Right Ventricular Morphology in PA/IVS: Integrating Developmental Pathology With Echocardiographic Prognostication

The manuscript by Moras et al. [1] introduces a critical framework for individualized post-interventional care in neonates with pulmonary atresia with intact ventricular septum (PA/IVS) or critical pulmonary stenosis (CPS) by leveraging echocardiographic classification of right ventricular (RV) morphology. Their work aligns directly with the developmental understanding of RV anatomy, as outlined in the next paragraph on RV developmental pathology.

Failure of development or muscular obliteration of the apical and/or infundibular segments leads to bipartite or monopartite RVs. (Figure 1) These developmental anomalies underlie many presentations of congenital heart disease, including tricuspid or PA, and significantly influence the RV's ability to respond to decompression interventions (See Table 1)

In their study, Moras et al. classify patients into two groups based on this anatomical distinction: Group A (tripartite RVs) and Group B (bipartite RVs). This classification strongly predicted complications post-Pulmonary Valve Balloon Dilatation (PVBD): Tripartite RVs were associated with left ventricular (LV) systolic dysfunction due to volume redistribution and interventricular interaction. Bipartite RVs were prone to infundibular spasm, evidenced by dynamic outflow obstruction requiring beta-blockade.

The clinical implications of this work are profound. Moras et al. demonstrate that 92.9% of patients with tripartite RVs experienced transient LV dysfunction, necessitating inodilator therapy and prolonged ventilation. In contrast, 76.9% of bipartite RV patients exhibited infundibular spasm managed effectively with beta-blockers.

In tripartite RVs, the left ventricle often encounters a sudden increase in preload following decompression due to restored antegrade pulmonary flow. This surge in pulmonary venous return, compounded by ventricular interdependence and an under-conditioned LV, can result in transient systolic dysfunction. The LV may be particularly susceptible if it was relatively underloaded in utero. These physiologic shifts necessitate early initiation of inodilator therapy, cautious fluid management, and delayed enteral feeding until hemodynamic stability is achieved [2].

By individualizing care based on early echocardiographic findings, outcomes may improve, and unnecessary interventions may be avoided.

In addition to phenotype-specific care, our knowledge of RV developmental pathology adds valuable context comparing transcatheter RV decompression with open-heart surgical strategies. Although transcatheter approaches offer minimally invasive access with the potential to promote RV growth, high reintervention rates and unsuitability for RV-dependent coronary circulation limit their use in certain morphologies. Open-heart surgery remains a viable, though more invasive, option with potential for definitive repair in select cases, typically RV-dependent coronary circulation and non-trabeculated or monopartite RV [3].

This dichotomy further reinforces the need for developmental and anatomical considerations in early decision-making. Understanding which RV segments are present prenatally or at birth may help anticipate whether a patient can achieve a biventricular repair or is destined for single-ventricle palliation.

The contribution by Moras et al. elegantly merges echocardiography with developmental anatomy to guide real-time neonatal care. As our understanding of RV morphogenesis advances, so too must our strategies to support these vulnerable infants.

These extensions could lead to a new era of precision neonatal cardiology—one grounded in the biology of development and expressed through the lens of bedside diagnostics (See Table 2)

Lastly, here is a table summarizing various echocardiographic methods to measure the RV function, which can be used in congenital heart disease, too. Unlike postnatal imaging, fetal echocardiography faces unique challenges, including limited views, high fetal heart rate, and absence of standardized RV pressure/volume measurements [4].

The author declares no conflicts of interest.