The objectives of this section are:
1) The recognition that children can be born with heart disease
2) The recognition that children with heart disease may present with signs and symptoms that are different from adult cardiac patients
3) To be able to identify many of these cardiac defects and their presenting signs and symptoms and clinical findings
4) The application of the general principles of cardiac physiology and pathophysiology to specific congenital heart lesions
1. Definition:
Congenital heart disease (CHD) is a heart condition present at birth
Etiology
Multifactorial- probably most common cause
Single gene mutations (3%)- Noonan’s Syndrome, DiGeorge syndrome
Chromosomal abnormalities (?%)- Turner’s, Down’s Syndrome, Trisomy 13, 18
Environmental factors (3%)- alcohol, lithium
An understanding of normal cardiac anatomy is necessary before one can understand the structural changes that occur with congenital heart disease.
It is important to remember that a cardiac chamber, valve, or vessel can be “anywhere” therefore the identity of a chamber must not be based on relative position alone. A left ventricle can be on the right side of the heart. There are morphologic features of the chambers and valves that identify them. For example, the right ventricle is heavily trabeculated and the left ventricle more smooth-walled. The AV valves typically “go with” their respective ventricles. Therefore the valve that empties into the “morphologic” left ventricle is the mitral valve.
CHD may result in:
· no symptoms
· congestive heart failure (CHF),
· cyanosis and others
2. Relevance to course
- Occurs in 8 - 10 per 1000 live births
- Increasing survival of children with CHD – 600,000 adults in US with CHD
- Increasingly diagnosed in utero and may affect maternal management
- Increasing complexity of the diagnoses of survivors
- Adults with congenital heart disease risks include:
1. Stroke
2. Endocarditis
3. Congestive heart failure
4. Pulmonary hypertension
5. Pregnancy complications
6. Arrhythmias (atrial fibrillation, atrial reentrant tachycardia, ventricular tachycardia, ventricular fibrillation)
7. Sinus node and AV node disease
8. Sudden death
Congestive Heart Failure (CHF)
Condition where the heart is unable to pump sufficient blood to meet the metabolic demands of the body
1 Excessive work load on the heart either volume load or pressure load, but with a normal myocardium (example: congenital heart disease)
2 Normal workload faced by a damaged or abnormal myocardium (example: myocarditis)
Signs and symptoms due to
low cardiac output
systemic adaptation to low cardiac output
systemic and/or pulmonary venous congestion
Signs and symptoms are age-dependent
Fetus: Hydrops – excessive accumulation of fluid by the fetus, scalp edema, pleural effusions, pericardial effusion, ascites
Most CHD well tolerated by the fetus
Exceptions: severe AV valve regurgitation (Ebstein’s anomaly), AV block, myocarditis, incessant tachycardias, large AV fistula, premature closure of the ductus
Infants: poor feeding, sweating with feeding, tachypnea (fast respiratory rate) and tachycardia (fast heart rate), cool extremities, diminished pulses, mottling, hepatomegaly (liver enlargement),
Children (similar to adults): exertional dyspnea (shortness of breath), orthopnea (inability to sleep comfortably while lying flat), chronic cough, hepatomegaly, neck vein distention, peripheral edema (fluid retention in the legs or ankles)
Cyanosis/Hypoxemia (and associated problems)
· respiratory causes (example: pneumonia)
· cardiac causes - shunting of blood from a right heart structure to a left heart structure (mixing of venous into arterial blood) - right-to-left shunt
Cyanosis - bluish discoloration of the skin
perceptible when > 5 gm of reduced hemoglobin in the capillaries
Clubbing - widening and thickening of the ends of the fingers and toes with hourglass deformity
- occurs with hypoxemia
- due to increased capillaries and increased blood flow through multiple arteriovenous aneurysms
- increased connective tissue in the terminal phalanges
Polycythemia - increased total RBC in the blood
- low arterial O2 content acts via renal erythropoietin - stimulates bone marrow to increase RBC production
- increased O2 carrying capacity and O2 delivery
- useful compensatory mechanism until hematocrit 70-80% - when blood becomes too viscous
Squatting - posture assumed after exertion in children with some cyanotic congenital heart diseases
- 1 - 2 year olds
- increases O2 saturation by increasing venous return
- increases peripheral resistance - decreases the right to left shunt and encourages increased pulmonary blood flow
Other: exercise intolerance, increased risk of brain abscesses and cerebrovascular accidents
Classification of Congenital Heart Diseases
Pulmonary Blood Flow | Acyanotic | Cyanotic |
