Hematology in Children

Chapter 34
Alterations of Cardiovascular
Function in Children
Developmental Anatomy of the
Cardiovascular System
Embryology
- Cardiogenesis begins at approximately 3 weeks’ gestation.
- Heart arises from the mesenchyme.
  - Develops as an enlarged blood vessel with a large lumen and muscular wall.
  - Midsection grows faster than the ends by the fifth week.
- Heart tube elongates and rotates to the right, creating a bulboventricular loop by the 28th day.
- Fetal heart contractions begin by the 28th day.
- All of the fetal heart and vascular systems are present by 4 weeks’ gestation.
Developmental Anatomy of the
Cardiovascular System (Cont.)
From muscular tube to full development
Developmental Anatomy of the
Cardiovascular System (Cont.)
Cardiac septation
- Endocardial cushions
  - Instrumental in closing the atrial septum, dividing the atrioventricular (AV) canals into the right and left AV orifices, and closing the septum
- Septum primum and septum secundum
  - Atrial septation
- Ostium primum
  - Gap that closes by the endocardial cushions
- Ostium secundum
  - Fenestrations or openings that develop in the superior portion of the septum primum
- Developmental Anatomy of the
  Cardiovascular System (Cont.)
- Cardiac septation (cont.)
  - Foramen ovale
    - Nonfused septum secundum and ostium secundum result in the formation of a flapped orifice.
  - Bulbus cordis
    - Separates the aorta from the pulmonary artery.
  - Truncus arteriosus
    - Torsion occurs within the anterosuperior region of the loop.
  - Ductus arteriosus
    - Communication exists between the aorta and the pulmonary artery.
  - Developmental Anatomy of the
    Cardiovascular System (Cont.)
  - Development of cardiac septa
  - In utero fetus blood circulation
    - Foramen ovale
      - Is the opening between the atria.
    - Ductus arteriosus
      - Joins the pulmonary artery to the aorta.
    - Ductus venosus
      - Connects the inferior vena cava to the umbilical vein.
    - Developmental Anatomy of the
      Cardiovascular System (Cont.)
  - In utero fetus blood circulation (cont.)
    - Receives blood-carrying oxygen and nutrients from the placenta through the umbilical vein.
    - Blood travels to the liver, where a portion enters the portal and hepatic circulation.
      - Approximately one-half of the flow is diverted away from the liver through the ductus venosus and into the inferior vena cava.
    - Blood enters the right atrium from the inferior vena cava and is shunted through the foramen ovale and then into the left atrium, left ventricle, and aorta.
  - Developmental Anatomy of the
    Cardiovascular System (Cont.)
  - In utero fetus blood circulation (cont.)
    - Less-saturated blood returns from the upper body, head, neck, and arms and travels from the superior vena cava into the right atrium.
    - A small portion of this blood flows into the right ventricle, out of the pulmonary artery, and enters the nonfunctioning lungs.
    - Most of the blood bypasses the lungs by flowing through the ductus arteriosus and into the descending aorta.
    - Blood from the descending aorta returns to the placenta through two umbilical arteries.
  - Developmental Anatomy of the
    Cardiovascular System (Cont.)
  - Fetal circulation
  - Developmental Anatomy of the
    Cardiovascular System
  - Transitional Circulation
  - Circulatory changes take place after birth.
  - Gas exchange shifts from the placenta to the lungs.
  - Fetal shunts close.
    - Ductus venosus
      - After closure, the round ligament of the liver forms.
    - Foramen ovale
      - Closes from increased pulmonary venous return and decreased inferior vena cava return.
    - Ductus arteriosus
      - Closes from increased oxygen saturation in the systemic arterial blood.
    - Postnatal Development
    - Changes in the position of the heart.
    - Changes in the size of the right ventricle.
    - Hemodynamics
      - Decreased pulmonary vascular resistance.
      - Increased systemic vascular resistance.
      - Heart rate ranges from 100 to 180 beats per minute (bpm).
        
