81. Athanassiadi KA. Infections of the mediastinum. Thorac Surg Clin 2009; 19(1):37–45, vi.

82. Wilson LD, Detterbeck FC, Yahalom J. Clinical practice. superior vena cava syndrome with

malignant causes. N Engl J Med 2007;356(18):1862–1869.

83. Yu JB, Wilson LD, Detterbeck FC. Superior vena cava syndrome–a proposed classification system

and algorithm for management. J Thorac Oncol 2008;3(8):811–814.

2324

SECTION M: VASCULAR DISEASE

2325

Chapter 81

Congenital Heart Disease

Jennifer C. Hirsch-Romano, Richard G. Ohye, and Edward L. Bove

Key Points

1 The first successful treatment of a congenital lesion was the closure of a patent ductus arteriosus

(PDA) by Gross and Hubbard in 1938. Prostaglandin inhibitors, such as indomethacin and ibuprofen,

can be used to induce closure of a PDA in the premature newborn with a success rate of 80%. When

this is not successful, surgical closure may be necessary in small infants. Coil occlusion can be

performed in older children presenting with a PDA.

2 An atrial septal defect (ASD) is a hole in the atrial septum. ASDs are the third most common

congenital heart defect, occurring in 1 out of 1,000 live births and representing 10% of congenital

heart defects. ASDs cause right heart volume overload and can lead to pulmonary vascular

obstructive disease later in life. The majority of ASDs are now closed with a device in the

catheterization laboratory.

3 Ventricular septal defects (VSDs) are the most common congenital heart defect (with the exception

of bicuspid aortic valve, which occurs in about 1.3% of the population). VSDs cause left heart

volume overload.

4 Over 50% of children with trisomy 21 have a congenital heart defect. The most common heart defect

in this patient population is an atrioventricular septal defect. All infants with trisomy 21 should have

an echocardiogram to rule out congenital heart disease.

5 Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect. It occurs in 0.6 per

1,000 live births and has a prevalence of about 5% among all patients with congenital heart disease.

The pathologic anatomy is frequently described as having four components: ventricular septal defect,

overriding aorta, pulmonary stenosis, and right ventricular hypertrophy.

6 Transposition of the great arteries is a congenital cardiac anomaly in which the aorta arises from the

right ventricle and the pulmonary artery originates from the left ventricle (ventriculoarterial

discordance). It is the most common congenital heart defect presenting with cyanosis in the first

week of life. This malformation accounts for approximately 10% of all congenital cardiovascular

malformations in infants.

7 Upper extremity hypertension with diminished femoral pulses are hallmark clinical findings in

patients with aortic coarctation.

8 Coronary arteriovenous fistula is the most common major coronary anomaly.

HISTORY

Cardiac surgery, as a specialty, is notable for the rapid technical advances that have been made during

the past few decades. Much of the original interest was focused on attempts to treat congenital heart

defects associated with cyanosis and early mortality. 1 The first successful treatment of a congenital

lesion was the closure of a patent ductus arteriosus (PDA) by Gross and Hubbard in 1938.1 The

description of the subclavian artery-to-pulmonary artery (PA) shunt by Blalock and Taussig in 19452

introduced the palliation of many complex cyanotic lesions – most notably, tetralogy of Fallot (TOF).

The 1950s represented the decade of greatest advances, which laid the foundation for the field of

cardiac surgery. Lewis and Taufic in 19523 performed the first open closure of an atrial septal defect

(ASD) by using surface hypothermia and inflow occlusion. In 1953, Gibbon4 performed the first repair

of an ASD with the use of a pump oxygenator that became the model for modern cardiopulmonary

bypass. Next, Warden et al.5 used controlled cross-circulation with an adult as the oxygenator during

intracardiac repairs. Building on the work of Gibbon, Kirklin et al.6 then published the first series of

eight intracardiac operations performed at the Mayo Clinic with the use of cardiopulmonary bypass.

