I. Application of anatomy
Ventricular septal defects can coexist with other congenital cardiac malformations, such as transposition of great vessels, tetralogy of Fallot, and complete atrioventricular coaptation. Simple ventricular septal defects can be divided into four categories according to the anatomic location of the defect.
1. supra-crural or (pulmonary artery) trunk defects Located in the right ventricular outflow tract (or funnel), above the supra-ventricular crest and immediately below the pulmonary valve as viewed from the right ventricle. From the left ventricle, it is located between the right coronary valve and the noncoronary valve of the aorta, immediately below the valve; sometimes it is located below the central part of the right coronary valve, and also near the junction of the left and right coronary valves. The defect is often circular in shape, with mostly muscular edges, but the superior aspect may abut the aortic and pulmonary valve annulus and become the superior border of the defect. The right aortic coronary valve often prolapses into the defect orifice due to lack of annular support, resulting in incomplete aortic valve closure and occasionally mild obstruction of the right ventricular outflow tract.
2. High or membranous defects are most common. It accounts for about 80% of ventricular septal defects. From the right ventricle, it is located in the membrane part of the septum, inferior and posterior to the supraventricular crest; sometimes it can extend to the inflow tract, outflow tract or septal trabeculae, forming a perimembranous defect, often covered by the tricuspid septal valve or its tendon part. From the left ventricle it lies just below the aortic noncoronary valve and the right coronary valve. The defect is often oval in shape, ranging from a few millimeters to more than 3 cm; sometimes there is an intact fibrous ring around the circumference of the defect, and sometimes the inferior border is muscular. The perimembranous defect between the atria may form a right atrial left ventricular tract and should be differentiated.
3, atrioventricular tract or septal posterior defect The defect is located in the right ventricular inflow tract posterior to the membranous defect, the deepest part of the septum, below the tricuspid septum, and there is no muscle tissue between it and the septum. It is often oval or triangular in shape, sometimes with an intact fibrous ring around its circumference and sometimes partially with muscle tissue. Because the defect is covered by the tricuspid septum, it is more difficult to detect during surgery and is easily missed. This site is similar to the site of complete atrioventricular coaptation.
This type of defect can be located anywhere in the muscular septum, including the inflow tract, outflow tract, or right ventricular trabecular area. The edges of the defect are muscular, often multiple, and vary in size with myocardial diastole. The defect is often difficult to see because of the majority of myocardial trabeculae covering it, but can be clearly visualized from the left ventricle. The course of the bundle of Hitchcock is closely related to the membranous or perimembranous or postseptal defects, and sutures can easily damage the conduction bundle and cause conduction block during repair surgery; it is farther away from the sub-stem and myocardial defects, and sutures are less likely to damage them.
Ventricular septal defects are often combined with aortic valve prolapse resulting in incomplete closure or right ventricular outflow tract stenosis, and sometimes with malformations such as patent ductus arteriosus, atrial septal defect, and pulmonary valve stenosis.
Indications
1, small ventricular septal defect may be automatically closed before the age of 10-12 years, some people do not advocate premature surgery; but because there is almost no death in such patients, and if not operated, not only will make parents and patients due to the presence of heart murmur and mental burden or admission difficulties, there is a risk of bacterial endocarditis or heart valve inflammation, so recently also included in the indications for surgery.
2.Patients with enlarged heart and large left-to-right shunt.
3, infants with large ventricular defect, pulmonary hypertension, left heart failure, recurrent pulmonary infections, rising pulmonary artery pressure and poor growth should be operated early.
4, ventricular defect with aortic valve closure insufficiency should be operated promptly.
5.Ventricular defect with pulmonary valve stenosis or outflow tract stenosis is mostly larger. If the stenosis is obvious, right-to-left shunt may appear, and surgery should be performed together.
6.Pulmonary hypertension, pulmonary artery pressure / aortic pressure <0,75 can be operated, but the high pressure can not be completely eliminated after surgery.
Contraindications
Pulmonary artery pressure/aortic pressure >0, 90 is contraindicated. If the pulmonary artery pressure/aortic pressure is 0.75~0.90, the postoperative long-term effect is not good.
IV. Surgical steps
1.Expose the heart and establish extracorporeal circulation.
2. Cardiac incision (1) Trans-right ventricular incision: commonly used. Check the tremor site outside the heart, parallel to the coronary vessels, and cut the right ventricular myocardium obliquely. Pay attention to protect the coronary vessels and do not damage them.
(2) Trans-right atrial incision: A lower ventricular defect repair from the right atrium through the tricuspid valve, or a high membrane defect with a left ventricular right atrial leak is quite satisfying to reveal, and the heart burden is much lighter than that of a trans-right ventricular incision, which is especially beneficial for those with pulmonary hypertension.
(3) Trans-pulmonary artery incision: repair of sub-stem type defects through the pulmonary valve.
(4) Trans-left ventricular incision: the myocardial defect, especially the multiple, sieve plate defect, can be clearly revealed by left ventricular incision if the right ventricular incision is not well exposed.
3, reveal the defect site Gently pull open the heart wall incision with traction wire and pull hook, and carefully search for the defect site. If it is covered by tendons or papillary muscles, it can be gently pulled away around a thick silk thread. If the defect opening cannot be found, ask the anesthesiologist to expand the lungs so that the blood in the lungs will enter the left ventricle and pour into the right ventricle through the defect opening to find the defect.
4.Repairing defect patch repair: If the defect is large, with a diameter of about 1,5 cm, more left-to-right shunt flow and higher pulmonary artery pressure, it should be repaired with polyester sheet. Take the repair of a membrane defect as an example.
