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***LISTEN TO THE PODCAST HERE***

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Click Here for Episode #11 – Review of Cyanotic Congenital Heart Defects

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Review of In-Utero and Neonatal Cardiovascular Physiology

• Ductus arteriosus
  • Connects the pulmonary artery to the descending aorta
  • Prostaglandin E₂ are produced by the placenta and keep this open, along with low arterial oxygen concentration
  • Begins to close 10-15 hours after delivery and should be completed by 2-3 weeks of age
• Foramen ovale
  • Communication between right and left atrium
  • Once the infant begins spontaneously breathing, increases in pulmonary blood flow and left atrial pressures mechanically seals the foramen ovale

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Review of Initial Approach to Screening for Congenital Heart Diseases

• The main approach to initial cardiac evaluation for infants with suspected heart disease is to determine:
  • Innocent vs Congenital Heart Disease
    • Cyanotic vs Acyanotic
    • Indications for emergent referral
• Historical Clues
  • Symptomatic
    • Cyanosis, respiratory, poor growth, poor feeding, syncopal episodes
  • Family History
    • Parent or sibling with congenital heart disease
      • 1^st degree relative with any CHD – RR 3.21
  • Genetic syndromes
  • Prenatal Evaluation
    • Abnormalities on prenatal ultrasound
    • Maternal factors that increase risk
      • Multifetal pregnancy, prematurity, preeclampsia, DM, HTN, Age > 40, alcohol/substance use, smoking,
  • Age of child
• Physical Examination
  • Murmurs
    • Innocent murmur
      • ≤ Grade 2
      • Short systolic phase
      • Minimal radiation
      • Soft intensity
  • Extra Heart Sounds
    • Abnormal S2
    • S3 or S4
    • Systolic click
    • Thrills and heaves
  • Other Findings
    • Abnormal vital signs
      • BP differences between right arm, left arm, and legs
      • Weak or bounding pulses
    • Hepatomegaly
• Diagnostic Studies
  • Pulse oximetry screening
    • Measure in right hand (pre-ductal) and either foot (post-ductal)
  • Chest radiograph
    • Cardiomegaly, increased pulmonary vascular markings, pulmonary edema
  • EKG
    • LVH, RVH, abnormal axis, dysrhythmias, prolonged QT
  • Echocardiogram

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Ventricular Septal Defect

Epidemiology

• 30% of all CHD (most common)

Normal Development

• Three main components
  • AV canal septum (1)
  • Muscular septum (2)
  • Parietal band or distal conal septum (3)

• Closure of the interventricular foramen is dependent on:
  • Right-sided endocardial cushions  projecting into the AV canal
  • Connective tissue growth on the crest of the muscular septum
  • Downward growth of ridges dividing the conus

Types

• Membranous Defects
  • Most common clinically significant VSD
  • Under aortic valve and behind septal leaflet of the tricuspid valve
    • May extend into muscular septum
  • Can be associated with LVOTO and coarctation
• Muscular Defects
  • Located along right ventricular free wall-septal junction, in the central muscular septum, or in the apical septum
  • Often close spontaneously
• Malalignment Defects
  • Result from anterior/posterior malalignment of the conal septum
  • Associated with Tetralogy of Fallot
• Subpulmonic Defects (outlet)
  • Superior and anterior conal septum defects
• AV Canal Defects (inlet)
  • Posterior and superior to annulus of tricuspid valve
  • Associated with ASDs

Pathophysiology

• Cause no problems in-utero
• Causes a left-to-right shunt ex-utero
  • Higher left ventricular pressures
• Categorization is based on:
  • Size
    • Small – < 4mm
    • Moderate – 4-6mm
    • Large – > 6mm
  • Shunt (Pulmonary:Systemic flow)
    • Small – Qp:Qs < 1.5
    • Moderate – Qp:Q 1.5-2.3
    • Large – Qp:Qs > 2.3
• Effects on Circulation
  • Pulmonary
    • Increased and causes tachypnea and increased respiratory effort
  • Systemic
    • LV output must increase to maintain systemic flow
    • As systemic flow decreases (large VSDs):
      • Increased alpha-adrenergic stimulation
      • Increased catecholamine release
      • Increased angiotensin release
    • Increases risk of heart failure

Natural History

• Small
  • 75% close spontaneously within 2 years of life
  • Those that persist in adulthood are benign
• Moderate
  • Spontaneous closure depends on pulmonary arterial pressure and size/location of defect
  • Can respond to medical management
• Large
  • Rarely spontaneously close
  • Surgery must be performed within 1^st year to avoid permanent pulmonary vascular resistance