2326

With these landmark efforts focused on congenital heart disease, the field of cardiac surgery was

established.

ATRIAL SEPTAL DEFECT

Cardiac septation occurs between the third and sixth weeks of fetal development. The septum primum,

which arises from the roof of the common atrium and descends inferiorly, initially divides the common

atrium. The ostium primum is the opening below the inferior edge of the septum primum, which is

obliterated as the septum primum fuses with the endocardial cushions. The ostium secundum forms in

the midportion of the septum primum prior to closure of the ostium primum. The septum secundum also

arises from the roof of the atrium and descends along the right side of the septum primum and covers

the ostium secundum. This creates a flap valve whereby blood from the inferior vena cava may

preferentially stream beneath the edge of the septum secundum and through the ostium secundum into

the left atrium. After birth, the increase in left atrial pressure usually closes this pathway.

2 An ASD is a hole in the atrial septum (Fig. 81-1). ASDs are the third most common congenital heart

defect, occurring in 1 out of 1,000 live births and representing 10% of congenital heart defects.7 The

most common ASD is the secundum defect, which occurs when the ostium secundum is too large for

complete coverage by the septum secundum. Ostium secundum defects account for about 80% of ASDs.

An ostium primum ASD, representing 10% of ASDs, occurs from failure of fusion of the septum primum

with the endocardial cushions. The ostium primum defect is discussed later in the section on

atrioventricular septal defects (AVSDs). A third type of ASD is the sinus venosus defect, seen in about

10% of cases. Sinus venosus ASDs are caused by abnormal fusion of the venous pathways with the

atrium and are characterized by defects high in the atrial septum near the orifice of the superior vena

cava or, less commonly, low in the atrial septum near the inferior vena cava. Sinus venosus defects are

frequently associated with partial anomalous pulmonary venous connection, usually with the right

upper pulmonary vein draining into the superior vena cava near the cavoatrial junction. The rarest type

of ASD is the unroofed coronary sinus septal defect. This occurs when there is loss of the common wall

between the coronary sinus and the left atrium adjacent to the atrial septum. This unroofing of the

coronary sinus leads to a communication between the right and left atria at the site of the coronary

sinus.

2327

Figure 81-1. The anatomy of atrial septal defects. In the sinus venosus type (A), the right upper and middle pulmonary veins

frequently drain to the superior vena cava or right atrium. B: Secundum defects generally occur as isolated lesions. C: Primum

defects are part of a more complex lesion and are best considered as incomplete atrioventricular septal defects.

Failure of postnatal fusion of the septum secundum to the septum primum results in a persistent slitlike communication known as a patent foramen ovale (PFO). PFOs are extremely common in the

general population, and autopsy studies have demonstrated a prevalence of 27%.8 PFOs are generally

considered separate from other ASDs due to the absence of significant shunting, but they remain

important clinically due to the occurrence of paradoxical embolization. A paradoxical embolus is a blood

clot arising from a systemic vein that would normally pass to the lungs, but in the presence of a septal

defect, may instead cross into the systemic circulation.

ASDs lead to increased pulmonary blood flow (PBF) secondary to left-to-right shunting. Shunting at

the atrial level is determined by the size of the defect and by the relative ventricular compliance (i.e.,

blood preferentially fills the more compliant ventricle). At birth, both chambers are equally compliant,

but as pulmonary vascular resistance (PVR) falls, the right ventricle remodels and becomes more

compliant. Shunting across the atrial septum causes a volume load on the right heart. A volume load is

created by additional venous return to a chamber during diastole.

The volume overload from an ASD is usually well tolerated, and patients are frequently

asymptomatic. Symptoms tend to develop when the ratio of pulmonary to systemic blood flow (Qp/Qs)

exceeds two. The most common symptoms are fatigue, shortness of breath, exercise intolerance, and

recurrent respiratory infections. Older patients with untreated ASDs tend to develop atrial

dysrhythmias, and adults may develop congestive heart failure (CHF) and right ventricular dysfunction.