        Newborns have a high oxygen demand.
      - Postnatal Circulation
      - Allows lungs to oxygenate the venous blood.
      - Allows fully saturated blood to be delivered to the systemic circulation.
      - Right ventricular myocardium thins as the pulmonary vascular resistance drops.
      - Increased systemic vascular resistance causes the left ventricular myocardium to become thicker and more dominant as it is in the adult heart.
      - Blood flow follows the same pathway as adults.
      - Congenital Heart Defects
      - Is the leading cause of death (except for prematurity) in the first year of life.
      - Cause is known in only 10% of defects.
      - Prenatal, environmental, and genetic risk factors
        
        Maternal: rubella, lupus, insulin-dependent diabetes, alcoholism, illicit drug use, age (> 40 years) phenylketonuria (PKU), and hypercalcemia
        
        Chromosomal aberrations
      - Classifications
      - Based on blood flow
        
        Lesions increasing pulmonary blood flow
        
        Defects that shunt from high-pressure left side to low-pressure right side with pulmonary congestion; a cyanosis
        
        Lesions decreasing pulmonary blood flow
        
        Generally complex with right-to-left shunt and cyanosis
        
        Obstructive lesions
        
        Right- or left-sided outflow tract obstructions that curtail or prohibit blood flow out of the heart; no shunting
        
        Mixing lesions
        
        Desaturated blood and saturated blood mix in the chambers or great arteries of the heart.
        
        Heart Failure
        
        Is a common condition associated with congenital birth defects.
        
        Is also called congestive heart failure (CHF).
        
        Occurs when the heart is unable to maintain sufficient cardiac output to meet the metabolic demands of the body.
        
        Neurohumoral and hemodynamic changes create abnormal ventricular wall stress and cause the myocardium to hypertrophy.
        
        Heart Failure (Cont.)
        
        Clinical manifestations
        
        Poor feeding and sucking; leads to failure to thrive
        
        Dyspnea, tachypnea, diaphoresis, retractions, grunting, nasal flaring, wheezing, coughing, rales
        
        Skin changes, such as pallor or mottling
        
        Hepatomegaly
        
        Heart Failure (Cont.)
        
        Treatment
        
        Decrease cardiac workload and increase the efficiency of heart function.
        
        Administer diuretics, such as furosemide.
        
        Reduce afterload: Administer angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers, and beta-blockers.
        
        Supplement calorie intake.
        
        Anticoagulation and mechanical circulatory support
        
        Hypoxemia
        
        Is a condition associated with congenital birth defects.
        
        Heart defects that allow desaturated blood to enter the systemic system without passing through the lungs result in hypoxemia and cyanosis.
        
        Hypoxemia: Arterial oxygen tension is below normal and results in low oxygen arterial saturations and cellular function alteration.
        
        Cyanosis: Blue discoloration of mucous membranes and nail beds; is the result of deoxygenated hemoglobin.
        
        Hypoxemia (Cont.)
        
        Eisenmenger syndrome
        
        Pulmonary vascular resistance increases that exceed or equal vascular resistance, resulting in a reversal of shunting
        
        Defects that cause hypoxemia and cyanosis
        
        Lesions that cause obstruction and shunting from the right side of the heart to the left side, as in the tetralogy of Fallot
        
        Defects involving the mixing of saturated and unsaturated blood, as in the univentricular heart
        
        Transposition of the great arteries
        
        Hypoxemia (Cont.)
        
        Clinical manifestations
        
        Mild hypoxemia
        
        Cyanosis only occasionally when stressed
        
        Severe hypoxemia
        
        Feeding intolerance, poor weight gain, tachypnea, and dyspnea
        
        Chronic hypoxemia
        
        Small for their age, may display cognitive and motor skill delays.
        
        Polycythemia, shortness of breath with exertion, easily fatigued, and exercise intolerance
        