Increased | L > R shunts- ASD, VSD, PDA | Admixture lesions- Transposition, Truncus |
Normal | obstructive lesions - AS, PS, Coarctation | none |
Decreased | none | obstructive lesions + defect Ebstein’s, Tetralogy of Fallot, Tricuspid atresia |
Left-to-Right Shunts
Abnormal shunting of blood from the systemic circulation to the pulmonary circulation
Allows oxygenated blood to recirculate back through the lungs therefore increases pulmonary blood flow
Ventricular Septal Defects, Atrial Septal Defects, Patent Ductus Arteriosus, Atrioventricular septal defect, Aorticopulmonary window
Ventricular Septal Defect (VSD)
Defect (hole) in a portion of the septum that separates the right and left ventricle
Most common congenital cardiac lesion
Location:
perimembranous septum
muscular septum
inlet septum (AV canal type)
subarterial septum
Defect size more important than location
Small to medium sized defects – the size restricts the amount of left to right shunting
Large defect – nonrestrictive, no resistance to flow across the defect
Shunt amount and direction determined by the relative resistances of the systemic and pulmonary circuits
Pathophysiology:
Oxygenated blood crosses septum from higher pressure chamber [left ventricle (LV)] to the lower pressure chamber [right ventricle (RV)]
Red blood from LV mixes with blue blood in RV (therefore no cyanosis)
Increased blood in RV (well tolerated)
Increased blood in pulmonary arterial circuit
Increased blood returning to left atrium (LA) and LV volume overload and LV- enlargement
Large VSD
Magnitude of the L > R shunt determined by relative resistances of the systemic and pulmonary circuits
Usually Left-to-Right shunt:
Systemic Vascular Resistance (SVR) - higher - systemic arterioles have a thick muscular wall, narrow lumen
Pulmonary Vascular Resistance (PVR) - lower - pulmonary arterioles have a thin wall, wide lumen
Reflected by higher aortic pressure compared to pulmonary artery pressure and hence higher LV pressure than RV pressure
Hemodynamics of Large VSD
(A) Red blood crosses from LV to RV through VSD resulting in increased O2 sat in RV
(B) Large hole allows equalization of LV and RV pressure (increased RV and PA pressure) not pressure restrictive
(C) Increased blood in pulmonary circuit and increased pressure and O2 saturation in pulmonary artery
(D) Increased LA volume due to increased blood returning from pulmonary circuit
(E) Increased blood in LV- results in LV enlargement
Increased LV radius - myocardial fibers lengthen
(F) With significant LV dilation, the myocardium cannot develop sufficient tension to maintain pressure - Congestive Heart Failure (CHF)
Two hemodynamic loads from a large VSD
1) Large VSDs allow equalization of the RV and LV pressure -Pressure load on the RV
2) Increased blood passes across the VSD into the RV and subsequently into the pulmonary circuit. Increased blood then returns to the LA and LV - Volume load on the LV
This results in CHF
Development of CHF with Large Ventricular Septal Defect
LV volume overload (increased preload)
- LV dilation
- increased LV radius (R)
-as LV radius increases LV tension (T) must increase to maintain pressure (P) (LaPlace relationship: T= P X R)
With continued LV dilation Þ the myocardium cannot develop sufficient tension to maintain the pressure volume relationship
- congestive heart failure
Compensatory mechanisms to maintain myocardial performance and cardiac output
- stimulation of the sympathetic adrenal system increased catecholamine release
- increased catecholamine release
- increased force of contraction and heart rate
‑ Myocardial hypertrophy
Clinical Picture
History:
Symptoms of congestive heart failure (CHF) often 2 - 3 months of age
tachypnea (rapid breathing)
increased work of breathing (retractions, tachypnea, grunting)
poor feeding
diaphoresis (sweating) with feedings
recurrent respiratory infections
Examination:
murmur - noise made by turbulent blood crossing the hole in the ventricular septum - high frequency holosystolic murmur
heart sounds: increased second heart sound (S2) due to increased pulmonary artery pressure
cardiac enlargement (left chest enlargement)
signs of CHF - tachycardia, tachypnea, dyspnea, retractions, growth failure, hepatomegaly
CXR: usually normal at birth
cardiac enlargement develops with time
LA and LV enlargement
increased pulmonary blood flow (increased size of the pulmonary vessels)
Management:
anticongestive medications (diuretics, afterload reduction, digoxin)
surgical closure
large defects do not close spontaneously
Small VSD
Hemodynamics
Small defects are pressure restrictive - do not allow equalization of LV and RV pressures
Shunt is left to right because LV systolic pressure greater than RV systolic pressure
Pressure restrictive
Normal pulmonary artery pressures
L > R shunt is small
Clinical Picture
History:
usually asymptomatic, no CHF
