Acute-Hypoxemia-Induced Right-To-Left Shunting in the Presence of Patent Foramen Ovale

Patent foramen ovale (PFO) is a common congenital abnormality of the heart. It results from incomplete closure of foramen ovale that persists in adulthood. Most individuals with PFO are asymptomatic and are discovered incidentally. The left atrial pressure is generally higher than the right atrial pressure, which prevents blood flow against the gradient; however, any medical condition that increases the pulmonary artery pressure can lead to reversal of blood flow from right to left by elevating right atrial pressure. We present a case of a 59-year-old female who presented with complaints of shortness of breath associated with bilateral lower-extremity edema and was found to have acute decompensated heart failure and atrial fibrillation. Transesophageal echocardiogram (TEE) with cardioversion was performed. Propofol was given for conscious sedation; however, the procedure was terminated as patient became hypoxemic and was noted to have moderately dilated right ventricle (RV) with hypokinesia and PFO with right-to-left shunting. It also demonstrated mild mitral regurgitation, mild left ventricular hypertrophy, and a left ventricular ejection fraction of 55-60%. In contrast to TEE findings, while the patient was having normal oxygen saturation, transthoracic echocardiogram showed left-to-right shunting instead of right-to-left and no RV hypokinesia was noted. In conclusion, this case draws attention to the relationship between acute hypoxemia and right-to-left shunting in a patient with PFO. This case illustrates and highlights the need for more prospective studies to establish a relationship between acute hypoxemia and right-to-left shunting in the presence of PFO.