Clinical Presentation

• Prenatal
  • Moderate to large VSD can be diagnosed during 20week ultrasound
• Postnatal
  • Small VSD
    • Can be asymptomatic and present with only a murmur
  • Moderate to Large VSD
    • Present 3-4 weeks from birth with signs and symptoms of heart failure
      • Tachypnea
      • Poor feeding or poor weight gain
      • Tachycardia
      • Hepatomegaly
      • Rales, retractions
    • Cardiac Examination
      • Murmur
        • Harsh or blowing holosystolic
        • Heard best at 3^rd-4^th intercostal space
        • May have a diastolic rumble
          • Increased flow across mitral valve
        • Loud, splitting of S2
          • Due to increased pulmonary arterial pressure
      • Palpable thrill may be present

Diagnostic Studies

• EKG
  • LVH, RVH, RAE
• Chest Radiograph
  • Increased pulmonary vascular markings
• Echocardiography
  • Two-dimensional Doppler confirms diagnosis

Management

• Expectant
  • Most small VSD close spontaneously
  • Follow-up every 6 months with cardiologist until murmur resolves or yearly if murmur persists but still asymptomatic
• Medical
  • Heart failure management
    • Diuretics are first line
  • Nutritional support
  • Pulmonary hypertension management
    • May need cardiac catheterization for accurate measurements and determination for surgical management
• Surgical
  • Indications
    • Persistent symptoms with maximal medical therapy
    • Moderate/large defects with pulmonary hypertension
    • Persistent left-to-right shunt with LV dilation
    • Associated aortic valve prolapse or aortic regurgitation
    • Double-chambered right ventricle
  • Direct patch closure is procedure of choice in most children
  • Transcatheter closure is technically challenging and not offered routinely due to higher incidence of AV block and valve injury

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Atrial Septal Defect

Epidemiology

• 10-15% of all CHD
• 1-2 per 1000 live births

Normal Development

• Begins at 5^th week and is made up of 3 structures
  • Septum primum and AV canal septum (endocardial cushions)
    • Arises from superior portion of common atrium
    • Grows caudally towards AV canal septum
      • These two fuse close ostium primum between right and left atria
  • Septum secundum
    • Covers the ostium secundum on the right atrial side of the septum primum
      • Forms the fossa ovalis
    • Leaves a small opening in-utero
      • Foramen ovale
        • Held open due to pressure gradients between the higher right atria and lower left atria
          • Allows for right to left flow

Types

• Primum Defect
  • 15-20% of ASDs
  • Occurs when primum septum does not fuse with endocardial cushions
• Secundum Defect
  • 70% of ASDs
  • 2x more common in females
  • Located within the fossa ovalis
• Sinus Venosus Defect
  • 5-10% of ASDs
  • Malposition of the insertion of the superior or inferior vena cava on the atrial septum
• Patent Foramen Ovale
  • Identified on 30% of adult autopsies
  • NOT considered an ASD because no septal tissue is missing

Natural History

• Most close spontaneously
  • >80% of small (<5mm)
  • 30-60% of moderate (6-10mm)
  • Large (>10mm) do not close spontaneously
• Persistent ASDs can cause pulmonary hypertension and heart failure in adulthood

Clinical Presentation

• Most are asymptomatic and diagnosed only by identification of murmur
• Murmur
  • Midsystolic pulmonary flow or ejection murmur
    • Heard best left 2^nd intercostal space
  • Wide, fixed split S2
    • ASD equalizes the respiratory effect on both right and left ventricular output
    • If pulmonary hypertension is present, there may be an accentuated pulmonic component of S2
  • May have associated mitral regurgitation murmur

Diagnostic Studies

• EKG
  • May show rSr’ or rsR’ pattern in V1
    • Incomplete RBBB
• Echocardiogram
  • Transthoracic may see, but a transesophageal is better

Management

• Often watch until child is 2yo as most will spontaneous
  • Even persistent defects are not recommended to close
• Closure Indications
  • Right heart enlargement
  • Pulmonary overcirculation
  • Substantial left-to-right shunt
• Types of Closures
  • Percutaneous
    • Criteria
      • < 30mm is diameter
      • ≥ 5mm or rim tissue around defect sufficient for effective closure without obstructing surrounding structures
    • Avoids bypass and major surgical incisions
    • Complications
      • Device embolization, malposition, dysrhythmias, cardiac perforation
  • Surgery
    • Indications
      • Sinus venosus defects
      • Coronary sinus defects
      • Primum ASDs
      • Large ASDs with heart failure
    • Closed with pericardial or Dacron patch

