The process of the fetal circulation: Oxygenated blood (placenta ) Liver Inferior vena cava Right atrium Left atrium Left ventricle Ascending aorta Upper part of the body Deoxygenated blood(upper part) Superior vena cava Right ventricle Puomonary artery Descending aorta Lower part of the body Lung Foramen ovale Righ atrium Ductus ateriosus Placenta Ductus venosus
Right-left blood shunts through the foramen ovale and ductus arteriousus occur because of the higher pulmonic resistance and lower systemic resistance Two ventricles work in parallel rather than in series The concentration of oxygen is highest in the liver, next is the upper part of the body and the last is the lower part of the body. Distinct features of the fetal circulation:
The changes of circulation after birth Establishment of pulmonary circulation Cessation of the umbilicus-placenta circulation Systemic resistance > pulmonic resistance Right-left blood shunt through the foramen ovale is limited and eventually eliminated, the foramen ovale anatomically closes within 5-7m after birth. Blood shunt through the ductus arteriosus is reduced. Higher oxygen content of the blood and loss of prostaglandins leads to gradual closure of the ductus arteriosus Functional closure within 10-15hs after birth and anatomically within 3m (80%)-1y(95%).
2. Heart rate The younger the child is , the faster the heart rate is. Age Heart rate Neonate 120-140/min Infancy 110-130/min Preschool age 80-100/min School age 70-90/min
3. Blood pressure Arterial pressure gradually increases with advancing age. A mature infant averages 10/6.67kPa(75/50mmHg) (1mmHg 0.133kPa, 1kPa 7.5mmHg) The formula for older children(>2y): Systolic pressure=age ×2+80mmHg Diastolic pressure=2/3 systolic pressure Hypertension: Systolic pressure is 20mmHg higher than the normal value Hypotension: Systolic pressure is 20mmHg lower than the normal value The blood pressure in the lower limbs is 20mmHg higher than that in the upper limbs
Congenital Heart Diseases (CHD) Diagnostic Techniques for CHD VSD Tetralogy of Fallot ASD PDA Introduction of CHD
Introduction of CHD
Definition of CHD
Congenital heart diseases are abnormalities of the heart's structure and function caused by abnormal or disordered heart development before birth.
Incidence of CHD
About 7-8 per 1000 alive births in developing countries and 2.2 in developed countries
Eight common lesions, which account for 85 percent of all cases:
[i] ventricular septal defect (VSD)
[ii] patent ductus arteriosus(PDA)
[iii] atrial septal defect (ASD)
[iv] pulmonary stenosis
[v] aortic valve stenosis
[vi] coarctation of the aorta
[vii] tetralogy of Fallot
[viii] transposition of great arteries.
Etiology of CHD
Environmental factors existing during first trimester of pregnancy:
Congestive Heart Failure: rapid and labored breathing
pallor with peripheral cyanosis
tachycardia and excessive sweating
Recurrent Respiratory Tract Infections
Complications of CHD
Left to right shunt
Recurrent respiratory infections (pneumonia)
Congestive heart failure
Right to left shunt
Treatment of CHD
Control heart failure
Control hypoxemic spells
Diagnostic Techniques for CHD
History taking Pregnant history of the mother: rubella infection, medications , radiation exposure Family history: family members with CHD Present ill history: all possible cardiac symptoms failure to thrive, feeding difficulty, cyanosis, squatting, respiratory distress, sweating, pallor, syncope.
General Examination Poor development Central cyanosis arterial deoxygenation (right - left shunt) Respiratory distress poor systemic output, increased pulmonary blood flow, heart failure Clubbing of fingers or toes prolonged hypoxia
Inspection Protrusion of the left precardium and sternum often indicates right ventricular enlargment. Position and range of the apex beat Cardiac Examination
location (normal: 5 th intercostal space just
medial to the left mid-clavicular line)
Character heaves ( systolic lift)
A thrill often is accompanied with a murmur
Can roughly estimate the size and position of the heart Percussion
First heart sound and second heart sound
P 2: earlier closure and accentuation; delay and softening
Murmur: loudness, frequency (pitch), form or shape, cardiac phase, position and radiation.
Electrocardiography(ECG,EKG) The utility of the ECG in the diagnosis of congenital heart disease is largely for the diagnosis of ventricular and atrial hypertrophy.
Echocardiography (UCG) The best way to diagnose CHD Safe, noninvasive and accurate. Demonstrate the structure of the components of the heart and the blood flow in the heart.
Catheterization Need to diagnose has decreased dramatically An invasive, radioactive modality Obtaining pressure measurement and accurate shunt flows which is beyond the scope of Echocardiography.
Relative Frequency of Congenital Heart Lesions
Lesions % of All Lesions
Ventricular septal defect(VSD) 25-30
Atrial septal defect (ASD) 6-8
Patent ductus arteriosus(PDA) 6-8
Tetralogy of Fallot 5-7
Pulmonary stenosis (PS) 5-7
Transposition of the great arteries (TGA) 3-5
The former four types are the focus of this chapter.
