Updated: 3/7/2018

Tetralogy of Fallot

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Snapshot
  • A 7-month infant presents with his mother for episodes of turning blue. The mother reports that his lips turn blue when he is crying or when he has fevers. The baby was born via a spontaneous vaginal delivery without any complications. His mother did not undergo routine prenatal care while pregnant with him. On physical exam, the infant is underweight. Cardiac exam reveals a harsh systolic ejection murmur. He starts crying in the middle of the exam and becomes cyanotic. The physician puts him in a knee-chest position, and the cyanosis resolves.
Introduction
  • Clinical definition
    • a congenital cardiac defect caused by anterosuperior displacement of the infundibular septum, characterized by PROV
      • Pulmonary infundibular stenosis
        • important prognostic factor
      • Right ventricular hypertrophy (RVH)
      • Overriding aorta
      • Ventricular septal defect (VSD)
  • Epidemiology
    • demographics
      • neonates are affected
      • the most common cyanotic cardiac lesion
    • risk factors
      • family history
      • maternal exposure to retinoic acid
  • Etiology
    • conotruncal abnormality from failure of neural crest cells to migrate
  • Pathogenesis
    • pulmonary stenosis causes right ventricular outflow obstruction and right-to-left shunting
      • in cases of severe lesions, neonates rely on a patent ductus arteriosus for survival
    • the right-to-left shunt across the VSD causes cyanosis
      • cyanosis causes marked clubbing and dyspnea on exertion if uncorrected
    • squatting or knee-chest position can increase systemic vascular resistance, alleviating the right-to-left shunting caused by right ventricular outflow obstruction, and thus relieves the cyanosis
  • Associated conditions
    • thymic aplasia (DiGeorge syndrome)
    • Down syndrome
  • Prognosis
    • severity of symptoms depends on the severity of right ventricular outflow obstruction
    • long-term survival is good with surgical repair
Presentation
  • Symptoms
    • tet spells (hypercyanotic episodes)
      • patients often present with tet spells caused by crying, fever, or any physical exertion
      • acute onset of restlessness causes increased cyanosis, dyspnea, and occasionally syncope
      • tet spells often resolve with knee-chest position, oxygen, or morphine
      • usual onset is around 2-6 months of age
  • Physical exam
    • systolic thrill along the left sternal border
    • loud and harsh systolic ejection murmur on the upper sternal border
      • may or may not have a preceding click
    • single S2
    • clubbing (in older children with uncorrected defect)
Imaging
  • Radiography
    • indication
      • for all patients
    • views
      • chest
    • findings
      • boot-shaped heart
      • dark lung fields
  • Echocardiogram
    • indication
      • performed as the gold standard diagnostic test
      • most sensitive test
    • findings
      • features of tetralogy of Fallot
        • VSD
        • overriding aorta
Studies
  • Electrocardiogram 
    • findings
      • right axis deviation
      • RVH
  • Making the diagnosis
    • based on clinical presentation and echocardiogram
    • in some cases, tetralogy of Fallot may be diagnosed prenatally with fetal echocardiogram
Differential
  • Transposition of the great vessels
    • distinguishing factors
      • early cyanosis that does not correct with squatting or knee-chest position
      • egg-on-a-string appearance on chest radiography
  • Truncus arteriosus 
    • distinguishing factors
      • electrocardiogram with left axis deviation and left ventricular hypertrophy
      • requires both atrial septal defect and ventricular septal defect
Treatment
  • Medical
    • prostaglandin E1
      • indication
        • for all patients who are cyanotic at birth
      • mechanism of action
        • maintains a patent ductus arteriosus for adequate lower extremity perfusion
    • β-blockers    
      • indications
        • for patients prior to surgical repair
        • to decrease the risk of tet spells
  • Operative
    • surgical repair
      • indication
        • definitive treatment
      • surgeries
        • closure of VSD
        • removal of pulmonary outflow obstruction
Complications
  • Thrombosis
  • Infective endocarditis
  • Heart failure
 

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Questions (4)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.CV.120) A 7-year-old boy is being evaluated in pediatric cardiology clinic. He appears grossly normal, but suddenly becomes tachypneic and cyanotic when his mom takes a toy away from him. These symptoms resolve somewhat when he drops into a squatting position. Transthoracic echocardiography reveals pulmonic stenosis, a ventricular septal defect, right ventricular hypertrophy, and an overriding aorta. Which of the following best predicts the degree of cyanosis and other hypoxemic symptoms in this patient? Review Topic

QID: 100636
1

Degree of pulmonic stenosis

36%

(5/14)

2

Size of ventricular septal defect (VSD)

36%

(5/14)

3

Degree of right ventricular hypertrophy (RVH)

14%

(2/14)

4

Degree to which aorta overrides right ventricle

14%

(2/14)

5

Presence of S3

0%

(0/14)

M1

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PREFERRED RESPONSE 1

(M1.CV.36) A 4-year-old Caucasian male suffers from cyanosis and dyspnea relieved by squatting. Which of the following abnormalities is most likely present? Review Topic

QID: 100552
1

Left ventricular hypertrophy

9%

(1/11)

2

Atrial septal defect

18%

(2/11)

3

Ventricular septal defect

55%

(6/11)

4

Coarctation of the aorta

0%

(0/11)

5

Patent ductus arteriosus

18%

(2/11)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(M1.CV.1) A 4-month-old is noted to have a grade 3/6, harsh, systolic ejection murmur heard at the left upper sternal border. The mother reports that the child's lips occasionally turn blue during feeding. A cardiologist recommends surgery. Later, the physician remarks that the infant's congenital abnormality was related to a failure of neural crest cell migration. Prior to surgery, which of the following was a likely finding? Review Topic

QID: 101895
1

Atrial septal defect

8%

(1/13)

2

Pulmonic stenosis

54%

(7/13)

3

Triscuspid atresia

0%

(0/13)

4

Coarctation of the aorta

0%

(0/13)

5

Transposition of the great vessels

38%

(5/13)

M1

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PREFERRED RESPONSE 2
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