Pulmonary atresia with an intact ventricular septum
Pulmonary atresia with an intact ventricular septum (PAIVS) constitutes a rare cardiac condition with a reported frequency of 1 in 22.000 pregnancies that accounts for approximately 2-3 % of all CHDs prenatally61. Although progression of severe PS and subsequent development of PAIVS during fetal life have been documented, studies on cardiac morphogenesis have suggested that this anomaly might occur shortly after cardiac septation. In contrast, pulmonary atresia with a ventricular septal defect (PAVSD)—also classified as a complex variant of tetralogy of Fallot—evolves shortly after partitioning of the conotruncus before closure of the ventricular septum62,63. Nevertheless, the exact pathomechanisms of PAIVS are not well understood to date. This may also be related to the striking heterogeneity of the size and physiology of the RV, the morphology of the tricuspid valve, the degree of valvular insufficiency and the presence of ventriculocoronary connections (VCCs)/fistulae. These morphological features dictate classification into Type I-III PAIVS. The pulmonary valve is usually imperforate, the ventricular septum is intact, and the pulmonary blood flow is maintained by a retrograde filling via a patent ductus arteriosus. In the vast majority of cases, the cardiac dimensions have changed into a massively enlarged heart with a hugely dilated right atrium due to retrograde jet across the insufficient TV, as displayed in figure 5 (wall-to-wall heart). This condition can subsequently lead to relevant compression of the lungs.
For further delineation of the disease with regard to postnatal outcomes, different scoring systems based on different predictive echocardiographic markers have been introduced61,64. A very recent retrospective cohort study revealed that cardiac parameters such as the RV-to-LV length ratio ≤ 0.6, TR < 2 m/s, and the presence of VCCs were significantly associated with a univentricular postnatal outcome62. The semiautomatic approach allows exact alignment of the cardiac diagnostic planes and precise calculation/assessment of predictive markers. The heart assessed in figure 5 had severe tricuspid regurgitation and no signs of ventriculoarterial circulation, which is in line with previous reports65.