Discussion
The left PV obstruction caused by compression between the LA and the DA has been rarely reported 2-5,11. Previous reports demonstrate that the left lower PV is usually involved, and four out of five patients exhibited left lower PV obstruction in the present study as well. Some of the possible factors that affect the left PV obstruction caused by compression between the LA and the DA should be considered. First, the abnormally anterior location of the DA can be a cause. The left PV can be narrowed due to compression from the back by the DA located forward 2. The PV has clearly low pressure as compared to the DA. Therefore, if the anteriorly located DA passes just behind the PV, it can cause narrowing of the involved PV. Second, an enlarged LA can compress the left PV from the front in the space between the LA and the DA. This phenomenon can be observed in the heart with left-sided volume loading, such as atrioventricular valvular (AVV) regurgitation or large left-to-right shunt lesions4,5. The third possible factor can be a cardiac compression that is seen posteriorly due to chest wall deformity such as the pectus excavatum
Direct surgical repair 13-15, balloon dilatation16,17, and stent implantation 18,19can be the treatment options for the PV obstruction caused by compression between the LA and the DA. Kotani et al. reported 15 patients with left PV obstruction among 494 consecutive single-ventricular patients. The authors performed the sutureless repair in seven patients and failed to achieve the Fontan operation. Posterior aortopexy was not attempted in any of the patients 4. O’Donnell et al. reported 29 cases (1.5%) of 1995 patients who underwent hemodynamic catheterization. Of these, 26 had a left aortic arch and a left lower PV compression, and three had a right aortic arch, right-sided descending aorta, and a right lower PV compression. Nineteen of 29 patients had a single-ventricular physiology. The authors performed PV stenting in two patients who had single ventricular physiology with poor results. Other surgical interventions for relief of PV obstruction including posterior aortopexy were not performed in any of the patients 5. We had a case of successful relief from PV obstruction with a posterior aortopexy in a post-Fontan patient (patient 1). Kotani et al. reported a case of successful relief from the left PV obstruction by posterior aortopexy and plication of a redundant LA wall in a patient with the complete atrioventricular septal defect and persistent left superior vena cava. The posterior aortopexy technique for patients with PV obstruction caused by compression between the LA and the anteriorly positioned DA has several advantages as mentioned earlier by Kotani et al. 3. First, external compression of the PV by the anteriorly positioned DA could be effectively treated. Second, the posterior aortopexy technique is a less invasive procedure as compared to the intra-cardiac repair of the PV under cardiopulmonary bypass. Third, avoiding direct surgical manipulation of the PVs could prevent post-repair PV stenosis.
Using the posterior aortopexy technique we have treated five patients with left PV obstruction between the LA and the DA. In two patients (Patient 1 and 3) with focal PV obstruction that was mainly caused by the anterior location of the DA, posterior aortopexy was effectively performed. The changes in the angle between the DA and the vertebra (ㅿa) were 37 and 38, respectively. In the patients with LA enlargement caused by left heart volume loading (Patient 4 and 5), the effectiveness of the posterior aortopexy was somewhat unclear. In patient 4, the improvement in the left PV obstruction occurred immediately after the operation. This improvement can be attributed to either posterior aortopexy (ㅿa = 20) or decreased blood flow to the left lung or both of them. In the case of patient 5, posterior aortopexy was not effectively performed (ㅿa = -1). The improvement in the left PV obstruction observed in patient 5 was thought to be due to the reduction in the volume loading of the heart by the PDA ligation. Finally, in patient 2, a preoperative CTR was 0.66. The left PV obstruction did not improve after the posterior aortopexy. In this patient, diffuse left PV obstruction was observed. The immediate postoperative CTR was still 0.64, showing the cardiomegaly, and the postoperative PG across the left lower PV was 20 mmHg. The cause of the left PV stenosis could be an intrinsic diffuse PV stenosis.
Based on our experiences with the five patients, it is hypothesized that posterior aortopexy is an effective option for the management of the PV obstruction caused mainly by the anterior location of the DA in the patients without left heart volume loading. However, the effectiveness of posterior aortopexy is somewhat unclear in patients with severe left heart volume loading. A sudden decrease in left lung blood flow can mask the effectiveness of the posterior aortopexy.
Our current study has some clear limitations. It is a retrospective study investigating a small number of patients with heterogeneous heart diseases, and there were no definite operative indications for the procedure. Also, we measured the CTR to evaluate the volume loading and enlarged LA of the patients, but it is not enough to show them sometimes. Moreover, the definition of focal and diffuse stenosis is not clear. To overcome these limitations, we performed preoperative and postoperative CT angiography for all 5 patients.
In conclusion, posterior aortopexy could be considered as an effective treatment option for patients with left PV obstruction that is mainly caused by the anterior location of the DA without the left heart volume loading. In patients with large left heart volume loading, the posterior aortopexy could be recommendable in cases where PV obstruction persists even after removal of the volume loading.