Pulmonary atresia with “intact ventricular septum” associated with a ventricular septal defect: An apparent paradox?

Introduction

Pulmonary atresia with intact ventricular septum (PA-IVS) means pulmonary valvar atresia without a ventricular septal defect (VSD). In PA-IVS, the right ventricle (RV) appears externally normal in size but the internal cavity is hypoplastic with major wall hypertrophy. Histology reveals myocardial disarray and endocardial fibroelastosis. The leaflets of the pulmonary valve are present but fused indicating an acquired lesion during fetal life.

Methods

The files of all children with PA-IVS in our institution between 1981 and 2023 were reviewed, using a data warehouse to look for associated VSD. Patients with Ebstein anomaly and pulmonary atresia were excluded. When available, echocardiographic examinations were reviewed. One patient had severe coronary arterial anomaly leading to death and autopsy.

Results

The total cohort included 300 consecutive patients. Among those, we found 8 children with an associated VSD (2.6% of the cohort). According to the IPCCC-ICD11 nomenclature, the VSD was central perimembranous in 3, muscular in 4, outlet in 1. In this last patient, autopsy revealed a hypoplastic but not malaligned outlet septum, without aortic overriding, which discarded the diagnosis of tetralogy of Fallot (Fig. 1).

Conclusion

Paradoxically, the presence of a VSD is compatible with diagnosis of PA-IVS. This rare association cannot be classified as “PA-VSD”: this last term should be reserved to extreme forms of tetralogy of Fallot, associating outlet VSD, anteriorly malaligned outlet septum, overriding aorta and PA. Conversely, PA-IVS may be due to a RV myocardial disease, leading to a diminutive RV cavity, tricuspid valve hypoplasia and progressive fusion of the pulmonary leaflets leading to atresia. The anatomic type of VSD, muscular and perimembranous, and their rarity, are in favor of an incidental association. The imprecise term “PA-IVS” does not reflect the defect's anatomy and pathogenesis. It should then be modified, as it is crucial to use an accurate terminology to better describe congenital heart defects.