What Is an Endocardial Cushion Defect?

Endocardial cushion defects are also called atrioventricular septal defects or atrioventricular channel defects. Embryonic stage due to developmental obstacles during the fusion of endocardial cushions in the ventricular inflow tract. The deformities include large atrioventricular septal defect under the atrioventricular valve, atrial septal defect at the plane of the near atrioventricular valve, single or common atrioventricular valve orifice , Accounting for 4% of congenital heart disease, more than half of patients with congenital stupidity (Down syndrome). ^[1]

Zhang Hui

(Deputy Chief Physician)

Pediatric Cardiac Surgery, Beijing Anzhen Hospital

Endocardial cushion defects are also called atrioventricular septal defects or atrioventricular channel defects, which are caused by developmental disorders during the embryonic period during the fusion of endocardial cushions into the ventricular inflow tract. The symptoms of patients with small shunts may not be obvious, and patients with complete endocardial cushion defects have typical symptoms of congestive heart failure early in life.

Introduction to Endocardial Pad Defective Diseases

Classification of endocardial cushion defects

Endocardial cushion defects are classified into partial, excessive, and complete types according to the degree of development of the atrioventricular septal tissue around the atrioventricular valve and the atrioventricular valve deformity.

Partial endocardial cushion defect

Partial endocardial cushion defects mainly include primary foratrial septal defect and mitral valve fissure defect and different degrees of mitral regurgitation. The primary foramen atrial septal defect is crescent-shaped, in the lower part of the atrial septum and above the atrioventricular valve. Most mitral regurgitation sites are in the anterior valve fissure.

Endocardial cushion defect type

Complete endocardial cushion defects include primary foratrial septal defect and ventricular septal inflow tract defect below the atrioventricular valve. A set of atrioventricular valves span the left and right hearts, forming the upper (anterior) and lower (rear) bridge valves. The patient forms a "naked area" on the ventricular septum.

Complete endocardial cushion defects are divided into three subtypes: Type A is the most common. The tendon cord of the anterior bridge flap is widely attached to the interventricular septum and can be effectively divided into "two valves", that is, the left upper bridge valve is completely in the left ventricle, and the right upper bridge valve is completely in the right ventricle, which is beneficial for the surgeon to reconstruct Left and right atrium ventricular valves. Type B is rare. The papillary muscle from the left anterior bridge flap attaches to the right ventricular septum. Type C refers to the anterior bridge flap suspended above the ventricular septum without tendon attachment.

Complete endocardial pad defects are easily associated with conic stem deformities, such as tetralogy of Fallot, double outlet of right ventricle, and aortic dislocation. Among them, tetralogy of Fallot is the most common, accounting for about 6%. Other concomitant malformations include open ductus arteriosus (10%), permanent left superior vena cava (3%), left ventricular outflow tract obstruction due to diffuse subaortic stenosis or residual atrioventricular valve tissue.

Endocardial cushion defect type

Hyperendocardial cushion defects are between partial and complete, with two distinct sets of atrioventricular valve orifices, primary atrial septal defect, and subventricular septal defect. Ventricular septal defects in patients are often located in the inflow tract septum, and there is no obvious "naked area" on the interventricular septum.

Patients with endocardial cushion defects often have atrioventricular conductive tissue ectopic due to the absence of the atrioventricular septum. His bundle often travels along the lower edge of the ventricular septal defect, with the bundle branch furcation further down. Therefore, this type of patients is the most susceptible to surgically induced conduction system damage. ^[1]

Pathogenesis of endocardial cushion defects

Atrial and ventricular level left-to-right shunting results in substantial pulmonary blood flow in almost all patients with endocardial cushion defects. Without ventricular septal defects, hemodynamics are similar to large atrial septal defects, with increased right ventricular stroke volume. The reverse flow through the atrioventricular valve fissure increases with time, and the left-to-right shunt will be greater, with significant progressive cardiac enlargement and congestive heart failure.

In patients with complete endocardial cushion defect, the four heart chambers in the heart communicate with each other, and there is a large amount of left-to-right shunt. . Patients often have a marked increase in pulmonary vascular resistance within a few months after birth. Pulmonary hypertension progresses faster in patients with congenital stupidity (Down syndrome). Atrioventricular valve reflux increases ventricular volume load, aggravates pulmonary hypertension and congestive heart failure, so early surgery is critical. ^[1]

Clinical manifestations of endocardial cushion defect

Partial endocardial cushion defect

Symptoms in patients with small shunts may be insignificant, and cardiac murmurs may be found only on physical examination. Patients with large shunts with severe decline in pulmonary vascular resistance after birth will suffer severe symptoms such as heavy sweating, shortness of breath, difficulty feeding, repeated upper respiratory infections, stunted growth, limited activity, and congestive heart failure.

