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Thursday, January 12, 2012

Congenital heart disease in the adults

Author : Elyse Foster, M.D. Professor of Clinical Medicine and Anesthesia San Francisco, CA

2008-07-28

What is Congenital Heart Disease?

The term congenital heart disease (CHD) refers to a large and varied group of birth defects of the heart and vessels. Taken together, these abnormalities are the most common birth defect in humans, present in nearly 1% of all newborns.  Because of improvements in medical and surgical therapy over the last 30 years, defects that once caused severe illness and death in childhood are now often associated with a normal or near-normal life expectancy.  As a consequence, CHD, once considered to be a childhood disease, now affects a growing number of adult patients and adults with CHD now outnumber children.  Because of the enormous variation in these defects, only the most common ones seen in adults are discussed here. 

Basic Glossary of terms, Cardiac Anatomy, and Physiology

Glossary – Some basic words that are used throughout this section are defined here;

Catheter:  A thin, plastic tube that can be threaded into the heart through a vein or artery, usually in the groin but sometimes from the arm or neck.  Procedures performed in the catheterization laboratory through these catheters are frequently referred to as percutaneous procedures and do not require surgery.
Cyanosis/cyanotic: Derived from the Latin word for “blue”, cyanosis refers to the bluish hue imparted to the skin when the blood has a low oxygen level.  Cyanotic heart defects are those congenital defects that result in a low oxygen levels, generally as a result of mixing of venous (“blue, oxygen-poor blood”) and arterial (“red, oxygen-rich”) blood, combined with reduced pulmonary blood flow.  Babies born with cyanotic defects may be “blue” at birth or may develop cyanosis sometime after birth.
Diastole:  The portion of the cardiac cycle during which the ventricles relax and fill with blood.
Great Vessels:  A term that refers collectively to the main pulmonary artery and the aorta.  They both start as a single vessel in the embryo called the truncus arteriosus.  The pulmonary artery normally lies in front (anterior) of the aorta, which is posterior.
Heart Failure:  A clinical state in which the heart fails to provide sufficient blood flow to meet the demands of the body, or can do so only by raising pressures within the heart and vessels.
Pulmonary circulation: The system of pulmonary arteries that carry deoxygenated blood from the heart to the lungs and pulmonary veins that carry oxygenated blood from the lungs back to the heart.
Regurgitation: Leakage of blood backward through a normally one-way valve.
Shunt:  Abnormal movement of blood from the arterial (left) to the venous (right) side of the circulation or vice-versa.  Shunts can occur within the heart (intracardiac) or outside the heart (extracardiac).
Stenosis/stenotic: Abnormal narrowing of a valve opening or reduction in valve leaflet mobility, resulting in restriction of leaflet movement during the cardiac cycle and resistance to blood flow through the valve.
Systemic circulation:  The system of arteries that carry oxygen-rich blood away from the heart to the rest of the body and veins that carry oxygen-poor blood back to the heart.
Systole: The portion of the cardiac cycle during which the ventricles contract and empty.

Normal Anatomy

The heart consists of four chambers and four valves.  The right and left atria (RA and LA) are thin-walled chambers that receive venous blood from the systemic and pulmonary veins, respectively and serve as reservoirs.  The two atria are separated by a thin wall called the atrial septum, at the center of which is a hole called the foramen ovale that normally seals shut by means of a thin flap of tissue shortly after birth.  In about 25% of people, this hole is never completely sealed shut, a condition termed patent foramen ovale (PFO).  The right and left ventricle (RV and LV) are the muscular pumping chambers of the heart.  Under normal conditions, the LV pumps at substantially higher pressure than the RV, and its walls are thicker. The ventricles are separated by the wall, called the ventricular septum, composed of a lower, thicker muscular portion, and an upper, thinner portion.  The right atrium and right ventricle are separated by the tricuspid valve, which is composed of three thin leaflets held to the right ventricular walls by fine threads called “chords”.  The valve normally allows flow only from the right atrium to the right ventricle.  The LA and LV are separated by the mitral valve, a two-leaflet valve which normally allows one-way flow of blood from the atrium to the ventricle.  Blood is ejected from the RV into the pulmonary artery through the three leaflet pulmonic valve and carried to the lungs.  Blood is ejected from the LV through the three-leaflet aortic valve into the aorta, which is the main artery that carries blood to the rest of the body.  Please see Figure 1.

Normal Physiology (How the normal heart works)

The normal heart functions as two mechanical pumps connected in series.  Venous blood returning from the body enters the RA through large veins termed venae cavae at a pressure of less than 6 mmHg.  It then passes through the tricuspid valve into the RV, which pumps it at a pressure of 20-25 mmHg through the pulmonic valve and to the lungs via the pulmonary arteries.  Passing through the lungs the blood replenishes its supply of oxygen.  Oxygen-rich blood returns from the lungs to the LA via four pulmonary veins at a pressure of less than 12 mmHg and passes through the mitral valve into the LV.  The LV normally pumps the blood at 100-130 mmHg (your blood pressure) through the aortic valve into the aorta.  The pumping activity of the heart is controlled by a complex electrical conduction system.  The rhythm of the heart is set by a pacemaker, comprised of special cells, in the right atrium, and electrical impulses from the pacemaker are conducted rapidly through the rest of the heart.

