Grown-up Congenital Heart Disease (GUCH)

Septal defects

Atrial septal defect

Introduction

Atrial septal defect (ASD) is common, accounting for approximately 7 percent of congenital heart disease. The ASD’s can occur in several different anatomic portions of the atrial septum, and the location of the defect generally reflects the abnormality of embryogenesis that led to the anomaly. The functional consequences of an ASD are determined by its diameter, the anatomic location and the presence or absence of other cardiac anomalies.

Classification

The various forms of ASD’s are differentiated from each other by the structures of the heart involved and the formation during embryological development.

The ostium secundum defect is the most frequent form of ASD (70%), localized at the fossa ovalis with a diameter of about 1 – 2 cm. It commonly arises from an enlarged foramen ovale, inadequate growth of the septum secundum or excessive absorption of the septum primum.

The sinus venosus defect (15% of all ASD’s) is localized high in the atrial septum, at the inflow of the superior caval vein. Note that in 80-90% of patients this defect is accompanied by an anomalous pulmonary venous drainage of the right pulmonary vein into the right atrium. Inferior sinus venosus defects do exist, but are very exceptional.

The ostium primum defect is localized low in the atrial septum at the atrioventricular junction. It forms the atrial component of the category of congenital heart disease referred to as atrioventricular defects, with a common atrioventricular junction and an abnormal atrioventricular valve.

The coronary sinus defect, localized at the atrial ostium of the coronary sinus, is rare and usually accompanied by other cardial defects like anomalous drainage of the superior vena cava.

Pathophysiology

The presence of an ASD will in all cases gradually lead to a left to right shunt across the defect. At birth the volume of blood shunting from systemic to pulmonary circulation is small, because the right ventricle is still relatively thick-walled and noncompliant. In response to a decrease in pulmonary vascular resistance after birth, the right ventricle remodels and its compliance increases. This leads to a decrease in right atrial pressure and an increase in shunt volume across the defect during the first years of life.

The blood shunts during the late systole and early diastole, leading to a diastolic volume overload of the right atrium and right ventricle, but also the pulmonary veins and arteries. This volume overload of the pulmonary circulation will consequently lead to right-sided dilatation. The end diastolic increase in pressure of pulmonary circulation can result in systemic venous stuwing. This stuwing is augmented by another mechanism caused by the right ventricular volume overload; deviation of the ventricular septum to the left and the decrease in left ventricle preload because of the left to right shunt, lead to a decrease in stroke volume of the left ventricle. The renine-angiotensin system is activated, leading to an increase in intravascular volume and signs of venous stuwing. The right-sided volume overload is usually well tolerated for years, but in adulthood hemodynamic factors can influence the shunt size in both directions. If the right ventricle will start failing due to chronic volume overlad, the left to right shunt can decrease. If the left ventricle function will decline due to hypertension or coronary artery disease, the lef to right shunt can increase. In 10-20% of adult patients with an isolated ASD pulmonary hypertension will develop, leading to a decrease in left to right shunt and eventually right to left shunt with cyanosis (Eisenmenger syndrome).

Evaluation and therapy

Most ASDs less than 8mm in diameter close spontaneously in infants, however above the age of 4 years spontaneous closure is unusual. During childhood and early adulthood most patients with moderate to large uncorrected ASDs are asymptomatic. Most of them will become symptomatic during adulthood (usually from the age of 40) and require closure of the defect. Indications for closure of an ASD in adulthood are development of symptoms and a high rate of shunt flow. Decreased exercise tolerance, fatigue, dyspnoe, syncope and paradoxal embolization are manifestions of such symptomatic ASDs that warrant closure of the defect. Atrial arrhythmias are usually one of the first presenting symptoms, however these symptoms alone are not an indication for closure, since the incidence after the procedure is not likely to be reduced.

When closure of the ASD is indicated, this can be performed with surgery or percutaneous intervention. Surgical closure is usually performed using a patch of pericardium or Dacron. Prior to surgery, a comprehensive noninvasive evaluation is essential to exclude pulmonary hypertension and associated anatomic defects such as anomalous pulmonary and systemic venous connections. In nearly all cases, echocardiography can resolve these questions, obviating the need for cardiac catheterization.Transcatheter closure avoids cardiopulmonary bypass, thoracotomy, and atriotomy, and is associated with excellent outcomes. As a result, this approach has largely replaced surgery in many centers for patients with a defect that is less than 20 mm in diameter.

Outcome

The short- and long-term outcomes are generally excellent after either surgical or transcatheter closure of an isolated ASD in children. Several investigations showed that there is almost no increase in long-term mortality or serious morbidity compared to controls, following surgical repair of an ASD under 25 years of age. The perioperative mortality is low (< 1%) and there are few perioperative complications (about 10%). However late in adulthood about 50% of all patients develop sinusknoopdysfunctie and symptomatic supraventricular tachyarrhythmias.

When the ASD is closed percutaneously the short-term outcomes (less than one year) are excellent, with reported procedure success rates of 88 to 98%.

