A 4-year-old child is referred for cardiac evaluation after a systolic ejection murmur is detected at the left upper sternal border during a school health checkup. The murmur increases with Valsalva maneuver. Chest X-ray is normal, and ECG shows left ventricular hypertrophy. Which investigation is most appropriate to assess the severity of the lesion and guide management?

Explanation

## Diagnosis: Aortic Stenosis (AS) ### Clinical Presentation The systolic ejection murmur at the left upper sternal border, accentuation with Valsalva (decreased preload increases murmur intensity), and LVH on ECG are classic for aortic stenosis. ### Investigation of Choice: Transthoracic Echocardiography with Continuous-Wave Doppler **Key Point:** Echocardiography with continuous-wave Doppler is the gold standard, non-invasive investigation for diagnosis and severity assessment of aortic stenosis. **High-Yield:** Continuous-wave Doppler allows: - Measurement of peak systolic pressure gradient across the aortic valve - Calculation of aortic valve area (AVA) using the continuity equation - Grading of stenosis severity (mild, moderate, severe) - Assessment of left ventricular function and wall thickness - Detection of associated lesions (aortic regurgitation, mitral valve disease) ### Severity Grading of Aortic Stenosis | Severity | Peak Gradient | AVA | Clinical Significance | |----------|---------------|-----|----------------------| | Mild | <20 mmHg | >1.5 cm² | Usually asymptomatic; serial follow-up | | Moderate | 20–50 mmHg | 1.0–1.5 cm² | Risk of progression; activity restriction | | Severe | >50 mmHg | <1.0 cm² | High risk; intervention indicated | **Clinical Pearl:** In children, the presence of LVH on ECG with a significant pressure gradient (>30 mmHg) warrants activity restriction and consideration for intervention to prevent sudden cardiac death. **Mnemonic — AS Severity:** **CAVE** = Continuous-wave Doppler Assesses Valve gradients and Evaluates severity ### Why Echocardiography? ```mermaid flowchart TD A[Systolic murmur at LUSB]:::outcome --> B[Echocardiography with CW Doppler]:::action B --> C[Measure peak gradient]:::action C --> D{Gradient severity?}:::decision D -->|<20 mmHg| E[Mild AS - Observe]:::outcome D -->|20-50 mmHg| F[Moderate AS - Restrict activity]:::outcome D -->|>50 mmHg| G[Severe AS - Consider intervention]:::urgent B --> H[Calculate AVA]:::action B --> I[Assess LV function]:::action ``` **Advantages of Echocardiography:** - Non-invasive, no radiation - Real-time valve morphology and function - Quantitative pressure gradients and valve area - Guides medical vs. interventional decisions - Allows serial follow-up without risk ### Role of Other Investigations - **Cardiac MRI:** Excellent for anatomical detail and myocardial fibrosis assessment but is not first-line for hemodynamic assessment; reserved for complex cases or when echocardiography is inconclusive - **Cardiac catheterization:** Invasive; reserved for therapeutic intervention (balloon valvuloplasty) or when echocardiography findings are discordant with clinical presentation - **Stress ECG:** May provoke symptoms but does not quantify stenosis severity; not indicated for initial assessment [cite:Park 26e Ch 11]