Congenital heart disease & GUCH (Grown Up Congenital Heart disease)
Echocardiography in Congenital Heart Disease (CHD) and Grown Up Congenital Heart (GUCH) disease
Survival in congenital heart disease (CHD) has increased dramatically over the past few decades. This has resulted in an increased prevalence of congenital heart disease in the general population, such that most clinicians will regularly encounter patients with CHD. Approximately 95% of all incident cases of congenital heart disease reach adulthood (Mandalenakis et al). The largest leap in survival has been observed among cases with the most complex malformations. Indeed, even the most severe malformations have become routine practice. The treatment repertoire includes surgery, catheter interventions, and medical therapies. Adults with congenital heart disease are mostly managed in GUCH clinics (Grown Up Congenital Heart disease).
Prevalence of congenital heart disease (CHD)
Congenital heart disease (CHD) is the most common class of major congenital malformations. CHD occurs in approximately 1% of live births, and 10% of aborted fetuses, with no significant geographical variations. Roughly 25% of children with congenital heart disease require intervention during their first year of life (Triedman et al).
According to the European Society for Cardiology, 2800 adults per 1 million individuals have congenital heart defects, and half of them have moderate or complicated defects; the remaining third have mild defects (Baumgartner et al). Approximately 40,000 children are born with CHD annually in the United States (Triedman et al).
The prevalence of congenital heart disease will increase in parallel with the prolongation of survival.
Neonatal screening with pulse oxymetry
The majority of all congenital heart defects are detected early in infancy or childhood. For obvious reasons, more complex defects are typically diagnosed earlier. Defects resulting in reduced oxygen saturation are generally detected with neonatal pulse oximetry (POX) screening, which is routine in all Western countries. According to a Cochrane review, for every 10,000 apparently healthy newborn infants, around six will have critical CHD, and the pulse oximetry test will correctly identify five of these with critical CHD (Plana et al). Minor defects can go unnoticed for many years. Occasionally, major defects may go unnoticed until adulthood.
Echocardiography in CHD
Echocardiography is performed in all patients with suspected CHD. Echocardiography provides detailed morphological and functional information. The vast majority of cases can be characterized by echocardiography.
In comparison with adult subjects, the echocardiographic evaluation in pediatric patients requires a different approach, with more emphasis on the heart position in the thorax, the atrial situs viscerum, the vein-atrial and the atrio-ventricular connections, the relationship between the ventricles, the ventriculo-arterial connection and the relationship of the great arteries (segmental analysis).
Ventricular function is evaluated using ejection fraction, fractional shortening, stroke volume, and myocardial thickness. Strain imaging is also used routinely to visualize regional myocardial function and mechanics. Loading conditions and heart rate may affect left ventricular function.
Transesophageal echocardiography (TEE) is superior to transthoracic echocardiography (TTE), although the latter is the most frequently used method.
Many patients require evaluation with additional modalities, e.g cardiac magnetic resonance imaging (MRI), cardiac computerized tomography (CT), ergospirometry (exercise stress testing), and cardiac catheterization.
Principles of management of congenital heart disease and GUCH
Complex malformations often require intervention (surgical or catheter-based intervention). In addition to the malformation, these subjects frequently develop associated complications, which may require specific treatments. Such complications include heart failure, ventricular arrhythmias (eg, ventricular tachycardia), supraventricular arrhythmias (eg, atrial fibrillation), pulmonary hypertension, arterial (systemic) hypertension, thromboembolism and endocarditis. Management of these complications follows conventional guidelines and principles. Unfortunately, randomized trials have not been conducted in these subjects, which explains why most recommendations are based on extrapolation of studies conducted in other patient populations. For example, management of heart failure in CHD follows the same principles as management of HFREF (heart failure with reduced ejection fraction).
Arrhythmias are also common among people with congenital heart disease, even after correction of the defect. Because individuals with GUCH often have impaired cardiac function, even mild arrhythmias can cause decompensation or hemodynamic deterioration.
Patients with GUCH who have suffered sudden syncope should be carefully evaluated since they are at increased risk of cardiac arrest and sudden death. The malformations associated with the greatest risk are tetralogy of Fallot, transposition of the great arteries (TGA), CCTGA (Congenitally corrected transposition of the great arteries), congenital aortic stenosis and single ventricle (UVH, univentricular heart).
