Congenital Heart Disease (CHD)

• Lecture given on Congenital Heart Diseases

Learning Objectives

• Identify the etiology of congenital heart diseases
• Know the classification of congenital heart disease
• Understand the clinical picture and management of Atrial Septal Defect (ASD)
• Understand the clinical picture and management of Ventricular Septal Defect (VSD)
• Understand the clinical picture and management of Coarctation of the Aorta (CoA)
• Understand the clinical picture and management of Tetralogy of Fallot (TOF)

Introduction to Congenital Heart Disease (CHD)

• CHD is a common congenital defect, occurring in approximately 0.6-0.8% of newborns
• Advances in therapy have dramatically improved outcomes
• 85% of infants with complex CHD are expected to reach adolescence and early adulthood
• Due to advances in pediatric cardiology and surgery, there are now more adults than children with CHD

Etiology of Congenital Heart Disease

• Common environmental factors are maternal illness, intake of teratogenic agents, and maternal age
• Maternal illnesses linked to CHD include diabetes, rubella, and systemic lupus erythematosus
• Teratogenic agents include lithium, isotretinoin, and antiseizure drugs
• Maternal age is a risk factor for certain genetic conditions that may include cardiac defects like Down syndrome
• Certain numerical chromosomal abnormalities exhibit strong associations with congenital heart disease
• Trisomy 21 (Down syndrome), trisomy 18, trisomy 13, and monosomy X (Turner syndrome)
• No identifiable genetic etiology is detected in about 72% of patients with congenital heart disease

Pathophysiology of Congenital Heart Anomalies

• Congenital heart anomalies are classified as cyanotic or acyanotic
• Acyanotic anomalies include left-to-right shunts or obstructive lesions
• Physiologic consequences vary greatly, ranging 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 (right-to-left shunt)
• This reduces systemic arterial oxygen saturation
• Cyanosis results if there is over 5 g/dL of deoxygenated hemoglobin in the blood
• 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 depending on the anomaly
• Heart failure, in addition to cyanosis, can result
• Heart murmurs are variably audible and are not specific

Left-to-Right Shunts

• Oxygenated blood shunts from the left heart (left atrium or left ventricle) or aorta to the right heart (right atrium or right ventricle) or pulmonary artery through an opening or communication between the two sides
• High-pressure shunts are apparent several days to a few weeks after birth while low-pressure shunts become apparent considerably later
• Untreated elevated pulmonary blood flow and pulmonary artery 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
• Large left-to-right shunts lead to lower lung compliance and higher airway resistance, increasing the likelihood of hospitalization in infants with respiratory infections

Obstructive Lesions

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

Congenital Heart Disease in Adults

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

Atrial Septal Defect (ASD)

• ASDs are common congenital heart defects in adults
• In ASD a hole connects the atria. -Ostium secundum defects (high in the septum) are the most common -Ostium primum defects (partial atrioventricular canal) -Sinus venosus defects

ASD Symptoms

• Primum ASDs manifest early
• Secundum ASDs are often asymptomatic until adulthood, as the left-to-right shunt depends on compliance of the right and left ventricles
• Decreased ventricular compliance with age augments left-to-right shunting, leading to dyspnea/heart failure around age 40-60
• Pulmonary hypertension, cyanosis, arrhythmia, hemoptysis, and chest pain may result

ASD Signs

• Atrial fibrillation
• Increased jugular venous pressure
• Wide, fixed S2 split
• Pulmonary ejection systolic murmur
• Pulmonary hypertension may cause pulmonary or tricuspid regurgitation

ASD Complications

• Reversal of left-to-right shunt, i.e., Eisenmenger's syndrome
• Initial left-to-right shunt leads to pulmonary hypertension
• Shunt reversal causes cyanosis, heart failure, and chest infections
• Paradoxical emboli (vein-artery via ASD), rare

ASD Investigations

• ECG: RBBB with LAD and prolonged PR interval (primum defect) or RAD (secundum defect)
• CXR: A prominent pulmonary artery, right ventricular enlargement, and pulmonary plethora
• Echocardiography: diagnostic for ASD

ASD Treatment

• Closure recommended for children before age 10
• Closure is indicated in adults with symptoms or pulmonary to systemic blood flow ratios ≥1.5:1
• Transcatheter closure is now more common than surgical closure

Ventricular Septal Defect (VSD)

• In VSD A hole connects the ventricles
• Membranous VSD: most common type of VSD accounting for about 80% of cases
• Muscular VSDs account for about 20% of VSDs in infants, and often present with multiple holes

