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PE22.1-11 | Cardiovascular System — PBL Case
CLINICAL SETTING
The emergency department of a district general hospital in rural Tamil Nadu. A 4-year-old boy, Arjun, is brought in by his parents on a Monday morning. His mother, a schoolteacher, tells you: 'Doctor, he suddenly started crying and his lips turned blue on the autorickshaw to the health post. He crouched down on his own — we thought he was going to die.' Arjun is now sitting on the examination table, no longer blue, looking exhausted. He has not been formally diagnosed with any heart condition, but his parents report that he has always been 'slow to gain weight' and gets 'blue lips' when he runs or cries, since he was a few months old. He is the second child; his elder sister is healthy.
Trigger 1: First Encounter — History and Examination
Vitals: HR 128/min, RR 32/min, SpO₂ 78% on room air. Weight 12 kg (50th percentile for 3 years, not 4 years). BP 88/54 mmHg. Temperature 37.1°C. On examination: mildly tachycardic; no central cyanosis at rest now but peripheral cyanosis of lips and nail beds. No precordial bulge. Apex beat in 4th left intercostal space, midclavicular line. No palpable thrill. Auscultation: a harsh grade 3/6 ejection systolic murmur at the left upper sternal border radiating to the back; single second heart sound (S2). Chest X-ray: boot-shaped heart (coeur en sabot), oligaemic lung fields, right-sided aortic arch. ECG: right-axis deviation, tall R in V1, deep S in V5/V6 (right ventricular hypertrophy pattern).
DISCUSSION POINTS
- What is the most likely diagnosis based on the clinical, CXR, and ECG findings? Which four anatomical components characterise this condition?
- What haemodynamic event occurred on the autorickshaw? Explain the physiological mechanism of the cyanotic episode using your knowledge of right ventricular outflow tract obstruction.
- What is the significance of squatting in this child? Explain in terms of changes in systemic vascular resistance.
- Interpret the CXR findings: what does 'boot-shaped heart' indicate? Why are the lung fields oligaemic?
Click to reveal Trigger 2: Emergency Stabilisation (discuss previous trigger first!)
Trigger 2: Emergency Stabilisation
While awaiting paediatric cardiology, Arjun starts to cry and becomes deeply cyanosed again (SpO₂ drops to 55%). He spontaneously squats on the bed. The nurse asks you what to do.
DISCUSSION POINTS
- List the immediate stepwise management of this hypercyanotic (tet) spell. In what order would you give knee-chest positioning, oxygen, morphine, and propranolol?
- What is the dose of morphine and propranolol for Arjun (weight 12 kg)? Why should furosemide and digoxin be avoided in this situation?
- If the spell does not resolve with the above, what additional agents can be used (sodium bicarbonate for metabolic acidosis; phenylephrine to increase SVR)?
- How would you communicate the urgency of this situation to Arjun's parents while maintaining their trust and managing their distress? (PE22.11)
Click to reveal Trigger 3: Echocardiography and Surgical Planning (discuss previous trigger first!)
Trigger 3: Echocardiography and Surgical Planning
The echocardiogram confirms Tetralogy of Fallot: large subarterial VSD with overriding aorta (50%), severe infundibular pulmonary stenosis, RVH. PA pressure estimated at 22 mmHg (sub-systemic). No additional lesions. The paediatric cardiologist recommends definitive corrective surgery (total intracardiac repair) and asks you to put Arjun on oral propranolol while awaiting the surgical date.
DISCUSSION POINTS
- Explain why propranolol is used as a bridge to surgery in TOF. What is the weight-based dose (Arjun weighs 12 kg)?
- Compare the haemodynamic profile of TOF (decreased pulmonary blood flow, R-to-L shunt) with a large VSD (increased pulmonary blood flow, L-to-R shunt). How do CXR and clinical findings differ between the two conditions?
