A 27-year-old man was referred to our hospital complaining of headaches. His medical history revealed heart murmur, but no hypertension, during his mid teens. Preoperative transthoracic echocardiography revealed a bicuspid aortic valve (BAV) and severe aortic insufficiency (AI), while computed tomography (CT) revealed aortic narrowing just distal to the left subclavian artery (LSCA) and multiple collateral vessels (Fig. 1A). The right and left ankle-brachial index was 0.65 and 0.69, respectively. These findings indicated a diagnosis of severe AI due to a BAV and aortic coarctation (CoA). Aortic valve replacement and endovascular stent placement were scheduled accordingly.
A transesophageal echocardiography (TEE) probe was inserted under general anesthesia. The midesophageal aortic valve short-axis view revealed a BAV with a raphe (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A560) and severe AI due to aortic valve prolapse. Gradually withdrawing the probe while turning it to the left, the upper esophageal descending aorta long-axis view revealed aortic narrowing just distal to the LSCA in the form of a posterior shelf, with color-flow Doppler showing turbulent flow across this area (Fig. 2; Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A560) and continuous-wave Doppler showing a peak systolic velocity and pressure gradient of 296 cm/s and 35.1 mm Hg, respectively, in the narrowest region (Fig. 3A).
Aortic valve replacement was performed with a mechanical valve under cardiopulmonary bypass with aortic cross-clamp. The aortic clamp was then released under partial cardiopulmonary bypass and endovascular stent placement performed via the right femoral artery. After balloon angioplasty, dilation of CoA was confirmed by TEE and the endovascular stent successfully implanted. Absence of stent malposition, aortic dissection, and occlusion of the LSCA was confirmed by both TEE and angiography. Weaning from cardiopulmonary bypass was uneventful. Postoperative TEE revealed dilation of CoA. Peak systolic velocity and pressure gradient were 103 cm/s and 4.25 mm Hg, respectively, with the ratio of diastolic/systolic velocity decreasing from 0.58 to 0.37, with decreased diastolic runoff (Fig. 3B). The postoperative ankle-brachial index improved to 0.8 bilaterally, while CT angiography revealed no stent malposition or recurrence of CoA (Fig. 1B). The patient’s condition remains satisfactory.
CoA is the fifth most common congenital heart disease, accounting for 6% to 8% of such cases. It is more common in men than in women, with a reported ratio of 1.27 to 1.74:1 and is associated with cerebral aneurysm, BAV, ventricular septal defect, mitral abnormalities such as parachute mitral valve, and various other types of left-sided obstructive lesion.1,2 CoA usually manifests as a short-segment narrowing of the thoracic aorta, typically just distal to the LSCA, and takes the form of discrete infolding of the aortic wall, resulting in a posterior shelf, or diffuse, hourglass narrowing.2,3
Currently, transthoracic echocardiography is recommended for the initial imaging and evaluation of suspected CoA, taking a suprasternal notch view of the aortic arch and proximal descending aorta. This should be combined with color-flow and continuous-wave Doppler, because this would reveal any turbulence in the proximal descending aorta and show the characteristic flow profile of prolonged diastolic runoff. However, in the presence of sizable collaterals, catheter-based and Doppler systolic pressure gradients may not reflect the severity of obstruction caused by CoA.3 Magnetic resonance imaging and CT remain the preferred methods of imaging CoA. The severity of the obstruction is calculated according to the coarctation index by determining the ratio of the narrowest cross-sectional area of coarctation to the area of the abdominal aorta at the diaphragm level. A value of <0.25 is taken to indicate significant narrowing of the CoA (equivalent to a ratio of <0.5 for the CoA diameter to the abdominal aorta at the diaphragm level).4 Tan et al.4 reporting on Doppler evaluation of the severity of CoA noted that a diastolic velocity (measured at the beginning of the T wave in electrocardiogram) of >193 cm/s and diastolic/systolic velocity (peak systolic velocity) ratio of >0.53 had high predictive value for severe CoA.
