Ventricular septal defect — 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. [1]

Questions

1. Give the most likely diagnosis and the pathophysiology that explains why it has presented now, at six weeks, rather than at birth. (4 marks) [1]
2. Outline your immediate investigations and the definitive test that confirms and sizes the lesion. (3 marks) [1] [9]
3. Outline your immediate medical management, including the specific drug doses you would use as a bridge. (5 marks) [1]
4. State the indications for definitive closure and the usual timing, and outline the options (surgical versus device). (4 marks) [9]
5. State the one complication that the entire management strategy is designed to prevent, and why closure is harmful once it has occurred. (4 marks) [6] [9]

Model answer (must-hit)

1. The most likely diagnosis is a moderate-to-large ventricular septal defect with pulmonary overcirculation and left-heart failure. The pathophysiology is a left-to-right shunt whose volume depends on the defect size and the pulmonary vascular resistance. At birth the resistance is high and the shunt is small, so the infant looks well; as the resistance falls over the first six to eight weeks, the shunt grows, the left ventricle (which pumps to the body and across the defect to the lungs) dilates and fails, and the infant presents with tachypnoea, poor feeding, sweating and failure to thrive. The apical flow rumble signals a large shunt dilating the left atrium. [1]

2. The definitive test is echocardiography, which confirms and locates the defect, measures the shunt (Qp:Qs) and the gradient, estimates the pulmonary artery pressure from the tricuspid regurgitation jet, and assesses the aortic valve for cusp prolapse. A chest radiograph is expected to show cardiomegaly with pulmonary plethora, and an ECG left atrial and left ventricular overload. [1] [9]

3. Immediate medical management is a bridge to closure: a loop diuretic such as furosemide 1 to 2 mg/kg/day to relieve pulmonary congestion; an angiotensin-converting-enzyme inhibitor (captopril or enalapril) to reduce afterload and therefore the shunt; and increased caloric density of feeds (with nasogastric supplementation if needed) to overcome the metabolic cost of the extra cardiac work. Oxygen is used cautiously because it lowers pulmonary resistance and can increase the shunt; intercurrent infection and anaemia are treated promptly. [1]

4. The indications for closure are a symptomatic child with a significant shunt, a Qp:Qs above roughly 1.5 to 2 with left ventricular overload, recurrent infective endocarditis, or aortic regurgitation from cusp prolapse. The usual timing is within the first year. Surgical patch closure is the standard for most perimembranous, inlet and large muscular defects; transcatheter device closure is an alternative for selected muscular and perimembranous defects with favourable anatomy. [9]

5. The complication to be prevented is fixed pulmonary vascular disease progressing to Eisenmenger syndrome. Once the resistance is fixed, the right ventricle depends on the defect as a pressure pop-off, and closing the defect removes that pop-off and is harmful and potentially fatal. This is why the whole strategy of paediatric VSD care is to close the defect before the resistance becomes fixed. [6] [9]

SAQ 2 — The adolescent with Eisenmenger physiology (20 marks, ~15 minutes)

A 16-year-old girl who was lost to follow-up after a large unrepaired ventricular septal defect was diagnosed in infancy presents with exertional cyanosis, clubbing and a single-day episode of haemoptysis. Her saturations are 84 percent in air. The systolic murmur that was noted in childhood is now soft and almost absent. [6]

Questions

1. Give the most likely diagnosis and explain why the murmur has softened. (4 marks) [6]
2. Explain why surgical or device closure of the defect is now contraindicated, and what the right ventricle stands to lose. (4 marks) [6] [9]
3. Outline the medical management, naming the drug class with randomised-trial evidence and the key trial. (5 marks) [6] [7]
4. Outline the counselling regarding pregnancy and the procedural precautions relevant to her right-to-left shunt. (4 marks) [9]
5. State the infective endocarditis prophylaxis position for this patient and the source that governs it. (3 marks) [8]

Model answer (must-hit)

1. The most likely diagnosis is Eisenmenger syndrome from a long-standing large unrepaired ventricular septal defect: the pulmonary vascular resistance has risen above the systemic resistance and the shunt has reversed to right-to-left, producing cyanosis, clubbing and haemoptysis. The murmur has softened because the pressures on the two sides of the defect have equalised, so the turbulent high-velocity jet that produced the original loud murmur is gone. [6]

2. Closure is contraindicated because the pulmonary vascular disease is fixed. The right ventricle is now hypertrophied and pumping against a high resistance, and the VSD acts as a pressure pop-off that decompresses it into the systemic circuit. Closing the defect removes that pop-off and forces the right ventricle to pump against the fixed high pulmonary resistance, which can precipitate right-heart failure and death. [6] [9]

3. Management is as pulmonary arterial hypertension, not as a lesion to close. Targeted therapy with an endothelin-receptor antagonist is first-line: the BREATHE-5 randomised, double-blind, placebo-controlled trial of bosentan in Eisenmenger syndrome showed improved pulmonary vascular resistance and exercise capacity, and the open-label extension (Gatzoulis) confirmed sustained functional benefit. Additional pulmonary vasodilator therapy (phosphodiesterase-5 inhibitors) is added as needed, with lifelong adult congenital heart disease care. [6] [7]

4. Pregnancy carries a substantial maternal mortality in Eisenmenger syndrome, so reliable contraception and pre-conception counselling are central. She should avoid dehydration, high altitude, and isometric exertion. Because of the right-to-left shunt, any intravenous access must use air and particulate filters and rigorous air exclusion to avoid paradoxical emboli, and invasive procedures should occur in an adult congenital specialist setting. [9]

5. Routine antibiotic infective endocarditis prophylaxis is no longer indicated for most congenital defects, including a VSD, under the 2021 American Heart Association scientific statement, which restricts prophylaxis to prosthetic valves, prior endocarditis, and certain complex unrepaired or repaired lesions. The emphasis is on excellent oral hygiene and prompt evaluation of unexplained fever. [8]