Ventricular septal defect

Introduction

The ventricular septal defect is the most common congenital heart defect in childhood (30%). Most patients have an isolated VSD, however a VSD also occurs in combination with other defects like Tetralogy of Fallot, which will be discussed elsewhere. About five percent of all patients with a VSD have a chromosomal abnormality, including trisomy 13, 18 and 21. Due to a high rate of spontaneous closure (50%) VSD is less seen in adulthood.

There are three main anatomic components of the interventricular septum (figure 3); the septum of the atrioventricular canal (1), the muscular septum (2), the parietal band or distal conal septum (3). VSDs may occur at various locations in any of the three components. The location of the defect is not of particular interest when taking the characteristics of the intracardiac shunt in account. However it is important in terms of the frequency of involvement of the atrioventricular valves and the rate of spontaneous closure and additionally the relation to the AV pathway when considering surgical correction.

Classification

The VSD can be classified into four types, related to the anatomic components involved;

Type 1 is the infundibular VSD, which results from a defect in the septum below the aortic and pulmonary valves. The loss of support to the adjacent septal leaflets of these valves causes cusp prolapse into the VSD leading to progressive aortic regurgitation, which is the hallmark of this defect.

Type 2, the membranous VSD, is the most common type of VSD (around 80%) and results from a deficiency of the membranous septum. This defect borders the septal leaflet of the tricuspid valve and might also extend into the muscular septum when it is referred to as a perimembranous VSD.

Type 3 are inlet VSDs, located beneath both mitral and tricuspid valves. Despite proximity to those valves, this type of defect is not associated with mitral or tricuspid regurgitation unless associated with atrioventricular canal defect. This typically large defect is often associated with Down syndrome.

Muscular defects (type 4) are located within the trabecular septum and accounts for 5 – 20% of all VSDs. It is bordered only by muscle, away from the cardiac valves. Muscular defects can be small or large in size and consist of a single or multiple defects.

1.2.4 Pathophysiology

The severity of the shunt across the VSD is determined by its size and the ratio of pulmonary to systemic vascular resistance. In small or restrictive VSDs the diameter of the defect is ≤25% of the aortic annulus diameter. These small defects cause small left to right shunts with no left ventricular overload or pulmonary hypertension.

Moderate sized VSDs, measuring 25 – 75% of the aortic annulus diameter, result into mild volume overload of the pulmonary arteries, left atrium and left ventricle with no or only mild pulmonary hypertension.

In large defects, defined as those with diameters equal or greater than 75% of the aortic annulus, there is no restriction of blood flow across the septum, leading to equal pressures in both right and left ventricle. The large left to right shunt initially only leads to excessive volume overload in the pulmonary arteries, left atrium and left ventricle. The chronic pressure and volume overload combined with the increase flow leads to irreversible changes of the pulmonary vasculature, which results in an increase in pulmonary vascular resistance. This increase in resistance leads to a reversal of the shunt through the VSD causing right to left shunt with cyanosis (Eisenmenger syndrome).

1.2.5 Evaluation

Small defects are usually asymptomatic, however are fairly easy to detect during physical examination. There can be a palpable thrill accompanied by a holosystolic murmur grade 4-6. In some muscular defects the murmur is non holosystolic, due to the contraction and therby closure of the defect during systole. In moderate sized defects, with a large systemic to pulmonary flow of at least 1:2, a middiastolic rumble is audible due to the increased flow across the mitral valve. The pulmonary component of the second heart tone is loud. Only in a large VSD accompanied by the Eisenmenger syndrome and central cyanosis there is barely any shunt murmur audible. However there are murmurs audible caused by the pulmonary hypertension; an earlydiastolic murmur due to the pulmonary valve regurgitation and a holosystolic murmur due to the tricuspid valve regurgitation. Defects with large shunts that cause symptoms like decreased exercise tolerance and dyspnoe are usually detected and closed early in childhood.

The ECG and chest X-ray of a patient with a small VSD are usually normal, but can show signs of left atrial and left ventricle overload in moderate sized defects.

With echocardiography the localisation, size and hemodynamic influence of the VSD can be investigated. Dilatation of the left atrium and left ventricle might be present and the pressures in the pulmonary artery can be estimated by means of the tricuspid regurgitation. Invasive measurement by means of catheterization is only indicated when there is doubt about the shunt size and the pulmonary vascular resistance.

1.2.6 Treatment

Treatment and prognosis of a VSD depends on the size en localisation of the defect, the pulmonary vascular resistance and possible concomitant defects. Spontaneous closure occurs mainly in small defects, of which 75 percent closes before age 10. In patients with a small defect no pulmonary hypertension develops, however there is an increased risk of endocarditis.

In patients with significant shunts studies have shown that surgical closure reduces pulmonary artery pressure and improves long-term survival. Therefore, repair of VSD should be considered in all adult patients who are symptomatic or have signs of left ventricular volume overload.