(1) Interrupted mattress sutures at the posterior inferior margin: After revealing the entire defect, 3 to 4 mattress sutures, each 3 to 4 mm wide, are first made at the posterior inferior margin at about 0.5 cm from the margin using 3-0 or 4-0 double-ended polyester thread with spacers in the direction of the margin; the sutures should not penetrate the entire septum, and a depth of half of the septal thickness is sufficient to avoid damage to the conduction bundle. The distance between each mattress interrupted suture should be small to avoid gaps and incomplete repair. One of the mattress sutures should pass through the septal muscle in addition to the tricuspid septal root close to the annulus, so that no gap is left between the septum and the tricuspid valve.
(2) Polyester sutures: Pass each interrupted mattress suture through the posterior lower edge of the polyester sheet that is slightly larger than the defect, tighten and tie it firmly respectively (because the polyester thread is slippery, six knots should be tied). Except for the top and bottom stitches, cut off the excess threads.
5. Continuous suture A long thread is used to continuously suture the remaining edges of the defect to the polyester piece, with the upper and lower threads tied with the retained interrupted mattress stitches. The lungs should be dilated or the left ventricle should be filled with water and exhausted before ligation. All sutures at the tricuspid septal site should be at the root, immediately adjacent to the annulus; the uppermost suture at the root of the flap should be passed and stretched tightly with the supraventricular ridge so as not to leave a gap in between.
Direct suture: If the defect is small, surrounded by an intact white fibrous ring, and the pulmonary artery pressure is not high, direct suture can be made.
(1) Interrupted mattress suture: depending on the size of the defect, 1 to 2 stitches with spacer mattress suture are first made, each penetrating the fibrous margin without ligation.
(2) 8-shaped or continuous sutures: 8-shaped or continuous sutures are also made in the fibrous ring. Usually one or two 8-shaped sutures are sufficient to cover the full length of the defect. After suturing, the lung is expanded or the left ventricle is drained and ligated.
(3) Ligation of mattress sutures: Finally, interrupted mattress sutures are ligated.
If left atrial or left ventricular drainage has been made when extracorporeal circulation is established, saline can be injected through the drainage tube to observe whether there is residual defect at the repair site and overflowing saline. If there is no drainage tube, ask the anesthesiologist to dilate the lung. If saline or blood still gushes out from the defect site, it means that there is still residual defect, that is, a mattress or 8-shaped suture should be added to the overflowing site until there is no more overflowing blood.
7.Suture myocardial incision If atrial or pulmonary artery incision is made, continuous mattress type plus continuous simple double suture can be used to close the incision without trauma stitches; if ventricular incision is made, the same continuous mattress type plus continuous simple double suture can be used, and double continuous simple suture can also be used to close the incision back and forth. In case of blood leakage, gentle compression with dry gauze can be used to stop the bleeding. If there is more blood leakage and compression cannot stop the bleeding, interrupted simple or mattress or 8-shaped sutures can be added.
8. Resuscitate, remove the tube, and suture the chest wall incision.
V. Intraoperative precautions
1.One of the keys of ventricular septal defect repair is to find the defect site quickly. It is necessary to be familiar with the anatomical parts of various types of defects. If there is any doubt about the hole seen, the tip of the vascular clamp can be gently probed to explore whether the tip of the clamp enters the left ventricle. Note whether the defect is covered or partially covered by the tricuspid valve. Note whether the left side of the defect is in close proximity to the aortic sinus. Note whether there is a fibrous diaphragm located between the inflow and outflow tracts and the hole in the center of this diaphragm is mistakenly sutured as a ventricular septal defect. In such cases, the tricuspid valve must be located before repair of the defect can begin.
2. When repairing subdural and membrane defects, special care should be taken not to injure the aortic valve with the suture, as this will result in incomplete closure of the aortic valve.
3.When repairing the membranous or perimembranous or posterior septal defects, especially when suturing the posterior inferior border of the defect, special care must be taken to avoid injury to the atrioventricular conduction bundle. The suture should not be inserted close to the posterior inferior edge but 0.5 cm away from the edge, the depth of the needle should not exceed half of the septal thickness, and the direction of the mattress line should be parallel to the defect edge to avoid damage to the conduction bundle along the posterior inferior edge of the ventricular defect, which travels under the left endocardium.
4.Repair of the inferior defect must be sutured with a patch to avoid distortion of the pulmonary valve or aortic valve caused by direct suturing and formation of incomplete closure. When suturing the patch, if the upper edge of the defect is close to the pulmonary valve annulus, interrupted mattress sutures can be threaded from above the valve through the annulus into the subvalvular, and then back through the patch, with the knot tied on the valve.
5, the myocardial defect is often very difficult to repair because it is covered by the right ventricular myocardial cord and resembles a porous defect [Figure 8-1]. A left ventricular paracoronary incision can be made [Figure 8-2], which means that it is easy to find a single large defect that can be repaired with a patch [Figures 8-3-4]. Because the conduction bundle of the muscle has been divided into most small branches, repair on the left side does not cause conduction block; moreover, the pressure of the left ventricle is higher than that of the right ventricle, so that the patch is close to the ventricular septum and is not easy to leave the defect hole.
6.High ventricular defect can be complicated by aortic valve prolapse, resulting in incomplete closure. The aortic wall can be incised at the same time and valve suspension can be performed to correct it. In the elderly, the effect of valve suspension is often incomplete or lasting, it is appropriate to make artificial valve transplantation.
7. The patch can be completely closed with continuous sutures or completely closed with interrupted sutures.
VI. Postoperative management
Special attention should be paid to the presence or absence of conduction block. Once it occurs, isoproterenol 1mg intravenous drip should be tried to raise blood pressure and relieve myocardial hypoxia. If it is not effective, a pacemaker should be installed to control the heartbeat until sinus rhythm is restored.