bubble_chart Overview

Atrioventricular canal defect is a complex congenital heart disease with inconsistent naming to date, also referred to as endocardial cushion defect, common atrioventricular canal, or atrioventricular septal defect. This condition accounts for approximately 3% of congenital heart diseases and is classified into: ostium primum atrial septal defect; partial atrioventricular canal defect, which includes not only an ostium primum atrial septal defect but also a cleft in the anterior mitral leaflet, with possible varying degrees of tricuspid valve dysplasia; and complete atrioventricular canal defect, where an ostium primum atrial septal defect is accompanied by a ventricular septal defect, combined with clefts in both the anterior mitral leaflet and the septal tricuspid leaflet, forming anterior and posterior common atrioventricular valves.

bubble_chart Clinical Manifestations

1. Symptoms of ostium primum atrial septal defect include grade I palpitations and shortness of breath after activity, along with frequent respiratory infections. In partial and complete atrioventricular canal defects, these symptoms appear earlier, often during infancy and childhood, with rapid disease progression leading to early cardiac enlargement and severe pulmonary congestion.
2. Affected children exhibit delayed growth and a bulging chest. Apart from ostium primum atrial septal defect, a blowing systolic murmur can be heard at the apex, radiating to the left axilla; a rougher systolic murmur is audible at the third and fourth intercostal spaces along the left sternal border, often accompanied by a tremor. At the pulmonary valve area, the second heart sound is markedly accentuated and split.

bubble_chart Diagnosis

1. Palpitation, shortness of breath, susceptibility to common cold, poor development. In severe cases, cyanosis is present. A blowing systolic murmur of mitral regurgitation is heard at the apex, and a rough systolic murmur accompanied by tremor (ventricular septal defect) is heard at the third and fourth intercostal spaces along the left sternal border. The pulmonary artery second sound is accentuated and split.
2. Electrocardiogram: Prolonged P-R interval exceeding 0.20 seconds, often with first-degree atrioventricular block and left axis deviation.
3. X-ray examination: Enlargement of the right atrium and right ventricle, with additional enlargement of the left ventricle and left atrium, increased pulmonary blood flow, and bulging of the pulmonary artery segment.
4. Echocardiography: Dilation of the right atrium, right ventricle, and pulmonary artery. Clefts in the mitral and tricuspid valves, revealing primum atrial septal defect and ventricular septal defect, with atrioventricular valve regurgitation.
5. Right heart catheterization: Left-to-right shunt at the atrial level, gradual increase in blood oxygen from atrium to ventricle. The catheter can directly pass from the right atrium into the left ventricle.
6. Left ventriculography: Left ventriculography shows elongation of the left ventricular outflow tract resembling a "goose" neck, termed the "gooseneck sign." In partial atrioventricular canal defects, the contrast sequence is left ventricle → left atrium → right atrium → right ventricle → pulmonary artery. In complete atrioventricular canal defects, all four chambers are opacified simultaneously.

bubble_chart Treatment Measures

1. Primary atrial septal defect (ASD) of the ostium primum type, repaired using the patch method. Care must be taken to avoid injury to the atrioventricular conduction bundle.
2. Partial atrioventricular canal defect. During surgery, left ventricular water injection is used to check for mitral valve cleft regurgitation. If regurgitation is present, the mitral valve cleft should be repaired to eliminate the regurgitation, followed by patch repair of the primary atrial septal defect.
3. Complete atrioventricular canal defect, with severe condition and complex intracardiac malformations. Reconstruction of the mitral valve major leaflet or mitral valve replacement is required, along with repair of the atrial and ventricular septal defects. Postoperative intensive monitoring is necessary. If third-degree atrioventricular block occurs and is unresponsive to isoproterenol (0.01–0.2 μg/kg/min), a temporary pacemaker should be initiated, along with corticosteroids and GIK solution. Strengthen cardiac function and diuresis, control fluid intake, and maintain left atrial pressure at 7–8 mmHg. For patients with pulmonary hypertension, vasodilators should be administered for more than one week to prevent postoperative pulmonary infections.

Atrioventricular canal defect is a complex congenital cardiac malformation. Partial atrioventricular canal defect is relatively simpler, allowing affected children to survive longer with higher surgical success rates and better outcomes. Surgery is recommended around preschool age (approximately 5 years old). Complete atrioventricular canal defect is more complex, with 40% of cases accompanied by other intracardiac malformations such as patent ductus arteriosus, tetralogy of Fallot, or double-outlet right ventricle, increasing the complexity and severity of the condition. Early-onset pulmonary hypertension occurs, with 96% of cases involving pulmonary vascular lesions, and 80% of infants dying before the age of 2. Some scholars advocate surgery within the first year of life, but surgical outcomes remain unsatisfactory, with mortality rates as high as 15%. Causes of death include postoperative mitral regurgitation, third-degree atrioventricular block, arrhythmias, and pulmonary infections. To improve surgical outcomes, further research by medical professionals is needed to better understand the pathological characteristics and surgical methods for this condition.

bubble_chart Cure Criteria

1. Cured: Symptoms disappeared, no complications. Normal activities unrestricted.
2. Improved: Symptoms alleviated, but palpitation persists.
3. Not cured: Symptoms show no improvement.