Congenital Heart Defects: Cyanotic vs. Acyanotic (Pediatrics)

Prepared for Pass the Shift (owner: Kristina, RN). Always follow your facility’s protocols, provider orders, and current references.

1. Overview and Pathophysiology

Congenital heart defects (CHDs) are the most common birth defect (nearly 1% of births in the U.S., per CDC). About 1 in 4 is critical — needing surgery or a procedure in the first year.

Fetal circulation shortcuts (bypass the lungs before birth): foramen ovale (right atrium → left atrium), ductus arteriosus (pulmonary artery → aorta), ductus venosus (bypasses the liver). After birth, lung resistance drops and left-sided pressures rise; these shortcuts close over hours to days.

The key concept is pressure: blood flows from high pressure (left side) to low pressure (right side).

Left-to-right shunt (e.g., VSD, ASD, PDA): oxygenated blood recirculates to the lungs → increased pulmonary blood flow → acyanotic, but risk of heart failure and pulmonary hypertension
Right-to-left shunt or mixing (e.g., tetralogy of Fallot, transposition): deoxygenated blood enters the systemic circulation →

Hemodynamic classification

Group	Examples	Cyanosis?
Increased pulmonary blood flow	VSD, ASD, PDA, AV canal defect	Acyanotic
Obstruction to ventricular outflow	Coarctation of the aorta, aortic stenosis, pulmonary stenosis	Acyanotic (usually)
Decreased pulmonary blood flow	Tetralogy of Fallot, tricuspid atresia	Cyanotic
Mixed blood flow	Transposition of the great arteries, truncus arteriosus, hypoplastic left heart syndrome, TAPVR	Cyanotic

2. Acyanotic Defects

Defect	What it is	Key signs	Treatment
(most common CHD)	Hole between ventricles	Loud holosystolic murmur at lower left sternal border; HF signs if large	Many small ones close on their own; surgical/catheter closure if large
ASD	Hole between atria	Often asymptomatic; systolic murmur, fixed split S2	Spontaneous closure or catheter/surgical closure
	Ductus stays open (common in preterm infants)	Continuous “machinery” murmur, bounding pulses, wide pulse pressure	Indomethacin, ibuprofen, or acetaminophen to close (preterm); catheter/surgical closure
	Narrowing of the aorta	High BP and bounding pulses in the arms; weak/absent femoral pulses, cool legs, low leg BP	Balloon angioplasty/stent or surgical repair; may need prostaglandin as a newborn
Aortic stenosis	Narrow aortic valve	Exercise intolerance, chest pain, dizziness, murmur	Balloon valvuloplasty, surgery
Pulmonary stenosis	Narrow pulmonary valve	Murmur; severe → cyanosis	Balloon valvuloplasty

3. Cyanotic Defects

Defect	What it is	Key signs	Treatment
	4 defects: Pulmonary stenosis, Overriding aorta, VSD, Right ventricular hypertrophy (“PROVe”)	Cyanosis (may worsen over months), murmur, “tet spells”, boot-shaped heart on X-ray, older children squat	Surgical repair (often in the first year)
Transposition of the great arteries (TGA)	Aorta comes off the right ventricle, pulmonary artery off the left → two separate circuits	Severe cyanosis soon after birth; survival depends on mixing (PDA, ASD)	Prostaglandin E1 to keep the ductus open; balloon atrial septostomy; arterial switch surgery
Hypoplastic left heart syndrome	Underdeveloped left heart	Gray/cyanotic, shock when ductus closes	Prostaglandin E1; staged surgeries (Norwood, Glenn, Fontan) or transplant
Tricuspid atresia, truncus arteriosus, TAPVR	Various	Cyanosis, HF	Surgery

Newborn screening: CCHD pulse oximetry at ≥ 24 h (right hand and a foot). Low readings or a big hand-foot difference → further evaluation (echocardiogram). Follow your screening algorithm.

4. Tet Spell (Hypercyanotic Spell) — Emergency

Triggered by crying, feeding, or stool; often in the morning. Pulmonary outflow tightens → more right-to-left shunting → severe cyanosis, rapid deep breathing, irritability, possible loss of consciousness.

Calm the child; have the parent hold
Knee-chest position (hold infant with knees to chest; older children squat) — increases systemic resistance so more blood goes to the lungs
Oxygen (blow-by)
Morphine (reduces hyperpnea and spasm), IV fluids, propranolol or phenylephrine per order
Notify the provider; prepare for urgent surgery if spells recur

5. Heart Failure in Infants

Common with large left-to-right shunts. Signs: tachypnea, tachycardia, sweating with feeds, poor feeding / tires while eating, poor weight gain (failure to thrive), hepatomegaly, periorbital edema (rather than ankle edema), crackles, irritability.

