Author : Elyse Foster, M.D. Professor of Clinical Medicine and Anesthesia San Francisco, CA
2008-07-28
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.
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.