Medical treatment is reserved for (1) asymptomatic patients without evidence of left ventricular volume overload and (2) patients with symptoms and/or left ventricular volume overload who are not candidates for repair such as those with large defects and Eisenmenger syndrome.

Medical treatment is reserved for (1) asymptomatic patients without evidence of left ventricular volume overload and (2) patients with symptoms and/or left ventricular volume overload who are not candidates for repair such as those with large defects and Eisenmenger syndrome.

Medical treatment is reserved for (1) asymptomatic patients without evidence of left ventricular volume overload and (2) patients with symptoms and/or left ventricular volume overload who are not candidates for repair such as those with large defects and Eisenmenger syndrome.

• Closure of a VSD is indicated when there is a Qp/Qs ≥2 and clinical evidence of LV volume overload.
• Closure of a VSD is indicated when the patient has a history of infective endocarditis.
• Closure of a VSD is reasonable when there is net left to right shunting with a Qp/Qs ≥1.5 with pulmonary artery pressure less than two thirds of systemic pressure and PVR is less than two thirds of systemic vascular resistance.
• Closure of a VSD is reasonable when there is net left to right shunting with a Qp/Qs ≥1.5 in the presence of LV systolic or diastolic dysfunction or failure.

Indications for surgical closure of VSD in infants and young children may include:

• Infants <6 months (<3 months for those with trisomy 21) who have uncontrolled heart failure despite maximal medical and dietary interventions or who have pulmonary hypertension.
• Children with a persistent significant shunt (Qp:Qs >2:1), should undergo surgical repair even in the absence of elevated PA pressures.
• Subpulmonic and membranous defects, regardless of size, with aortic regurgitation should be surgically corrected before the aortic valve is permanently damaged. The decision to close small defects with aortic valve prolapse without aortic regurgitation is controversial.

Closure of a VSD is not recommended in patients with severe irreversible pulmonary artery hypertension.

Transcatheter device VSD closure is a treatment option for isolated uncomplicated muscular VSDs, and for certain membranous VSDs, in selected patients with suitable anatomy. Appropriate anatomy for transcatheter closure includes a VSD location remote from the tricuspid and aortic valves with an adequate rim. Successful transcatheter closure has been accomplished in the presence of multiple muscular or membranous fenestrations.

The technical success rate of transcatheter closure of selected muscular and membranous VSDs is high (93-100%) and the mortality rate is low (0 – 2.7%).

Outcome

The long-term outcome for children who undergo surgical closure of VSD in childhood is generally excellent. Early surgical repair results in near normal long-term growth in the vast majority of patients. Most survivors are asymptomatic and lead normal lives.

Adults with repaired VSD without residua have excellent outcomes and normal survival, with a 25year survival of 83%. However, long-term survival is less favorable when repair is done at older age or in presence of pulmonary hypertension. Although the prognosis after surgical repair of uncomplicated VSD is excellent in the majority of patients, long-term residua and sequelae are not uncommon including conduction disease, cardiac arrhythmias, residual VSD, endocarditis, tricuspid regurgitation, ventricular dysfunction, pulmonary hypertension, and aortic regurgitation.

Development of complete atrioventricular block is the most significant of the transcatheter procedural complications. Approximately 6% of patients who underwent transcatheter closure of membranous defects, developed complete heart block necessitating pacemaker implantation. Real-time three-dimensional transesophageal echocardiography has been increasingly used to guide such procedures. Given the lack of data on long-term outcomes following catheter closure of VSD in adults, patients should be followed every one to two years at an adult congenital heart disease center.

Atrioventricular septal defect

Introduction

The atrioventricular septal defect (AVSD) consist of several different lesions with a common atrioventricular (AV) junction and abnormal AV valves, consisting of five leaflets (figure 5). The AVSD makes 3 procent of all congenital heart defects in children.

When the AVSD is complete it consists of a defect on the atrial and on the ventricular side of the common AV-valve ring. (figure 5, middle). The complete AVSD is usually associated with Down Syndrome, but also with other cardiac defects like ASD type 2, persisting left inferior caval vein and tetralogy of Fallot.

In an incomplete AVSD the superior and inferior bridging leaflets are connected with each other and with the interventricular septum in the centre. (figure 5, right) Due to this connection there are two divided AV inlets, leaving no open communication between the ventricles, thus no VSD exists. However there is a rather large defect in the interatrial septum. The incomplete AVSD is often referred to as ostium primum defect or ASD type 1. The left AV-valve consist of three leaflets (there is a cleft in the mitral valve) and is usually incompetent. Due to one common AV junction in both types of AVSD, the aortic valve is not in the usual wedged position between the two separate AV inlets, but located more anterior. Therefore the outflow tract of the left ventricle is elongated and slightly constricted. In angiography this abnormally shaped outflow tract is known as a gooseneck.

Pathophysiology

The exact pathophysiology depends on the location and severity of the defect. In a complete AVSD there is combined right and left ventricular overload due to the left-to-right shunt at atrial and ventricular level combined with the regurgitation of the right and left AV valve. As a result the elevated pulmonary pressures due to the extremely high flow will rapidly convert to pulmonary hypertension. This will lead to bidirectional shunting across the defect with a preferably right-to-left shunt and cyanosis (Eisenmenger syndrome).