murmur typically at the first newborn outpatient evaluation
murmur usually not present at birth because of the high pulmonary resistance at birth results in high RV pressures and therefore little shunting of blood across the defect
even small VSDs often have very loud murmurs
Examination:
usually no CHF or cardiomegaly
often a loud murmur
Natural history/management:
many become smaller or close spontaneously
50% of perimembranous get smaller or close, usually within 6 months - 1 year
muscular defects commonly close especially in infants
Patent Ductus Arteriosus (PDA)
Persistence of fetal communication between the aorta and pulmonary artery
close by 1st day of life
embryonic left 6th arch
More common in premature infants than term infants
Direction and magnitude of shunt through the PDA depends on relative SVR and PVR
Large PDA
Aortic pressure = pulmonary artery pressure (large defect allows equalization of pressures)
But systemic resistance remains higher than pulmonary resistance (SVR > PVR)
L > R shunt
Hemodynamics of PDA
A) Shunting of red blood from the aorta to pulmonary artery
B) Increased pulmonary blood flow, increased pulmonary artery pressure and increased O2 saturation in the pulmonary artery
C) Low diastolic blood pressure due to “run-off” into the pulmonary artery
D) Increased blood in the pulmonary circuit – this results in increased blood returning to the LA and increased LA pressure. Because of poor gas exchange in the lung as a result of CHF, there is a low LA saturation
E) Increased blood in the LV results in LV enlargement and increased LV end diastolic pressure (LVEDP) and CHF develops
Clinical Picture
History
More common in females (2:1)
Associated with maternal rubella, high altitude, Down syndrome, prematurity
Many present with asymptomatic murmur within days to weeks of birth
Large PDA - CHF symptoms (similar to VSD)
Examination
murmur: noise made from continuous shunting of turbulent blood from aorta to pulmonary artery
classic murmur of large PDA - continuous machinery murmur
wide pulse pressure
low diastolic blood pressure
due to “run-off” of blood from Aorta to Pulmonary artery
bounding pulses-due to large difference btw systolic and diastolic pressure
CXR:
increased pulmonary blood flow
cardiac enlargement
prominent aortic and pulmonary trunks
small PDA - normal CXR
Catheterization:
only if planning coil occlusion
Management:
ligation if symptoms of CHF
some small PDAs close spontaneously in infancy but usually not after age 1 year
ligation of large or moderate PDA to prevent pulmonary vascular disease or CHF
PDAs (even tiny PDA) are usually closed (after age 1 year or so) to prevent endocarditis (infection of the heart) - risk = 0.45% per year
Atrial Septal Defect (ASD)
usually in region of fossa ovalis
may be single or multiple
Location: Secundum (fossa ovalis) - most common
Sinus venosus (near SVC/RA junction) – may be associated with anomalous venous drainage
Primum defect – AV canal type defect
Location important because of associated defects
Amount of shunt depends on relative RV and LV compliance not by size or location of defect
RV more compliant then LV - direction of the shunt is from the least compliant to the most compliant chamber
therefore L > R shunt: red blood from LA crosses ASD into right atrium (RA)
no cyanosis (acyanotic)
ASD - Neonate
Neonates have decreased RV compliance immediately after birth
less L > R shunt at birth
may even be R > L shunt - cyanosis
RV compliance increases with age and L > R shunt increases
Hemodynamics of ASD
A) Red blood crosses from LA to RA
B) Increased O2 saturation in RA and increased RA volume
C) Increased O2 saturation in RV and increased RV volume
D) Increased blood in pulmonary circuit, but normal pulmonary artery pressures and resistance
Clinical Picture
History:
more common in females
cyanosis occurs (rarely) in neonates due to R > L shunt due to decreased RV compliance
usually diagnosed in preschool and school aged children with a murmur
usually asymptomatic
rarely children develop CHF and growth failure in infancy (usually only if there are associated defects)
Adult unrepaired ASD patients:
pulmonary vascular disease (> 20 years) more common in females
atrial arrhythmias (atrial fibrillation, atrial flutter)
paradoxical emboli
Examination:
RV precordial bulge (due to enlarged RV)
murmur: systolic ejection murmur due to increased blood flow across the pulmonary valve - not due shunting across the ASD, this is a low velocity shunt and does not make noise
S2 (second heart sound): widely split - due to delayed emptying of the volume-overloaded RV
S2 fixed split - due to unlimited communication between the 2 atria
ASD allows for equalization of the influence of respiratory variation on RV and LV output
CXR: increased pulmonary blood flow
prominent right heart border due to enlargement of RA and RV
