IMPORTANT PEDIATRIC CARDIAC SUYGERY.....

  pediatric cardiac surgery 

INTRODUCTION

Although many children who have congenital heart defects do not need surgical treatment, most need some form of intervention.The treatment the child receives depends on the type and severity of his or her heart defect. Other factors include child's age, size, and general health. Some conditions need urgent surgical correction in the neonatal period. A child may need open-heart surgery if his or her heart defect can't be fixed using a catheter procedure. In most conditions full correction can be achieved by at single stage, but some diseases need a staged approach needing 2-3 or more stages.

Types of congenital heart defects

·         Obstructive congenital heart lesions

·         Congenital heart lesions that increase pulmonary arterial blood flow

·         Congenital heart lesions that decrease pulmonary arterial blood flow

Obstructive congenital heart lesions

They impede the forward flow of blood and increases ventricular after loads. They are
a) pulmonary stenosis, b) aortic stenosis, c) coarctation of the aorta.

Pulmonary stenosis

No symptoms occur in mild or moderately severe lesions. Cyanosis is seen if there is a communication between right and left sides of the heart and right-sided heart failure occurs in patients with severe lesions. There is a high-pitched systolic ejection murmur maximal in second left intercostal space. Ejection click is often present.

Aortic stenosis

Valvular aortic stenosis, subaortic stenosis, supravalvular aortic stenosis, asymmetric septal hypertrophy (Idiopathic hypertrophic subaortic stenosis) comes under this.

Percutaneous balloon valvuloplasty is usually successful in these patients and should be considered first-line therapy. Valvotomy is preferred in the neonate, infant, and child. Valvotomy is a salvage operation in neonates and infants and has high operative risk. In older children; valvotomy is the palliative operation of choice. Replacement of the aortic valve is performed in adults and the elderly.

Coarctation of aorta

It is characterized by absent or weak femoral pulses. Systolic pressure is higher in upper extremities than in lower extremities; diastolic pressures are similar. Males are affected twice as frequently as females. 98% of all coarctations occur at the segment of aorta adjacent to ductus arteriosus. Blood flow to the lower body is maintained through collateral vessels. In the infantile form of coarctation, the blood flow to the lower body is maintained by the ductus arteriosus. Post natally, as the ductus closes, these children go for severe heart failure with no perfusion of lower body. This is a surgical emergency, child should be resuscitated with prostaglandin infusion and early surgical correction should be done

Neonate with severe failure, operation indicated at time of diagnosis. If cardiac failure or failure to thrive not present, delay 3-6 months. Increased incidence of recurrent stenosis if operated at less than 3 months. Increased incidence of HTN if coarctation is repaired beyond infancy.The operative strategy includes left anterolateral thoracotomy via the 4th ICS.Maintain proximal blood pressure high to lessen the risk of paraplegia. Maintain distal pressure of 45 mmHg. Resection and end-to-end anastomosis (ETE); subclavian flap aortoplasty (SFA); resection and extended end-to-end anastomosis and combined end-to-end anastomosis and SFA are preferred.

Congenital heart lesions that increase pulmonary arterial blood flow

·         Atrial septal defect

·         Complete atrioventricular canal defect

·         Ventricular septal defect

·         Patent ductus arteriosis (closed heart procedure )

·         Total anomalous pulmonary venous connection

·         Cor triatriatum

·         Truncus arteriosus

Atrial septal defect (ASD)

 The child can be acyanotic, asymptomatic, or can have only dyspnea on exertion. It results in right ventricular lift, with fixed, widely split second heart sound. The average life expectancy is reduced because of right ventricular failure, dysrhythmias, and pulmonary vascular disease. Surgical closure is recommended. Selected ASDs can be closed using a device in the cathlab. Surgical closure of ASD is an open-heart procedure. Closure of the defect either directly or with patch depends on the type and size of the defect.