In an incomplete AVSD the hemodynamic consequences are comparable to an ASD type 2. However the serious left AV-valve regurgitation can cause an increase in the atrial left-to right shunt.

Evaluation

The complete AVSD leads to symptoms of heart failure early in childhood and most patients will have been surgically corrected in adulthood. During physical examination signs of a residual shunt or regurgitation of the AV-valves might be present. This defect is rarely diagnosed in adulthood and usually there is Eisenmenger syndrome present, with clinical signs previously described in isolated ASD or VSD. The clinical symptoms of an incomplete AVSD are comparable with those of an ASD type 2. During physical examination a murmur of the regurgitant AV-valve might be audible.

The ECG shows a deviation of the heart axis to the left, in contrast to the right axis deviation in atrial septal defects. This is due to the abnormal position of the His bundle which causes a delay in conduction through the left anterior fascicular branch.

Treatment and outcome

The survival for patients with a complete AVSD without corrective surgery is very limited, most patients will not reach adulthood. Therefore surgical correction at an early age (usually in the first year of life) is advised. Patients with a corrected complete AVSD need lifelong cardiologic follow up, due to frequent residual defects like residual VSD, progressive regurgitation of the left AV-valve, pulmonary hypertension and often rhythm- or conduction disorders. Patients with Down Syndrome and complete AVSD are more likely to develop progressive pulmonary hypertension, even after corrective surgery.

The aberrant anatomy of the AV-valves, even after corrective surgery, is important when reviewing echocardiographic images. They can, for example, be easily mistaken for vegetations in endocarditis.

The survival for patients with an incomplete AVSD is higher compared to the complete AVSD, but generally worse compared to other ASD types. This is due to the concomitant disorders of the left AV-valve and the conduction system. Left AV-valve regurgitation will lead to an increase in left-to-right shunt and earlier development of pulmonary hypertension compared to ASD type 2. In childhood there is usually already an indication for correction of the defect in which the anatomically abnormal AV-valve can be repaired. However a slight amount of regurgitation will remain present. In some cases the progressive failure of the AV-valve will require a second repair or replacement, but in most patients the insufficiency will remain mild.

Besides the AV-valve problems there are frequent rhythm and conduction disorders; atrial fibrillation, supraventricular tachycardia, complete heartblock or sinus dysfunction. Depending on the kind of disorder patients can require medical treatment or a pacemaker.

Patent ductus arteriosus

Introduction

The ductus arteriosus (DA) is a fetal vascular connection between the main pulmonary artery and the descending aorta that diverts blood away from the pulmonary bed (figure 6). After birth, the DA undergoes active constriction and eventual obliteration. A patent ductus arteriosus (PDA) occurs when the ductus fails to completely close postnatally.

The incidence of PDA has increased dramatically over the last two decades. This is due to the improved survival rate of premature infants, because the incidence of PDA significantly increases in infants born before 30 weeks gestation.

The reported incidence of an isolated PDA among term infants ranges from 0.03 to 0.08 percent.

There is a female predominance for PDA with a 2:1 female to male ratio in most case series of term infants. The incidence of PDA is also greater in infants born at high altitude compared to those born at sea level, and in infants with congenital rubella.

PDA may present with other congenital heart lesions, especially those associated with hypoxemia. PDA should be considered when the clinical features of left-to-right shunt seem out of proportion to the particular lesion being considered.

Evaluation

The clinical manifestations of a PDA are determined by the degree of left-to-right shunting, which is dependent upon the size and length of the PDA, and the difference between pulmonary and systemic vascular resistances.

The hemodynamic consequences of the PDAs can be categorized by the degree of left-to-right shunting based upon the pulmonary to systemic flow ratio (Qp:Qs) [21].

• Small — Qp:Qs <1.5 to 1
• Moderate — Qp:Qs between 1.5 and 2.2 to 1
• Large — Qp:Qs >2.2 to 1

Typical findings during physical examination are a continuous murmur and a low diastolic blood pressure. In small shunts the ECG and chest x-ray are normal. In larger left-to-right shunts signs of left atrial and left ventricular overload might be present.

Echocardiography is a very sensitive and specific method to identify the left-to-right shunt.

Treatment and outcome

Patients with an open PDA have an increased risk of infectious endarteritis, heart failure, pulmonary hypertension and most of these patients become symptomatic in adulthood. Patients with a non-restrictive PDA rarely reach adulthood, unless the pulmonary vascular resistance increases leading to a decrease in left ventricular overload. This hemodynamic state is known as Eisenmenger syndrome in which the shunt is reversed and there is cyanosis present. Patients in who the ductus is closed in childhood have a normal life expectancy.

In patients with a PDA, the primary management decision is whether to actively close the PDA, or to conservatively observe and monitor the patient's cardiac status on a regular basis.

