Congenital Heart Diseases (CHD)

Congenital Heart Diseases (CHD) Overview

• CHD is one of the most common congenital defects, occurring in approximately 0.6-0.8% of newborns
• Advances in therapy have led to a dramatic improvement in outcome; more than 85% of infants with complex CHD are expected to reach adulthood
• Paediatric cardiology and surgery have resulted in more adults than children living with CHD

Etiology of Congenital Heart Disease

• Common environmental factors contributing to CHD include maternal illness like diabetes, rubella, and systemic lupus erythematosus
• Maternal intake of teratogenic agents like lithium, isotretinoin, and antiseizure drugs is also a factor
• Maternal age is a known risk factor for genetic conditions, especially Down syndrome, which may include cardiac defects
• Chromosomal abnormalities like trisomy 21 (Down syndrome), trisomy 18, trisomy 13, and monosomy X (Turner syndrome) are strongly associated with CHD
• No identifiable genetic etiology is detected in about 72% of patients with CHD

Pathophysiology of Congenital Heart Anomalies

• Congenital heart anomalies are classified as cyanotic or acyanotic (left-to-right shunts or obstructive lesions)
• The physiological consequences range from heart murmurs or pulse discrepancies in asymptomatic children to severe cyanosis, heart failure, or circulatory collapse

Cyanotic Heart Anomalies

• Varying amounts of deoxygenated venous blood are shunted to the left heart, reducing systemic arterial oxygen saturation
• Cyanosis results when there is more than 5 g/dL (50 g/L) of deoxygenated hemoglobin
• Complications of persistent cyanosis include polycythemia, clubbing, thromboembolism (including stroke), bleeding disorders, brain abscess, and hyperuricemia
• Pulmonary blood flow may be reduced, normal, or increased, often resulting in heart failure in addition to cyanosis, resulting in cyanosis of variable severity
• Heart murmurs are variably audible and are not specific

Left-to-Right Shunts

• Oxygenated blood from the left heart or aorta shunts to the right heart or pulmonary artery through an opening
• High-pressure shunts become apparent within weeks after birth; low-pressure shunts become apparent considerably later
• Untreated elevated pulmonary blood flow and pressure may lead to pulmonary vascular disease and Eisenmenger syndrome
• Large left-to-right shunts cause excess pulmonary blood flow and left ventricular volume overload, leading to heart failure and failure to thrive in infancy
• Large left-to-right shunts can lead to lower lung compliance and higher airway resistance

Obstructive Lesions

• Blood flow is obstructed, causing a pressure gradient
• Pressure overload proximal to the obstruction may cause ventricular hypertrophy and heart failure
• A heart murmur results from turbulent flow through the stenotic point
• Congenital aortic stenosis accounts for 3-6% of congenital heart anomalies; congenital pulmonic stenosis accounts for 8-12%

Congenital Heart Disease in Adults

• Acyanotic lesions can include atrial septal defect, ventricular septal defect, atrioventricular septal defect, pulmonary stenosis, coarctation of the aorta, and patent ductus arteriosus
• Cyanotic lesions include transposition of the great arteries, tetralogy of Fallot, and congenitally corrected transposition of the great arteries

Atrial Septal Defect (ASD)

• ASDs are common congenital heart defects in adults in which the atria are connected by a hole
• Ostium secundum defects are the most common type, are high in the septum, and are followed by ostium primum defects and sinus venosus defects
• Primum ASDS symptoms present early
• Secundum ASDS are often asymptomatic until adulthood
• Secundum ASDS symptoms are dictated by left and right ventricle compliance, increasing with age and eventually causing dyspnoea/heart failure at 40-60 years
• Pulmonary hypertension, cyanosis, arrhythmia, haemoptysis, and chest pain may occur
• Signs include AF, increased JVP, a wide and fixed split S2, and a pulmonary ejection systolic murmur
• Pulmonary hypertension may cause pulmonary or tricuspid regurgitation
• Complications include Eisenmenger syndrome and paradoxical emboli
• ECG may show RBBB with LAD and prolonged PR interval (primum defect) or RAD (secundum defect)
• A chest radiograph shows a prominent pulmonary artery, right ventricular enlargement, and pulmonary plethora
• Echocardiography is diagnostic
• Closure is recommended before age 10 in children and if symptomatic/pulmonary to systemic blood flow ratios are high in adults
• Transcatheter closure is more common than surgical