        Clubbing of the nail beds
        
        Hypoxemia

Defects Increasing Pulmonary
Blood Flow

Patent ductus arteriosus (PDA)
- Failure of the ductus arteriosus to close
  - Normally closes within first few hours of birth.
  - PDA allows blood to shunt from the pulmonary artery to the aorta.
- Clinical manifestation
  - Continuous, machinery-type murmur
  - Bounding pulses, active precordium, thrill upon palpation, and signs and symptoms of pulmonary overcirculation.
- Treatment
  - Surgical closure involving ligation by incision, catheter, or video-assisted thoracoscopy
- Defects Increasing Pulmonary
  Blood Flow (Cont.)
- PDA (cont.)
- Defects Increasing Pulmonary
  Blood Flow (Cont.)
- Atrial septal defect
  - Abnormal communication between the atria
    - Allows blood to be shunted from left to right.
  - Clinical manifestations: Often asymptomatic; diagnosed by murmur
  - Three major types of defect
    - Ostium primum
    - Ostium secundum
    - Sinus venosus
  - Treatment
    - Surgical closure before school age results in better health.
  - Defects Increasing Pulmonary
    Blood Flow (Cont.)
  - Atrial septal defect (cont.)
  - Defects Increasing Pulmonary
    Blood Flow (Cont.)
  - Ventricular septal defect (VSD)
    - Abnormal communication between ventricles
      - Shunting from the high-pressure left side to the low-pressure right side
    - Common congenital heart lesion (15% to 20%)
    - Pulmonary overcirculation accounts for symptoms associated with a large VSD.
    - Symptoms depend on age of child, size of defect, and level of PVR.
    - Treatment
      - Catheter closure
      - Transcatheter muscular devices
    - Defects Increasing Pulmonary
      Blood Flow (Cont.)
    - Defects Increasing Pulmonary
      Blood Flow (Cont.)
    - VSD (cont.)
    - Defects Increasing Pulmonary
      Blood Flow (Cont.)
    - Atrioventricular canal (AVC) defect
      - Results from nonfusion of the endocardial cushions.
      - Abnormalities demonstrated in the atrial and ventricular septa and AV valves
      - Complete, partial, and transitional AVC defects
      - Clinical manifestations: Presents with a murmur; heart failure; respiratory tract infections.
      - Treatment: Complete repair between 3 and
        6 months of life
    - Defects Increasing Pulmonary
      Blood Flow (Cont.)
    - AVC defect (cont.)
    - Defects Increasing Pulmonary Blood Flow
    - Defects Decreasing Pulmonary
      Blood Flow
    - Tetralogy of Fallot
      - Syndrome represented by four defects
        
        Large VSD
        
        Overriding aorta straddles the VSD
        
        Pulmonary stenosis
        
        Right ventricle hypertrophy
      - Cyanosis, hypoxia, and clubbing, feeding difficulty, dyspnea, restlessness, squatting
      - Hypercyanotic spell or a “tet spell” that generally occurs with crying and exertion
      - Most cases corrected surgically in early infancy before 1 year of age; Blalock-Taussig shunt, transcatheter pulmonary valve replacement, patch
    - Defects Decreasing Pulmonary
      Blood Flow (Cont.)
    - Tetralogy of Fallot (cont.)
    - Defects Decreasing Pulmonary
      Blood Flow (Cont.)
    - Tricuspid atresia
      - Imperforate tricuspid valve
      - No communication between the right atrium and the right ventricle
      - Additional defects
        
        Septal defect
        
        Hypoplastic or absent right ventricle
        
        Enlarged mitral valve and left ventricle
        
        Pulmonic stenosis
      - Defects Decreasing Pulmonary
        Blood Flow (Cont.)
      - Tricuspid atresia (cont.)
        
        Clinical manifestations
        
        Central cyanosis and growth failure
        
        Exertional dyspnea, tachypnea, and hypoxemia
        
        Polycythemia, clubbing, hepatomegaly
        
        Treatment
        
        Prostaglandin administration
        
        Blalock-Taussig shunt
        
        Rashkind procedure: balloon atrial septostomy
        
        PA band
        
        Closure of septal defects
        
        Defects Decreasing Pulmonary
        Blood Flow (Cont.)
        
        Tricuspid atresia (cont.)
        
        Obstructive Defects
        
        Coarctation of the aorta
        
        Narrowing of the lumen of the aorta that impedes blood flow (8% to 10% of defects)
        
        Is almost always found in the juxtaductal position, but it can occur anywhere between the origin of the aortic arch and the bifurcation of the aorta in the lower abdomen.
        
        Clinical manifestations: Newborns usually exhibit HF.
        
        Once the ductus closes, rapid deterioration occurs from hypotension, acidosis, and shock.
        
        Obstructive Defects (Cont.)
        
        Coarctation of the aorta (cont.)
        