PDA closure is recommended for patients with a significant left-to-right shunt who are symptomatic, have evidence of left-sided volume overload or have reversible pulmonary arterial hypertension. Closure results in resolution of symptoms and a decrease in the likelihood or severity of PAH, and the development of irreversible pulmonary vascular disease (Eisenmenger syndrome).

PDA closure is not recommended in patients with severe and irreversible PAH because of the procedural risk, the fact that closure does not improve survival, and right to left ductal shunting may be necessary to maintain cardiac output during episodes of increasing pulmonary vascular resistance.

Interventions for PDA closure include: pharmacological treatment which is used exclusively in premature infants, surgical ligation or percutaneous catheter occlusion. Surgical closure has a low mortality (<1%) in children and young adults. In adult patients the perioperative risk is increased (around 3%) due to a higher rate of complications like bleeding, heart failure in a compromised left ventricular function and damage to the recurrent laryngeal nerve or phrenic nerve.

Percutaneous PDA occlusion was first introduced in 1967 and provides an alternative to surgical ligation. Many different techniques have been developed, however the two techniques most commonly used are coils or occlusion devices. Both techniques lead to a full occlusion of the PDA and normalization of left ventricular hemodynamics.

Coarctation of the aorta

Introduction

Coarctation of the aorta is a narrowing of the thoracic aorta, typically located in the region of the obliterated ductus arteriosum. (figure 9) The relation to the position of the left subclavian artery differs, in most patients the left subclavian artery is located anterior of the coarctation. Aortic coarctation is frequently associated with diffuse hypoplasia of the aortic arch and isthmus.

The incidence of coarctation of the aorta is 4 in 10.000 live births, accounting for 5–9% of the children with congenital heart defects, occurring two to five times more frequently in males than females.

Coarctation of the aorta can be an isolated congenital heart defect, however usually it coincides with other congenital defects. Associated heart defects are patent ductus arteriosus, ventricular septal defect, mitral valve stenosis and valvular and subvalvular aortic stenosis. Furthermore around 75% of all patients with a coarctation of the aorta have a bicuspid aortic valve.

The development of coarctation aorta depends on genetic as well on non-genetic factors. Parents with coarctation aorta have a 2% (male) or 4% (female) chance of passing this defect to their child.

Pathophysiology

Coarctation aorta has no hemodynamic consequences in utero, because only 10% of the total cardiac output crosses from the ascending to the descending aorta. However after birth the ductus arteriosus and foramen ovale close, leading the whole cardiac output through the narrowed aortic segment. This leads to an increase in resistance in the left ventricular outflow tract, resulting in an elevated systolic pressure in the left ventricle and upper extremities. When coping with the elevated pressures, the left ventricle will become hypertrophic.

If the coarctation is severe or in the acute phase (after birth when the ductus is closed), systolic dysfunction of the left ventricle and heart failure can occur.

Most adult patients are asymptomatic unless severe hypertension is present leading to headache, epistaxis, heart failure, or aortic dissection. In addition, claudication may occur due to reduced flow to the lower extremities.

Evaluation

Coarctation of the aorta is easily diagnosed without invasive methods, by means of physical examination, echocardiography or MRI. The combination of weak or absent femoral arterial pulses and upper body hypertension in physical examination points into the direction of coarctation of the aorta. Nevertheless, studies have shown that the diagnosis in hypertensive patients is often missed by the referring doctor. As a consequence, a significant number of asymptomatic subjects with aortic coarctation are probably not detected until adult life, so their incidence at birth is likely to be underestimated. Late detection of subjects with aortic coarctation can have detrimental effects on survival. For, without correction, the mean life expectancy of patients with aortic coarctation is 35 years and 90% of those patients die before reaching the age of 50 years.

Chest radiograph varies with age and severity of the coarctation. In infants with heart failure, the chest radiograph shows generalized cardiomegaly with increased pulmonary vascular markings due to pulmonary venous congestion. In older children and adults, the heart size may be normal but notching of the posterior one-third of the third to eighth ribs due to erosion by the large collateral arteries might be present.

Transthoracic echocardiography, including suprasternal notch views, is useful for initial imaging and hemodynamic evaluation in suspected aortic coarctation. Echocardiographic evaluation should also include measurement of the dimensions of the aortic annulus, aortic sinuses, sinotubular ridge, and ascending aorta; identification of aortic valve anatomy; determination of left ventricular size and function; and identification of any potential associated lesions such as ventricular septal defect, subvalvular aortic stenosis and mitral valve deformity.

Treatment and outcome

Since surgical repair of aortic coarctation became available in 1944, survival of patients with aortic coarctation has dramatically improved and the number of patients who were operated on and reach adulthood is steadily increasing. However, life expectancy is still not as normal as in unaffected peers. Survival of patients operated at a median age of 16 years was 91% at 10 years, 84% at 20 years and 72% at 30 years after operation. Survival of post-coarctectomy patients is significantly affected by age at operation and nowadays early repair is advocated. Even after early repair—before the age of 5 years—the estimated survival is still reduced, with 91% of the operated patients alive at 20 years and 80% at 40 to 50 years after surgery. However, repair of aortic coarctation is still recommended in patients at older age when diagnosis is delayed, because it improves blood pressure regulation and is probably associated with a lower risk of cardiovascular events in later years and improved survival.

