A partial atrioventricular canal defect (PAVCD) is a form of endocardial cushion defect. It’s a rare congenital cardiac malformation, few reported patients have survived into the seventh decade of life. A 71-year-old female with a history of diabetes and hypertension was admitted for heart failure (HF) symptoms. Transthoracic echocardiography revealed a left to right shunt in the basal portion of the interatrial septum, 19mm ostium primum atrial septal defect (ASD), a mitral valve cleft, and severe mitral valve regurgitation. PAVCD consists of an ostium primum ASD and the dividing of the common atrioventricular (AV) valve into 2 separate AV orifices, resulting in a so-called cleft in the mitral valve. The ventricular septum is intact. Echocardiography is the key tool for diagnosis and anatomic classification. Surgical repair is recommended in adults with primum ASDs causing impaired functional capacity, right atrial or right ventricular enlargement, and left-to-right shunt without cyanosis, as long as systolic pulmonary artery pressures are lower than 50% of systemic pressures. Reconstructive surgery includes, in addition to the closure of the interatrial septum, a suturing of the mitral cleft. The estimated mean age at death of the patients with ostium primum ASD is about 40 years. The objective of this clinical case is to highlight the good clinical tolerance of atrial shunts and the anatomical particularities in the PAVCD.