        Clinical manifestations: Older children
        
        Hypertension in the upper extremities
        
        Decreased or absent pulses in the lower extremities
        
        Cool mottled skin
        
        Leg cramps during exercise
        
        Treatment
        
        Prostaglandin administration
        
        Mechanical ventilation
        
        Inotropic support
        
        Maintain cardiac output
        
        Surgery
        
        Obstructive Defects (Cont.)
        
        Coarctation of the aorta (cont.)
        
        Obstructive Defects (Cont.)
        
        Aortic stenosis
        
        Narrowing of the aortic outflow tract (10% of defects)
        
        Caused by malformation or fusion of the cusps.
        
        Causes an increased workload on the left ventricle.
        
        Clinical manifestations
        
        Often asymptomatic
        
        Signs of exercise intolerance in preadolescence
        
        Syncopal episodes, epigastric pain, and exertional chest pain in more severe forms
        
        Murmur
        
        Treatment
        
        Commissurotomy; aortic valvotomy; Ross procedure
        
        Obstructive Defects (Cont.)
        
        Aortic stenosis (cont.)
        
        Obstructive Defects
        Question 4
        
        Obstructive Defects
        
        Pulmonary stenosis
        
        Narrowing of the pulmonary outflow tract
        
        Abnormal thickening of the valve leaflets
        
        Narrowing of the valve
        
        Pulmonary atresia: Severe form
        
        Clinical manifestations
        
        Often asymptomatic
        
        Exertional dyspnea, murmur, fatigue, thrill, cyanosis, HF
        
        Treatment
        
        Mild: Not treated, closely observed
        
        Severe: Balloon angioplasty; pulmonary valvotomy
        
        Obstructive Defects (Cont.)
        
        Pulmonary stenosis (cont.)
        
        Obstructive Defects (Cont.)
        
        Hypoplastic left heart syndrome
        
        Left-sided cardiac structures develop abnormally.
        
        Obstruction to blood flow from the left ventricular outflow tract
        
        Left ventricle, aorta, and aortic arch are underdeveloped; mitral atresia or stenosis is observed.
        
        As the ductus closes, systemic perfusion is decreased, resulting in hypoxemia, acidosis, and shock.
        
        Obstructive Defects (Cont.)
        
        Hypoplastic left heart syndrome (cont.)
        
        Treatment
        
        Prostaglandin administration
        
        Correction of acidosis
        
        Inotropic support for adequate cardiac output
        
        Ventilatory manipulation
        
        Obstructive Defects (Cont.)
        
        Hypoplastic left heart syndrome (cont.)
        
        Treatment
        
        Surgical intervention includes a three-stage approach.
        
        Norwood procedure: Atrial septectomy, pulmonary-to-systemic artery shunt, permanent communication between the right ventricle and aorta, and patching the hypoplastic aorta.
        
        Glenn procedure: Performed between 2 and 9 months of age; the superior vena cava is joined to the pulmonary artery, and the takedown of the shunt to the lungs.
        
        Fontan procedure: Performed between 2 and 4 years of age, separates the systemic from the pulmonary circulation.
        
        Cardiac transplantation
        
        Obstructive Defects (Cont.)
        
        Hypoplastic left heart syndrome (cont.)
        
        Mixed Defects
        
        Transposition of the great arteries
        
        Aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle.
        
        Results in two separate, parallel circuits.
        
        Unoxygenated blood continuously circulates through the systemic circulation.
        
        Oxygenated blood continuously circulates through the pulmonary circulation.
        
        Extrauterine survival requires communication between the two circuits.
        
        Clinical manifestations: Cyanosis may be mild shortly after birth and worsen during the first day.
        
        Treatment: Surgery to switch the arteries.
        
        Mixed Defects (Cont.)
        
        Transposition of the great arteries (cont.)
        
        Mixed Defects (Cont.)
        
        Total anomalous pulmonary venous connection (TAPVC)
        
        Pulmonary veins connect to the right side of the heart, directly or indirectly, through one or more systemic veins that drain into the right atrium.
        
        Nonobstructive vs. obstructive
        
        Clinical manifestation: Cyanosis
        
        Treatment
        
        Obstructed lesions are repaired at the time of diagnosis.
        
        Unobstructed lesions are generally repaired during infancy.
        
