What diagnosis is suggested by lower blood pressure and reduced oxygen saturation in the left upper limb compared to the lower limb in a 5‑year‑old boy?

Coarctation of the Aorta

The finding of lower blood pressure and reduced oxygen saturation in the left upper limb compared to the lower limb in a 5-year-old boy is highly suggestive of coarctation of the aorta located proximal to the left subclavian artery. 1

Diagnostic Reasoning

This presentation represents an atypical pattern that indicates the coarctation is positioned before (proximal to) the origin of the left subclavian artery, rather than the more common juxtaductal location just distal to it. 1

Classic vs. Atypical Presentation

• Classic coarctation (juxtaductal, distal to left subclavian): Upper extremity blood pressures are higher than lower extremity pressures, with weak or delayed femoral pulses compared to radial pulses. 1

• Proximal coarctation (as in this case): The left upper limb shows lower blood pressure and saturation than the lower limb because the left subclavian artery arises after the coarctation, receiving poorly perfused blood similar to the descending aorta. 1

Key Clinical Features to Confirm

Blood pressure assessment:

• Measure blood pressure in both arms and at least one leg simultaneously or sequentially. 1
• A gradient >20 mmHg between upper and lower extremities indicates hemodynamically significant coarctation. 1
• In proximal coarctation, the right arm pressure will be elevated while the left arm pressure will be similar to or lower than leg pressures. 1

Pulse examination:

• Check for radio-femoral pulse delay (radial pulse felt before femoral pulse). 1
• Assess for differential pulses between right and left arms. 1
• Palpate for collateral vessels over the back and chest wall. 1

Auscultation:

• Listen for a midsystolic murmur over the anterior chest and interscapular region. 1
• The murmur may become continuous over time due to collateral flow. 1

Associated Conditions to Evaluate

Cardiac anomalies:

• Bicuspid aortic valve is present in 30-40% of coarctation cases and requires echocardiographic assessment. 1
• Evaluate for ventricular septal defects or other structural abnormalities. 1

Extracardiac associations:

• Consider screening for Turner syndrome, particularly in females, as coarctation prevalence is increased. 1
• Intracranial berry aneurysms occur in 10% of coarctation patients, though routine screening in asymptomatic children remains controversial. 1

Diagnostic Confirmation

Transthoracic echocardiography is the initial confirmatory test, providing information on:

• Site, structure, and extent of coarctation 1
• Left ventricular function and hypertrophy 1
• Associated cardiac abnormalities 1
• Doppler findings showing diastolic run-off phenomenon (most reliable sign of significant coarctation) 1

Advanced imaging (MRI/MRA or CT angiography) provides comprehensive visualization of:

• The entire thoracic aorta including arch anatomy 1
• Coarctation site and severity 1
• Collateral vessel development 1
• This is particularly valuable for surgical planning and long-term follow-up 1

Cardiac catheterization with manometry remains the gold standard at many centers, with a peak-to-peak gradient >20 mmHg indicating hemodynamically significant coarctation in the absence of well-developed collaterals. 1

Treatment Approach

Surgical repair (extended resection with end-to-end anastomosis) remains the gold standard for native coarctation in this age group. 1

Transcatheter balloon angioplasty with or without stent placement has emerged as an alternative for:

• Patients >6 months of age with discrete narrowing 1
• Recurrent/residual coarctation after surgical repair (where it is the preferred option) 1
• However, there is a small but important incidence of aneurysm formation after balloon dilation of native coarctation 1

Critical Pitfalls to Avoid

Do not rely solely on oxygen saturation screening in older children, as coarctation typically presents with blood pressure gradients rather than significant desaturation unless there are associated cardiac defects. 2, 3

Do not assume normal blood pressure in the right arm excludes coarctation when the left arm shows lower values—this pattern specifically suggests proximal coarctation. 1

Do not delay evaluation even if the child appears asymptomatic, as untreated coarctation leads to persistent hypertension, premature coronary artery disease, ventricular dysfunction, and risk of aortic or cerebral aneurysm rupture. 1

Recognize that Doppler gradients alone are unreliable for quantifying severity, particularly in the presence of extensive collaterals or after surgical repair due to altered aortic compliance. 1