Coarctation of the Aorta Workup

Updated: Nov 20, 2018
  • Author: Syamasundar Rao Patnana, MD; Chief Editor: Stuart Berger, MD  more...
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Workup

Laboratory Studies

Studies that may be indicated in evaluation of patients with suspected coarctation of the aorta (CoA) are summarized below.

Laboratory studies in neonatal patients who present in shock include the following:

  • Septic workup includes blood, urine, and cerebral spinal fluid (CSF) cultures.

  • Electrolyte levels, BUN, creatinine, and glucose concentrations should be tested.

  • Measure arterial blood gases and serum lactate levels.

Laboratory studies in older patients who present with hypertension include urinalysis, electrolyte levels, BUN, creatinine, and glucose concentrations.

Preductal and postductal pulse oximetry readings may show evidence of ductal right-to-left shunting, especially in the neonate.

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Electrocardiography

ECG in the neonate or infant with early onset of coarctation of the aorta may reveal right ventricular rather than left ventricular (LV) hypertrophy. The reasons for right ventricular preponderance in the face of LV outlet obstruction are mentioned in Pathophysiology.

ECG findings in patients with late onset of coarctation of the aorta may be normal or may reveal LV hypertrophy and may show signs of LV ischemia or strain. Sometimes, LV hypertrophy may manifest as increased S waves in leads V5 and V6, the so-called posterobasal LV hypertrophy.

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Chest Radiography

Radiography in patients with early onset of coarctation of the aorta may reveal cardiomegaly, pulmonary edema, and other signs of congestive heart failure (CHF).

Radiography in patients with late onset of coarctation of the aorta may reveal cardiomegaly. An inverted "3" sign of the barium-filled esophagus or a "3" sign on a highly penetrated chest radiograph (frontal view) may be visualized. Rib notching secondary to collateral vessels may also be seen.

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Echocardiography

Echocardiography delineates intracardiac anatomy and allows assessment of associated significant intracardiac anomalies. The suprasternal notch 2-dimensional echocardiographic view allows evaluation of the aortic arch to assess the transverse aortic arch, isthmus, and severity of coarctation. Doppler echocardiography is used to measure the gradient at the site of coarctation and to identify the pattern of diastolic runoff typically seen in patients with severe obstruction.

Instantaneous peak pressure gradients across the aortic coarctation can be estimated with a modified Bernoulli equation, as follows:

ΔP = 4 (V22 – V12)

ΔP is the peak instantaneous gradient, and V2 and V1 are the peak flow velocities in the descending aortic, distal to coarctation (continuous-wave Doppler) and proximal to the coarctation (pulsed Doppler), respectively. The calculated gradient usually overestimates the measured blood pressure gradient. Presence of pan-diastolic flow indicates significant obstruction. Inclusion of duration-related Doppler flow parameters in the gradient calculation may improve the accuracy of Doppler prediction of coarctation gradient. [32]

When aortic arch cannot be adequately evaluated, abdominal aortic Doppler parameters may help in the diagnosis. [33] Absence of early diastolic reversal along with corrected pulse delay of 2.8 microseconds1/2 or more may best predict significant obstruction.

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Magnetic Resonance Imaging and Computed Tomography Scanning

MRI and CT are useful in older or postoperative patients to assess residual arch obstruction, arch hypoplasia, or formation of aneurysms (see image below). [34, 35] Ultrafast CT scanning is preferable if multiple surgical clips or a stent is present in the area of coarctation.

Apart from defining the anatomy, peak systolic pressure gradients may also be calculated using MRI-based computational fluid dynamics. [36]

Aortic coarctation visualized by aortic angiograph Aortic coarctation visualized by aortic angiography.
Aortic coarctation visualized by MR imaging. Aortic coarctation visualized by MR imaging.
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Cardiac Catheterization

Cardiac catheterization and selective cineangiography may not be required for diagnosis; however, they allow evaluation of the severity of coarctation, anatomic nature of the aortic obstruction (discrete vs long segment), and arch anatomy, including hypoplasia of the transverse arch or isthmus.

Cardiac catheterization helps to confirm the diagnosis when echocardiography findings are not completely clear, allows the evaluation of intracardiac anatomy and the contribution of associated lesions to the overall hemodynamic disturbance, and is a prerequisite for intervention in the form of either balloon angioplasty or stent implantation in native or recurrent coarctation.

When catheterization is performed, elevations of left ventricular and ascending aortic peak systolic pressures with a peak-to-peak systolic pressure gradient across the coarcted segment are usually found. A peak-to-peak gradient in excess of 20 mm Hg is generally considered indicative of significant obstruction. However, the magnitude of the gradient is not necessarily indicative of the degree of narrowing because the gradient depends on not only the extent of aortic narrowing but also the size and number of collateral vessels. In addition, cardiac output and the state of ductus arteriosus, particularly in the neonate and young infant, also determine the pressure gradient.

Selective aortic root or aortic arch angiography is necessary to clearly demonstrate the aortic narrowing. Aortography is useful in demonstrating the type of aortic coarctation (diffuse, long segment, aortic kinking [pseudocoarctation]); extent of collateral circulation; the size of ductus arteriosus, if patent; and the presence and degree of hypoplasia of transverse aortic arch and aortic isthmus, especially in neonates. If thoracic coarctation is not demonstrated despite clinical features of coarctation or if neurofibromatosis is suspected, abdominal aortography may be needed to demonstrate (or exclude) abdominal coarctation.

LV angiography is particularly useful in neonates and infants who demonstrate ventricular septal defects (VSDs) and in evaluating LV function.

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Histologic Findings

Coarctation of the aorta results from marked ridgelike thickening of the media of the aortic wall opposite the insertion of the patent ductus arteriosus or ligamentum arteriosum.

The intima in this area may be thin initially but may thicken over time.

This ridge or shelf becomes an obstruction when the patent ductus involutes and when ductal tissue in the wall of the aorta involutes.

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