Pulmonary vascular obstructive disease may occur rarely as a late complication of an untreated ASD.

Paradoxical embolization is also an important potential complication of an ASD.

2328

The classic physical findings in patients with ASDs include fixed splitting of the second heart sound

and a systolic ejection murmur at the left upper sternal border due to relative pulmonary stenosis (PS)

(increased flow across a normal pulmonary valve). A diastolic flow murmur across the tricuspid valve is

occasionally audible. A prominent right ventricular lift and increased intensity of the pulmonary

component of the second heart sound may occur with pulmonary hypertension. Chest radiography

shows cardiomegaly, with enlargement of the right atrium, right ventricle, and pulmonary artery.

Electrocardiography (ECG) frequently demonstrates right axis deviation and an incomplete right bundle

branch block. When right bundle branch block occurs with a leftward or superior axis, the diagnosis of

AVSD should be considered. Echocardiography confirms the diagnosis of ASD and defines the anatomy.

Cardiac catheterization is important in selected cases to assess PVR in older patients, but it is used more

frequently with therapeutic intent for device closure of ASDs.

Due to the long-term complications associated with ASDs, repair is recommended for all patients with

symptomatic defects and in asymptomatic patients in whom the Qp/Qs is greater than 1.5 or signs of

right heart enlargement. Repair is usually performed in children prior to school age. Closure of ASDs

may be performed surgically or using a device deployed in the cardiac catheterization laboratory.

Surgical repair is usually recommended for large secundum defects and for most other types of ASDs.

The heart is exposed by median sternotomy. Other surgical approaches have been proposed, including

minimally invasive techniques, but there are technical drawbacks associated with each of the alternative

approaches. In most cases, a limited midline incision with a partial lower sternal split provides adequate

exposure and a cosmetically acceptable scar. The heart is carefully inspected for anomalies of systemic

and pulmonary venous return.

Cardiopulmonary bypass is required with minimal cooling. The superior and inferior vena cava are

separately cannulated for venous drainage, and the arterial cannula is placed in the ascending aorta.

Following aortic clamping and arrest of the heart with cardioplegia, the atrial septum is exposed

through a right atriotomy. Small secundum defects or PFOs may sometimes be closed primarily by

suturing the edge of the septum primum to the edge of the septum secundum. More commonly, larger

defects are closed using a patch (polytetrafluoroethylene or autologous pericardium) and a running

polypropylene suture. When anomalous pulmonary venous drainage is present, a baffle is created to

redirect the flow across the ASD. In all cases, care is taken to de-air the left atrium to avoid the

complication of air embolization. Surgical closure of an ASD can be accomplished with a mortality

approaching zero and minimal morbidity.9 Common postoperative complications include atrial

arrhythmias and postpericardiotomy syndrome.

The first transcatheter device closure of an ASD was performed in 1976.10 A number of devices are

currently available for percutaneous closure of secundum ASDs.11 The contemporary success rate for

device deployment is 96% with complete closure at 24 hours of 99% or greater.12,13 The presence of a

deficient rim is the most common reason for failed implantation.13 Device closure has the advantages of

fewer complications and a shorter hospitalization. Device closure of small to moderate secundum ASDs

and PFOs has now become the standard of care at most large centers. Surgical closure remains the

procedure of choice for large or multiple defects, insufficient rims, sinus venous–type defects, and

primum ASDs.

The long-term survival for patients undergoing ASD repair in childhood is normal.14,15 The major

long-term complication following surgical closure of ASD is the development of supraventricular

arrhythmias, although the risk is lowered when the ASD is closed in childhood.15,16 The persistence of

this risk despite relief of right-sided volume overload is thought to be related to incomplete atrial

remodeling or due to the presence of the atriotomy scar. Longer follow-up will be required to determine

whether device closure alters the risk of atrial dysrhythmias.