Ventricular Septal Defect (VSD)

• VSDs are characterized by a hole connecting the ventricles
• The four main types of VSD are membranous, muscular, inlet, and subarterial
• Membranous VSD is the most common, making up 80% of cases
• Muscular VSDs account for around 20% of VSDs in infants
• Inlet VSDs occur just below the tricuspid valve in the right ventricle and the mitral valve in the left ventricle
• Subarterial VSDs occur in the ventricular septum immediately under the pulmonary valve
• Congenital VSD has a prevalence of 2:1000 births and acquired through post-MI
• Moderate to large VSD in infants can cause heart failure symptoms such as shortness of breath, sweating or fatigue during feeding, failure to thrive, and frequent respiratory infections
• VSD in older children and adults can cause tiredness or breathlessness during exercise, and very pale skin or a bluish tinge due to cyanosis after Eisenmenger syndrome develops
• Smaller holes are haemodynamically less significant and give louder murmurs
• Larger holes are associated with signs of pulmonary hypertension
• A harsh pansystolic murmur is heard at the left sternal edge, with a systolic thrill and parasternal heave
• Complications include AR, Infundibular stenosis, IE/SBE, Pulmonary hypertension, and Eisenmenger’s syndrome
• ECG is normal in small VSD, LAD + LVH in moderate, and LVH + RVH in large
• CXR: normal heart size in small, cardiomegaly and pulmonary arteries in large
• Echocardiography identifies size/location
• Computed tomography (CT) scan can also be used
• Treatment involves spontaneous closing or surgical interventions
• Indications for surgical closure include failed medical therapy, symptomatic VSD, LV volume overload, and SBE/IE
• Another treatment option is Endovascular closure

Coarctation of the Aorta

• Characterized by a congenital narrowing of the descending aorta, usually distal to the origin of the left subclavian artery
• Associations include bicuspid aortic valve and Turner's syndrome
• Radiofemoral delay, weak femoral pulse, BP increase, scapular bruit, and systolic murmur are signs
• Heart failure and infective endocarditis are complications
• CT or MRI-aortogram and CXR showing rib notching are testing methods
• Surgical and balloon dilations are treatments

Tetralogy of Fallot (TOF)

• TOF is the most common cyanotic congenital heart disorder, with a prevalence of 3-6 per 10,000
• The most common cyanotic heart defect that survives, accounting for 10% of all congenital defects
• Arises from abnormalities in the separation of the truncus arteriosus into the aorta and pulmonary arteries during early gestation
• The 4 features typical include ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta
• The aorta overriding the VSD is a typical feature
• Sometimes a few children also have an atrial septal defect, which makes up the pentad of Fallot
• Severity of illness depends on the degree of pulmonary stenosis
• Infants may be acyanotic at birth, with a pulmonary stenosis murmur as the only initial finding
• They gradually become cyanotic, especially after closure of the ductus arteriosus, due to decreased flow of blood to the lungs and a right-to-left shunt across the VSD
• Restlessness and agitation occurs during a hypoxic spell
• Toddlers may squat, which increases peripheral vascular resistance and decreases the degree of right-to-left shunt along with difculty in feeding, failure to thrive, and clubbing
• Adult patients commonly present as asymptomatic
• Unoperated adult patient: cyanosis is common, squatting is uncommon
• Repaired patients: exertional dyspnoea, palpitations, RV failure, syncope, and even sudden death
• ECG shows RV hypertrophy with a right bundle-branch block
• CXR may be normal or shows a boot-shaped heart
• Echocardiography shows the anatomy as well as the degree of stenosis
• Cardiac CT and cardiac MRI provide information when planning surgery
• Give O2 and place the child in the knee-chest position
• Morphine can sedate the child as well as relaxing the pulmonary outflow
• Long-term B-blockers may be needed, alongside endocarditis prophylaxis if recommended by a microbiologist
• Without surgery, mortality rate is ~95% by age 20
• Surgery is usually done before 1 year of age with closure of the VSD and correction of the pulmonary stenosis leading to a 20-yr survival rate of ~90-95% after repair