Abnormal Physiology

In the presence of CHD, the ventricles may be required to adapt to abnormally high blood volumes or pressures.  Pressure overload occurs when a ventricle is required to pump blood through an abnormally small (or stenotic) valve.  In response to pressure overload, the ventricle undergoes a process termed concentric ventricular hypertrophy, in which the ventricular walls become thicker relative to the chamber diameter.  This process may allow for a greater force of contraction, but it also results in a stiffening of the ventricle.  Volume overload occurs when a ventricle is forced to accept an abnormally large volume of blood so that the cavity enlarges but the walls are normal in thickness.  This typically occurs when one of the valves is regurgitant or when a shunt is present.

How is congenital heart disease diagnosed?

When is congenital heart disease suspected?

Congenital heart diseases range from severe abnormalities that produce critical life threatening illness during infancy – as early as the first day of life – to milder abnormalities that produce symptoms during adulthood or that are discovered only on routine examinations.  Congenital abnormalities typically manifest themselves in one of three different ways. 
First, some abnormalities can produce cyanosis because of low oxygen in the blood.  This is often readily apparent to patients and their families and prompts medical attention.  Second, some abnormalities can produce heart failure, characterized by fatigue, shortness of breath, and swelling; this typically prompts a visit to a physician.  Finally, many congenital heart defects produce abnormalities on the physical exam, principally murmurs, which are abnormal heart sounds heard through a stethoscope.  A murmur may be detected in a patient who feels well and this may trigger an evaluation.  The evaluation of these complaints typically begins with a thorough medical history and physical examination, an electrocardiogram (EKG), and, if abnormalities are detected, the performance of one or more specialized diagnostic tests.

What tests are used to make the diagnosis?

1. Chest X-ray:  Once a mainstay in the diagnosis of congenital cardiac abnormalities, the chest or X-ray can provide information regarding heart size, the position and size of the great vessels, and the amount of blood flow to the lungs.  While this information can be very useful, newer techniques (see below) provide greater detail.
2. Echocardiography:  An echocardiogram is a clinical examination of the heart that uses sound waves to generate both moving and still pictures of the heart.  It can also be used to show blood flow patterns within the heart and therefore provides highly detailed information on both the anatomy and physiology of the heart.  It has become a standard initial test in the evaluation of congenital heart disease in both children and adults  (Please see echocardiography KNOL).
3. Cardiac Catheterization:  (see glossary)  Catheterization is an invasive technique by which thin tubes are inserted into peripheral arteries and veins (typically in the groin) and advanced into the heart and arteries.  Contrast material, “dye” that is opaque to X-rays, can be injected through these catheters, creating moving pictures of the internal structures of the heart.  Pressure measurements can also be made through these catheters, which provide information about how the heart is working.  In recent years, many therapies have been developed using devices that can be delivered into the heart and great vessels through catheters to expand arteries and veins, to close holes through which shunts occur, and to open areas of obstruction
4. Advanced imaging/MRI, CT:  These newer techniques can provide highly detailed pictures of the heart and great vessels.  Computed tomography (CT) uses X-rays to create images that are assembled by computer.  Magnetic Resonance Imaging (MRI) is accomplished by exposing the patient to a magnetic field, leading to vibration of the molecules in the body’s tissues.  These vibrations can then be analyzed by a computer that generates images.  MRI can also be used to calculate blood flows in some circumstances.

Specific Abnormalities


CONGENITAL ABNORMALITIES WITHOUT CYANOSIS


CONGENITAL AORTIC STENOSIS

Congenital aortic stenosis is the most common congenital heart abnormality and makes up 7% of all forms of congenital heart disease. Men are affected two to three times as often as women. In this condition, the aortic valve, which normally has three leaflets, is often termed “bicuspid” because two of the leaflets are fused together. The valve does not open properly and therefore results in obstruction to blood flow, usually mild in childhood. Over time the leaflets can be come thick and rigid with worsening obstruction that causes high pressures in the left ventricle. This increase in pressure causes hypertrophy of the LV. The valve often does not close properly either, resulting in aortic regurgitation (leakage of blood back from the aorta into the left ventricle during diastole) which may cause the ventricle to enlarge. Please see Figure 2.

Symptoms generally appear in the forties and fifties and typically include shortness or breath, chest discomfort (angina pectoris), and fainting (syncope) with exertion.

There is a murmur on physical examination. The EKG is typically abnormal in congenital aortic stenosis, showing evidence of hypertrophy, or thickening, of the LV, and this may provide a clue to diagnosis. Echocardiography is the most reliable test in the diagnosis of congenital aortic stenosis. It provides images of the abnormal valve, measures the severity of the obstruction and the back leak, and evaluates the effect of the valve disease on the left ventricle. Cardiac catheterization, once a mainstay in the diagnosis of congenital aortic valve disease, is no longer necessary in every case. It is still performed, however, to identify coronary artery blockages prior to valve surgery in older patients and those with risk factors for coronary artery disease.

Once the patient develops symptoms of aortic stenosis, the prognosis without treatment is poor; 90% of these patients die within five years. The primary treatment in adults is surgical valve replacement. Surgery is indicated in the symptomatic patient with severe aortic stenosis (valve area less than 1.0 cm2) and is recommended in the asymptomatic patient with critical stenosis when the patient requires cardiac surgery for another reason. Although balloon valvuloplasty, which is a percutaneous method that uses an inflated balloon to open the valve, has been successful in children and adolescents, the results in most adults have been disappointing.