Endocardial cushion defect type

Patients with complete endocardial cushion defect have typical symptoms of congestive heart failure early in life, including repeated upper respiratory infections, difficulty feeding, weight gain, and sweating when eating. Physical examination revealed tachycardia, dyspnea, hepatomegaly, and increased pulsation in the precardiac area. If the atrioventricular valve reflux is obvious, a loud systolic murmur is heard. The chest radiograph showed biventricular and pulmonary congestion. ECG showed double-chamber hypertrophy, prolonged PR interval, and left axis deviation. ^[1]

Endocardial cushion defect diagnosis

Two-dimensional echocardiography of endocardial cushion defect

Has become a routine means of diagnosing endocardial cushion defects. It can clarify the nature of valvular abnormalities, the morphology of the ventricular septal defect and the atrial septal defect, and their associated deformities.

Endocardial pad defect color Doppler

Can provide accurate atrial, ventricular shunt and atrioventricular valve regurgitation.

Endocardial pad defect cardiac catheter

At present, it is limited to estimating the pulmonary vascular resistance to determine whether there are still indications for surgery.

Endocardial cushion defect surgery

Timing of Endocardial Pad Surgery

Partial endocardial cushion defects are usually operated between 2 and 4 years of age. If there is obvious mitral regurgitation or left heart structural dysplasia such as aortic constriction, mitral valve malformation, and subaortic stenosis, early surgery should be performed. Complete endocardial cushion defects have severe congestive heart failure 2 to 4 months after birth and should be performed within 3 to 6 months. There is a risk of irreversible increase in pulmonary vascular resistance if surgery is postponed until after 1 year of age. The operation time of hyperendocardial pad defect depends on the size of the ventricular defect. The larger the defect, the earlier the operation time should be. Patients with endocardial pad defect combined with tetralogy of Fallot and obvious right ventricular outflow stenosis previously had multiple stages of surgery. At present, early surgery is recommended.

Endocardial cushion defect contraindications

Organic pulmonary hypertension and irreversible pulmonary vascular disease are absolute contraindications for this disease.

Endocardial cushion defect surgery

"Pulmonary arterial annulus surgery is more commonly used when the previous surgical technique is immature, but it aggravates mitral regurgitation, and does not have the effect of palliative treatment. It is currently less used, but only for small infants within 3 months Pneumonia, heart failure, and medical treatment are not effective. Pulmonary artery ring contraction can be considered first. Radical surgery should be performed 3 to 6 months after the heart and general conditions improve.

The principle of radical surgery is to close the ventricular septal defect and atrial septal defect, restore the mitral valve without stenosis and reflux, and avoid damage to the conduction beam. The key to successful surgery is the effect of left atrioventricular angioplasty to avoid stenosis of the left ventricular outflow tract.

Surgical methods for complete endocardial cushion defects include monolithic, dual-sheet, and modified monolithic methods. From the surgical mortality and reoperation rates due to mitral regurgitation, pacemaker implantation, left ventricular outflow tract obstruction, residual ventricular septal defect, or atrial septal defect, the effects of the three surgical methods were roughly the same.

In comparison, complete endocardial cushion defects are the most complicated, with the highest risk of surgery, with a mortality rate of about 3 to 5%. In general, the long-term reoperation rate of patients with endocardial cushion defects is about 10% to 15%.

Endocardial cushion defect complications

1. Atrioventricular block. If permanent, a pacemaker needs to be implanted.

2. Low cardiac output syndrome. It is the most serious postoperative complications that endanger patients' lives.

3. Atrial and ventricular horizontal residual shunt and residual valve regurgitation. Residual shunts with small atrioventricular and ventricular levels or a small amount of valvular regurgitation will generally not affect the patient. If the residual shunt is large or residual moderate or higher valvular regurgitation is required, surgery will be required again.

4. Pulmonary hypertension crisis. It is a serious postoperative complication that endangers the life of the patient.

Precautions after endocardial cushion defect

1. Take at least 3 months of postoperative cardiac strengthening, diuretic and vasodilator drugs to help restore heart function. Early prevention of respiratory infections after surgery to prevent severe infections from causing cardiac insufficiency and even life-threatening.

2. Echocardiography should be reviewed 3 to 6 months after surgery, mainly to observe the status of atrioventricular reflux, and whether there is residual shunt and left ventricular outflow tract obstruction. In the future, long-term follow-up of the atrioventricular valve, especially the mitral valve, is needed. ^[2-3]