VSD Types

• Inlet: hole just below the tricuspid valve in the right ventricle and the mitral valve in the left ventricle
• Subarterial: occurs in the ventricular septum immediately under the pulmonary valve
• Also known as supracristal, conoseptal, or doubly committed subarterial defects
• Congenital (prevalence 2:1000 births) or acquired (post-MI)

VSD Symptoms

• In infants, moderate to large VSD causes symptoms of heart failure like shortness of breath, sweating or fatigue during feeding, failure to thrive, and frequent respiratory infections
• In older children and adults, VSD can cause fatigue when exercising
• Very pale skin or a bluish tinge to skin and lips may happen after Eisenmenger syndrome develops

VSD Signs

• Depends on size and site of the VSD
• Smaller holes that are hemodynamically less significant give louder murmurs
• Classically, a harsh pansystolic murmur is heard at the left sternal edge
• A systolic thrill or left parasternal heave may be present
• Larger holes are associated with signs of pulmonary hypertension

VSD Complications

• Aortic regurgitation (AR)
• Infundibular stenosis
• Infective endocarditis/subacute bacterial endocarditis (IE/SBE)
• Pulmonary hypertension and Eisenmenger syndrome

VSD Investigations

• ECG: normal (small VSD), LAD + LVH (moderate VSD) or LVH + RVH (large VSD)
• CXR: normal heart size ± mild pulmonary plethora (small VSD) or cardiomegaly, large pulmonary arteries, and marked pulmonary plethora (large VSD)
• Echocardiogram is used to identify the size and exact location of the VSD
• Computed tomography (CT) scan

VSD Treatment

• Medical management is the first approach, as many VSDs close spontaneously
• Surgical closure is indicated in cases of failed medical therapy, symptomatic VSD, left ventricular volume overload, or SBE/IE
• Endovascular closure is also possible

Coarctation of the Aorta (CoA)

• Congenital narrowing of the descending aorta, usually occurring just distal to the origin of the left subclavian artery

CoA Associations

• Bicuspid aortic valve & Turner's Syndrome

CoA Signs

• Radiofemoral delay
• Weak femoral pulse
• Elevated blood pressure
• Scapular bruit
• Systolic murmur best heard over the left scapula

CoA Complications

• Heart failure and infective endocarditis

CoA Tests

• CT or MRI-aortogram
• CXR shows rib notching

CoA Treatment

• Surgery
• Balloon dilatation with or without stenting

Tetralogy of Fallot (TOF)

• The most common cyanotic congenital heart disorder
• Its prevalence is 3-6 per 10,000 births
• Most common cyanotic heart defect that survives to adulthood
• Accounts for 10% of all congenital defects

TOF Etiology

• Believed to be due to abnormalities in the separation of the truncus arteriosus into the aorta and pulmonary arteries that occur in early gestation

TOF Features (4)

• Ventricular Septal Defect (VSD)
• Pulmonary Stenosis
• Right Ventricular Hypertrophy
• Overriding Aorta

TOF + ASD

• A few children also have an atrial septal defect, which makes up the pentad of Fallot

TOF Presentation

• Severity of illness depends on degree of pulmonary stenosis
• Infants may be acyanotic at birth, with a pulmonary stenosis murmur as the initial finding
• Closure of the ductus arteriosus results in cyanosis
• Reduction in blood flow to the lungs and right-to-left shunt across the VSD can cause cyanosis
• Hypoxic spell leads to a child that becomes restless and agitated
• Toddlers may squat, which is typical of TOF
• Squatting increases peripheral vascular resistance and decreases the degree of right-to-left shunt
• Difficulty in feeding, failure to thrive & clubbing are apparent

TOF Presentation

• Adult patients are often asymptomatic
• Cyanosis is common in the unoperated adult patient, although extreme cyanosis or squatting is uncommon
• In repaired patients, late symptoms include exertional dyspnea, palpitations, RV failure, syncope, and even sudden death

TOF Investigations

• ECG shows RV hypertrophy with right bundle-branch block
• CXR may be normal or show classic boot-shaped heart
• Echocardiography shows anatomy and degree of stenosis
• Cardiac CT and cardiac MRI aid in planning the surgery

TOF Management

• Give O2
• Place the child in knee-chest position
• Morphine can sedate the child and relax the pulmonary outflow
• Long-term β-blockers may be needed
• Give endocarditis prophylaxis only if recommended by a microbiologist
• Without surgery, mortality rate is approximately 95% by age 20
• Surgery (before 1 year of age), involves closure of the VSD and correction of the pulmonary stenosis
• 20-year survival rate after repair is approximately 90-95%