Rapid Review·Cardiovascular
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Congenital Heart Disease
T2High yieldHypoplastic Left Heart Syndrome
Focus on
A left ventricle too small to pump, so the right ventricle supplies the body through the ductus. The newborn looks fine until the duct closes at day 3–7, then collapses in cardiogenic shock with weak pulses everywhere, a single S2 and no murmur. Prostaglandin E1 saves the child; the Norwood–Glenn–Fontan sequence or transplant follows.
Key takeaways
What it is
Hypoplastic left heart syndrome
hypoplasia of the left ventricle with abnormal mitral and aortic valves and a tiny ascending aorta.Who pumps what
pulmonary venous blood crosses an atrial defect to the right heart, and the right ventricle supplies both the lungs and, through the ductus, the whole body, as on the Hypoplastic left heart anatomy.Survival depends on a patent ductus (right-to-left) and an atrial septal defect.
Prenatal diagnosis
in 50 to 70 percent on the second-trimester scan.Clinical features
May be asymptomatic at birth
the presentation is delayed until the ductus closes a few days after birth, when systemic perfusion collapses into heart failure and cardiogenic shock.Shock
pallor or grey mottled skin, respiratory distress, hypotension, weak pulses in all four limbs (unlike coarctation, which spares the arms), cool extremities, acidosis.Cyanosis not corrected by oxygen
from mixing.Heart sounds
a loud single S2, typically without a murmur (the aortic component is absent).Diagnosis
Newborn pulse-oximetry screening
the right hand and a foot are checked in every newborn; a low reading, or a foot reading clearly lower than the hand, flags a critical lesion.Echocardiography is the confirmatory test after birth
the hypoplastic ventricle and aorta, the valves, the ductus, the atrial communication, and right-ventricular and tricuspid function.Chest film and electrocardiogram
cardiomegaly and pulmonary venous congestion; right ventricular hypertrophy with diminished left forces (Approach to Neonatal Cyanosis).| Hypoplastic left heart syndrome | Critical Coarctation of Aorta | Transposition of the Great Arteries | |
|---|---|---|---|
| Timing | Days 1 to 7 as the duct closes | Days 3 to 14 as the duct closes | First hours (cyanosis, not shock) |
| Pulses | Weak in all limbs | Normal arms, weak or absent femorals | Normal |
| Saturation | Mildly low, equal in all limbs | Preductal higher than postductal | Very low |
| S2 and murmur | Single S2, no murmur | Ejection murmur over the back | Single loud S2, no murmur |
| Prostaglandin E1 | Yes (systemic flow) | Yes (lower-body flow) | Yes (mixing) |
| Definitive | Staged palliation or transplant | Surgical repair | Arterial switch |
Management and prognosis
Alprostadil (prostaglandin E1) immediately
keeps the ductus open; with transcatheter septostomy for a restrictive atrial defect, both are life-saving.- Inotropes and correction of acidosis; avoid high oxygen and hyperventilation; never close the duct.
Three-stage single-ventricle surgery
so the right ventricle becomes the systemic pump.- Norwood: in the first week; the pulmonary artery is joined to a reconstructed aorta, plus a shunt for pulmonary flow.
- Bidirectional Glenn: at 4 to 6 months.
- Fontan: at 2 to 4 years.
Alternatives
heart transplantation; comfort care is an ethical option.Prognosis
fatal within weeks without intervention; even with surgery the 5-year survival is only about 65 percent.- Long-term: systemic right-ventricular failure, arrhythmias, neurodevelopmental delay and the Fontan complications (protein-losing enteropathy, liver disease, thromboembolism).
A 4-day-old who seemed well at birth is now grey, mottled and hypotensive, with weak pulses in all four limbs, a single S2 and no murmur. What is the likely lesion, why did it appear now, and what is the first drug?
Hypoplastic left heart syndrome: the body depended on the ductus, and it has just closed. Give alprostadil (prostaglandin E1) immediately (avoid high oxygen), septostomy if the atrial defect is restrictive, then staged surgery (Norwood, Glenn, Fontan).
How it's tested
A term newborn discharged well returns on day 5 grey, lethargic and mottled, with weak pulses in all four limbs, a single S2, no murmur, saturation 82%, and a lactate of 9: hypoplastic left heart syndrome with ductal closure — prostaglandin E1 now, intubate, inotropes, echo, then Norwood.
Why not give 100% oxygen to this infant: it drops pulmonary vascular resistance, diverting the single RV's output to the lungs and starving the body (and the coronaries) — keep saturations around 75–85%.
How is HLHS distinguished from critical coarctation at the bedside: in HLHS all four limb pulses are weak; in coarctation the arm pulses are preserved and the femorals are weak.
Which structure fills the coronary arteries in HLHS: retrograde flow up the hypoplastic ascending aorta from the ductus.
A 6-year-old with a Fontan for HLHS develops recurrent expectoration of rubbery casts: plastic bronchitis — a Fontan complication.
Go deeper
Guidelines: 2018 AHA/ACC Adult Congenital Heart Disease Guideline
Related Step 2 pages: Approach to Neonatal Cyanosis, Coarctation of Aorta, Tricuspid Atresia, Fetal Circulation & Transition at Birth, Approach to Congenital Heart Disease, Cardiogenic Shock
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