The diseased valve is replaced by a mechanical or bioprosthetic valve. The choice of prosthetic valve requires consideration of several factors. Mechanical valves last longer but require anticoagulation (blood-thinners) to reduce the risk of clot forming on the valve – and long-term anticoagulation carries a risk of bleeding. Bioprosthetic valves, which are made of a variety of animal or human tissues, usually do not last much beyond 10 years because they become calcified and stenotic, particularly in younger patients, but they do not require long-term anticoagulation. The Ross procedure (in which the patient’s own pulmonary valve replaces the aortic valve, and an aortic or pulmonary homograft replaces the pulmonary valve) has been performed and does not require anticoagulation. However, long term complications have diminished enthusiasm for the Ross prodedure in adults.

After valve replacement, patients typically have normal exercise tolerance and their life expectancy is good, although not quite normal. As noted above, prosthetic valves tend to degenerate over time; bioprosthetic valves usually last approximately 10 years while mechanical valves may last 30 or more years. Young patients therefore are likely to require reoperation later in their lives and must be followed at least annually over the course of their lives.

PULMONIC STENOSIS

Pulmonary valve stenosis (PS) is characterized by a conical or dome-shaped valve with a narrow outlet at its apex. While it may be the only abnormality, it can occur with other congenital heart defects, such as an atrial septal defect [ASD], ventricular septal defect [VSD], patent ductus arteriosus, or tetralogy of Fallot [TOF]). The outlet of the RV is obstructed, so right venticular pressure increases and the the right ventricular wall increases in thickness. Patients are often aysmptomatic and PS is detected because of a murmur. When severe obstruction is not relieved, the patient may develop exercise intolerance, fatigue, shortness of breath, chest pain, fainting spells, and swelling of the legs. The normal increase in blood volume during pregnancy may lead to right ventricular failure in patients with severe PS, although mild and even moderate stenosis are usually well tolerated. Please see Figure 3.

Echocardiography is usually the diagnostic test of choice. On this test, the pulmonic valve is abnormal and there is increased flow velocity across the valve that correlates with the pressure drop (gradient) across the valve. PS is classified as mild when the maximum gradient is less than 50 mmHg, moderate when the gradient is 50-79 mmHg, and severe when the gradient is greater than 80 mmHg. Transesophageal echocardiography provides more detailed pictures of the valve and may help guide treatment.
In most patients cardiac catheterization is not required to make the diagnosis and should only be performed by cardiologists who can perform percutaneous balloon valvuloplasty, which has become the treatment of choice in most children and adults with pulmonary valve stenosis. During heart catheterization a catheter is inserted into the femoral vein in the groin and advanced into the heart and out to the pulmonary artery. A balloon is carefully positioned in the narrowed opening of the valve and inflated to expand it.  This procedure may not be adequate if the obstruction is primarily below the valve due to muscle bands in the right ventricle.  In these cases, surgical excision of the abnormal muscle may be required. 
Many adults had PS corrected surgically as children, usually opening the valve. In a small percentage of these patients, the valve may develop progressive regurgitation and eventually require replacement. These patients should have echocardiograms every three to five years to screen for this complication. When valve replacement is need because of severe regurgitation, a bioprosthesis is used. As is the case in patients after aortic valve replacement, patients who have had pulmonic valve replacement typically have normal exercise tolerance and near-normal expected longevity. Bioprosthetic valves tend to last longer in the pulmonic position than in the aortic position, but are still prone to eventual degeneration and may need to be replaced later in life.

ATRIAL SEPTAL DEFECT (asd)

The term atrial septal defect refers to a hole between the RA and LA.  It is a common abnormality that is often diagnosed for the first time in adults. Please see Figure 4.  Blood shunts mostly from left to right across the ASD when pressures in the lungs are normal.  The RV becomes enlarged due to the increased blood flow  Over time, excessive flow in the pulmonary arteries can lead the arterial walls to thicken.  This increases the pressure in the pulmonary circulation and the  RV walls become thicker and stiffer.  Blood then flows less readily into the RV and ultimately oxygen-poor blood can begin to flow from right to left, producing cyanosis.  This entire phenomenon is called Eisenmenger’s Syndrome and only affects about 15% of patients with an atrial septal defect.
The hole may occur in different locations in the atrial septum.  The most common type is in the middle of the septum and is called an “ostium secundum” ASD. When the defect occurs low in the atrial septum close to the mitral valve (termed “ostium primum” ASD, commonly seen in patients with Down syndrome), it may be associated with a misshapen and leaky mitral valve.  There may also be a hole in the membranous ventricular septum, also known as an atrioventricular septal defect (AVSD) or AV canal defect. The third major type is a sinus venosus ASD higher in the septum which often has some of the veins draining the lungs emptying into the right instead of left atrium. 
Patients with ASDs often have no symptoms through early adulthood and the defect is often discovered during routine physical examination, because of a murmur. Patients will occasionally notice fatigue and exercise intolerance. The echocardiogram typically demonstrates enlargement of the RA and RV. The abnormal blood flow through the ASD may be seen, and injection of saline into a peripheral vein during the study is usually performed to allow the physician to see the shunt. Transesophageal echocardiography may also be performed to provide greater anatomic detail of location and size of the hole, information that is important if closure is contemplated. Cardiac catheterization is often no longer necessary to make the diagnosis, but may be helpful in quantifying the degree of the shunt, and in some cases is therapeutic.

In the past, patients with very large amounts of shunted blood had some reduction in their life expectancy, so closure is recommended for adult patients with RV enlargement and large shunts, if severe pulmonary hypertension is not present. Options for treatment include surgery, in which a patch is sewn over the ASD, and percutaneous therapy, in which a device that closes the defect is introduced through the major vein in the leg and placed in the ASD. The choice of therapy is determined primarily by the size and location of the ASD and its relationship to the pulmonary veins. Patients with ostium primum and sinus venosus ASDs require surgery, while most patients with secundum ASDs are able to have catheter based closure. Patients who have had their ASDs closed either surgically or percutaneously and who do not have severe RV enlargement or pulmonary hypertension typically have normal exercise tolerance and life expectancy.