- What are the complications of untreated TOF (polycythaemia, paradoxical embolism, brain abscess, Eisenmenger — NOT applicable here since PA pressure is low)? Why is brain abscess a recognised complication?
- At what age is elective total correction ideally performed? What palliative shunt procedure (Blalock-Taussig shunt) might be used if surgery must be deferred?
Click to reveal Trigger 4: Discharge Planning and Follow-Up (discuss previous trigger first!)
Trigger 4: Discharge Planning and Follow-Up
Arjun is stabilised. Before discharge, the paediatric ward consultant asks you to counsel the parents on secondary prophylaxis because during further history-taking, the grandmother reveals that 18 months ago Arjun had a 3-week illness with joint pains and a 'heart murmur' detected at a local clinic that was attributed to fever. You also note that Arjun's BP today, taken on his right arm with an appropriately-sized cuff, is 104/62 mmHg. You calculate that for a 4-year-old male with a height at the 50th percentile, this is approximately at the 90th percentile — elevated but not hypertensive. You decide to monitor at the next visit.
DISCUSSION POINTS
- The grandmother's history raises suspicion of an undiagnosed first attack of acute rheumatic fever 18 months ago. Which clinical and laboratory workup would you do now to determine if Arjun has concomitant rheumatic heart disease (ASO titre, echocardiography for valve lesions)?
- If ARF is confirmed, what secondary prophylaxis would you prescribe for Arjun, and for how long? State the dose and formulation of benzathine penicillin G for his weight (12 kg — he is <27 kg, so use 600,000 units IM every 3–4 weeks).
- Arjun's BP is at the 90th percentile — he is not hypertensive. How will you monitor? What threshold (≥95th percentile for age/sex/height on ≥3 occasions) must be reached before diagnosing hypertension in a child?
- Construct a discharge counselling checklist for Arjun's parents: medications, activity restrictions, signs of a tet-spell and immediate actions, dental hygiene for IE prevention, surgery appointment, follow-up schedule, and contact-tracing for rheumatic fever in household contacts.
Group Task Assignments
Group 1: Collaborative Task
Group 2: Collaborative Task
Group 3: Collaborative Task
Learning Issues
Research these questions and bring your findings to the discussion.
- [PE22.1] What are the haemodynamic consequences, clinical signs, CXR, and ECG findings of the three commonest acyanotic CHDs (VSD, ASD, PDA), and when does each require surgical or catheter intervention?
- [PE22.2] What are the anatomical components, haemodynamics, clinical features, emergency management, and surgical options for the five cyanotic CHDs (5 Ts), with particular emphasis on TOF and TGA?
- [PE22.3] How do you diagnose and manage paediatric cardiac failure (causes, clinical signs, weight-based pharmacotherapy with digoxin, furosemide, captopril)?
- [PE22.4] How do you apply the 2015 Revised Jones Criteria (high-risk population) to diagnose ARF, and what is the evidence-based secondary prophylaxis regimen and duration?
- [PE22.5] How do the Modified Duke Criteria classify infective endocarditis in children, what organisms are involved, and what is the standard antibiotic treatment duration?
- [PE22.6] How is hypertension defined in children using age-sex-height normative tables, and what is the stepwise management approach from lifestyle to pharmacotherapy?
- [PE22.8] What is the systematic approach to cardiovascular examination in a child, including assessment of JVP, precordial pulsations, murmur characterisation, and S2 splitting?
- [PE22.9] How do you interpret a paediatric CXR for cardiomegaly (CTR), pulmonary vascular markings, and characteristic cardiac silhouette shapes (boot, egg-on-a-string, snowman)?
- [PE22.10] What are the age-specific normal ECG parameters in children, and how do you recognise RVH, LVH, axis deviation, and the transition from RV to LV dominance?
- [PE22.11] How do you communicate a serious cardiac diagnosis to the parents of an infant or young child, managing their distress while building therapeutic alliance for long-term follow-up?