Since surgical repair of aortic coarctation became available in 1944, survival of patients with aortic coarctation has dramatically improved and the number of patients who were operated on and reach adulthood is steadily increasing. However, life expectancy is still not as normal as in unaffected peers. Survival of patients operated at a median age of 16 years was 91% at 10 years, 84% at 20 years and 72% at 30 years after operation. Survival of post-coarctectomy patients is significantly affected by age at operation and nowadays early repair is advocated. Even after early repair—before the age of 5 years—the estimated survival is still reduced, with 91% of the operated patients alive at 20 years and 80% at 40 to 50 years after surgery. However, repair of aortic coarctation is still recommended in patients at older age when diagnosis is delayed, because it improves blood pressure regulation and is probably associated with a lower risk of cardiovascular events in later years and improved survival.

Transcatheter interventions for native aortic coarctation have been used for over 20 years. Transcatheter treatment for native aortic coarctation has been shown to be feasible, relatively safe and effective at short term and intermediate follow-up and is rapidly becoming the treatment of choice. Older age, however, seems to be a risk factor for suboptimal outcome after balloon angioplasty possibly due to a more fibrotic and rigid aorta. Especially in the full grown patient, stent placement seems a particularly attractive option, resulting in an almost complete relief of the gradient in 95% of the patients. Another benefit of stent placement is the ability to address longer segment coarctations, which typically have a poorer outcome after balloon angioplasty alone. Long-term results, however, are to be awaited. Concern after surgery or catheter intervention falls chiefly in seven categories: recoarctation, aortic aneurysm formation or aortic dissection, coexisting bicuspid aortic valve, endocarditis, premature coronary atherosclerosis, cerebrovascular accidents and systemic hypertension.

Transposition of the great arteries

Introduction

Transposition of the great arteries (TGA) accounts for 5-8% of all congenital heart defects and occurs 2-3 times more frequently in males. TGA is best defined as a normal atrioventricular connection with an abnormal ventricular–arterial connection; the morphological left atrium is connected through the left ventricle with the pulmonary artery and the morphological right atrium through the right ventricle with the aorta. (figure 12)The aorta is often located on the right side and in front of the pulmonary artery (D-TGA). In 70 percent there is an isolated form of TGA, in 30 percent the TGA is accompanied by other heart defects, like VSD or obstruction of the left ventricle outflow tract.

Pathophysiology

The circulation in TGA patients is not serial but parallel (figure 13); the venous blood is returned to the systemic circulation through the right atrium and ventricle, while the arterial oxygenated blood is directed back into the pulmonary artery through the left atrium and ventricle. Due to this abnormal circulation there is severe cyanosis directly after birth, therefore it is critical for the ductus arteriosus and foramen ovale to remain open. Without treatment there is a mortality of 30% within one week, 50% within one month and 90% within one year. When an associated VSD is present the chances of survival are higher due to more shunting thus more oxygenated blood in the systemic circulation. These patients are able to reach early adulthood without corrective surgery or intervention. However the pulmonary hypertension that develops in this situation will eventually lead to severe problems.

Treatment

Mortality of TGA has dramatically improved from 90 percent for unoperated patients to rates of less than 5 percent following corrective surgery using the arterial switch operation. Most patients are referred for surgical repair during the first three to five days of life. The choice of surgical procedure is dependent on the presence and nature of other cardiac anomalies. In patients without any other cardiac defect (simple D-TGA), arterial switch operation is the recommended procedure. In general, the arterial switch operation has replaced the earlier atrial switch procedures developed by Mustard and Senning. In patients with D-TGA and a ventricular septal defect (VSD), the preferred procedure is arterial switch operation and VSD closure. In patients with D-TGA, large VSD, and significant pulmonary stenosis, the Rastelli procedure, an alternative surgical approach, should be considered. In some cases, arterial switch operation with or without repair of the left ventricular outflow obstruction is used. Both the arterial switch operation and Rastelli procedures are surgical anatomic corrections resulting in a morphologic left ventricle as the systemic ventricle. In comparison to atrial switch procedures, which involved the rerouting of venous return in the atria and are now only rarely performed, the arterial switch operation appears to have similar long-term survival rates with reduced long-term morbidity primarily due to a lower risk of atrial arrhythmias and heart failure. As a result, it is the recommended procedure in most patients with D-TGA.

Outcome

The long-term survival rates for patients with D-TGA following surgical correction are excellent for both arterial switch operation and atrial switch procedures. The long-term survival 20 years after discharge is about 95 and 80 percent for arterial switch and atrial switch respectively. Progressive congestive heart failure and sudden death are the principal causes of death. Perioperative mortality is greater in patients with complex (additional cardiac anomaly) D-TGA compared to those with simple D-TGA. There are no clinical trials comparing outcomes of arterial switch and atrial switch procedures. Reintervention is common following both approaches.