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Atrioventricular Septal Defect

Epidemiology

• 4-5% of CHD
• 0.3-0.4 per 1000 live births
• Up to a 50% risk of trisomy 21

Normal Development

• Primitive AV canal connects the atria with the ventricles
• At 4-5 weeks gestation, the superior and inferior endocardial cushions fuse and form the AV canal
  • This contributes to the AV valves and septum

Types and Classifications

• Classified based on the degree of the defect
  • Complete
    • Complete failure of fusion between the superior and inferior endocardial cushions
      • Combined primum ASD and posterior VSD with a single, common AV valve
    • Can be balanced (both ventricles get same flow) or unbalanced (one gets more than the other)
      • Unbalanced can lead to hypoplasia
  • Partial
    • Incomplete fusion of superior and inferior endocardial cushions
      • Primum ASD, single AV valve annulus with 2 valve orifices
  • Transitional
    • Large primum defect, cleft mitral valve, and inlet VSD

• Rastelli Classification
  • Type A
    • Most common form and most common ASVD with Down syndrome
  • Type B
    • Least common
  • Type C
    • Frequently found with other conditions
      • Tetralogy of Fallot, Transposition of Great Vessels

Pathophysiology

• Complete AV Canal Defect
  • Increased pulmonary blood flow due to left-to-right shunting
    • Leads to heart failure and pulmonary hypertension
• Partial AV Canal Defect
  • Volume overload of right atrium and right ventricle with pulmonary overcirculation due to left-to-right shunting
    • No pulmonary hypertension
  • Mitral regurgitation can be severe
• Transitional AV Canal Defect
  • Shunting often mild due to small VSD

Clinical Presentation

• In-Utero
  • Can be diagnosed early during pregnancy
  • Rarely cause any fetal distress or growth disturbances
• Complete
  • Heart failure develops early in infancy
    • Tachypnea, poor feeding, poor growth, sweating, and pallor by 2 month
    • Severity of symptoms depends on size and degree of AV valve regurgitation
  • Physical examination
    • Hyperactive precordium with inferior/laterally displaced PMI
    • Increased S2
    • Systolic ejection murmur heard best at left upper sternal border
• Partial and Transitional
  • Asymptomatic during childhood and only diagnosed on routine examination
  • Physical examination
    • Wide and fixed S2 during respiration
    • Systolic ejection murmur heard best at left upper sternal border
      • Diastolic rumble may be heard
      • Holosytolic murmur of MR

Diagnostic Studies

• Echocardiography
  • Transthoracic is adequate
  • Apical four chamber or subcostal view is best to see defect

Management

• In general, surgical correction is recommended because of significant morbidity and mortality of the pulmonary circulation effects
• Complete
  • Correction by 6 months of age to prevent permanent pulmonary hypertension
  • Close the ASD and VSD and create to separate, competent AV valves
    • Single-patch or double-patch

• Partial and Transitional
  • Primum ASD does not close spontaneously and leaves the patient at risk for atrial fibrillation and heart failure later in life
  • Surgical goal is to close intraatrial communication and restore/preserve AV valve competence
    • Patch closure of ostium primum defect and mitral valvuloplasty
  • Timing is usually between 18 months and 3 years

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Patent Ductus Arteriosus

Epidemiology

• 3-8 per 10,000 live births
• 2:1 female predominance

Normal Development

• Derived from the embryonic left sixth arch
• Actually has different tissue than the aorta or pulmonary artery
  • Intima is thicker
  • Media contains more smooth muscle
• In utero, allows from RV flow to placenta to get oxygenated
• Keep open by low arterial oxygen and prostaglandin E2 from placenta
• At birth, increased levels of arterial oxygen and the lack of prostaglandin E2 begins the process of spontaneous closure

Clinical Presentation

• Symptoms depend on the degree of left-to-right shunting
  • Dependent on size and length of PDA, as well as the difference between the pulmonary and systemic vascular resistances
• Classic murmur
  • Continuous, holosystolic murmur
    • Machinery murmur
  • Heard best over left upper sternal border