Complete atrio-ventricular canal defect

Heart failure is common in infancy and cardiomegaly with blowing pansystolic murmur is common. Deficiencies of both atrial and ventricular septal cushions and abnormalities of both mitral and tricuspid valves seen. Partial and complete AV canal defects frequently accompany Down's syndrome. Complete AV cannal defect is often associated with severe PAH. Early surgical correction is needed. Reconstruction of the AV valves and closure of the septal defects by a single or double patch technique is done. These patients need to be in follow-up to detect any regurgitation through abnormal AV Valves.

Ventricular septal defect (VSD)

Asymptomatic, if defect is small. Heart failure with dyspnea, frequent respiratory infections, and poor growth occurs if defect is large. Pan systolic murmur maximal at the left sternal border is seen. It is often one of the components of another complex congenital heart lesion. Heart is enlarged and lung fields are over circulated.  Many of the defects will close spontaneously by age 7-8 years. Larger defects if untreated can lead to pulmonary hypertension, aortic regurgitation, cardiac failure or infective endocarditis. VSDs can be closed directly or with a patch, depending on the size of the defect. Most VSDs are closed through the right atrium across the tricuspid valve. Some VSDs are approached through the pulmonary artery, right ventricle or rarely left ventricle.

Patent ductus arteriosis (PDA)

Murmur is usually systolic, sometimes it may be continuous, "machinery". Poor feeding, respiratory distress, and frequent respiratory infections are seen in infants with heart failure. Physical examination and echocardiography reveals the defect. Selected PDAs can be closed percutaneously using coils or device. Surgical treatment is, by ligation, clipping, or division of the ductus and suturing. It is a closed heart procedure done under left thoracotomy, when not associated with other intra cardiac defects.

Aortopulmonary window (AP window)

It is a communication between ascending aorta and pulmonary artery.Separate aortic and pulmonary valves are present.

Total anomalous pulmonary venous connection (TAPVC)

Pulmonary veins do not make a direct connection with the left atrium. Blood reaches the left atrium only through an atrial septal defect or patent foramen ovale, presents with pulmonary congestion, tachypnea, cardiac failure, and variable cyanosis. Diagnosis is by cardiac catherization or echocardiography. Operative repair is needed in all cases. An obstructed TAPVC, in which pulmonary venous return to heart is obstructed, is a surgical emergency as there is no medical or interventional palliation.The surgical treatment aims at creating a large unobstructed connection between the pulmonary vein and the left atrium.

Cor triatriatum

Pulmonary veins enter proximal LA chamber and are separated from distal LA chamber by a diaphragm, a small hole in this diaphragm allows some communication to the distal chamber.The RV is enlarged, the fossa ovalis is patent, which allows left-to-right shunting. This interatrial connection usually communicates the proximal chamber to the RA and occasionally the distal chamber to the RA. The distal chamber contains the mitral valve and left atrial appendage.Operative techniques include left atrial approach and right atrial approach.

Truncus arteriosus

Single large vessel overrides the ventricular septum and distributes all the blood ejected from the heart. Large VSD is present. One great artery arises from the base of heart with a single semilunar "truncal" valve. This truncal artery gives origin to coronary arteries, systemic arteries and one or two pulmonary arteries. Associated anomalies are- interrupted aortic arch or coarctation with PDA in 10-20%, persistent left superior vena cava in 10%, Di-George syndrome and right aortic arch in 25-30%. Treatment is early operative intervention, palliative operations are not useful and complicate later repair.Operation is performed under deep hypothermia, circulatory arrest or hypothermia with low flow. Close VSD to right of truncal valve, truncal valve repair or replacement if necessary, is also done. Remove PA from aorta, repair aorta, RVOT is reconstructed, with a valved conduit between right ventricle and pulmonary vessels. Conduit will need to be changed as child grows but likelihood to develop pulmonary vascular disease is greatly reduced.

Congenital heart lesions that decrease pulmonary arterial blood flow

Tetralogy of Fallot, transposition of the great arteries; tricuspid atresia and Ebstein's anomaly come under this category.

Tetralogy of Fallot (TOF)

Four defects ie. pulmonary stenosis, membranous VSD; over riding of aorta and right ventricular hypertrophy comprise iv) right ventricular hypertrophy comprise TOF. Addition of ASD makes it pentalogy of Fallot. It presents with hypoxic spells, squatting, cyanosis and clubbing. The VSD and infundibular stenosis determine the pathophysiologic features. The operative technique consists of dissecting and resecting infundibular stenosis through the right atrium; closing ASD/PFO; opening and enlarging the pulmonary valve and or annulus; and closing VSD, which corrects overriding of aorta.

