a right heart bypass operation. Therefore, we believe that it is mandatory to obtain further information on the impact of a non-pulsatile flow pattern on pulmonary arterial growth. This applies particularly to children in whom a bidirectional Glenn procedure or a total cavopulmonary anastomosis is performed in infancy or early childhood. We plan a reassessment of the pulmonary arteries and the clinical condition of our patients in three to five years.

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