Occasionally, adults will present with a newly diagnosed ASD. Many studies have confirmed that ASD

closure in adults over the age of 40 increases survival and limits the development of heart failure.17,18

When the Qp/Qs is less than 1.5 and the ratio of pulmonary to systemic vascular resistance (Rp/Rs) is

greater than 0.7, significant pulmonary vascular obstructive disease is usually present. A PVR in excess

of 10 to 12 Woods units/m2 represents a contraindication to ASD closure.

VENTRICULAR SEPTAL DEFECT

Ventricular septation is a complex process that requires accurate development and alignment of a

number of structures including the muscular interventricular septum, the atrioventricular (AV) septum

2329

(arising from the endocardial cushions), and the infundibular septum (which divides the outflow tracts

of the right and left ventricles). The membranous septum is a fibrous portion of the ventricular septum

that is adjacent to the central fibrous body (where the mitral, tricuspid, and aortic valve annuli make

contact).

3 Ventricular septal defects (VSDs) are the most common congenital heart anomalies (with the

exception of bicuspid aortic valve, which occurs in about 1.3% of the population). VSDs are present in

about 4 of 1,000 live births and represent about 40% of congenital heart defects.7 VSDs are classified

based on their location in the ventricular septum (Fig. 81-2). The most common defects are

perimembranous (80%), which are located in the area of the membranous septum. Inlet defects (5%)

are located beneath the septal leaflet of the tricuspid valve and are sometimes called AV canal-type

defects. Defects located high in the ventricular septum are outlet defects (10%). Outlet VSDs are

typically adjacent to both the pulmonary and aortic valves. Outlet defects are also known by several

other names, including supracristal, infundibular, or doubly committed subarterial. Outlet defects are

more common in the Asian population. Trabecular (or muscular) VSDs (5%) are completely bordered by

muscle. Trabecular VSDs are frequently multiple and may be associated with perimembranous or outlet

defects. The size of VSDs varies. By definition, a VSD is nonrestrictive when its size (or the cumulative

size of multiple defects) is greater than or equal to the size of the aortic annulus.

Figure 81-2. The anatomy of ventricular septal defects (VSDs) as seen through the right ventricle. A: Outlet, or subarterial, VSDs

are generally bordered superiorly by the pulmonary valve annulus. B: Perimembranous VSDs are most common, extending from

the membranous septum into the infundibular septum. C: Inlet defects are located predominantly beneath the septal leaflet of the

tricuspid valve. D: Muscular VSDs are situated away from the valves, toward the cardiac apex.

A VSD causes increased PBF due to left-to-right shunting primarily during systole. This creates a

volume load on the left heart (the left atrium and ventricle receive the increased venous return during

diastole). The right ventricle is not volume loaded (blood is ejected from the left ventricle [LV] through

the VSD and directly into the pulmonary circulation); however, it does experience a pressure load. The

volume of shunt flow is determined by the size of the defect and by the ratio of pulmonary to systemic

vascular resistance. After birth, the PVR is still high and shunting across a VSD is sometimes minimal.

Over the first several weeks of life, shunting tends to increase as the PVR normally falls. Therefore, a

2330

patient with a large VSD may be asymptomatic at birth and develop severe CHF symptoms over the first

6 weeks of life.

The natural history for patients with isolated VSDs is highly variable. Most VSDs are restrictive and

tend to close spontaneously during the first year of life. Large VSDs are nonrestrictive, resulting in right

ventricular and pulmonary pressures that are systemic or nearly systemic, and high PBF with Qp/Qs

ratios greater than 2.5 to 3. Moderate VSDs are restrictive, with pulmonary pressures that are one-half

systemic (or less) and Qp/Qs ratios of 1.5 to 2.5. Small VSDs are highly restrictive; right ventricular

pressures remain normal, and the Qp/Qs is less than 1.5. Patients with large VSDs tend to develop

symptoms of CHF by 2 months of age. Patients with smaller VSDs may remain asymptomatic. In

patients with outlet VSDs, prolapse of the aortic valve may occur, producing aortic insufficiency.19

