SLC9A1 and hydrops fetalis: In tissue samples from human patients, NHE1 was found to be expressedmore abundantly in atrial myocytes isolated from patients with HFpEF and atrialfibrillation, as well in atrial and ventricular myocytes isolated from patientswith end-stage HF, which may be due to a greater impairment in atrial contractilefunction in patients with atrial fibrillation and globally impaired contractilityin patients with end-stage HF [115].