Patients who undergo surgical repair for D-TGA have a reduced exercise capacity primarily due to pulmonary disease. Patients after arterial switch operation appear to have better exercise capacity than those who underwent atrial switch procedures. The decrease in exercise capacity, however, does not limit ordinary activity as most patients meet the criteria for New York Heart Association functional class I.

It appears that patients with D-TGA may have mild long-term neurodevelopmental impairment, most likely due to perioperative factors including hypoxemia, acidosis, cardiopulmonary bypass, and hemodynamic instability.

Congenitally corrected transposition of the great arteries

Introduction

The congenitally corrected transposition of the great arteries (ccTGA) is characterized by a normal anatomical position of both atria, with an abnormal connection between the atria and the ventricles. The right atrium is connected with the left ventricle and the left atrium is connected with the right ventricle. (figure 14) Furthermore the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. There are, in conclusion, abnormal atrioventricular connections and abnormal ventricular-arterial connections present in ccTGA. CcTGA is a very rare defect, accounting for about 1% of all congenital heart disease.

Pathophysiology

The blood flow in ccTGA is ‘corrected’ because oxygenated blood flows through the systemic circulation and deoxygenated blood is transported to the lungs. In this particular heart defect the right ventricle functions as a systemic ventricle. With the atrioventricular valves following the position of the ventricles, the tricuspid valve is now the systemice AV-valve.

Additionally the coronary arteries are a mirror image of the normal anatomic situation. The coronary artery on the right side of the heart runs like a morphological left coronary artery; starting with a main stem which divides into a left anterior descending and circumflex branch. The coronary artery on the left is the morphological right coronary artery, which now runs around the tricuspid valve on the left.

Even the conduction system is abnormal in this congenital heart defect. Normally the AV node is positioned at the base of the interatrial septum, from where the His bundle arises into the interventricular septum. Due to misalignment in ccTGA there is no bundle directly from the normal AV node into the interventricular septum. Usually there is an additional AV node located more anterior and laterally from where a long bundle arises which runs beneath the pulmonary valve leaflets into the interventricular septum. Due to the long route this bundle is rather vulnerable. Where in normal hearts the electrical activation of the ventricles in the septum runs from left to right, in ccTGA it is the exact opposite; the septum is activated from right to left, which is visible on the ECG as an abnormal initial activation.

There is a VSD present in 60% of all ccTGA patients, who will often become symptomatic at younger age. Pulmonary valve stenosis is seen in 30 – 50% of patients, usually in those who already have a VSD as well. Abnormal anatomy of the tricuspid valve (M. Ebstein like) is seen in 25-30% of patients, sometimes accompanied by VSD or pulmonary valve stenosis. More than 80 percent of patients have an abnormal function of the tricuspid valve, which often becomes insufficient.

Evaluation

When only ccTGA is present, without other cardiac defects, the diagnosis is often not recognized until adulthood. However, when there is a VSD and/or pulmonary valve stenosis present, it presents short after birth with cyanosis and heart failure or even a total AV-block.

Adult patients are usually recognized due to an abnormal ECG, abnormal chest radiograph, systolic murmur due to the regurgitation of the systemic AV-valve, occurrence of atrial tachycardia or an AV-block. Reduced exercise capacity might be present.

The ECG is the most typical for ccTGA; left heart axis deviation, septum activation in mirror image (no Q-wave in I, aVL and V6, no R-top in V1) and a rather deep Q-wave in III and aVF. Echocardiography is a good diagnostic tool to review the exact anatomy. The right ventricle positioned on the left side is identified by the typical morphology of the trabeculae. Furthermore the tricuspid valve has a lower insertion compared to the mitral valve.

Treatment and outcome

Patients with ccTGA require lifelong follow up due to the risk of arrhythmias and associated sudden death, increase of pulmonary valve stenosis, increase of tricuspid valve regurgitation, supraventricular tachycardia, heart failure or endocarditis. Due to the complex anatomy and the low incidence of this pathology, this is best acquired at a specialised centre of congenital heart disease.

Arrhythmias need treatment, preferably not with negative inotropic agents, but digoxin and possibly amiodaron are preferred. When presenting with atrial arrhythmias conversion to sinus rhythm is highly important in these patients, who are in need of their ‘atrial kick’.

Many patients with ccTGA require pacemaker placement, often already in childhood or early adulthood. Frequent followup in these patients is required due to the high complication rate; dislocation of the lead which is located in the smooth-walled left ventricle and risk of infection or endocarditis.

Determining the right time to replace the tricuspid valve is difficult in these patients. Preferably this is done just before the right systemic ventricle starts dilating and fails, but it remains an estimation which should be made for each individual patient.