Transposition of the great arteries (TGA)

Connections of the great vessels are reversed; aorta arises from right ventricle, and pulmonary artery from left ventricle. Cyanosis from birth, hypoxic spells and heart failure is often present. Cardiac enlargement and diminished pulmonary artery segment on X-ray is seen. Survival beyond infancy is rare without surgical treatment. Neonates with TGA, intact ventricular septum and post saturation are first stabilized with balloon atrial septostomy to improve inter circulatory mixing.

Tricuspid atresia

Tricuspid valve is completely absent in about 2% of newborns with congenital heart disease.Blood flows from right atrium to left atrium through foramen ovale. Early cyanosis and these patients are palliated through- Fontan procedure, with bi-directional Glenn shunt as the first stage in infancy, and completion of Fontan when they are older is the treatment.

Ebstein's anomaly

Septal and posterior leaflets of the tricuspid valve are small and deformed, usually displaced toward the right ventricular apex. Most patients have an associated ASD or patent foramen ovale. Cyanosis and arrhythmias in infancy are common. Right heart failure occurs in half of patients. Tricuspid valve repair is preferred. Replace the valve if unable to repair, plicate the atrialized right ventricle, close any associated ASD, consider Maze procedure for atrial arrythmias, and interrupt accessory conduction pathways if present. Neonates with severe forms of Ebstein's are treated with closure of tricuspid valve and conversion to univentricular physiology.

Palliative operations

1) Increase pulmonary blood flow: aortopulmonary shunts

Indications

·         Tetralogy of Fallot less than 3 months of age, as patient is too small for adequate reconstruction of RVOT

·         Pulmonary atresia with or without VSD

·         Tricuspid atresia with PS

·         Single ventricle with PS

·         TGA with VSD and PS; although there is good mixing at the level of the ventricle, there is inadequate pulmonary flow.

Types

Classic Blalock-Taussig shunt: Subclavian to PA, first performed in 1940s. Constructed on opposite side from arch; orifice of subclavian artery controls flow. Subclavian artery to PA anastomosis is technically challenging.

Modified Blalock-Taussig shunt: Goretex subclavian to PA. Generally constructed on same side as arch, although either side works; orifice of subclavian or graft itself controls flow (3 mm or 5 mm PTFE is used depending on the weight of the baby). This is more reproducible, causes less PA distortion and better PA growth.

2) Decrease pulmonary artery blood flow - pulmonary artery banding

Indications

The most common general indication for banding is congestive heart failure in infancy with anticipated delayed repair. Single ventricle is the most common lesion requiring banding, as this protects the pulmonary bed for future Fontan conversion. Also indicated in unbalanced AV canal; multiple VSD's and VSD and coarctation. Single stage correction is preferred.

3) Improve mixing: atrial septectomy

Types

Blalock-Hanlon septectomy: It is a closed procedure. Clamp is placed behind right pulmonary veins and across portions of both atria. The lateral portion of the atrial septum is excised.

Rashkind balloon septostomy: It is 90% effective.

Park- blade septostomy: used for thicker septum or when larger intra-atrial communication is desired.

Open atrial septectomy: concomitant procedure, most commonly during repair of hypoplastic left heart.

4) Reduce ventricular work: Glenn shunt

Types

Bi-directional Glenn shunt: SVC to PA (end-to-side). Flow goes to both lungs, so subsequent Fontan procedure will use both lungs. Can be done as preparation for Fontan conversion or in combination with Fontan procedure. Much less likely to produce right heart failure from over circulation as aortopulmonary shunt can. Complications include decreased shunt flow over time as pulmonary vascular resistance gradually rises.

Classical Glenn: SVC to RPA (end-to-end). Divides pulmonary circulation. Results in late arterio-venous fistula, diverts all venous return to the larger right lung, so subsequent Fontan procedure can only use the smaller left lung.

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