VENTRICULAR SEPTAL DEFECT (VSD)

Ventricular septal defect (VSD) is a common congenital heart defect consisting of a hole between the RV and LV.  VSDs may be located either in the lower, muscular portion of the ventricular septum, or in the upper, membranous portion of the ventricular septum.  Because RV pressure is usually much lower than LV pressure, blood tends to be shunted from left to right across the VSD during systole (ventricular contraction).  Please see Figure 5.  As with ASD, the result is an increased output from the RV compared to the LV but in this case it is the left atrium and left ventricle that enlarge. These patients are more prone to develop Eisenmenger’s Syndrome if a large VSD is not closed in childhood than those with ASDs.  Finally, unlike patients with ASDs those with VSDs are at risk for endocarditis (bacterial infection).
The clinical manifestations depend largely on the size of the VSD.  Patients with very large VSDs can develop heart failure in infancy.  Conversely, small VSDs may only be discovered incidentally during adulthood when a murmur is heard or, rarely, when the patient comes to medical attention because of endocarditis.  Additionally, VSDs may become smaller as the heart grows, and many VSDs close spontaneously during childhood usually before age 12. 
The diagnosis of VSD is usually suspected by the physician who hears a characteristic murmur.  The diagnosis is readily confirmed by echocardiography, which may also demonstrate LV and LA enlargement.  Cardiac catheterization is usually not necessary to make the diagnosis, but is often important in determining whether surgery is required. 
Closure of the VSD is recommended for patients with moderate to large shunts, particularly when there is evidence of LV enlargement.  Surgery has been the mainstay of treatment for over 40 years, and the procedure can be done very safely with excellent long-term outcomes.  Devices like those used to close ASDs percutaneously are available for VSDs in the lower portion of the septum but not in the upper portion.  Patients who have had VSDs closed and who do not have significant LV enlargement or pulmonary hypertension typically have normal exercise tolerance and life expectancy.

PATENT DUCTUS ARTERIOSUS (PDA)

In normal fetal development, the lungs are not functional, so the fetus receives its oxygen-rich blood through the veins returning from the placenta.  In the fetus it is normal for the venous blood coming into the right atrium to be shunted  across the atrial septum through the foramen ovale.  Some of the blood that passes through the tricuspid valve and into RV is pumped to the pulmonary artery and then enters the aorta across a connection called the ductus arteriosus (arterial duct).  Please see Figure 6.  This duct normally closes on the first day of life.  If the duct remains patent (open), blood can flow from the high-pressure aorta into the low-pressure pulmonary artery.  The result of this shunt is analogous to the situation seen in VSD, namely increased pulmonary blood flow and enlargement of the left ventricle. Eisenmenger’s Syndrome can develop if the pulmonary blood flow is excessive. 
Babies born with a large PDA can develop heart failure in infancy.  Smaller shunts may be detected only by the presence of a characteristic continuous murmur sometimes called a machinery murmur because of its sound  The PDA is also prone to the development of infection (endarteritis).  Because of this risk, closure of the PDA is recommended in all adults.  Options for closure include surgery and percutaneous insertion of a device or coils to block the duct, and the choice between these two is determined by the size and shape of the defect.  Patients who have had PDAs closed and who do not have significant LV enlargement or pulmonary hypertension typically have normal exercise tolerance and life expectancy.

COARCTATION OF THE AORTA

Coarctation of the aorta refers to a narrowing of the aorta. This condition is approximately two to five times more common in men than in women. Most often, the aorta is narrowed by a shelf of tissue just after the take-off of the artery to the left arm (subclavian artery), but sometimes the aorta is narrowed over a long portion. Please see Figure 7. It is commonly associated with bicuspid aortic valve. Additional coexisting problems may include congenital mitral valve disease and small aneurysms of arteries in the brain (the latter are present in approximately 10-25% of patients with coarctation). The primary problem caused by aortic coarcation is elevated blood pressure in the upper body.
Adults with coarctation typically feel well, but may develop symptoms of shortness of breath, leg fatigue, headache, and exertional intolerance in their twenties and thirties. Heart failure can occur over time because of the strain on the LV. Additional significant complications, usually occurring between the ages of 15 and 40, include bacterial infection at the site of coarctation or on an associated bicuspid aortic valve and, very rarely, stroke or rupture of the aorta. Patients with coarctation are at risk for developing blockages of the coronary arteries at relatively early age.
The physical examination shows that blood pressures are higher in the arms than in the legs.  It is important that any younger patient diagnosed with high blood pressure has the pressures in legs measured at least once.  There also may be a delay detected between the pulse in the arm and the pulse in the groin.  A murmur may be heard in the front of the chest as well as the back.  The chest X-ray may show characteristic “rib notching” that prompts further evaluation.  Echocardiography can diagnose the bicuspid aortic valve, but often does not show the coarctation itself in adults.  The best current tests for identifying the site and extent of coarctation are MRI and CT.  Patients with coarctation documented by one of these methods are often referred for cardiac catheterization, particularly because percutaneous techniques now exist to repair the defect nonsurgically.
Coarctation is usually detected and corrected during childhood; untreated coarctation of the aorta has a poor prognosis , with 50% of patients dying by age 30 and 90% by age 60.  Options for therapy include surgery and percutaneous balloon angioplasty and stenting.  Surgical techniques have improved considerably over the years.  The choice between surgery and percutaneous therapy is somewhat controversial: compared with surgical therapy, stenting has similar morbidity and mortality, but is associated with a significantly higher incidences of recurrence of coarctation, need for repeated procedures, and persistent hypertension.  After coarctation repair, patients remain at risk for stroke, aortic aneurysm, aortic dissection, and disease of the coronary arteries.  For this reason, the life expectancy after surgery or stenting is not quite normal, and patients must be followed regularly by a physician.  Patients who have had surgery or stenting must be monitored with periodic CT or MRI to detect the complications above.  It is essential to screen women of child bearing age for post-repair aneurysms as the risk of rupture during pregnancy is high.