To restore normal blood flow through the ventricles, with the left ventricle functioning as the systemic ventricle, there is an option to perform a double switch operation. During this procedure both atria and both great arteries are switched, meaning a combination of the arterial switch and the atrial switch procedure. From a physiologic point of view this operation is worth considering while the left ventricle will function as systemic ventricle, however it is associated with a high perioperative mortality due to the extent of surgery. Furthermore the left ventricle requires training prior to surgery, to be able to cope with the high arterial pressure after years of low pulmonary pressure. In conclusion the chance of success of this double switch operation is very low in patients above 16 years of age.

Univentricular heart

Introduction

Around 10 percent of all congenital heart defect patients have just one functioning ventricle. The other ventricle is present, however it is rudimentary or underdeveloped so it can not function normally. In utero this causes rarely any problems, due to the parallel circulation the other ventricle takes over both functions. It is after birth, if the ductus arteriosus closes, when problems arise.

Pathophysiology

The hypoplastic left heart syndrome (HLHS) is the most common type of univentricular heart. (figure 15) Not only the left ventricle, but often the aortic valve, ascending aorta and aortic arch are hypoplastic as well. This will redirect blood from the left atrium into the right atrium, where is will be mixed with venous blood and pumped into the right ventricle and pulmonary artery. The whole systemic circulation depends on the shunt from pulmonary artery through the ductus arteriosus into the aorta. When the ductus starts closing the consequences are dramatic, with severe cyanosis and acidosis.

When a hypoplastic right ventricle is present with associated atresia of the pulmonary artery, the pulmonary circulation after birth will solely depend on the left-to-right shunt through the ductus arteriosus.When the ductus starts closing, progressive cyanosis is the main presenting symptom.

Other cardiac defects associated with only one functional ventricle are: tricuspid valve atresia, mitral valve atresia, severe form of Ebstein anomaly, double inlet left ventricle and unbalanced AVSD.

All patients with one functioning ventricle have complete mixing of saturated and desaturated blood leading to chronic hypoxemia (figure 24). Furthermore there is a chronic volume overload to the ventricle, serving as both pulmonary and systemic ventricle, leading to an early development of heart failure.

Due to the obligatory intracardiac shunting the pulmonary ‘filter’ is bypassed, which will increase the chance of cardiovascular accidents and brain abscesses.

Treatment

In case of a ductus-dependent defect initial treatment immediately after birth consists of prevention of ductus closure. At first this can be achieved pharmacologically with prostaglandin, however due to the many side effects this is no long-term solution. When there is a dependent pulmonary circulation an aortopulmonary shunt will be constructed during the first weeks of life to ensure accurate blood flow to the lungs after discontinuation of the prostaglandin.

If there is a dependent systemic circulation the surgical treatment usually consists of three different steps. Since the anatomy is by no means normalized, one can not speak of a surgical correction, it is referred to as a definitive palliation. At first a Norwood or Sano procedure is performed in neonates where a neo-aorta is constructed by dividing the pulmonary artery. Second stage is the construction of a cavopulmonary shunt, also known as bidirectional Glenn shunt, which is performed at 4 -6 months of age. The third and final stage is known as Fontan procedure and performed at 18 – 30 months of age, where a total cavopulmonary connection is created. (figure 16) All surgical procedures are described in more detail separately.

Outcome

With an expanding cohort of survivors of surgical palliation through Fontan completion, increasing information is being accumulated on the long-term morbidity of these patients. Active areas of interest include exercise tolerance, neurodevelopmental outcome, and quality of life.

When assessed prospectively by formal exercise testing, children with HLHS after surgical repair showed considerable age-related decline in exercise performance. Among patients participating in treadmill or bicycle ergometry, those aged 8 to 12 performed at 70 percent of predicted peak oxygen consumption, whereas older children reached only 60 percent of predicted performance.

Several reports have demonstrated significant neurodevelopmental impairment in survivors of HLHS following staged repairs or cardiac transplantation. There is a paucity of data on the quality of life for patients with HLHS. In one report of survivors and their families, parents reported poorer functional health status than patients assessed at 18 years of age.

Risk factors that lower survival include noncardiac congenital anomalies and/or genetic disorder, particularly chromosomal defects, prematurity, low birth weight for gestational age, and living in a high poverty neighborhood.

With an expanding cohort of survivors of surgical palliation through Fontan completion, increasing information is being accumulated on the long-term morbidity of these patients. Active areas of interest include exercise tolerance, neurodevelopmental outcome, and quality of life. When assessed prospectively by formal exercise testing, children with HLHS after surgical repair showed considerable age-related decline in exercise performance. Among patients participating in treadmill or bicycle ergometry, those aged 8 to 12 performed at 70 percent of predicted peak oxygen consumption, whereas older children reached only 60 percent of predicted performance. Several reports have demonstrated significant neurodevelopmental impairment in survivors of HLHS following staged repairs or cardiac transplantation. There is a paucity of data on the quality of life for patients with HLHS. In one report of survivors and their families, parents reported poorer functional health status than patients assessed at 18 years of age. Risk factors that lower survival include noncardiac congenital anomalies and/or genetic disorder, particularly chromosomal defects, prematurity, low birth weight for gestational age, and living in a high poverty neighborhood.