Nursing:

Feeding: small, frequent feeds; limit feeding time (~20–30 min); soft nipple with larger hole; higher-calorie formula/fortified breast milk (e.g., 24–30 kcal/oz as ordered); NG feeds if needed
Rest: cluster care, semi-upright (infant seat)
Daily weight, strict I&O (weigh diapers)
Oxygen as ordered; prevent infection (hand hygiene, RSV prevention per eligibility)
Monitor polycythemia, clotting risk, and hydration in cyanotic children (dehydration raises clot/stroke risk)

6. Medications

Drug	Use	Nursing points
Digoxin	Improves contractility, slows HR	Apical pulse for a full minute. Typical hold thresholds: infant < 90–110, child < 70, adolescent < 60 (follow the order). Small doses in mcg — double-check with another nurse. Give at regular times; if a dose is missed, don’t double; if vomiting, don’t repeat. Toxicity: vomiting, poor feeding, bradycardia, dysrhythmias. Low K⁺ ↑ toxicity
Furosemide	Diuresis	Hypokalemia, dehydration, weights
Spironolactone	K⁺-sparing diuretic	Hyperkalemia
ACE inhibitors (captopril, enalapril)	Afterload reduction	Hypotension, cough, hyperkalemia, renal function
Prostaglandin E1 (alprostadil)	Keeps ductus open in ductal-dependent lesions	Apnea (most serious — have airway support ready), fever, flushing, hypotension
Indomethacin / ibuprofen	Closes PDA in preterm infants	Watch urine output, bleeding, GI (NEC)
Propranolol	Prevent tet spells	Bradycardia, hypoglycemia masking

Prostaglandins open, indomethacin/ibuprofen close the ductus.

7. Cardiac Catheterization Care (Pediatric)

Before: baseline VS, pedal pulses marked, weight/height, allergies (iodine/contrast), NPO
After: keep the affected leg straight for the ordered time (often 4–6 h); check site for bleeding, distal pulses, color, temperature of the extremity frequently (pulse may be weaker initially; absent = report); VS and SpO₂; hydration (contrast); watch for dysrhythmias; glucose in infants (NPO). If bleeding: direct continuous pressure 1 inch above the site

8. Education

How to give digoxin (oral syringe, take pulse if taught, don’t mix in food/bottle), recognize toxicity
Feeding and weight gain plans; signs of HF worsening (fast breathing, sweating with feeds, fewer wet diapers, puffy eyes)
Tet spell first aid (knee-chest, call for help)
Endocarditis prevention: good dental care; antibiotic prophylaxis before certain dental procedures only for specific high-risk conditions per AHA (e.g., unrepaired cyanotic CHD, prosthetic material in the first 6 months after repair)
Immunizations on schedule (plus RSV protection per eligibility); lifelong cardiology follow-up

9. Memory Aids

“Pink (acyanotic) = left-to-right; Blue (cyanotic) = right-to-left”
Cyanotic “T” defects: Tetralogy, Transposition, Tricuspid atresia, Truncus, TAPVR (and hypoplastic left heart)
Tetralogy = “PROVe”: Pulmonary stenosis, RV hypertrophy, Overriding aorta, VSD
Coarctation = “Strong arms, weak legs”
PDA = “Machinery murmur”
Prostaglandin keeps the duct Patent; Indomethacin Inhibits (closes)
Digoxin hold: “Infant < 90, child < 70, teen < 60” (verify the order)

10. NCLEX-Style Practice Questions

1. An infant with tetralogy of Fallot becomes deeply cyanotic and breathes rapidly after crying. What should the nurse do first?

A. Lay the infant flat and start chest compressions
B. Place the infant in a knee-chest position
C. Give digoxin
D. Encourage feeding to calm the infant

Answer: B. This is a tet spell. Knee-chest positioning increases systemic vascular resistance, pushing more blood through the pulmonary circulation. Then give oxygen and medications as ordered.

2. Which assessment finding is most consistent with coarctation of the aorta?

A. Continuous machinery murmur
B. Bounding arm pulses with weak femoral pulses
C. Squatting after play
D. Boot-shaped heart on X-ray

Answer: B. The aortic narrowing causes high pressure in the upper body and low pressure in the lower body. A is PDA; C and D are tetralogy of Fallot.

3. The apical pulse of a 6-month-old prescribed digoxin is 84/min. What should the nurse do?

A. Give the dose and recheck in an hour
B. Hold the dose and notify the provider
C. Give half the dose
D. Give the dose with formula

Answer: B. An infant HR below ~90–110 (or the ordered parameter) is a common reason to hold digoxin and report. Never adjust the dose yourself.

4. A newborn with transposition of the great arteries is started on prostaglandin E1. Which adverse effect is the priority to monitor?

A. Hyperglycemia
B. Apnea
C. Constipation
D. Hypertension

Answer: B. Apnea is the most serious side effect of prostaglandin E1; keep airway and ventilation equipment ready. Fever, flushing, and hypotension also occur.

5. Which signs suggest heart failure in a 3-month-old with a large VSD? Select all that apply.

A. Sweating during feedings
B. Tachypnea at rest
C. Poor weight gain
D. Ankle edema as the first sign
E. Hepatomegaly

Answer: A, B, C, E. Infants with HF show feeding fatigue with sweating, fast breathing, failure to thrive, and an enlarged liver. Edema in infants appears around the eyes, not usually in the ankles first.

References

Centers for Disease Control and Prevention. (2026). About congenital heart defects. https://www.cdc.gov/heart-defects/about/index.html

Horenstein, M. S., Diaz-Frias, J., & Guillaume, M. (2024). Tetralogy of Fallot. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK513288/

National Council of State Boards of Nursing. (2026). 2026 NCLEX-RN test plan. https://www.nclex.com/test-plans.page

Wilson, W. R., Gewitz, M., Lockhart, P. B., Bolger, A. F., DeSimone, D. C., Kazi, D. S., Couper, D. J., Beaton, A., Kilmartin, C., Miro, J. M., Sable, C., Jackson, M. A., & Baddour, L. M. (2021). Prevention of viridans group streptococcal infective endocarditis: A scientific statement from the American Heart Association. Circulation, 143(20), e963–e978. https://doi.org/10.1161/CIR.0000000000000969