CONGENITALLY CORRECTED TRANSPOSITION OF THE GREAT VESSELS

This confusing term refers to an uncommon abnormality in which the ventricles are inverted, meaning that the LV pumps blood to the lungs while the RV pumps blood into the aorta and the RA, which receives venous blood in the normal fashion, is connected to the LV, while the LA is connected to the RV.  The circulation of blood is therefore normal, but the right ventricle is required to pump at higher than normal pressures (about 120 mmHg vs. 25 mmHg).  In addition to the inverted ventricles, the pulmonary artery, which is normally located in front of the aorta, is positioned behind the aorta.  Please see Figure 8.  This condition is sometimes associated with other cardiac abnormalities such as ventricular septal defect (see VSD, below), subvalvular PS, and heart block (defined as a loss of electrical connection from the atria to the ventricles). 
Most patients have no symptoms through early adulthood.  Patients with PS and VSD may develop cyanosis if venous blood travels from the LV across the VSD into the RV.  Over time, the right ventricle tends to enlarge in the face of systemic arterial blood pressure and heart failure can develop.  This is particularly true of patients with significant regurgitation of the tricuspid valve or with a large VSD.  Patients with heart block may complain of fatigue or fainting spells, and are at risk for sudden death and require a pacemaker. 
While patients with corrected transposition who develop heart failure may be managed initially by routine medical means (see section V.-C.), many are eventually considered for specialized surgery or even heart transplant.  The optimal surgical approach is controversial.  Some experts advocate a “double switch” procedure that combines an atrial switch with an arterial switch (see section V.-A.).  Patients with VSD or significant tricuspid regurgitation, both of which impose a volume overload on the right ventricle, may benefit from surgical correction of these lesions.  In any case, decisions regarding surgical therapy in these cases is difficult, and patients with this rare condition should be seen by doctors who specialize in congenital heart disease.

EBSTEIN’S ANOMALY

Ebstein’s anomaly is a rare abnormality of the tricuspid valve in which the leaflets are located further toward the apex or tip of the RV than normal, causing it to leak. The right atrium enlarges with the back leak of flow. The right ventricle is small and may be inadequate to pump the normal volume of blood to the lungs. An atrial septal defect (ASD) or patent foramen ovale (PFO) occurs in roughly 80-90% of these patients. This hole may allow blood to be shunted from right to left across the atrial septum, resulting in cyanosis. Arrhythmias, abnormally fast heart rates, are common in Ebstein’s anomaly, and may result from the abnormal enlargement of the right atrium or from a common abnormal electrical connection between the atria and ventricles (termed the Wolff-Parkinson-White syndrome).
Patients’ symptoms may vary greatly. Some develop heart failure and cyanosis in infancy, while others live a normal life span and the abnormality is only found incidentally or when the patient has palpitations due to a rapid heart beat. The diagnosis is readily made by echocardiography, which may show the abnormal tricuspid valve as well as tricuspid regurgitation.
Patients with severe tricuspid regurgitation may require surgery to repair or replace the tricuspid valve. Because this surgery is very complicated, it should be performed by surgeons who specialize in congenital heart disease. Other surgical procedures may be required when the right ventricle is too small. Because arrhythmias are common, patients should have periodic monitoring, and many arrhythmias can now be cured by percutaneous ablation procedures.

CYANOTIC ABNORMALITIES

Most people with cyanotic heart disease have one of the four “T’s” – Tetralogy of Fallot, Tricuspid Atresia, Transposition of the Great Arteries, or Total Anomalous Pulmonary Venous Drainage. Others may have even more complex disease in which one of the two ventricles is so small that these are called single ventricle syndromes.  The last category of cyanotic disease involves people who start out with shunt lesions (ASD, VSD, PDA) and end up with reversing their shunt (the Eisenmenger syndrome, see above).  Adult patients with cyanosis should be followed in special centers for congenital heart disease.  There is a great deal of individual variation within this population of patients, and general statements about prognosis are difficult.  However, while surgical innovations in the last 40 years have greatly improved the quality of life and life expectancy of patients with cyanotic heart diseases, these operations cannot be seen as complete corrections.  Exercise capacity after surgery is rarely normal, and the life expectancy is nearly always shorter than normal.

