Congenital Heart Disease Overview

Congenital Heart Disease à a general term used to describe several different abnormalities of the heart or great vessels that are present at birth

• It’s the most common form of heart disease in children
• Developing during embryogenesis in utero during the 3^rd – 8^th weeks when the heart & great vessels are being formed

Causes are both genetic & environmental à most causes are probably multifactorial

• Genetic à trisomy 13, 15, 18, 21, and Turner Syndrome
• Environmental à rubella virus infection

Most congenital heart diseases fall into 1 of 2 functional categories:

• Shunt = left à right is most common but you can also have right à left
  • Can be between cardiac chambers (ex: atria or ventricles) or between great vessels (ex: aorta & pulmonary artery)
• Obstruction to flow à usually due to stenosis or stricture in a cardiac chamber, valve, or great vessel

Cardiac Shunts

Shunt à an abnormal communication between heart chambers, between blood vessels, or both

Left à Right Shunt:

• Oxygen rich blood from the left side of the circulation is going to enter the right side of the heart or pulmonary artery
• Pulmonary blood flow is increased, which can result in the following: increased pulmonary pressure and/or volume à pulmonary HTN à right ventricular hypertrophy à heart failure
• Babies are NOT cyanotic at birth but may become so later
  • Pulmonary resistance & pressures eventually approach that of the systemic circulation à reversal of the shunt to right-to-left à unoxygenated blood now gets into the systemic circulation à cyanosis
    • This is known as Eisenmenger Syndrome or late cyanotic congenital heart disease

• The most common causes are:
  • Atrial Septal Defect (ASD) à abnormal opening in the atrial septum
    • Blood flows from left atrium à right atrium à left ventricle à pulmonary circulation
    • Most are isolated
    • Location à secundum (in proximity to the fossa ovale) is the most common, primum (next to atrial ventricular valve), coronary sinus (rare), or sinus venosus (near the entry of the superior vena cava)
      • With a primum location its not unusual to also have a defect in one of the valve leaflets à predisposes to fibrin-platelet thrombus formation
  • Ventricular Septal Defect (VSD) à there’s an abnormal opening in the ventricular septum
    • Blood can flow from the left ventricle à right ventricle à pulmonary circulation
    • Most occur in association with another cardiac anomaly
    • Location à usually located in the high membranous portion of the septum, can be in the muscular portion of the septum, or they can be below the pulmonary valve
• Patent Ductus Arteriosus (PDA) à normal channel during fetal development that connects the aorta & the pulmonary artery that permits bypassing of the fetal lungs
  • After birth it should shut down within the first day or so & it becomes the ligamemtum arteriosum
  • If it remains patent then oxygen rich blood from the aorta, which is at a higher pressure, will be diverted into the pulmonary artery & into the pulmonary circulation

Right à Left Shunt:

• Unoxygenated blood from the right side of the heart enters the left side
• Babies ARE cyanotic at birth or shortly thereafter
• The most common causes:
  • Tetralogy of Fallot à has 4 essential features:
    • VSD à usually very large & causes pressure differences between the right & left heart to be almost equal
    • Obstruction to the right ventricular outflow tract into the pulmonary artery

ü       The obstruction can be below the valve, a stricture affecting the valve, or above the valve

ü       The shunting of blood is dependant on the degree of obstruction à the more severe then the more diversion of blood into the left side

• An aorta that overrides the VSD
• Right ventricular hypertrophy
• Transposition of the great arteries
  • The aorta arises from the right ventricle & the pulmonary artery arises from the left ventricle à poorly oxygenated blood goes to the right heart & then to the aorta and systemic arterial circulation and blood is also going from the left side of the heart through the pulmonary artery into pulmonary circulation – there are 2 completely separate circulations

ü       Not compatible with life unless you have a way of mixing blood (ex: patent ductus arteriosus, ASD, or VSD)

Can see the aorta arising from the right side of the heart and the pulmonary artery arising from the left side of the heart.
 

Obstruction to Flow

Congenital obstructive cardiac lesions are due to abnormal narrowing (coarctation or stenosis) of the chambers, valves, or blood vessels

Examples include:

• Pulmonary stenosis & atresia
• Aortic stenosis & atresia
• Coarctation of the aorta à there’s a stricture or stenosis
• The obstruction is usually just distal to the origin of the left subclavian artery and in proximity to the ligamentum arteriosum
• The stricture is usually a very rigid diaphragm that inserts itself into the aorta
• The body can bypass the obstruction by creating a very elaborate & extensive collateral circulation involving the axillary artery, intercostals arteries, & internal thoracic artery, which can now provide oxygen rich blood to the descending aorta
  • May have augmented blood flow through these arteries & they become engorged à on a chest x-ray you can see pressure atrophy/erosion on the 3^rd – 8^th ribs that appear as notches in the ribs

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