ASD (Atrial Septal Defect)
Atrial septal defect (ASD) allows blood to flow from the left atrium to the right atrium. Left atrial pressure is greater than right atrial pressure, which explains why blood flows from left to right. The shunting of blood from left to right results in volume overload on the right side, and ultimately dilation of the right atrium and right ventricle. Conditions leading to increased pressure on the left side (hypertension, cardiomyopathy, aortic regurgitation, aortic stenosis, mitral regurgitation, mitral stenosis) may further increase the shunting from left to right.
Volume overload in the right ventricle leads to bulging of the septum into the left ventricle. This gives the left ventricle a D-shaped appearance in PSAX (parasternal short-axis view). As a result of volume overload, right ventricular stroke volume increases, which leads to increased flow through the pulmonary circulation. Over time, PVR (pulmonary vascular resistance) and pulmonary artery (PA) pressure tend to increase. The increase in PVR and PA pressure may result in the pressure on the right side ultimately exceeding the pressure on the left side, which leads to blood being shunted from right to left. The shunting of deoxygenated blood into the left ventricle results in the development of cyanosis. This condition is referred to as Eisenmenger’s syndrome.
Estimation of shunt size in ASD
The size of the shunt is calculated by estimating blood flow through the pulmonary and systemic circulation. This is achieved by comparing right and left ventricular stroke volumes. The right ventricular stroke volume is calculated with the pulsed wave doppler placed in the pulmonary trunk (truncus pulmonalis) or RVOT. Left ventricular stroke volume is calculated with the pulsed wave doppler placed in LVOT.
Left ventricular stroke volume (SV):
SVLVOT = areaLVOT · VTILVOT
Right ventricular stroke volume (SV):
SVRVOT = areaRVOT · VTIRVOT
The shunt size is calculated by the following formula:
If the stroke volume is 120 ml and 40 ml, respectively, then the shunt size is calculated as:
120/40 = 3
This is expressed as a 3:1 shunt (“3 to 1 shunt”). The calculation is uncertain in pulmonic regurgitation and aortic regurgitation since these conditions render the calculation of stroke volume uncertain.
Types of atrial septal defect (ASD)
Atrial septal defect (ASD) is – second to bicuspid aortic valve – the most common congenital heart defect. ASDs are subdivided into four types (Figure 1):
- Secundum defect (ostium secundum defect)
- Primum defect (ostium primum defect)
- Sinus venosus defect
- Coronary sinus defect (sinus coronarius defect)
Approximately 80% of all atrial septal defects are secundum defects, which are located in the fossa ovalis and its surroundings. Secundum defects include defects of the foramen ovale. Multiple secundum defects may exist. Transthoracic echocardiography (TTE) can visualize major ASDs, but transesophageal echocardiography (TEE) is required in most cases.
Primum defects represent 15% of all ASDs. These defects are located in lower parts of the atrial septum, near the atrioventricular plane. Primum defects are often accompanied by mitral or tricuspid valve defects (typically a cleft in the anterior leaflet of the mitral valve, which can lead to mitral regurgitation). TEE is superior to TTE for visualizing primum defects.
Sinus venosus defect
Sinus venosus defects affect the superior vena cava (5%) or the inferior vena cava (< 1%). These defects may lead to pulmonary veins emptying oxygenated blood into the right atrium or into the superior/inferior vena cava. TEE is required to detect this defect.
Coronary sinus defect
Coronary sinus defect (< 1%) is rare and located in the coronary sinus ostium in the right atrium. In these cases, the coronary sinus lacks a roof (“unroofed coronary sinus”), which results in a communication between the atria.
Prognosis in ASD
ASD is typically asymptomatic until adulthood. After 40 years of age, patients tend to develop signs of right heart failure. Supraventricular arrhythmias (atrial fibrillation, atrial flutter) are common. Severe pulmonary hypertension affects < 5%. Paradoxical embolisms occur but are likely to be less common than emboli arising in the left atrial appendage during rounds of atrial fibrillation.
Right ventricular load (volume load) is the main finding on echocardiography.
Ventricular septal defect (VSD)
Ventricular septal defect (VSD) is common and may be detected throughout the life course. The larger the defect, the greater the hemodynamic impact, and the earlier the diagnosis. Most defects are diagnosed in childhood or adolescence. Defects detected in adulthood are generally smaller and rarely cause hemodynamic effects. Most VSDs diagnosed during infancy close spontaneously during the first year of life.
