Medical Emergencies · patient case with 2 questions
Child with tetralogy of Fallot presenting for a dental examination
Patient: Male, 5 years old
Chief Complaint: Mother: “He needs a check-up and I was told two of his back teeth have cavities.”
Background: Tetralogy of Fallot diagnosed in infancy, NOT yet repaired. Mother reports the pregnancy was unplanned and she took no prenatal vitamins. Episodes of cyanosis on exertion. Followed by a paediatric cardiologist, last seen fourteen months ago.
Vital Signs: BP 92/58 mmHg · HR 108 bpm · SpO₂ 91% on room air · T 98.6°F
Findings: Mild central cyanosis and clubbing of the fingers. Occlusal caries in #B and #I. Generalized plaque. No acute infection.
Question 1
Which maternal factor is a recognised risk factor for tetralogy of Fallot?
Show answer and explanation
Correct answer: D. Inadequate folic acid supplementation during pregnancy
- A. Vitamin C deficiency in pregnancy is rare in developed settings and is associated with connective tissue and bleeding problems, not cardiac septation defects.
- B. Maternal iron deficiency causes anaemia, low birth weight and preterm delivery. It is not linked to conotruncal cardiac malformation.
- C. Excess calcium intake is not teratogenic and has no association with congenital heart disease.
- D. CORRECT. FOLIC ACID deficiency in early pregnancy is an established risk factor for congenital heart defects, tetralogy of Fallot among them, alongside neural tube defects and orofacial clefts. The defect arises from anterocephalad deviation of the outlet septum during the fourth to eighth week of gestation — before many women know they are pregnant, which is precisely why periconceptional supplementation is recommended. Other recognised risks are maternal diabetes, phenylketonuria, rubella, alcohol, retinoic acid, and the chromosomal associations with 22q11.2 deletion (DiGeorge) and trisomy 21.
Note: The four components of tetralogy of Fallot, from the single embryologic error: PULMONARY STENOSIS (right ventricular outflow obstruction), VENTRICULAR SEPTAL DEFECT, an OVERRIDING AORTA, and RIGHT VENTRICULAR HYPERTROPHY. Mnemonic: PROVe. Right-to-left shunting through the VSD is what produces the cyanosis.
Question 2
What is the most appropriate next step before restorative treatment is begun?
Show answer and explanation
Correct answer: A. Consult his paediatric cardiologist
- A. CORRECT. An UNREPAIRED cyanotic congenital heart defect places this child in the HIGHEST-RISK category for infective endocarditis under the AHA guidance, and it has been over a year since his last cardiology review with a resting SpO₂ of 91%. The cardiologist confirms his current status, the prophylaxis indication and the dosing, and advises on any limits to treatment. Medical consultation precedes the dental plan — it does not follow it.
- B. Taking the history afterwards inverts the entire process. In a cyanotic cardiac child, the history is what determines whether and how you treat.
- C. A paediatric dentistry referral may well be appropriate later, but the question is one of MEDICAL risk, not behaviour. Referring on without establishing cardiac status simply moves the unanswered question elsewhere.
- D. Prophylaxis is a SINGLE dose given 30 to 60 minutes BEFORE the procedure — amoxicillin 50 mg/kg in a child — not a week-long course. A week of antibiotic is both ineffective as prophylaxis and a driver of resistance.
Note: Prophylaxis is indicated for the highest-risk cardiac categories: prosthetic valves or prosthetic material used in valve repair; previous infective endocarditis; UNREPAIRED cyanotic congenital heart disease; a repair using prosthetic material within the first SIX MONTHS; a repair with a RESIDUAL defect at or adjacent to the prosthetic material; and cardiac transplant recipients with valvulopathy. A SUCCESSFULLY repaired tetralogy with no residual defect and more than six months elapsed needs NO prophylaxis — the contrast between that and this child is the examinable point.