Case Presentation: A 49-year-old man with known history of class III obesity (body mass index 43), hypertension, hyperlipidemia, and insulin dependent diabetes presented to the emergency department with bilateral lower extremity swelling and dyspnea on exertion of two weeks duration. Pertinent vitals included blood pressure 161/74 mmHg, heart rate 99 beats per minute, and saturation of 95% on 5 liters nasal cannula. Physical exam was unremarkable. Labs were notable for brain natriuretic peptide 305.8 pg/mL and troponin of 0.96 ng/mL. Electrocardiogram (ECG) showed normal sinus rhythm with incomplete right bundle branch block (iRBBB). Transthoracic echocardiogram revealed a dilated right atrium (RA), dilated right ventricle (RV) with reduced systolic function and moderate pulmonary hypertension (57 mmHg). The left ventricular (LV) size, systolic, and diastolic function were normal. Chest Computed tomography angiography was negative for pulmonary embolism. Right heart catheterization was performed to confirm the diagnosis of pulmonary hypertension however, during the procedure, after advancement of the catheter from the RA, pressure tracing and oxygen saturation were consistent with LV physiology. There was no RV pressure tracing noted during catheter pullback and a large interatrial shunt was suspected. A subsequent transesophageal echocardiogram (TEE) revealed a large, 2-centimeter sinus venosus atrial septal defect (ASD) located at the junction of superior vena cava and RA with left-to-right shunting. Patient was then referred for sinus venosus ASD repair.

Discussion: Herein, we present the case of a patient with class III obesity found to have right atrial dilatation and right ventricular dilatation with reduced systolic function secondary to sinus venosus ASD. Due to the patient’s body habitus, the leading diagnosis was severe obstructive sleep apnea and obesity hypoventilation syndrome with subsequent cor pulmonale. Atrial Septal Defects are often asymptomatic until adulthood and must be considered in the setting of right atrial and right ventricular dilatation with reduced systolic function. Ostium secundum and ostium primum are the two most common types of ASD and can be definitively evaluated by TTE. Although TTE is the initial diagnostic imaging modality, detection rates have been as low as 12% for sinus venosus defects due to their posterior location, thus TEE should be pursued [1]. TEE is also helpful in identifying partial anomalous pulmonary venous return which frequently accompanies superior venosus defects [2]. Timely diagnosis is important, as in uncorrected older patients, severe pulmonary hypertension with shunt reversal, Eisenmenger syndrome, may develop, at which point ASD repair would no longer be indicated.

Conclusions: Isolated Right heart dilatation with reduced systolic function has several potential etiologies. In addition to valvular disease and cor pulmonale, evaluation for atrial septal defect also needs to be performed. In the absence of Ostium primum and secundum defects or significant valvular disease on TTE, additional imaging must be pursued to evaluate for ASD. In unexplained dilatation of the right side of the heart on TTE, TEE should be undertaken in order to evaluate for either sinus venosus or coronary sinus ASD [3].

IMAGE 1: TEE: LA = left atrium; RUPV = right upper pulmonary vein; IAS = interatrial septum; RA = right atrium; ASD = atrial septal defect.