TETRALOGY OF FALLOT

The most common cyanotic congenital heart defect, Tetralogy of Fallot (TOF), refers to a collection of four findings: pulmonary stenosis, membranous ventricular septal defect (VSD), rightward displacement of the aortic valve so that it straddles the VSD, and RV hypertrophy.  Please see Figure 9.  Because the path for blood flow from the right ventricle to the pulmonary artery is blocked, the pressure in the right ventricle builds up.  When it is higher than the pressure on the left side, the oxygen-poor blood goes into the left ventricle across the VSD.  This produces cyanosis and decreases blood flow to the lungs.  The right ventricular walls get thicker in response to the high pressure, and muscle bundles below the pulmonic valve may worsen obstruction to flow into the pulmonary artery. 
The outlook for the patients depends mostly on the severity of the blockage .  Patients with severe pulmonic stenosis will be very blue as infants, while those with mild pulmonic stenosis will have fairly normal pulmonary blood flow, with little shunting, and will may only develop cyanosis during exercise (“pink tetralogy”).
The vast majority of adults with TOF will have had corrective surgery during childhood.  In the past, surgery usually consisted of creation in infancy of a Blalock-Taussig shunt (see V.-A.), to increase flow to the lungs, followed by patching of the VSD and opening the path from the right ventricle to the pulmonary artery, usually at school age.  Today, most patients undergo complete repair during infancy.  After repair, patients usually have near-normal exercise capacity, and the life expectancy is excellent (98% twenty-year survival among patients discharged from the hospital after repair).  However, during adolescence and early adulthood many patients develop progressive pulmonic valve leak (regurgitation) and the RV enlarges.  These patients can then develop heart failure and arrhythmias, and put the patient at risk for sudden cardiac death.  Patients therefore require periodic echocardiography and/or magnetic resonance imaging (MRI) to assess the degree of pulmonic regurgitation and RV enlargement.  In patients with severe pulmonic regurgitation and RV enlargement, reoperation is recommended to replace the regurgitant pulmonic valve with a bioprosthetic valve. Roughly a quarter of patients with TOF carry a genetic mutation (del22q11) that can be passed to 50% of their offspring and genetic counseling is recommended for both mean and women who contemplate having families.  Pregnancy is generally safe for women with prior surgery for TOF, but correction of pulmonary regurgitation may be recommended first.

TRICUSPID ATRESIA

In tricuspid atresia, the tricuspid valve fails to form and there is no connection between the RA and RV.  Venous blood returning to the right atrium can only leave the right atrium through an atrial septal defect so the patient is cyanotic from birth. Please see Figure 10.  Without any surgery to increase the flow to the lungs, most infants will die.
Therefore, nearly all adult patients with tricuspid atresia will have had some type of surgery. Most patients ultimately undergo a Fontan operation that essentially bypasses the right ventricle by directly connecting the venous supply to the pulmonary artery. (see section V.-A.)  Patients who have repaired tricuspid atresia can do very well into adulthood but need specialized care by experts in congenital heart disease throughout their lives. After the Fontan operation, prognosis varies widely.  The exercise tolerance is often greatly improved, but not normal, and the life expectancy is significantly reduced.  Patients should generally be seen on at least an annual basis and have annual examinations and echocardiograms performed by physicians who are experts in congenital heart disease.  Please see section V.-A. for details of complications after the Fontan operation.

TRANSPOSITION OF THE GREAT VESSELS

In transposition of the great vessels (TGV), also termed (d-) transposition of the great arteries (d-TGA), the great arteries are abnormally positioned and connected to the “wrong ventricle.”  The aorta, which is normally behind the pulmonary artery (PA), is located in front of the PA and arises from the RV, while the PA arises from the LV and is in back of the aorta.  The result is that there is continuous movement of oxygen-poor blood returning from the veins in the body back to the aorta and the oxygen rich blood coming back from the lungs going back to the lungs. Please see Figure 11.  Survival in the first day of life depends on maintaining the connections between the right and left heart that normally are present in the fetus and sometimes medications or procedures are performed to keep these open until surgery can be done. This defect is three times more common in infant boys than in girls.  Cyanosis is present at birth.           
Virtually all adult patients with TGA have had surgery in infancy or early childhood. The type of surgery has changed over the years.  Until approximately 20 years ago, the standard operation was an atrial switch procedure, termed the Mustard or Senning operation (see section V.-A.).  More recently, surgeons have favored the arterial switch, or Jatene procedure, in which the aorta is removed from the RV and transplanted to the LV, while the PA is removed from the LV and transplanted to the RV (see section V.-A.)  Adults who had the Mustard or Senning generally due well but have a relatively high rate of developing abnormal heart rhythms and heart failure.  The arterial switch operation will likely be associated with a lower incidence of these problems, but has its own set of complications.  These patients should have specialized care.

TRUNCUS ARTERIOSUS

The aorta and pulmonary artery develop in the embryo as a single vessel (the truncus arteriosus) which then becomes divided in two.  When this division fails to occur completely, the result is a single arterial trunk, connected to a single valve which sits above a ventricular septal defect, a condition referred to as truncus arteriosus.  Please see Figure 12.  The single “truncal valve” is often misshapen, containing four or more cusps, and is leaky.  There are a number of variations in the type of connection between the aorta and the pulmonary artery, which influences the type of surgery that is done.
This uncommon abnormality, which occurs equally in girls and boys, usually produces severe symptoms in infancy. Therefore, adults who never had surgery for this condition are rarely found. Before surgery, patients have cyanosis because the arterial and venous blood is combined resulting in lower oxygen levels in the blood reaching the body. In addition, the LV becomes enlarged and heart failure may develop. Surgical repair consists of closing the ventricular septal defect, separating the pulmonary arteries from the aorta, and placement of a tube containing a valve to connect the RV and the pulmonary arteries. Common problems after the operation include continued leaking of the truncal valve and late problems with the valve in the implanted conduit, both of which may require reoperation. In either case, patients may begin to develop shortness of breath and exercise intolerance and the physician may hear an increasing murmur. These problems may also be detected by routine surveillance echocardiograms.

