CONGENITAL HEART DISEASE

ACYANOTIC

INCREASED PULMONARY BLOOD FLOW

ATRIAL SEPTAL DEFECT (ASD)VENTRICULAR SEPTAL DEFECT (VSD)PATENT DUCTUS ARTERIOSUS (PDA)ATRIOVENTRICULAR CANAL (AVC)

DEFECT

Abnormal opening between the atria, allowing blood from the higher-pressure left atrium to flow into the lower-pressure right atrium.

ATRIAL SEPTAL DEFECT (ASD)

OSTIUM PRIMUM (ASD 1) – opening at lower end of the septum; may be associated with mitral valve abnormalities.

OSTIUM SECUNDUM (ASD 2) – opening near center of the septum.

SINUS VENOSUS DEFECT – opening near junction of superior vena cava and right atrium; may be associated with partial anomalous pulmonary venous connection

3 TYPES OF ASD

ASD: PATHOPHYSIOLOGY Because left atrial pressure slightly exceeds

right atrial pressure, blood flows from left to right atrium, causing an increased flow of oxygenated blood into the right side of the heart. Despite the low pressure difference, a high rate of flow can still occur because of low pulmonary vascular resistance and the greater distensibility of the right atrium, which further reduces flow resistance.

‣ This volume is well tolerated by the tight ventricle because it is delivered under much lower pressure than in a ventricular septal defect. Although there is right atrial and ventricular enlargement, cardiac failure is unusual in an uncomplicated ASD. Pulmonary vascular changes usually occur only after several decades if the defect is unrepaired.

ASD: PATHOPHYSIOLOGY

Patients may be asymptomatic. They may develop congestive heart failure (CHF). There is a characteristic murmur. Patients are at risk for atrial dysrhythmias (probably caused by atrial enlargement and stretching of conduction fibers) and pulmonary vascular obstructive disease and emboli formation later in life from chronic increased pulmonary blood flow.

ASD: CLINICAL MANIFESTATIONS

Surgican dacron patch closure of moderate to large defects similar to closure of ventricular septal defects. Open repair with cardiopulmonary bypass is usually performed before school age.

In addition, the sinus venosus defect requires patch placement, so the anomalous right pulmonary venous reutn is directed to the left atrium with it baffle. The ASD 1 may requir repair or, rarely, replacement of mitral valve.

ASD: SURGICAL TREATMENT

ASD 2 may also be closed using devices during cardiac catheterization.

NONSURGICAL TREATMENT

Very low operative mortality, less than 1%.

ASD: PROGNOSIS

Abnormal opening between the right and left ventricles. May be classified according to location: membranous (accounting for 80%) or muscular.

May vary in size from a small pinhole to absence of the septum, resulting in a common ventricle.

A left-to-right shunt is caused by the flow flow of blood from the higher-pressure left ventrcile to the lower-pressure right ventricle.

VENTRICULAR SEPTAL DEFECT (VSD)

Because of the higher pressure within the left ventricle and because the systemic arterial circulation offers more resistance than the pulmonary circulation, blood flows through the defect into the pulmonary artery. The increased blood volume is pumped into the lungs, which may eventually result in increased pulmonary vascular resistance.

VSD: PATHOPHYSIOLOGY

Increased pressure in the right ventricle as a result of left-to-right shunting and pulmonary resistance causes the muscles to hypertrophy. If the right ventricle is unable to accommodate the increased workload, the right atrium may also enlarge as it attempts to overcome the resistance offered by incomplete right ventricular emptying.

VSD: PATHOPHYSIOLOGY

CHF is common. There is a characteristic murmur. Patients are at risk for bacterial endocarditis

and pulmonary vascular obstructive disease.

In severe defects Eisenmenger syndrome (s defined as the process in which a left-to-right shunt caused by a ventricular septal defect in the heart) may develop.

VSD:CLINICAL MANIFESTATIONS

PALLIATIVE: Pulmonary artery banding (placing a band around the main pulmonary artery to decrease pulmonary blood flow) in infants severe CHF was common in the past. It is less common now as improvements in surgical techniques and postoperative care make complete repair in infancy the preferred approach.

VSD: SURGICAL TREATMENT

COMPLETE REPAIR (PROCEDURE OF CHOICE): Small defects are repaired with a purse string approach. Large defects usually require a knitted Dacron patch sewn over the opening. Both procedures are performed via cardiopulmonary bypass. The repair is generally approached through the right atrium and the tricuspid valve. Postoperative complications include residual VSD and conduction disturbances.