VSD can exist in isolation or in combination with more complex heart defects (e.g tetralogy of Fallot, transposition of the great arteries, etc).
VSD leads to volume load on the left ventricle, despite the fact that blood is shunted from the left to the right ventricle. It is presumed that this is due to the fact that the right ventricle receives shunted blood during systole and manages to eject it to the lungs, and further to the left atrium and ventricle. Therefore, VSD leads to left ventricular overload and dilatation. As with ASD, perfusion through the pulmonary circulation increases, which may lead to pulmonary hypertension. With continuous wave doppler, the flow through a VSD can be used to calculate the pressure gradient between the ventricles.
Based on the location of the VSD, the following types are defined (Figure 2):
- Membranous VSD – The most common (80%) type of VSD. It affects the membranous part of the interventricular septum. These defects are best seen in parasternal views; notably in SAX at 10 o’clock. Spontaneous closure is common. In case of spontaneous closure, an aneurysm may develop. Coexisting aortic regurgitation is common.
- Muscular VSD (15%) – Muscular VSDs can exist anywhere in the muscular segments of the septum. Multiple defects may exist. Spontaneous closure is very common. Muscular VSD may be seen in apical four-chamber view (A4C) and short-axis view (SAX).
- Outlet VSD (5%) – This VSD is seen in SAX view and is localized at 2 o’clock, below the wall of the aortic valve and pulmonary valve. The support of the aortic valve is impaired, with a risk of aortic regurgitation. Spontaneous closure is less common.
- Inlet VSD (< 1%) – Inflow VSD is localized in the inflow of the septum. It is typical in Down syndrome and the defect is often large. Spontaneous closure is less common.
Since the tricuspid valve is more apical than the mitral valve, a VSD can cause blood shunting from the left ventricle to the right atrium, as shown in Figure 6. This type of defect is called Gerbode defect.
Persisting ductus arteriosus (PDA)
Ductus arteriosus is the connection, during fetal life, between the pulmonary artery and the descending aorta. Persisting ductus arteriosus (PDA) implies that this connection fails to close after birth. PDA is rare in adulthood. The defect leads to volume load on the left ventricle and the risk of developing pulmonary hypertension. PDA is best seen with color Doppler in suprasternal view or short-axis view (SAX). The image should focus on the pulmonary trunk and bifurcation. Blood flow through PDA goes from the aorta to the pulmonary trunk.
Coarctatio Aortae (CA)
Coarctatio aortae implies that there is a narrowing along the aorta and this narrowing is most often located along the descending aorta, which is why it can be visualized from the suprasternal view. Color Doppler reveals turbulent flow and continuous wave Doppler reveals increased velocities.
Normally, the tricuspid valve is more apically located than the mitral valve. Ebstein’s anomaly implies that the tricuspid valve sits lower than normal (Figure 9). The criterion for Epstein’s anomaly is that the tricuspid valve plane is located >10 mm apical about the mitral valve plane. The tricuspid valve may shift right down the apex of the right ventricle and, generally, there is a more or less pronounced tricuspid regurgitation.
Congenital corrected transposition of the great arteries (CCTGA)
Transposition of the Great Artiles (TGA) implies that two or more of the large vessels have switched locations. Most often, the aorta and pulmonary artery have switched positions, which results in the left ventricle pumping blood into the lungs, and the right ventricle pumping blood to the systemic circulation. The blood on the left side circulates between the lungs and the left heart. The blood on the right side circulates between the systemic circulation and the right heart. This means that blood flowing through the systemic circulation is not oxygenated, which leads to fatal hypoxia. The only chance of survival is if there is a shunt that allows shunting of blood between the circulations. The open ductus arteriosus, ASD and VSD are in these cases life-saving. Today, these malformations are detected quickly and they can be corrected surgically.
Correction of transposition implies reconnecting the large vessels so that they conduct blood from the right ventricle. The right ventricle will then function as the left ventricle and vice versa.
- Survivorship in Children and Young Adults With Congenital Heart Disease in Sweden. Mandalenakis Z et al. JAMA Intern Med. 2017;177(2):224-230.
- Trends in Congenital Heart Disease The Next Decade. Triedman et al. Circulation. 2016;133:2716–2733
- Plana et al. Pulse oximetry for diagnosis of critical congenital heart defects. Cochrane Collaboration.