Is measuring blood pressure (BP) in both arms a reliable method to screen for coarctation of the aorta, particularly in pediatric and young adult patients?

Blood Pressure Measurement in Both Arms for Coarctation Screening

Measuring blood pressure in both arms is a reasonable initial screening step for coarctation of the aorta, but it is insufficient as a standalone diagnostic tool and must be combined with upper-to-lower extremity BP comparison for reliable detection. 1

Why Both-Arm Measurement Alone is Inadequate

The primary hemodynamic abnormality in coarctation of the aorta is a pressure gradient between the upper and lower body, not between the two arms. 2, 3 The classic diagnostic finding is:

• Elevated BP in the arms with reduced or delayed femoral pulses 2
• Arm-to-leg systolic BP difference ≥20 mmHg (arm higher than leg) is considered diagnostic evidence 2, 3
• An invasive peak-to-peak gradient >20 mmHg confirms hemodynamically significant coarctation 1

The Correct Screening Approach

In patients with suspected or known coarctation, BP measurements should include both arms AND at least one lower extremity. 1 This is explicitly recommended by:

• The 2024 ESC guidelines state: "In patients with coarctation, BP measurements at both arms and one lower extremity are recommended" 1
• The 2019 AHA/ACC guidelines mandate: "Resting blood pressure should be measured in upper and lower extremities in all adults with coarctation of the aorta" 1

Why Measure Both Arms?

Measuring BP in both arms serves a different purpose than detecting coarctation itself:

• Identifies the arm with higher readings for consistent future monitoring 4, 5
• Detects aberrant subclavian artery anatomy that can occur with coarctation (e.g., right subclavian arising distal to the coarctation) 4, 6
• Rules out concurrent vascular pathology such as subclavian stenosis 6, 5

The 2017 AAP pediatric hypertension guidelines recommend obtaining "right and left arm and a lower extremity BP to rule out coarctation of the aorta" when applying ambulatory BP monitoring. 1

Critical Technical Considerations

Normal Arm-to-Leg BP Relationships

In healthy individuals, leg BP is typically HIGHER than arm BP, not lower:

• In children aged 4-8 years: leg systolic BP averages 9 mmHg higher than arm 7
• In children aged 9-16 years: leg systolic BP averages 5 mmHg higher than arm 7
• In young adults: leg systolic BP is 12-16 mmHg higher than arm 8

Therefore, finding equal or lower leg BP compared to arm BP is abnormal and warrants investigation. 7, 8

Measurement Pitfalls

The arm-to-leg BP gradient has significant limitations:

• Wide variability exists even in normal subjects (range up to 60 mmHg) 9
• Sequential measurements in the same limb decrease with repetition—the first measurement should be discarded 8
• Proper technique is essential: both sites must be at heart level, appropriate cuff sizes used, and measurements repeated 8
• The arm-to-leg gradient is an unreliable tool to estimate severity of recoarctation in post-surgical patients 9

Recommended Screening Algorithm

For suspected coarctation in an outpatient setting:

1. Measure BP in both arms to identify the higher-reading arm 4, 5
2. Measure BP in the higher-reading arm AND in the legs (thigh or ankle) 1, 8
3. Discard the first measurement in each limb and use subsequent readings 8
4. A positive screen is defined as arm systolic BP ≥5-10 mmHg higher than leg BP 8
5. Confirm with physical examination: palpate femoral pulses simultaneously with brachial pulses to detect delay or diminution 2, 3

When to Pursue Advanced Imaging

If screening suggests coarctation:

• Echocardiography with suprasternal notch views and Doppler flow velocities across the suspected coarctation site 2, 3
• CMR or cardiac CT is recommended for definitive anatomic assessment in adults and children when coarctation is confirmed or strongly suspected 1
• Ambulatory BP monitoring is useful in patients with repaired coarctation to evaluate for masked hypertension and abnormal nocturnal BP patterns 1

Special Populations

Post-Coarctation Repair Patients

• Lifelong follow-up with regular imaging (CMR/CT every 3-5 years) is mandatory 1
• ABPM is particularly valuable to detect masked hypertension and evaluate for sustained HTN, which occurs frequently despite successful repair 1
• Hypertension associated with genetic syndromes (Turner syndrome, Williams syndrome) may only manifest with activity during ABPM 1

Pediatric Considerations

The 2017 AAP guidelines list coarctation among high-risk conditions where ABPM is useful to evaluate for masked hypertension and nocturnal hypertension patterns. 1

Bottom Line

Measuring BP in both arms detects inter-arm differences that may indicate vascular pathology, but the diagnostic hallmark of coarctation is elevated arm BP relative to leg BP. 1, 2 Both measurements are complementary: bilateral arm BP identifies the correct arm for monitoring, while arm-to-leg comparison actually screens for the coarctation gradient. 1, 8 Neither measurement alone is sufficient—comprehensive screening requires BP assessment in both arms and at least one lower extremity. 1