| Keywords [eng] |
Congenital heart disease, Eisenmenger syndrome, Pulmonary arterial hypertension, Haemodynamic progression, Pulmonary vascular resistance, Shunt physiology, CircAdapt, Computational modelling |
| Abstract [eng] |
BACKGROUND: Congenital heart defects causing left-to-right shunting (atrial septal defects [ASD], ventricular septal defect [VSD], patent ductus arteriosus [PDA]) drive progressive pulmonary vascular disease culminating in Eisenmenger syndrome. Current clinical assessment relies on hemodynamic thresholds but does not capture dynamic progression toward irreversibility. AIM: To characterise how defect size, location, chronic adaptation, and rising pulmonary vascular resistance (PVR) shape haemodynamics behaviour and drive progression toward Eisenmenger physiology using computational simulation. METHODS: CircAdapt was applied to ASD, VSD, and PDA (5–25 mm diameters). Simulations were performed in three stages: acute response, chronic adaptation, and stepwise PVR elevation representing mild-to-severe pulmonary arterial hypertension. Key outputs included: pulmonary-to systemic flow ratio (Qp/Qs), mean pulmonary arterial pressure (mPAP), the ratio of pulmonary to systemic vascular resistance (PVR/SVR), the ratio of mean pulmonary arterial to mean systemic arterial pressure (mPAP/MAP). RESULTS: Defect size demonstrated a non-linear relationship with Qp/Qs and mPAP; greatest changes occurred between 5–15 mm. At identical diameters, both parameters increased stepwise from ASD to VSD to PDA. Chronic adaptation amplified pressure responses whilst Qp/Qs remained modestly attenuated. Under progressive PVR elevation, mPAP rose disproportionately relative to Qp/Qs decline; PVR/SVR and mPAP/MAP approached systemic equivalence whilst left-to-right shunting persisted. DISCUSSION: Defect location determines haemodynamic phenotype, establishing pressure burden from ASD to PDA independent of size. Chronic adaptation increases the pressure cost of shunt flow without resolving the load. Haemodynamic indices approach systemic levels before shunt reversal, indicating that irreversibility precedes flow reversal and that shunt direction alone is insufficient. mPAP/MAP is proposed as a complementary pressure convergence marker. CONCLUSION: Progression to Eisenmenger physiology follows a structured, lesion-specific trajectory. Combined assessment of PVR, PVR/SVR, Qp/Qs, and mPAP/MAP may more accurately reflect disease trajectory than any single parameter. |