Ventricular septal defect (VSD)
(VSD) a hole in the septum between the right and left ventricles. The shunt occurs predominantly during ventricular systole. Blood passes from the left to right ventricle and is ejected directly into the pulmonary artery along with systemic venous blood.
Left-to-right shunting at the level of ventricles
Increased flow to RV -LA-LV dilatation or hypertrophy
Eisenmenger's syndrome Refers to patients with reversed or bi-directional shunt and sustained cyanosis as a result of a pulmonary vascular obstructive disease (PVOD) and pulmonary hypertension resulting from Long-term presence of the large left to right blood shunt.
Small defect (Roger’s disease, <0.5cm):
No obvious symptoms
Characteristic murmur: a high-pitched, harsh, holosystolic murmur, well localized between the third and fourth intercostal spaces along the left sternal border .
Large defect (>1cm): Manifestations of congestive heart failure: irritability, increased respiratory effort, poor feeding; tachycardia, tachypnea, dyspnea, pallor, diaphoresis, failure to thrive Recurrent respiratory infections Growth retardation Hoarseness in the voice: the recurrent laryngeal nerve being pressed by dilated pulmonary artery Symptoms
Hyperactive precordial impulse , and a thrill is often palpable Accentuated P2 The murmur: loud, low-pitched, harsh, holosystolic, and loudest along the left sternal border, less well localized than a small VSD, radiate to the right of the sternum Older children with Eisenmenger's syndrome: resting cyanosis , nail-bed clubbing Signs
Normal in small defects
Small or normal aortic knob in size.
Dilated main pulmonary artery segment.
Cardiomegaly (both the left and right
ventricles and the left atrium).
Increased pulmonary vascular markings
ECG The ECG suggests left ventricular hypertrophy (LVH), and can show RVH as the pulmonary resistance rises. V 1 V 1 Inverted T wave suggests no pulmonary hypertension Upright T wave indicates pulmonary hypertension
demonstrates the precise anatomy and physiology of the defect:
A medium-sized muscular ventricular septal defect
A left-to-right shunt during systole
A small right-to-left shunt during diastole
Increased oxygen saturation at the right ventricular level.
Direct measurement of pulmonary artery pressures and calculation of the pulmonary to systemic flow ratio.
small, usually need no treatment.
large, needs medical management and then surgery to repair the VSD
----Early surgical repair of VSD is indicated if congestive heart failure appears in infancy and is difficult to control, or the pulmonary : systemic flow ratio>2:1. Otherwise, the operation is performed at preschool age.
Eisenmenger's syndrome, a heart- lung transplantation.
Atrial septal defect (ASD)
1. Patent ostium secundum (secundum ASD) :
a deficiency of the flap valve of the fossa ovalis
a defect in the growth of the septum secundum
2. Patent ostium primum (primum ASD):
locate at the atrioventricular junction
3. Patent foramen oval
The pressure in the right atrium is higher than that in the left atrium at birth and during early neonatal period
----right-to-left shunt, transient cyanosis.
The pressure in the left atrium is higher than that in the right atrium when the pulmonary blood flow increases
Large left-to-right shunt at the level of atrial septum
----Increased blood flow and enlargement of the right atrium, right ventricle, and pulmonary arteries
----Decreased blood flow to aorta (systemic circulation )
Clinical manifestations Small ASDs usually go undiagnosed for years because children are asymptomatic and physical signs are subtle. Symptoms of congestive heart failure are rare compared to VSDs. However, a few patients do present with a history of recurrent respiratory tract infections . Symptoms
Signs Protrusion of the precardium may be seen and the right ventricular tap (a systolic lift) is especially palpable from the left sternal border to the midclavicular line. Systolic murmur due to an increased right ventricular stroke volume and relative pulmonary stenosis is heard best in the second intercostal space just along the left sternal border and usually is grade 2 to 3.
Signs Accentuated second heart sound with fixed and wide splitting the increased right ventricular volume prolonging the right ventricular systole the increased time interval between the aortic and pulmonic component of the second heart sound A soft mid-diastolic murmur the increased tricuspid flow and relative stenosis of the tricuspid is best appreciated along the lower left sternal border
Normal in small defects
Small or normal aortic knob in size.
Dilated main pulmonary artery
Cardiomegaly (the right atrium and
Increased pulmonary vascular
The electrocardiogram shows evidence of the right ventricular volume load.
The QRS axis in frontal plane is shifted to the
The characteristic electrocardiographic
pattern is an rsR’ pattern in AVR and the
right precordial leads (right bundle branch
A part of the patients have right atrial and
UCG Echocardiography can define the precise position of the atrial defect and demonstrate the volume-loaded right ventricle. And it allows definition of the entire cardiac structure and the exclusion of associated defects.
Higher oxygen saturation in the right atrium than the superior vena cava.
The catheter frequently enters the left atrium from the right atrium.
Treatment Surgical correction is accomplished under direct vision through a right atriotomy while on cardiopulmonary bypass. Most defects are closed by direct suture and surgical mortality is less than 1%.
Patent ductus arteriosus(PDA) An abnormal persistence of a normal fetal pathway between the main pulmonary artery and the descending aorta .