TOTAL ANOMALOUS PULMONARY VENOUS RETURN

In total anomalous pulmonary venous return, the pulmonary veins drain either directly or indirectly into the right atrium rather than the left atrium. There is always an atrial septal defect, the hole between the two atria. Patients usually come to attention in infancy, and 80% die within the first year of life without treatment. Those with a large ASD and low pressures in the lungs may occasionally reach adulthood without surgery. To correct the problem, the surgeon must connect the pulmonary veins to the left atrium. Patients usually do well after surgery, but some develop obstruction of the pulmonary veins where they’ve been connected, leading to shortness of breath and occasionally to recurrent bronchitis and pneumonias.

“SINGLE VENTRICLEs” AND OTHER COMPLEX ABNORMALITIES

As noted in the introduction, there are almost an infinite number of variations in the types of congenital heart disease.  Many of the remaining diverse anomalies can be conceptualized in broad categories.  In one category, both the pulmonary artery and aorta arise from one ventricle, usually the right.  There is always a ventricular septal defect and the LV is usually small.  In another category of defects, both the tricuspid and mitral valves empty into one ventricle, typically the LV.  In this case, the RV is usually small and underdeveloped.  Within both of these categories, tremendous variability exists.
As with many of the other complex congenital heart defects, diagnosis of these conditions usually occurs in infancy.  Surgical treatment is determined by the anatomic details in the individual patient.  Surgery cannot completely correct the abnormality and patients usually have a shunt created to increase the flow to the lungs or undergo the Fontan procedure, similar to those with tricuspid atresia.(See section V.-A.)

EISENMENGER’S SYNDROME

As has already been described, patients with shunts due to atrial septal defect, ventricular septal defect, or patent ductus arteriosus can develop pulmonary hypertension over time, due to the high flow in the lungs.  Pressures rise to levels close to that of the systemic blood pressure, the pressure in the arteries equivalent to the blood pressure measured in the arm. When this occurs, the shunt can reverse from left to right to right to left.  The venous blood entering the arterial blood, lowers the oxygen content.  The cyanosis is associated with many problems that are listed below.  Importantly, women with this problem are at extremely high risk for pregnancy with mortality as much as 50%.  Recently, special medications called pulmonary vasodilators may be improving the outlook for these patients.

Treating congenital heart disease

Surgical Techniques and Catheter-Based Procedures 

Over the past forty years, there has been enormous progress in surgical techniques for congenital heart disease.  These operations are often named for the surgeons who invented them.
The Fontan operation redirects blood from the right atrium or the large veins feeding it into the pulmonary artery, bypassing the right ventricle.  It is performed when the RV cannot support the pulmonary circulation or when flow of blood from the  RA to the RV is obstructed.  The original use of this operation was for tricuspid atresia in which there is essentially  congenital absence of the valve. Please see Figure 14.  While this operation is initially successful in relieving the obstruction and providing adequate flow to the lungs, there are many long-term complications. Exercise tolerance is usually markedly improved after the Fontan operation, but is not normal.  The life expectancy is significantly reduced.  The most frequent problems faced by patients after the Fontan operation include arrhythmias, which may be treated by ablation procedures (see section V.-D.), heart failure, swelling of the legs and abdomen caused by loss of serum proteins from the gut, swelling due to obstruction of the Fontan conduit, and clot formation in the Fontan conduit. The care of Fontan patients is complex and should generally be undertaken in a specialized center by experts in congenital heart disease.
The Rastelli operation involves placement of a conduit (tube) to connect the RV to the pulmonary artery in situations where the pulmonary valve is absent or severely blocked. The conduit may be made of either synthetic or biologic material and may contain a valve that is analogous to the pulmonic valve. Please see Figure 13. The most frequent problems are caused by obstruction of the conduit or its valve, or by deterioration of the valve, resulting in leakage. If the leakage or obstruction becomes severe enough to impose a significant hemodynamic burden on the RV, surgery is often necessary to replace the conduit.

