Disease Overview
Ventricular septal defect refers to the embryonic underdevelopment of the ventricular septum, which forms abnormal traffic and produces a left-to-right shunt at the ventricular level; it can exist alone or as a component of some complex cardiac malformation. Ventricular defects are the most common form of congenital heart disease.
Ventricular septal defects account for approximately 20% of all congenital heart disease and can exist alone or in conjunction with other malformations. Defects range from 0.1-3 cm, larger in the membranous region and smaller in the muscular region, which is also known as Roger’s disease. If the defect is <0.5 cm, the flow is small and there are no clinical symptoms. In small defects, the right ventricle is predominantly enlarged, while in large defects, the left ventricle is more enlarged than the right ventricle.
Types of disease
According to the location of the defect, it can be divided into five types.
1, supraventricular crest defect: located in the right ventricular outflow tract, above the supraventricular crest and below the main and pulmonary valves, and in a few cases combined with incomplete closure of the main and pulmonary valves.
2, subventricular crest defect: located in the septal membrane, this type is the most common, accounting for about 60-70%.
3, posterior septal defect: located in the right ventricular inflow tract, posterior to the tricuspid septal valve, accounting for about 20%.
4, myocardial defect: located in the apical part, for myocardial trabecular defect, systolic time septal myocardial contraction to make the defect smaller, so the left to right shunt flow is small.
5.Common ventricle: the septal membrane part and myocardial part are not developed, or multiple defects, which is less common.
Symptoms and signs
A left-to-right shunt is produced at the ventricular level, and the amount of shunt flow depends on the size of the defect. If the defect is large, the blood flow in the pulmonary circulation increases significantly. After flowing into the left atrium and ventricle, it flows into the right ventricle at the ventricular level through the defect and enters the pulmonary circulation, thus increasing the load on the left and right ventricles, increasing the size of the left and right ventricles, increasing the blood flow in the pulmonary circulation leading to an increase in pulmonary artery pressure and an increase in the systolic load on the right ventricle, and finally entering the phase of obstructive pulmonary hypertension, which can occur in both directions or right-to-left shunt.
1.Symptoms
Small defects can be asymptomatic. If the defect is large, the symptoms appear early and obvious, so that the development is affected. There are palpitations and shortness of breath, weakness and easy lung infection. In severe cases, heart failure may occur. Cyanosis may occur in the presence of significant pulmonary hypertension, and the disease may predispose to infective endocarditis.
2. Physical signs
The typical sign is a grade 4-5 rough systolic murmur between ribs III-IV at the left edge of the sternum, conducted to the precordial region, accompanied by fine systolic tremor. If the fractional flow is high, there may be a functional diastolic murmur in the apical region. The second pulmonary valve sound is hyperactive and split. In severe pulmonary hypertension, there is a diastolic murmur of relative pulmonary valve insufficiency in the pulmonary valve region, and the systolic murmur of the original septal defect may be diminished or absent.
Diagnostic tests
1.X-ray examination
Mild to moderate enlargement of the heart shadow in moderate or above defect, left heart edge lengthening downward to the left, pulmonary artery cone bulging out, aortic node becoming smaller, and pulmonary hilar congestion. In severe obstructive pulmonary hypertension, the enlargement of heart shadow is not significant, the right pulmonary artery is coarse, the distal protrusion is small, the branches are rattle-like, and the peri-pulmonary field texture is sparse.
2.Heart examination
There is often a mild elevation in the precordial region. Systolic tremor can be felt between the 3rd and 4th ribs at the left edge of the sternum, and a grade III-IV all-systolic murmur can be heard; in the case of high funnel defect, the tremor and murmur are located in the 2nd intercostal region. The second tone in the pulmonary valve area is hyperactive. In high fractional flow, a soft functional mid-diastolic murmur can still be heard in the apical region. In cases of reduced fractional flow due to pulmonary hypertension, the systolic murmur gradually decreases or even disappears, while the second tone of the pulmonary valve area is significantly hyperactive and split, and may be accompanied by a diastolic murmur of pulmonary valve closure insufficiency.
