Bronchopulmonary Dysplasia Complicated by Pulmonary Hypertension and Pulmonary Vascular Disease: a Case Report and Literature Review

Technical Summary: Bronchopulmonary Dysplasia Complicated by Pulmonary Hypertension and Pulmonary Vascular Disease

Problem Statement
Bronchopulmonary dysplasia (BPD) complicated by pulmonary hypertension (PH) and pulmonary vascular disease (PVD) represents a severe cardio-pulmonary phenotype in preterm infants associated with high mortality. While advances in neonatal care have improved survival rates for extremely preterm infants, the incidence of BPD remains stable, and its pathophysiology has evolved to include arrested lung development, impaired alveolarization, and vascular abnormalities. A critical clinical challenge is the heterogeneity of BPD-PH; there is no uniform therapeutic solution because the underlying pathophysiology varies significantly between patients. Specifically, the mechanisms driving cardiovascular remodeling in BPD-PH, particularly those involving the left heart and pulmonary veins, remain under-recognized. Standard treatments, such as pulmonary vasodilators, may be ineffective or harmful if the PH is driven by post-capillary mechanisms (e.g., pulmonary venous obstruction) rather than pre-capillary vascular remodeling.

Methodology
This study presents a single case report of a female infant born at 28 weeks gestation with a birth weight of 1100 grams. The infant developed severe BPD and PH. The clinical course was monitored through:

• Longitudinal Clinical Assessment: Tracking respiratory status, ventilation requirements, systemic blood pressure, and response to therapies (including surfactant, ibuprofen for PDA, dexamethasone, inhaled nitric oxide, and sildenafil).
• Imaging and Diagnostics: Serial chest radiographs (Days of Life [DOL] 1, 7, 15, and 55) and echocardiograms (including a targeted neonatal echocardiogram on DOL 55) were utilized to assess lung parenchyma, cardiac structure, and hemodynamics.
• Laboratory Analysis: Monitoring of inflammatory markers (C-reactive protein), blood counts, and blood cultures.
• Comparative Observation: The clinical outcome of the patient was compared with her monozygotic twin sister to assess the relative contributions of genetics versus environmental factors.
• Literature Review: The case findings were contextualized against existing literature regarding BPD phenotypes, PVD, and pulmonary hypertension management.

Key Results

• Clinical Presentation: The infant required prolonged mechanical ventilation, exhibited tracheomalacia, hypercapnia, hypoxemia, and unexpectedly high systemic blood pressure (>97th percentile).
• Cardiovascular Findings: Initial echocardiograms showed a patent ductus arteriosus (PDA) and patent foramen ovale (PFO) with left-to-right shunts but no structural anomalies. However, on DOL 55 (36+4 weeks postmenstrual age), a new finding emerged: an abnormal linear echo in the left atrium, suggestive of a pulmonary vein ridge and raising suspicion of cor triatriatum.
• Hemodynamic Profile: The patient developed severe PH (estimated pulmonary artery pressure of 70 mmHg) and was refractory to inhaled nitric oxide and oral sildenafil.
• Pathophysiological Trajectory: The authors propose a specific mechanism: a prolonged, large left-to-right PDA shunt led to increased pulmonary blood flow, causing marked volume and pressure overload on the left atrium. This resulted in left atrial enlargement and remodeling (potentially cor triatriatum), leading to possible pulmonary vein stenosis and post-capillary PH.
• Outcome: The patient died on DOL 61 after treatment was suspended. In contrast, the monozygotic twin had a favorable respiratory outcome, suggesting environmental factors played a dominant role in this case's severity.

Key Contributions

• Identification of a Novel Phenotype: This report describes, to the authors' knowledge, the first instance of acquired left atrial anatomical abnormalities (specifically cor triatriatum or pulmonary vein ridge) in a patient with established BPD.
• Pathophysiological Insight: The study highlights a specific "systemic hypertension-associated" phenotype of BPD-PH. It elucidates a pathway where prolonged PDA shunting causes left heart dysfunction and left atrial remodeling, leading to pulmonary venous congestion and post-capillary PH.
• Therapeutic Implications: The case demonstrates that pulmonary vasodilators (e.g., nitric oxide, sildenafil) may be ineffective or contraindicated in BPD-PH driven by pulmonary venous obstruction or left heart disease. The authors suggest that management should focus on afterload reduction (e.g., ACE inhibitors/ARBs), optimizing lung volume, and considering surgical or transcatheter closure of the PDA if pharmacological closure fails.

Significance and Claims
The paper claims that this case enriches the understanding of the phenotypic spectrum of BPD complicated by PH and PVD. By identifying left atrial remodeling as a specific cardio-pulmonary phenotype, the authors argue for the necessity of individualized therapeutic strategies based on underlying pathophysiology rather than a one-size-fits-all approach. The study emphasizes that early detection of cardiovascular remodeling and pulmonary venous obstruction is critical, as these conditions alter the hemodynamic profile and response to treatment. The authors conclude that comprehensive evaluation of phenotype and pathophysiology is essential for enabling physiology-guided decision-making in the management of severe BPD-PH.