Heart failure in infants and children — formative SAQs

SAQ 1 — The six-week-old infant in overcirculation (20 marks, ~15 minutes)

A six-week-old term infant presents with a three-week history of worsening tachypnoea, taking 40 minutes to finish 60 mL of feeds while sweating, and crossing two weight centiles downward. On examination there is a pansystolic murmur at the lower left sternal border, an apical mid-diastolic murmur, a hyperactive precordium, and hepatomegaly. Oxygen saturations are 98 percent in air. ^[3]

Questions

1. Give the most likely diagnosis and the mechanism that explains why it has presented now, at six weeks, rather than at birth. (4 marks) ^[3]
2. Grade the severity using the modified Ross classification and explain why the apical mid-diastolic murmur is significant. (4 marks) ^[5]
3. Outline your immediate medical management with the specific drug doses you would use as a bridge. Explain your approach to oxygen. (6 marks) ^[6]
4. State the investigations that confirm the diagnosis and the definitive management. (3 marks) ^[4]
5. State the principle that guides the family counselling and the immediate outlook. (3 marks) ^[6]

Model answer (must-hit)

1. The most likely diagnosis is heart failure from pulmonary overcirculation caused by a moderate-to-large left-to-right shunt (a ventricular septal defect is most likely given the pansystolic murmur at the lower left sternal border). The mechanism is a volume load: as the pulmonary vascular resistance falls from its high neonatal level over the first six to eight weeks, the left-to-right shunt increases, the left atrium and left ventricle dilate from the increased pulmonary venous return, and the infant develops the overcirculation picture of tachypnoea, sweating with feeds and failure to thrive. This is why the presentation is at four to eight weeks and not in the delivery room. ^[3]
2. The severity is modified Ross class III: marked limitation, tachypnoea (likely at rest or with feeds), prolonged sweaty feeds, failure to thrive and marked hepatomegaly. The apical mid-diastolic murmur is the flow rumble of increased blood crossing a normal mitral valve, and it is the auscultatory sign of a large shunt that has dilated the left atrium; a small shunt never produces a flow rumble, so its presence signals significant overcirculation. ^[5]
3. Immediate management is a bridge to closure: a loop diuretic (furosemide 1 to 2 mg/kg/day) to relieve pulmonary congestion, an ACE inhibitor (enalapril or captopril) to reduce afterload and the shunt, and increased caloric density of feeds with nasogastric supplementation if needed. Oxygen is used cautiously and titrated to saturations, because oxygen is a pulmonary vasodilator that lowers pulmonary vascular resistance and can increase the left-to-right shunt and worsen the overcirculation; this infant, who is well saturated at 98 percent, does not need supplemental oxygen. Treat any intercurrent infection or anaemia promptly. ^[6]
4. Echocardiography is the definitive investigation: it confirms the lesion, sizes the shunt (Qp:Qs), estimates the pulmonary artery pressure, and assesses chamber size and function. The ECG and chest radiograph are supportive. The definitive management is closure of the shunt (surgical patch or transcatheter device) within the first year, once the infant is stabilised. ^[4]
5. The guiding principle is that most childhood heart failure is surgically curable because the cause is structural: with a medical bridge followed by closure in infancy, the immediate outlook is excellent, and the family can be counselled that the child should achieve normal growth, activity and quality of life. ^[6]