The Mustard and Senning operations are known as atrial switch procedures designed to correct the circulation of patients with transposition of the great vessels (TGA). In both procedures, a channel, called a baffle, is created to redirect the blood flow so that blood returning from the body goes to the lungs to pick up oxygen and the blood returning from the lungs rich in oxygen can go to the aorta. Please see Figure 15.  This procedure corrects the circulatory abnormality, but leaves the right ventricle in the high-pressure systemic circulation.  After the atrial switch procedure, patients’ exercise capacity and life expectancy are much improved, but usually not normal.  The most common problems encountered are abnormal heart rhythms (both fast and slow), obstruction in the pathways, regurgitation of the tricuspid valve, and enlargement and weakening of the right ventricle.
The Jatene operation has become the procedure of choice for many patients with TGA, switching the pulmonary artery and aorta, rather than the atria. Please see Figure 16.  The long-term results of the operation appear to be excellent, with the major advantage being that the left ventricle is restored to the systemic circulation.  However, there are some late complications of the operation as well.  The most common long-term complication is narrowing of the pulmonary artery above the pulmonic valve, a situation analogous to congenital pulmonic stenosis.  Another frequent complication is enlargement of the aortic root and leakage (regurgitation) of the aortic valve, resulting in volume overload of the left ventricle.  Finally, because the operation involves removal and reimplantation of the coronary arteries in the repositioned aorta, coronary artery occlusion can occur, resulting in a loss of blood supply to regions of the heart muscle.
The Blalock-Taussig shunt is performed when patients with cyanotic heart disease have inadequate pulmonary blood flow (such as tetralogy of Fallot), and has most frequently been performed in infancy to allow babies to grow so that more complete surgery can be performed.  Through an incision in the side of the chest, the subclavian artery (the artery to the arm usually on the left side) is connected to the PA.  Please see Figure 16.  These shunts can become obstructed with recurrence of cyanosis.  Patients who had the operation performed using the older technique will have a loss of pulses in the arm on the side of the operation. This may result in underdevelopment of the arm.  From a practical standpoint, physicians and nurses must remember to take the blood pressure in the other arm in order to get an accurate reading.
The Glenn shunt is also performed to increase pulmonary blood flow in patients with cyanotic heart disease.  It has also often been used as the first stage of the Fontan procedure.  It involves connection of the superior vena cava (the vein that carries venous blood from the upper body to the right atrium) directly to the pulmonary artery.  Please see Figure 17.
In addition to these surgical procedures, newer percutaneous procedures, can now be performed through tubes, or catheters, that are inserted into peripheral arteries and veins, usually in the leg.  These catheters can be used to deliver devices such as balloons to expand vessels, stents to keep vessels open after balloon inflation, and devices to block holes in the heart.  These percutaneous techniques have become routine treatments for atrial septal defects, pulmonary valve stenosis, coarctation, patent ductus arteriosus, , and narrowing of the pulmonary arteries.  The absolute risk of serious complications from these procedures is generally similar to or lower than that of surgery for the same conditions.  The most common significant complications from these procedures are bleeding and injury to the vessels at the site at which the catheters are inserted.

Management of Cyanotic Heart Disease

Patients with cyanotic heart disease are at risk for problems involving multiple organ systems and must be followed carefully. The low oxygen level in the blood causes the bone marrow to produce more red blood cells (a condition termed polycythemia). If the number of red cells in the blood becomes too high, the blood can become too thick or viscous, leading to fatigue, headaches and, rarely stroke. These problems are more likely with dehydration. Finally, the increased production of red blood cells increases the concentration of uric acid in the blood, which can predispose to the development of gout.
The treatment for problems related to excessively high red blood cell counts is the cautious removal of blood and infusion of saline (phlebotomy). However, excess blood removal can result in iron deficiency, which can produce symptoms similar to hyperviscosity. Patients are also advised to drink adequate amounts of water and to avoid dehydration. Abnormalities of both bleeding and clotting can also occur, and care needs to be taken to avoid medications and situations that may exacerbate this risk. Counseling of the young adult with reference to contraception, pregnancy, and exercise is especially important in this group of patients.

Management of Heart Failure

Patients with heart failure often complain of fatigue, swelling of the legs, and have shortness of breath when they exert themselves or lie flat. The treatment for heart failure ideally involves correction of the anatomical abnormality (for example, correcting a shunt to reduce volume overload).  Diuretic medications are often used to remove fluid, which reduces symptoms due to the back-up of blood.  Blood pressure-lowering medications are often used to reduce the workload of the heart, returning it towards its normal size, and preserving its pumping function.

Management of Arrhythmias

The rhythm of the heart is set by a pacemaker in the right atrium, and electrical impulses travel from there to rest of the heart through a special set of cells called the conduction system.  Loss of function within this system causes abnormal heart rhythms (arrhythmias).  Patients with congenital heart disease are at increased risk of arrhythmias for a number of reasons: 
1) Abnormal development of the conduction system 
2) Chamber enlargement that stresses the heart.
3) Scars in the heart due to previous surgery.
The symptoms associated with arrhythmias include palpitations, lightheadedness, fainting spells, or severe fatigue.  In some cases, patients can be at risk for dangerous arrhythmias that cause cardiac arrest.  Symptoms suggesting arrhythmias must be investigated and sometimes asymptomatic patients are screened with special recorders called Holter monitors or event monitors. 
Patients with slow rhythms may require pacemakers.  In the past, fast heart rhythms have been suppressed with drugs.  Now, percutaneous techniques have been developed to treat a variety of arrhythmias by creating small burns using radio waves at the precise location in the heart that is producing the arrhythmia.  Finally, patients who have suffered or at high risk for cardiac arrest may receive implanted cardioverter-defibrillators, (ICDs), a pacemaker-like device that can deliver electrical shocks to terminate dangerous rhythms.

Endocarditis Prophylaxis/General care

Certain congenital cardiac abnormalities cause abnormal blood flow within the heart, which sets the stage for a bacterial infection in the heart termed endocarditis.  Bacteria most commonly enter the blood stream from lining of the mouth and through breaks in the skin.  Patients with CHD are advised to maintain good oral hygiene and those at the highest risk for endocarditis should take antibiotics during dental procedures to prevent infection.  Patients with complex congenital heart disease also tend not to tolerate severe infections such as pneumonia well, and they are advised to maintain current vaccinations for influenza (the virus that causes the flu) and for pneumococcus (a bacterium that causes pneumonia and other infections).

Summary

Patients with congenital heart disease are as varied as the diseases that affect them.  Adults with these diseases are now surviving in significant numbers.  Most require specialized care with careful anticipation of the problems they can develop, permitting them to lead long and productive lives.


www.nhlbi.nih.gov

References

John M. Miller and Douglas P. Zipes  Catheter Ablation of Arrhythmias  Circulation, Dec 2002; 106: e203 - e205.

Jacques I. Benisty Pulmonary Hypertension Circulation, Dec 2002; 106: e192 - e194.