ATRIOVENTRICULAR SEPTAL DEFECTS

Atrioventricular septal defects (AVSD) represent a group of congenital heart diseases characterized by abnormalities in the development of the atrioventricular plane. These conditions arise from incomplete fusion of the endocardial cushions during the embryonic stage, significantly affecting the structure and function of the heart. They are often associated with malformations of the atrioventricular valves, contributing to a complex clinical picture.

Complete Form

The complete form of AVSD is characterized by the presence of a single central atrioventricular valve that does not adequately divide to form two separate valves. This anomaly is associated with a large interventricular defect, resulting from the failure of the interventricular septum to fully close, and an atrial septal defect of the ostium primum type, due to incomplete separation of the atrial septum.

As a result, there is communication between all four heart chambers, leading to mixing of arterial and venous blood. This phenomenon causes ventricular overload and, over time, the progression of pulmonary hypertension. The clinical presentation may vary depending on the morphology of the atrioventricular valve: a balanced form allows for equal blood flow between both ventricles, while an unbalanced form favors one ventricle over the other, potentially leading to functional complications.

When the single valve is competent, the defect may mimic a large atrial septal defect, resulting in a rapid increase in pulmonary pressures and early onset of cardiac decompensation. If the valve is incompetent, ventricular-atrial regurgitation occurs, leading to more severe and early heart failure.

The treatment is exclusively surgical and involves closing the atrial and ventricular septal defects, as well as separating the single valve into two functionally competent valves. However, surgical success is not always complete: the majority of patients exhibit some degree of **residual valvular insufficiency**, although in most cases, it is mild.

Partial Form

The partial form, also known as partial atrioventricular canal, differs from the complete form in that the interventricular septum is intact, and two atrioventricular valves are present. However, a persistent atrial communication of the ostium primum type remains, resulting in a left-to-right shunt and right heart overload, with symptoms similar to atrial septal defects.

The atrioventricular valves exhibit structural abnormalities. The left atrioventricular valve, although tricuspid, often has a hypoplastic septal leaflet and a tendency toward insufficiency. The right atrioventricular valve, also tricuspid, may present anomalous divisions of the anterior leaflet, with possible regurgitation.

Clinically, findings are similar to those of atrial septal defects, with the addition of a systolic murmur due to valvular insufficiency. The electrocardiogram (ECG) shows signs of right ventricular overload, with possible incomplete right bundle branch block and anterior left hemiblock, which often persist even after surgical correction.

COMMON ARTERIAL TRUNK

The Common Arterial Trunk (CAT) is a rare congenital heart disease in which the aorta, pulmonary arteries, and coronary arteries originate from a single vessel instead of separate structures. This condition results from abnormal division of the embryonic arterial trunk, leading to significant hemodynamic consequences.

Morphologically, the arterial trunk typically overrides a ventricular septal defect, leading to mixing of arterial and venous blood. The symptomatology is dominated by peripheral cyanosis, progressive pulmonary hypertension, and the risk of early congestive heart failure. In many patients, the trunk valve has a significant insufficiency, resulting in diastolic overload of the left ventricle, with potential early heart failure episodes.

The physical examination may reveal an aortic click, a single second heart sound, and a systolic murmur at the mesocardium. Echocardiography with Doppler is the gold standard for diagnosis, allowing for the assessment of cardiac structures and blood flow dynamics. In some cases, angiography can provide additional morphological details.

The only effective treatment is corrective surgery, which involves separating the arterial trunk into its physiological components and closing the ventricular septal defect.

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