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.