The Paradoxical Protector: A Stretched Patent Foramen Ovale in Severe Pulmonary Arterial Hypertension and Right Heart Failure in an Adolescent — A Case Report

Abstract

Introduction: In severe pulmonary arterial hypertension (PAH), a small interatrial communication identified on echocardiography is frequently misinterpreted as the congenital lesion responsible for the disease. Physiologically, however, such a communication may function as a right atrial decompression pathway. The distinction is decisive, because closure of a decompressing shunt may precipitate fatal right heart failure. Case report: A 17-year-old undernourished girl (weight 30 kg, height 140 cm; BMI 15.3 kg/m²) with pulmonary tuberculosis diagnosed in November 2024 and treated until May 2025 presented with a one-month history of progressive dyspnoea, abdominal distension and bilateral leg oedema, with acute worsening one day before admission. Examination revealed central cyanosis (SpO2 89% on room air), tachypnoea, cardiomegaly, a grade 4/6 systolic murmur at the fourth left parasternal intercostal space, fixed splitting of S2, bibasal rales, ascites and pitting oedema. Laboratory tests showed microcytic hypochromic anaemia, hyponatraemia (128 mmol/L), severe hypokalaemia (2.6 mmol/L), hypochloraemia and hypoalbuminaemia. Electrocardiography demonstrated sinus tachycardia, right atrial enlargement and right ventricular hypertrophy with strain. Chest radiography and computed tomography showed cardiomegaly, pulmonary congestion, bilateral pleural effusions, pneumonia and ascites. Transthoracic echocardiography revealed right atrial and right ventricular dilatation, a small left ventricle with preserved ejection fraction (67%), severe tricuspid regurgitation (gradient 46 mmHg; estimated peak velocity ≈3.4 m/s), TAPSE 17 mm, a dilated main pulmonary artery and a small interatrial communication at the fossa ovalis. Treatment comprised intravenous furosemide, spironolactone, digoxin, sildenafil, beraprost, ceftriaxone and supportive measures; no septal intervention was undertaken. Discussion: The size of the defect was disproportionate to the severity of pulmonary vascular disease. The clinical and echocardiographic profile is most consistent with group 1 pulmonary hypertension, either idiopathic PAH with a coincidental patent foramen ovale (PFO) or PAH with a small, coincidental defect, in which right atrial hypertension has stretched the foramen ovale open. The communication therefore represents a consequence rather than a cause of the disease and is not haemodynamically significant congenital heart disease. By permitting right-to-left decompression, it may help preserve left ventricular preload and systemic output at the expense of hypoxaemia. Current guidelines consider closure of such defects contraindicated. Post-tuberculous lung disease and a post-capillary component must nevertheless be excluded by right heart catheterisation and targeted investigations. Conclusion: A small interatrial communication in an adolescent with severe PAH and right heart failure should be interpreted as a potential “paradoxical protector” and managed as idiopathic PAH with risk-guided targeted therapy, correction of electrolyte and iron disturbances, and referral to a pulmonary hypertension centre. Closure should be avoided.