The ductal shunt is from the aorta to the
pulmonary artery throughout the cardiac
cycle left atrial and left ventricular
volume overload left atrial and left
ventricular enlargement and hypertrophy
With large and long-term shunts
pulmonary hypertension occurs right
If the pulmonary pressure > aortic pressure
a right-to-left shunt differential cyanosis
Clinical manifestations Symptoms Children with small shunts will be asymptomatic. In the presence of a large shunt, signs and symptoms of congestive heart failure, and recurrent respiratory infections will exist.
Typical murmur: continuous machinery murmur heard best at the second intercostal space along the left sternal border and thrill can be palpable at the loudest area continuous systolic and diastolic turbulent flow from the aorta to the pulmonary artery.
A wide systemic pulse pressure that produces bounding pulses is the hallmark of a patent ductus arteriosus diastolic flow from the aorta to the pulmonary artery lowering aortic diastolic pressure.
Differential cyanosis severe pulmonary hypertension
Normal in small ductus
Normal or prominent aortic knob .
Prominent pulmonary arterial segment
and increased pulmonary vascular
Cardiomegaly resulting from left atrial and
ECG Left ventricular hypertrophy may be present. Some cases also have left atrial hypertrophy. In patients with pulmonary hypertension due to increased blood flow, there is usually biventricular hypertrophy.
Increased left atrial and left ventricular dimensions are observed with a large ductus.
Continuous systolic and diastolic turbulent flow from the aorta to the pulmonary artery is diagnostic
There is evidence of increased oxygen content or saturation at the level of the pulmonary artery.
Catheter may pass through the ductus from the pulmonary artery to the descending aorta.
Treatment Surgical ligation through a left thoracotomy is performed safely and at low risk after a noninvasive evaluation.
Tetralogy of Fallot (TOF) 1. Pulmonary stenosis 2. Ventricular septal defect 3. Overriding aorta 4. Right ventricular hypertrophy
Pathophysiology Decrease in systemic arterial oxygen saturation and cyanosis is the main pathologic result caused by PS, VSD and overriding aorta oxygen-poor blood returning to the RV is shunted across the VSD to the LV, and/or pumped directly into the overriding aorta in the presence of marked PS Right ventricular outflow tract obstruction results in compensatory right ventricular hypertrophy.
The hemodynamic consequences and severity of clinical manifestations depend on the degrees of PS: mild PS:Pulmonary outflow resistance<systemic left to right shunt acyanotic or pink TOF moderate-severe PS: right to left shunt decreased pulmonary blood flow causes cyanotic insufficient blood oxygenation TOF A systolic murmur caused by PS P 2 is either faint or absent because of low pulmonary pressure
Clinical manifestations Cyanosis and clubbing fingers and toes .
Fatigability, dyspnea and a squatting position for the relief of dyspnea.
squatting an increase in systemic vascular resistance that decreases the right-to-left shunting and increases pulmonary blood flow
decrease in systemic venous return that reduces a volume burden on the heart
Hypoxemic spell Increasing cyanosis, restlessness, and increased rate and depth of respiration suddenly, even syncope. Disappearance or attenuation of the systolic murmur. Convulsions or hemiparesis, coma and death. The physiologic change: suddenly further increase in resistance at the right ventricular outflow tract further increase in right-to-left shunt and a further decrease in the pulmonary blood flow
Growth and development may be delayed in severe untreated tetralogy of Fallot. Cardiac signs: The left sternal bordor may bulge forward A cardiac lift (right ventricular impulse) is palpable A systolic thrill is palpable in 50% of cases Systolic murmur: is frequently loud and harsh, heard best from the second to fourth intercostal spaces along the left sternal border pulmonary stenosis The pulmoanry component of the second heart sound is either faint or absent.
Chest x-Ray Concave main pulmonary arterial segment and remarkably clear lung fields owing to the diminished pulmonary blood flow. Boot-shaped heart The hypertrophied right ventricle makes the cardiac apex upturned The aortic knob is prominent or shiffted to the right .
Right axis deviation
Right ventricular hypertrophy .
UCG Cardiac catheterization The anatomic features of TOF are identified by echocardiography
The right ventricular pressure is elevated.
The pulmonary artery pressure is extremely low.
Catheter frequently passes from the right ventricle into the overriding ascending arota .
Injection of contrast material into the right ventricle reveals the right ventricular outflow obstruction and right to left shunt at the ventricular level .
Laboratory findings Polycythemia and high hematocrit and hemoglobin Complications Cerebral thrombosis Brain abscess Bacterial endocarditis
Treatment Palliative surgery to increase pulmonary blood flow: Infants with symptomatic TOF in the first few months of age Corrective surgery: at around 6 m Hypercyanotic spells: Knee-chest position Oxygen inhalation Sedation Correct metabolic acidosis Propranalol
Keys to be remembered
The components of the first and second heart sound
Special structures in the fetal CVS
Distinct features of the fetal circulation
The changes of circulation after birth
Normal Heart rate of different ages
Keys to be remembered
The etiology and classification of CHD
The pathophysiology, clinical manifestations and chest X-ray of VSD, ASD, PDA, TOF