2.1 Cardiac Malformations

2.1 Cardiac Malformations

Quick Answer: In the PICU, congenital heart disease is managed by physiology first—mixing lesions, obstructive (ductal-dependent) lesions, and shunt lesions—then by named anatomy. Cyanosis with pulmonary overcirculation suggests mixing or unrestricted pulmonary flow; gray shock with weak femoral pulses suggests left-sided obstruction and a closing duct. PGE1, atrial communication, and careful Qp:Qs balance are recurring themes across HLHS, critical coarctation, and d-TGA.

Structural lesions dominate pediatric cardiovascular CCRN content because they drive preoperative stabilization, postoperative ICU trajectories, and sudden decompensation when the ductus arteriosus closes. Acquired structural problems (myocarditis with dilated ventricle, Kawasaki coronary aneurysms, rheumatic valve disease) appear less often on the exam outline than congenital disease but share the same bedside logic: match oxygen delivery to demand, protect coronary and cerebral perfusion, and anticipate ductal or shunt physiology.

Physiology Before Names

Qp:Qs (pulmonary-to-systemic flow ratio) is the PICU mental model. Unrestricted pulmonary flow (low PVR, large VSD, or HLHS with large PDA) raises Qp:Qs, floods the lungs, and steals from systemic and coronary perfusion. High PVR or severe RVOTO lowers Qp:Qs and deepens cyanosis. Nursing interventions that change FiO₂, PaCO₂, pH, hematocrit, and afterload all move this balance.

Septal Defects: ASD and VSD

Atrial septal defect (ASD) allows left-to-right atrial shunting. Infants may be asymptomatic; older children develop right ventricular volume overload, fixed splitting of S2, and eventual pulmonary hypertension if unrepaired. PICU encounters are often post-device or surgical closure: watch for arrhythmia (especially atrial), residual shunt, and pericardial effusion after surgical ASD repair.

Ventricular septal defect (VSD) is the most common congenital heart defect. Large VSDs present with CHF signs once PVR falls in the first weeks of life—tachypnea, diaphoresis with feeds, hepatomegaly, and failure to thrive. Auscultation classically reveals a holosystolic murmur at the left lower sternal border. Preoperative nursing focuses on caloric density, diuretics, afterload reduction, and infection prevention. Postoperative VSD repair priorities include residual VSD assessment, AV block risk (especially with perimembranous defects near the conduction system), and pulmonary hypertension crises in infants with longstanding high Qp.

Tetralogy of Fallot (TOF)

TOF comprises four features: large VSD, overriding aorta, right ventricular outflow tract obstruction (RVOTO), and secondary RV hypertrophy. Degree of cyanosis tracks RVOTO severity. “Pink” TOF has mild obstruction and may behave like a large VSD with CHF; severe TOF is ductal-dependent for pulmonary flow.

Hypercyanotic (Tet) spells are acute increases in RVOTO and right-to-left shunting. Triggers include crying, pain, dehydration, and agitation. Presentation: deepening cyanosis, hyperpnea, irritability, and possible syncope.

Spell management sequence (know this cold):

1. Knee-chest or squatting position to raise SVR and reduce right-to-left shunt
2. Calm environment; morphine or other sedation to reduce catecholamine-driven infundibular spasm
3. Supplemental oxygen
4. Volume bolus if hypovolemic
5. Sodium bicarbonate if severe metabolic acidosis
6. Phenylephrine (or other pure vasoconstrictor) to raise SVR when positioning and sedation fail
7. Beta blockade (e.g., propranolol/esmolol) in selected protocols to reduce infundibular spasm

Never assume “more oxygen alone” will abort a spell driven by dynamic RVOTO and falling SVR. Document spell frequency, SpO₂ nadir, and response—these data guide timing of complete repair or palliative shunt.

d-Transposition of the Great Arteries (d-TGA)

In d-TGA, the aorta arises from the RV and the pulmonary artery from the LV, creating parallel circulations. Survival requires mixing at atrial, ductal, and/or ventricular levels. Profound cyanosis in a newborn with little respiratory distress is classic. Chest radiograph may show an “egg on a string” narrow mediastinum, though imaging is supportive, not diagnostic.

Nursing priorities before arterial switch:

• Start PGE1 to maintain ductal mixing and monitor for apnea (common PGE1 effect—prepare for airway support)
• Support balloon atrial septostomy (Rashkind) when atrial mixing is inadequate; expect transient arrhythmia and careful post-procedure SpO₂ trending
• Avoid extreme hyperoxia and hypocapnia that abruptly drop PVR and destabilize mixing
• Maintain adequate hematocrit for oxygen-carrying capacity in cyanotic neonates

Hypoplastic Left Heart Syndrome (HLHS)

HLHS includes underdevelopment of the left ventricle, mitral and/or aortic valves, and ascending aorta. Systemic cardiac output depends on the PDA (right-to-left) and a nonrestrictive atrial communication (left-to-right decompression of the left atrium). When the duct closes, cardiogenic shock, metabolic acidosis, and end-organ ischemia ensue—often misdiagnosed initially as sepsis.

Balanced circulation goals (pre-Norwood):

Restrictive atrial septum is a surgical emergency—profound pulmonary edema and cyanosis with left atrial hypertension require urgent relief.

Coarctation of the Aorta and Critical Left Obstruction

Coarctation is narrowing typically near the ductal insertion. Critical neonatal coarctation is ductal-dependent for lower-body perfusion. Classic findings: higher BP and bounding pulses in the right arm versus weak femoral pulses, metabolic acidosis, oliguria, and gut ischemia as the duct closes. Always compare right-arm and lower-extremity blood pressures and pulses; left-arm readings may be falsely low if the left subclavian is involved.

Other left-sided lesions (critical aortic stenosis, interrupted aortic arch) share the PGE1-and-shock pathway. Acquired aortic or mitral disease in older PICU patients (rheumatic, endocarditis, Kawasaki sequelae) presents with murmur change, pulmonary edema, or coronary ischemia rather than ductal physiology.

Nursing Priorities Across Lesions

• Know ductal dependence before any transport, extubation, or PGE1 wean discussion
• Trend lactate, urine output, near-infrared spectroscopy (NIRS), and distal pulses as early shock detectors
• Protect the airway with PGE1 (apnea risk) and have volume/vasoactive plans for cath lab septostomy
• Family teaching: cyanosis targets in balanced circulations are intentional, not “failure to oxygenate”
• Infection and feeding: necrotizing enterocolitis risk rises with diastolic runoff and low systemic perfusion—slow advancement of feeds in ductal-dependent infants

Exam questions rarely ask for embryology trivia. They ask whether you recognize parallel circulations, ductal-dependent shock, Tet-spell physiology, and which intervention raises SVR versus lowers PVR.