An endocardial cushion defect, also known as the atrioventricular septal defect, encompasses several congenital heart disease forms of abnormal atrioventricular septation and formation of a single atrioventricular valve. Cyanosis is principally seen in milder forms, whereas congestive heart failure and even death may develop in more severe cases, especially if the condition is not recognized early on. Clinical workup and echocardiography, either prenatal or postnatal, are used to make the diagnosis.
Signs and symptoms of an endocardial cushion defect arise from a variable degree of blood shunting due to the absence of separate atrioventricular valves  . Instead, a common atrioventricular valve exists and is accompanied by a large atrial septal defect (ASD) and a ventricular septal defect (VSD), designated as complete endocardial cushion defect . On the other hand, partial (two atrioventricular orifices and the absence of an ASD) and intermediary (a markedly smaller VSD) forms have been described as well  . Regardless of the anatomical severity, initial left-to-right shunting due to increased pressures of the left heart will cause pulmonary hypertension and induce a simultaneous right-to-left shunting   . The bidirectional blood shunting in the heart is known as the Eisenmenger's syndrome, which leads to congestive heart failure in the majority of cases with a complete endocardial cushion defect . Tachycardia, tachypnea, poor peripheral circulation, feeding difficulties and excessive sweating are encountered in the first few months of life, and in the absence of an early diagnosis, 50% of infants will die during the first year of life   . In most severe cases, in whom marked regurgitation of the common AV valve and the presence of other anomalies further impede blood flow through the aorta, heart failure can develop as early as one week after delivery . Central and less commonly peripheral cyanosis are a frequent finding as well  .
Due to the life-threatening risk in the very first weeks of life, the diagnosis of an endocardial cushion defect must be made promptly. Identification of a heart murmur (most likely pansystolic, but also ejection systolic or apical mid-diastolic) during cardiac auscultation can raise sufficient clinical suspicion toward heart disease in infants and neonates, especially if accompanying symptoms are present  . For this reason, the role of a proper physical examination is vital  . Plain radiography often reveals cardiomegaly and deviation of the cardiac axis, but electrocardiography (ECG) and more importantly, echocardiography should be immediately performed, with the latter being the gold standard in confirming the presence of a congenital heart disease (CHD), both prenatally and postnatally   . Direct imaging of the heart through ultrasonography will show a common atrioventricular valve and the absence of an atrioventricular septum, defects of the ventricular septal and atrial flow, as well as bi-directional blood flow on doppler ultrasonography   . Magnetic resonance imaging (MRI) of the heart has also proven to be a useful method for assessing the cardiac anomalies seen in endocardial cushion defect . Isolated studies have confirmed a very potent relationship of this CHD with Down syndrome, suggesting that a meticulous prenatal diagnostic workup is necessary for ensuring an early diagnosis, which will allow early therapy and reduction in mortality rates  .