Untreated, excessive PBF leads to pulmonary vascular obstructive disease by the second year of life. The

histologic changes associated with pulmonary vascular obstructive disease have been classified by Heath

and Edwards based on severity.20 Grade 1 consists of medial hypertrophy; grade 2 reflects intimal

proliferation; grade 3 is characterized by intimal fibrosis and vascular occlusion; and grades 4 through 6

describe progressive vessel dilatation, angiomatoid malformation, and necrotizing arteritis. Grades 1

and 2 are considered reversible, whereas the latter stages are irreversible.

Signs of heart failure in infants with large VSDs include tachypnea, hepatomegaly, poor feeding, and

failure to thrive. On physical examination, there is a holosystolic murmur at the left sternal border.

Usually, the murmur is louder with smaller defects. The precordium is active. The pulmonary

component of the second heart sound is accentuated in the presence of pulmonary hypertension. Chest

radiography shows increased pulmonary vascular markings and cardiomegaly. ECG is significant for

right ventricular hypertrophy. Patients with small VSDs have little shunting and are usually

asymptomatic, having only a pansystolic murmur. Patients with moderate VSDs manifest symptoms and

signs that are proportional to the degree of shunting. In patients who have developed significant

pulmonary vascular obstructive disease, the volume of left-to-right shunting is decreased, and the

murmur may disappear. Eisenmenger physiology results when the shunt flow reverses to right to left,

creating cyanosis.

The diagnosis of VSD is confirmed by echocardiography, which accurately defines the anatomy and

excludes the presence of associated defects. Cardiac catheterization is used selectively in older children

and adults in whom elevated PVR is suspected. PVR is calculated by the following formula:

PVR = (PAmean

- LA)/Qp

where PAmean

is the mean pulmonary artery pressure and LA is the left atrial pressure. The units of

resistance by this formulation (using pressures in millimeters of mercury and pulmonary flow in liters

per minute) are Woods units (which can be expressed in dynes/s per cm5 by multiplying by 80). In the

pediatric population, vascular resistance is frequently calculated using the cardiac output indexed to the

body surface area (in square meters) with the resulting indexed resistance units of Woods units/m2. PVR

may be fixed or reactive, and, at the time of cardiac catheterization, response to nitric oxide or 100%

fraction of inspired oxygen (FiO2

) may be assessed.

The management of a patient with a VSD depends on the size of the defect, the type of defect, the

shunt volume, and the PVR. In general, patients with large defects who have intractable CHF or failure

to thrive should undergo early surgical repair. If the congestive symptoms can be moderated by medical

therapy, then surgery may be deferred until 6 months of age. Patients with moderate VSDs may be

safely followed. If closure has not occurred by school age, then surgical closure is indicated. Small VSDs

with a Qp/Qs ratio of less than 1.5 do not require closure unless there is evidence of left-sided chamber

enlargement. There is a small long-term risk of endocarditis for these patients, but this can be

minimized with the appropriate use of prophylactic antibiotics.21 Patients with outlet VSDs have a risk

of developing aortic insufficiency due to leaflet prolapse, and, therefore, all of these patients should

undergo surgical closure.22 Older children and adults must undergo catheterization to assess the

pulmonary circulation. When there is a fixed PVR greater than 8 to 10 Woods units/m2, then surgery is

contraindicated.

Surgical closure is performed through a median sternotomy. Cardiopulmonary bypass is employed

with bicaval cannulation, and the patient is typically cooled to 32°C. After aortic cross-clamping, cold

cardioplegia is delivered through the aortic root to arrest the heart. Exposure of the ventricular septum

is most often achieved by making a right atriotomy and retracting the leaflets of the tricuspid valve.

This provides access to perimembranous, inlet, and most trabecular VSDs. Outlet VSDs are frequently

best exposed via a pulmonary arteriotomy because the defect lies just beneath the valve. Trabecular

2331