VSD: SURGICAL TREATMENT

Device closure during cardiac catheterization is under clinical trials in some centers for closure of muscular defects that carry a high operative risk.

VSD: NONSURGICAL TREATMENT

Risk depend on the location of the defect, number of defects, and other associated cardiac defects. Single membranous defects have a low mortality (less than 5%); multiply muscular defects can have a risk of more than 20%.

VSD: PROGNOSIS

Incomplete fusion of endocardial cushions. Consists of a low atrial septal defect that is continuous with a high ventricular septal defect and clefts of the mitral and tricuspid valves, creating a large central atrioventricular (AV) valve that allows blood to flow between all four chambers of the heart.

The directions and pathways of flow are determined by pulmonary and systemic resistance, left and right ventricular pressures, and the compliance of each chamber, although flow is generally from left to right. It is the most common cardiac defect in children with Down syndrome.

ATRIOVENTRICULAR CANAL (AVC) DEFECT

The alterations in the hemodynamics depend on the defects severity and the child’s pulmonary vascular resistance. Immediately after birth, while the newborn’s pulmonary vascular resistance is high, there is a minimum shunting of blood through the defect. Once the resistance falls, left-to-right shunting occurs and pulmonary blood flow increases. The resultant pulmonary vascular engorgement predisposes to develop of CHF.

AVC: PATHOPHYSIOLOGY

Patients usually have moderate to severe CHF.

There is a characteristic murmur. There may be mild cyanosis that increases

with crying. Patients are at high risk for developing

pulmonary vascular obstructive disease.

AVC: CLINICAL MANIFESTATIONS

PALLIATIVE: Pulmonary artery banding for infants with severe symptoms that are caused by increased pulmonary blood flow in some centers. Other centers believe complete repair can be performed in infants.

AVC: SURGICAL TREATMENT

COMPLETE REPAIR: Surgical repair consists of patch closure of the septal defects and the reconstruction of the AV valve tissue(either repair of the mitral valve cleft or fashioning two AV valves). If the mitral valve defect is severs, a valve replacement may be needed. Postoperative complications include heart block, CHF, mitral regurgitation, dysrhythmias and pulmonary hypertension.

AVC: SURGICAL TREATMENT

Operative mortality is less than 10%. Potential later problem in mitral regurgitation, which may require valve replacement.

AVC: PROGNOSIS

Failure of the fetal ductus arteriosus (artery connecting the aorta and pulmonary artery) to close within the first weeks of life. The continued patency of this vessel allows blood to flow from the higher-pressure aorta to the lower-pressure pulmonary artery, causing a left-to-right shunt.

PATENT DUCTUS ARTERIOUSUS (PDA)

PDA:PATHOPHYSIOLOGY The hemodynamic consequences of PDA

depend on the size of the ductus and the pulmonary and systemic circulations is almost identical, thus equalizing the resistance in the aorta and pulmonary artery. As the systemic pressure exceeds the pulmonary pressure, blood begins to shunt the aorta, across the duct, to the pulmonary artery (left-to-tight shunt)

The additional blood is recirculated through the lungs and returned to the left atrium and left ventricle. The effect of this altered circulation is increased workload on the left side of the heart, increased pulmonary vascular congestion and possible resistance, and potentially increased right ventricular pressure and hypertrophy.

PDA:PATHOPHYSIOLOGY

Patients may be asymptomatic or show signs of CHF.

There is a characteristic machinery-like murmur.

A widened pulse pressure and bounding pulses result from runoff of blood from the aorta to the pulmonary artery.

Patients are at risk for bacterial endocarditis and pulmonary vascular obstructive disease in later life from chronic excessive pulmonary blood flow.

PDA:CLINICAL MANIFESTIONS

Administration of indomethacin (prostaglandin inhibitor) has proved successful in closing a patent ductus in premature infants and some newborns.

PDA: MEDICAL MANAGEMENT

Surgical division or ligation of the patent vessel via a left thoracotomy. A newer technique, visual assisted thoracoscopic surgery (VATS), uses a thoracoscope and instruments placed through three small incisions on the left side of the chest and eliminates the need for a thoracotomy, thereby speeding postoperative recovery.

PDA: SURGICAL TREATMENT

Use of coils to occlude the ODA in the catheterization laboratory is done in many centers. Small infants (with small-diameter femoral arteries) and those patients with large or unusual PDAs may require surgery.

PDA: NONSURGICAL TREATMENT

Both procedures can be done at low risk with less than 1% mortality.

PDA: PROGNOSIS