Natural History and Management:
surgical (or device) closure at approx. 3 - 5 years if L > R shunting is proven (rarely close spontaneously after age 3)
prevents development of pulmonary vascular disease, late rhythm problems (atrial tachycardia)
unrepaired ASDs result in pulmonary vascular disease in 5 - 10% of patients
unrepaired there is a risk of paradoxical emboli – stroke
Obstructive Lesions
Basic Hemodynamic Principles
outflow obstruction more common than inflow
elevated pressure proximal to obstruction leads to hypertrophy of chamber proximal to the obstruction
the smaller the orifice the greater pressure needed to deliver cardiac output beyond obstruction
cardiac output is maintained
signs and symptoms of obstruction are due to pressure elevation proximal to obstruction and to chamber hypertrophy
Obstruction leads to:
hypertrophy
fibrosis results if there is inadequate O2 to meet demands
fibrosis leads to chamber dilation
Coarctation of the Aorta
Narrowing of descending Aorta
Usually discrete area of stenosis
Juxtaductal (opposite the site where the ductus arteriosus enters aorta) in location, almost without exception
Histologic examination demonstrates intimal thickening and medial ridges that protrude posteriorly and laterally into the aortic lumen
Upper extremity hypertension
Upper extremity blood pressure >> lower extremity blood pressure
Associated bicuspid aortic valve in approx. 50%
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Hemodynamics Of Coarctation
A) mechanical obstruction to blood flow
pressure elevation proximal to obstruction
B) decreased pressure distal to obstruction
C) development of collaterals (internal mammaries, intercostals) to bypass the obstruction
D) LV hypertrophy
E) LVH helps maintain LV wall stress and systolic function (normal LV ejection fraction)
F) LV diastolic function may not be normal due to decreased compliance of the hypertrophied LV
Clinical Picture
History: M > F (in females consider Turner syndrome)
10% present in infancy with CHF
may be life-threatening in infancy usually requiring immediate and aggressive treatment
older children present with hypertension, decreased lower extremity pulses, murmur, claudication (leg pain with walking), and headaches
Examination: normal growth and development in children out of newborn period
Neonates: may present with severe CHF, low cardiac output, shock
Children:
upper extremity blood pressure at least 20 mmHg greater than lower extremity blood pressure
decreased femoral pulses with pulse delay (lower extremity pulse later than upper extremity pulse)
murmur- systolic ejection murmur best heard between scapulae, left sternal border, apex, extends into diastole, turbulent blood crossing the coarctation site
CXR: neonate/infant: cardiac enlargement, pulmonary edema, pulmonary venous congestion
children: normal heart size, rib notching, dilation of descending aorta, “3” sign
Natural History and Management
Neonates with decreased cardiac output - emergency
Prostaglandin E to maintain PDA patency until surgery- allows blood to bypass coarctation to promote perfusion of the organs supplied by the descending aorta
Surgical repair once medically stabilized
Children if hypertensive, significant UE - LE gradient, LV hypertrophy – surgical repair
recoarctation may occur after repair, increased in smaller children (< 1 years)
hypertension may persist after repair
Repair: end-to-end anastomosis, subclavian flap, interposition graft, balloon angioplasty
Valvar Pulmonary Stenosis
Systolic obstruction to outflow from the RV at the pulmonary valve
Fused or absent pulmonary valve commissures
Pulmonary valve cusps are thickened
RV pressure must increase in order to deliver cardiac output beyond the obstruction
Hemodynamics of PS
A) To maintain cardiac output, the RV pressure must increase enough to overcome the stenosis
B) Increased RV pressure results in RV hypertrophy and decreased RV compliance
C) Decreased RV compliance results in a need for higher RA pressures to pump blood into RV
D) Increased RA pressure may result in right to left shunting across a patent foramen ovale if one is present - cyanosis may occur
Clinical Picture
History:
usually asymptomatic with a murmur
neonates may present with cyanosis (R > L shunting at atrial level)
fatigue with exercise if severe stenosis
Examination:
murmur: systolic ejection murmur at upper left sternal border, turbulent blood crossing the stenotic pulmonary valve
systolic ejection click
CXR: usually normal
poststenotic dilatation of main and left pulmonary artery
neonate with cyanosis and severe pulmonary stenosis - decreased pulmonary blood flow
if severe there may be RV enlargement
Natural History and Management:
mild - does not usually progress
moderate and severe - may be progressive
balloon angioplasty has replaced surgical valvotomy in most instances
