Cardiomyopathies in children — formative SAQs

SAQ 1 — The adolescent with exertional syncope and a family history of sudden death (20 marks, ~15 minutes)

A 14-year-old competitive runner collapses briefly during a 1500-metre race, recovering fully within seconds. His father died suddenly at age 38 of an unspecified "heart attack". On examination he is well, with a soft ejection systolic murmur at the left sternal border that grows louder on standing. [4]

Questions

1. Give the most likely diagnosis and the bedside sign that supports it, and explain why the family history is central. (4 marks) [4] [6]
2. Outline the investigations you would order and what each contributes to diagnosis and risk stratification. (5 marks) [5] [9]
3. Describe the sudden-death risk stratification and the intervention proven to reduce sudden death in this condition, citing the key trial. (6 marks) [5]
4. Explain the family-screening strategy and what is done for a first-degree relative who is genotype-positive but phenotype-negative. (3 marks) [4]
5. State your advice on competitive sport. (2 marks) [4] [9]

Model answer (must-hit)

1. The most likely diagnosis is hypertrophic cardiomyopathy (HCM) presenting with exertional syncope; the murmur that grows louder on standing is dynamic left ventricular outflow tract obstruction that worsens as preload falls. The family history of a father's sudden death at 38 is central because childhood HCM is usually autosomal dominant (sarcomeric, classically MYH7 or MYBPC3), and a first-degree family history of cardiomyopathy or premature sudden death is the single highest-yield risk factor. The combination of exertional syncope plus this family history marks him as a presumed sudden-cardiac-death risk until stratified. [4] [6]
2. Investigations are a 12-lead ECG (almost always abnormal in HCM with voltage for LV hypertrophy, repolarisation changes, deep T inversions, pathological Q waves), echocardiography (the cornerstone: wall thickness, pattern of hypertrophy, LVOT gradient, systolic and diastolic function), ambulatory Holter monitoring (ventricular ectopy and non-sustained VT), exercise testing (functional capacity and the blood-pressure response, a blunted or falling BP being adverse), cardiac MRI (late gadolinium enhancement mapping fibrosis and arrhythmic risk), and a targeted cardiomyopathy gene panel. [5] [9]
3. Risk stratification integrates the personal history (syncope), family history (premature sudden death), echocardiographic findings (massive hypertrophy, apical aneurysm), Holter findings (non-sustained VT), exercise test (abnormal BP response), and MRI (extensive late enhancement) into a risk estimate. Children meeting a high-risk threshold are offered an implantable cardioverter-defibrillator, the one intervention proven to reduce sudden death in HCM, on the strength of Maron and colleagues' landmark study. The decision weighs the absolute risk against the real burden of inappropriate shocks and lead complications in a young, active patient. [5]
4. Family screening is cascade: clinical and genetic evaluation of every first-degree relative once the proband's pathogenic variant is identified. A genotype-positive phenotype-negative relative is not discharged but placed on structured lifelong surveillance, because the phenotype can emerge at any age; a genotype-negative relative of a genotype-positive proband can usually be released from surveillance. [4]
5. The advice is restriction from competitive sport pending specialist assessment in an inherited cardiac conditions service, because competitive sport accelerates HCM and raises the sudden-death risk. [4] [9]

SAQ 2 — The infant in heart failure with a fast heart rate (20 marks, ~15 minutes)

A three-month-old infant presents with a two-week history of poor feeding, tachypnoea, sweating with feeds, and crossing two weight centiles downward. The heart rate is sustained at 230 per minute. Echocardiography shows a dilated left ventricle with an ejection fraction of 28 percent. [7]

Questions

1. Give the morphological diagnosis and the single most important reversible cause that must be actively excluded before labelling this as primary disease. (4 marks) [8]
2. Outline your immediate medical management with the specific drug classes and doses you would use as a bridge. (5 marks) [7]
3. Summarise what the Shaddy carvedilol trial established in children with heart failure and its implication for your pharmacotherapy. (4 marks) [7]
4. State the endpoint of definitive therapy and the bridge technology that may be needed in the decompensating child. (4 marks) [7]
5. Outline the prognosis and what predicts a good versus a poor outcome. (3 marks) [8]

Model answer (must-hit)

1. The morphological diagnosis is dilated cardiomyopathy with systolic heart failure. The single most important reversible cause to exclude is tachycardiomyopathy from an incessant supraventricular tachycardia, suggested by the sustained heart rate of 230. A careful rhythm strip and a 12-lead ECG are mandatory, because tachycardiomyopathy can recover completely once the rhythm is controlled, whereas mislabelling it as primary DCM commits the child to an unnecessary transplant pathway. [8]
2. Immediate management is a bridge with a loop diuretic (furosemide 1 to 2 mg/kg/day) to relieve congestion, an ACE inhibitor to reduce afterload, and once the child is euvolaemic and stable a carefully titrated beta-blocker and a mineralocorticoid antagonist, with increased caloric density of feeds and nasogastric supplementation for failure to thrive; mimics such as viral myocarditis, thyroid disease, and anaemia are excluded. [7]
3. The Shaddy randomised controlled trial of carvedilol in children and adolescents with chronic heart failure (most with DCM) found no significant benefit of carvedilol over placebo, in contrast to the adult trials. It does not prove carvedilol is useless in children, but it removed the confident claim of benefit. The implication is that background therapy is continued but the child is watched closely for non-response, because non-response in DCM is the signal to move toward transplant assessment. [7]
4. The endpoint of definitive therapy for end-stage DCM is cardiac transplantation, and DCM is the single largest indication for paediatric heart transplant. A ventricular assist device may be needed as a bridge to transplant in the decompensating child who fails medical therapy. [7]
5. The prognosis is response-driven: children who recover left ventricular function do well, while non-responders progress to transplant. A reversible cause (tachyarrhythmia, myocarditis), a higher ejection fraction at baseline, and younger age favour recovery; a family history of DCM, persistent severe dysfunction, and non-response to therapy favour progression to transplant. [8]