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]

SAQ 2 — The adolescent with acute myocarditis (20 marks, ~15 minutes)

A previously well 14-year-old boy presents with a one-week history of a flu-like illness followed by three days of increasing breathlessness, fatigue on walking across the room, and abdominal discomfort. On examination he is tachypnoeic, has a gallop rhythm, a displaced apex beat and a palpable liver 4 cm below the costal margin, and oxygen saturations of 92 percent in air. A chest radiograph shows cardiomegaly and pulmonary venous congestion. [4]

Questions

1. Give the most likely diagnosis and the mechanism of heart failure it produces. (4 marks) [4]
2. State the investigations that confirm the diagnosis and assess severity, and what each shows in this scenario. (5 marks) [4]
3. Outline your management, including the escalation pathway if he deteriorates. (7 marks) [6]
4. Discuss the role of beta-blocker therapy, citing the paediatric evidence. (2 marks) [7]
5. State the prognosis and the two outcome trajectories. (2 marks) [4]

Model answer (must-hit)

1. The most likely diagnosis is acute myocarditis presenting as pump-failure heart failure, following a viral prodrome. The mechanism is direct injury to the myocardium producing loss of contractility: the ventricle dilates, the ejection fraction falls, and the syndrome is one of low cardiac output (fatigue, poor perfusion) combined with backward failure (pulmonary congestion from the left side, hepatomegaly from the right side). The gallop rhythm and the displaced apex in the absence of a flow murmur are the bedside signature of a failing ventricle rather than an overcirculation lesion. [4]
2. Echocardiography is definitive: it shows a globally impaired, often dilated left ventricle with a low ejection fraction, and excludes a structural lesion or a pericardial effusion. The ECG may show non-specific ST and T changes, low voltages, or arrhythmia, and can be deceptively normal. Troponin is typically elevated and supports the diagnosis; NT-proBNP is markedly raised and grades severity. A chest radiograph shows cardiomegaly and pulmonary venous congestion. Cardiac MRI adds tissue characterisation (late gadolinium enhancement, oedema) in selected cases, and viral PCR and an autoimmune screen address the aetiology. [4]
3. Management begins with admission and haemodynamic stabilisation: ABC, titrated oxygen for the hypoxia, a loop diuretic (furosemide) for congestion, and an ACE inhibitor to reduce afterload. Avoid pure fluid loading. Treat any arrhythmia promptly. Escalation, which must be anticipated because myocarditis can deteriorate rapidly, is to intensive care with milrinone for low cardiac output, non-invasive or invasive ventilation, and — for refractory low output or shock — mechanical circulatory support such as VA-ECMO or a ventricular assist device (Berlin Heart EXCOR) as a bridge to recovery or transplantation. Intravenous immunoglobulin or steroids are used in selected centres. [6] [10]
4. Beta-blockers are used selectively in chronic stable heart failure on physiologic rationale and adult evidence, but the paediatric carvedilol randomised controlled trial (Shaddy 2007) found no overall benefit over placebo in children and adolescents with heart failure, so beta-blockade is not routine and is avoided in the acute decompensated phase. [7]
5. The prognosis is bimodal: a proportion of children recover ventricular function fully, while others progress to a dilated cardiomyopathy phenotype and require listing for heart transplantation. The fulminant presentation carries the highest early risk, and the first days to weeks are the most dangerous. [4]