• Small (Qp:Qs < 1.5 to 1)
  • Asymptomatic and detected on routine physical examination
• Moderate (Qp:Qs 1.5-2.2 to 1)
  • May present with exercise intolerance and heart failure
    • Left-to-right shunt increasing left atrial and ventricular volume
      • Progress to left ventricular dilation and dysfunction
  • Displaced PMI
  • Widened pulse pressure
• Large (Qp:Qs > 2.2 to 1)
  • Due to increased left sided pressures, can lead to increased pulmonary pressures
    • May be irreversible if not corrected
    • Can lead to right-to-left shunt if pressure is high enough
      • Eisenmenger syndrome (cyanosis)
    • Split S2 with prominent pulmonary component
    • Murmur may disappear as pulmonary pressure increases
  • Heart failure, poor feeding, failure to thrive, respiratory distress
  • Dynamic PMI with a thrill
  • Wide pulse pressures and bounding pulses

Diagnostic Studies

• Transthoracic, doppler color flow echocardiography
  • The ductus is best viewed on the parasternal short-axis and suprasternal view

Management

• Decisions are made on whether to actively close the PDA or monitor cardiac status
  • Term vs pre-term
    • Pre-term respond well to prostaglandin inhibitors
  • Size of the PDA
    • Moderate to large warrant closure
    • Small, audible PDA also benefit from closure to lower long term complications
      • Especially bacterial endocarditis
  • Degree of left-to-right shunt
  • Degree of left sided volume overload
  • Evidence of pulmonary hypertension
    • Closure not recommended in severe PAH

• Closure Options
  • Medical/Pharmacologic Therapy
    • Prostaglandin inhibitors
      • Indomethacin, ibuprofen
        • Ibuprofen > indomethacin in term infants and older patients
  • Surgery
    • Posterolateral thoracotomy with direct PDA ligation
    • Video-Assisted Thoracoscopic Surgery (VATS) is less invasive option
      • Not indicated if PDA size > 9mm
    • Percutaneous closure using coils or commercial occlusion devices

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Coarctation of the Aorta

Definition

• Narrowing of the descending aorta at the insertion of the ductus arteriosus distal to the left subclavian artery

Epidemiology

• 4-6% of all CHD
• 4 cases per 10,000 live births
• More common in males

Pathogenesis

• Unknown, but two theories prevail:
  • Decreased intrauterine blood flow leading to under development of the fetal aortic arch
  • Migration/extension of ductal tissue into the wall of thoracic aorta
• Genetic associations and increased familial risk
• Usually accompanied with other CHD

Pathophysiology

• As PDA and FO begin to close after birth, increased pressure over the narrowed aorta
  • Leads to left ventricular outflow tract obstruction
  • Increased collateral blood flow across the intercostals, internal mammary, and scapular vessels

Clinical Manifestations

• Classic findings
  • Absent/delayed femoral pulses
  • Difference in upper extremity and lower extremity blood pressures
• Neonates
  • Asymptomatic as long as there is a patent ductus
  • Murmurs of other CHD
• Infants and Older Children
  • Complain of lower extremity claudication symptoms with exertion
  • Hypertension may be prominent
• Adults
  • Hypertension is may sign
    • If severe, may lead to heart failure, aortic pathologies
  • Claudication can also be present

Diagnostic Studies

• Chest radiography
  • Infants
    • Cardiomegaly with increased pulmonary vascular markings
  • Older children and adults
    • Rib notching from large collateral development
    • “3” sign from indentation of aortic wall at coarctation site

• Echocardiography
  • Transthoracic, doppler flow can visualize coarctation and evaluate for other defects
  • Ideal view is high parasternal long axis or suprasternal view

• Cardiovascular MRI/CT
  • Recommended for adolescent and adult patients

• Cardiac catheterization
  • Generally performed in conjunction with therapeutic interventions, or in adults with associated coronary disease

Management

• Indications for inventions
  • Neonates with critical coarctation
    • Emergent medical therapy
      • Continuous infusion of prostaglandin E1
      • Inotropic support
      • Support care to correct metabolic derangements
  • Gradient > 20 mmHg
  • Radiologic evidence of clinically significant collateral flow
  • Hypertension or heart failure attributed to the defect

• Types of Interventions
  • Balloon angioplasty (only)
    • Infants > 4 months and young children < 25kg
    • Preferred therapy for isolated coarctation
  • Stent Placement (after angioplasty)
    • Children > 25kg and adults
  • Surgical repair
    • Falling out of favor with increasing advancement and safety of transcatheter techniques

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