3.Electrocardiographic examination
Small defects show normal or left-sided electrical axis. If the defect is large, it will show high voltage and hypertrophy of the left ventricle or hypertrophy of the right and left ventricles as the fractional flow and pulmonary artery pressure increase. In severe pulmonary hypertension, right heart hypertrophy or strain is indicated. X-rays: If the defect is small, there is no change in cardiac shadow. When the defect is moderately large, the heart shadow has different degrees of enlargement, with the right ventricle predominant. In large defects, both left and right ventricles are enlarged, the pulmonary artery trunk is protruding, the pulmonary vascular shadow is enhanced, and in severe pulmonary hypertension, the lateral band of the lung field is clear instead.
4.Echocardiography
The left atrium, left and right ventricular internal diameter is enlarged, and there is continuous interruption of septal echo. Doppler ultrasound: maximum turbulence can be deeply measured by tracing from the defective right ventricular surface to the defective orifice and left ventricular surface.
5.Cardiac catheterization
The oxygen content at the right ventricular level is higher than 0.9% of the volume of the right atrium, and occasionally the catheter can reach the left ventricle through the defect. Depending on the amount of fractional flow, there is a variable increase in pulmonary artery or right ventricular pressure.
Treatment options
1.Medical treatment
Mainly to prevent and treat infective endocarditis, pulmonary infection and heart failure.
2.Surgical treatment
If the defect is small and the X-ray and electrocardiogram are normal, surgery is not necessary. If there is/ or there is no pulmonary hypertension, surgery is best if the left-to-right shunt is predominant, and the age of 4-10 is appropriate. The surgery is not recommended for those with predominantly right-to-left shunts.
Indications for surgery
In large ventricular septal defects, 25%-50% of patients die within 1 year of age due to pneumonia and heart failure. Therefore, infants with recurrent heart failure should be treated with defect repair. About half of the small defects may close on their own, except for complications of bacterial endocarditis, which can be observed until 10 years of age before considering surgical treatment. Very small defects may not require surgery for life. Infants and children with a fractional flow of more than 50% or with increased pulmonary artery pressure should be operated early to prevent a continuous rise in pulmonary hypertension. If severe obstructive pulmonary hypertension has been achieved, surgery is contraindicated.
Surgical approach
Under general anesthesia with tracheal intubation, a median sternotomy is made to establish extracorporeal circulation. After blocking the cardiac circulation, the anterior wall of the right ventricular outflow tract is incised, which can reveal all types of ventricular septal defects, but there is some damage to the myocardium. The right heart function is affected and the right bundle branch is damaged. Currently, the trans-right atriotomy route is mostly used, which is better for revealing membrane defects. For higher defects, the transpulmonary route is preferred. Smaller defects with fibrous tissue at the edges can be sutured directly, while those with defects >lcm can be patched with polyester woven sutures. The conduction bundle goes through the lower edge of the membranous defect, and the postseptal defect is easy to be accidentally injured when sutured, so it should be avoided and sutured against the root of the septum.
Postoperative treatment
1.For those who have obvious pulmonary hypertension before surgery, it is advisable to apply respirator continuously until the next morning after surgery, and if the respirator cannot be removed 48 hours after surgery, tracheotomy should be done instead of endotracheal intubation.
2.Pulmonary hypertension patients often have postoperative circulatory instability and need to maintain blood pressure with positive inotropic drugs.
In some cases, it is a transient injury of the conduction bundle, and the conduction function will be restored automatically within a few days.
Surgical results
1. It depends on the severity of the patient’s disease, the early or late stage of the disease, as well as the degree of perfection of the operation and whether the postoperative treatment is appropriate. For those without obvious pulmonary hypertension, the surgical mortality rate is within 2%.
2.For those who have serious secondary pulmonary vascular lesions before surgery, the incidence of respiratory and circulatory complications after surgery is high, and the mortality rate is also significantly higher, and the recovery depends on the degree of pulmonary vascular lesions, and if the lesions have become irreversible, the prognosis is poor