Diagnostic Criteria for Coarctation of the Aorta
The diagnosis of significant coarctation of the aorta requires both clinical evidence of hemodynamic impact (upper extremity hypertension >140/90 mmHg in adults OR left ventricular hypertrophy) PLUS one of three gradient measurements: >20 mmHg blood pressure difference between arms and legs, peak-to-peak catheter gradient >20 mmHg, or mean Doppler gradient >20 mmHg across the coarctation. 1
Clinical Diagnostic Features
Blood Pressure Findings (Essential)
- Upper extremity hypertension (>140/90 mmHg in adults) with lower extremity hypotension is the hallmark finding 1, 2
- Blood pressure must be measured in both arms AND at least one lower extremity 1, 2
- A blood pressure gradient >20 mmHg between upper and lower extremities indicates significant coarctation 1
- The location of coarctation determines whether differential blood pressure exists between right and left arms (if near left subclavian origin) 1, 2
Physical Examination Findings
- Radio-femoral pulse delay is pathognomonic—the femoral pulse is felt after the radial pulse 1, 2
- Diminished amplitude or absent femoral pulses 1, 2
- Systolic murmur or bruit in the left interscapular region (between shoulder blades) 1, 2
- Suprasternal thrill may be palpable 1, 2
- Palpable collateral vessels around the scapula 1, 2
- Continuous murmurs from collateral circulation 1, 2
Hemodynamic Gradient Criteria (One Required)
Significant coarctation is defined by meeting ONE of these three gradient measurements: 1
1. Non-invasive Blood Pressure Gradient
- Blood pressure difference >20 mmHg between upper and lower extremities 1
2. Invasive Peak-to-Peak Catheter Gradient
- Peak-to-peak gradient >20 mmHg across the coarctation 1
- Lower threshold of >10 mmHg applies when decreased left ventricular systolic function OR significant collateral flow is present 1
3. Doppler Echocardiography Mean Gradient
- Mean gradient >20 mmHg across the coarctation 1
- Lower threshold of >10 mmHg applies when decreased left ventricular systolic function OR significant collateral flow is present 1
- A diastolic "run-off" phenomenon (continuous forward diastolic flow in descending aorta) is the most reliable echocardiographic sign 1, 2
Anatomic Imaging Criteria
Anatomic Narrowing (Required for Diagnosis)
- ≥50% aortic narrowing relative to the aortic diameter at the diaphragm level on MRI, CT, or invasive angiography 1
- Anatomic evidence for coarctation is necessary in addition to abnormal gradients 1
Preferred Imaging Modalities
- MRI and CT are the preferred non-invasive techniques to evaluate the entire aorta, depicting site, extent, and degree of narrowing, the aortic arch, pre- and post-stenotic aorta, and collaterals 1
- Transthoracic echocardiography (TTE) detects gradients and assesses for associated abnormalities 1
- Cardiac catheterization with manometry remains the gold standard at many centers 1
Additional Diagnostic Markers
Left Ventricular Hypertrophy
- The presence of left ventricular hypertrophy is an important marker of hemodynamically significant disease 1
Associated Findings
- Bicuspid aortic valve coexists in at least 50% of cases 1, 2
- Collateral vessel formation visible on imaging 1
Critical Diagnostic Pitfalls
When Gradients Underestimate Severity
- Extensive collateral circulation may reduce measured gradients, falsely suggesting mild disease 1, 2
- In the presence of well-developed collaterals, gradients are not reliable 1
- After surgical repair, increased systolic flow rates may develop even without significant narrowing due to lack of aortic compliance 1
Additional Considerations
- Exercise-induced hypertension may be present despite normal resting blood pressures 1, 2
- Ambulatory blood pressure monitoring may be necessary to detect hypertension 1
- Always use appropriately sized blood pressure cuffs for accurate measurements 2