Fontan Physiology without Surgery: A Hemodynamic Paradox in RV Endomyocardial Fibrosis

Abstract Endomyocardial fibrosis (EMF) is a form of restrictive cardiomyopathy that often involves the right ventricle (RV). In rare cases, advanced RV EMF can mimic the hemodynamics of surgically created Fontan circulation, a phenomenon known as acquired Fontan physiology. We report the case of a 48-year-old female with features of right heart failure. Echocardiography showed the features of RV EMF. Doppler echocardiography showed continuous pulmonary artery flow throughout systole and diastole. Hemodynamic catheterization revealed elevated right atrial pressure (mean 20 mmHg) and near-equalization of RV diastolic and systolic pressures. The mean pulmonary artery pressure was 18 mmHg, consistent with low-resistance passive pulmonary flow. The patient’s findings fulfill the hemodynamic criteria of Fontan physiology – elevated systemic venous pressure, low pulmonary vascular resistance, and nonpulsatile pulmonary flow – in the absence of surgical intervention. Similar cases have been reported in advanced EMF and isolated RV cardiomyopathy.