        Surgery: Anastomosis of the common pulmonary vein to the left atrium; closure of the atrial septal defect.
        
        Mixed Defects (Cont.)
        
        TAPVC (cont.)
        
        Mixed Defects (Cont.)
        
        Truncus arteriosus
        
        Is the failure of the embryonic artery to divide into the pulmonary artery and aorta.
        
        Trunk straddles an always present VSD.
        
        Types I through IV
        
        I: Most common; the main pulmonary artery arises from the truncus.
        
        II: Pulmonary arteries arise from the posterior aspect of the truncus.
        
        III: Pulmonary arteries arise from the lateral aspect of the truncus.
        
        IV: Pseudotruncus; is a severe form of tetralogy of Fallot with the bronchial arteries arising from the descending aorta to supply the lungs.
        
        Mixed Defects (Cont.)
        
        Truncus arteriosus (cont.)
        
        Clinical manifestations
        
        Cyanosis; mild-to-moderate cyanosis that worsens with activity
        
        Murmur
        
        Treatment
        
        Modified Rastelli procedure involving VSD patch closure to divert the blood flow from the left ventricle outflow tract into the truncus
        
        Correct pulmonary arteries
        
        Mixed Defects (Cont.)
        
        Hypoplastic left heart syndrome (HLHS)
        
        Abnormal development of left-sided cardiac structures
        
        Obstructs blood flow from the LV outflow tract.
        
        Clinical manifestations
        
        Hypoxemia, acidosis, shock
        
        Loud and single second heart sound
        
        Treatment
        
        Prostaglandin infusion
        
        Correction of acidosis
        
        Inotropic support
        
        Ventilatory manipulation
        
        Surgery
        
        Mixed Defects (Cont.)
        
        Truncus arteriosus
        
        Acquired Cardiovascular Disorders
        
        Kawasaki disease
        
        Formerly known as mucocutaneous lymph node syndrome.
        
        Is an acute, self-limiting systemic vasculitis that may result in cardiac sequelae.
        
        Approximately 80% of cases occur in children under the age of 5.
        
        Cause
        
        Unknown
        
        Theories: An immunologic response to an infectious, toxic, or antigenic substance (including superantigen)
        
        Acquired Cardiovascular Disorders (Cont.)
        
        Acquired Cardiovascular Disorders (Cont.)
        
        Acquired Cardiovascular Disorders (Cont.)
        
        Kawasaki disease (cont.)
        
        Diagnosis
        
        Fever
        
        Conjunctivitis
        
        Oral changes (strawberry tongue)
        
        Irritability
        
        Rash
        
        Lymphadenopathy
        
        Treatment
        
        Aspirin and intravenous (IV) administration of immunoglobulin during the acute phase
        
        Acquired Cardiovascular Disorders Question 5
        
        Acquired Cardiovascular Disorders
        
        Systemic hypertension
        
        Hypertension in children differs from adults.
        
        Children often have underlying renal disease or coarctation
        of the aorta.
        
        Children with hypertension are commonly asymptomatic.
        
        Treatment: Appropriate diet, regular physical activity, avoidance of smoking, drugs
        
        ACE inhibitors
        
        ARBs
        
        Calcium channel blockers
        
        Acquired Cardiovascular Disorders (Cont.)
        
        Childhood obesity
        
        Is considered an epidemic.
        
        Centers for Disease Control and Prevention (CDC) suggests two levels of overweight.
        
        85th percentile: “At-risk” level
        
        95th percentile: More severe level
        
        Is multivariable and multidimensional.
        
        Risk factors
        
        Race, socioeconomic status, lack of health insurance
        
        Early childhood nutrition
        
        Low level of physical activity, engagement in sedentary activities (television viewing, computer use)
        
        Sleep disturbances
        
        Acquired Cardiovascular Disorders (Cont.)
        
        Childhood obesity (cont.)
        
        Is associated with parental obesity.
        
        Places the child at risk for asthma, sleep apnea, hypertension, type 2 diabetes, dyslipidemia, cardiovascular disease.
        
        Has social and economic consequences.
        
        Treatment: Prevention
        
        Combines physical activity with nutritional improvements.
        
        Needs intervention, immediate referral, and support from health care professionals.
        
        Requires change in lifestyle at home and involvement of family members.

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