Intervention for coarctation is recommended in patients with a peak-to-peak coarctation gradient ≥20 mm Hg, or peak-to-peak pressure gradient of <20 mm Hg in the presence of anatomic imaging evidence of significant coarctation with radiological evidence of significant collateral flow.3
Surgical repair comprising extended resection with end-to-end anastomosis had been the “gold standard” treatment for CoA. However, balloon angioplasty with or without endovascular stent placement has emerged as an alternative.2,3 Various complications can occur after stent placement, including aortic rupture (reported incidence of 1.6%), aneurysmal formation (estimated incidence of 5%–9%), restenosis of the implanted stent (estimated incidence of 4%), and cerebral vascular accident (<1%), and the role of perioperative TEE is unclear because stent implantation is usually performed with angiography.5 However, retrospective analysis of Doppler echocardiographic profiles and the CoA index in 24 consecutive adult patients revealed significant reductions in the peak systolic pressure gradient, diastolic velocity, end-diastolic tail velocity (velocity measured at end of Q wave in electrocardiogram), diastolic pressure half-time index (time taken for diastolic pressure gradient to decrease to half of its value), and diastolic velocity half-time index (time taken for diastolic velocity to decrease to half of its value) after stenting.4
Moreover, TEE imaging of the narrowest region of CoA may be difficult.2 To visualize this region, one can start with the midesophageal descending aorta long-axis view, gradually withdrawing the probe to the LSCA ostium. Identifying the LSCA is important, because the narrowest region is typically just distal to it. Alternatively, a leftward turn of the probe from the upper esophageal aortic arch short-axis view allows visualization of the LSCA ostium with or without probe flexion and avoidance of tracheal interposition.6 After identifying the LSCA ostium, the narrowest region of the CoA can be visualized by slightly advancing the probe. Doppler interrogation of the narrowest region is sometimes challenging due to poor alignment. Therefore, TEE is not recommended for evaluating the pressure gradient through the narrowest region.6,7 Color-flow Doppler imaging of CoA characteristically reveals turbulent flow near the narrowest region, while continuous-wave Doppler shows flow acceleration continuing into diastole, decreased flow pulsatility, and the absence of early diastolic flow reversal.2,3 However, with aortic stenosis rather than AI, the typical spectral Doppler flow pattern of CoA may be obscured due to flow limitation before the narrowest region. Moreover, spectral Doppler velocity may be influenced by change in flow, a potential limitation of Doppler assessment. Specific echocardiographic findings of significant CoA are summarized in Table 1.
In summary, we have reported TEE imaging of CoA treated with endovascular stent placement. Although TEE of CoA is challenging, it provides the advantage of specific characteristic findings, including maximum narrowing just distal to the LSCA, a discrete, infolding posterior shelf, and turbulent flow across the CoA.
Doppler imaging of CoA shows flow acceleration, turbulent jets, and the change in pressure gradient through to diastole. Intraoperative TEE imaging of CoA has the potential to play an important role in the pre- and postoperative evaluation of endovascular stent placement. E
Clinician’s Key Teaching Points
By Kent H. Rehfeldt, MD, Nikolaos J. Skubas, MD, andMartin J. London, MD
- Aortic coarctation typically presents as a narrowing of the aortic lumen just distal to the left subclavian artery. It ranges from a diffuse, hourglass narrowing to a focal infolding of the posterior aortic wall. It is frequently associated with other lesions such as bicuspid aortic valve, parachute mitral valve, ventricular septal defects, or cerebral artery aneurysms.
- Transesophageal echocardiography (TEE) imaging of aortic coarctation is performed using the midesophageal descending aorta short-axis view by withdrawing and turning the probe leftward. Typically, the coarctation diameter is <0.5 of the diameter of the abdominal aorta and has turbulent flow on color Doppler imaging. Using spectral Doppler, a peak gradient of 20 mm Hg (or higher) and a peak diastolic/systolic velocity ratio of >0.53 is considered severe coarctation. Transthoracic echocardiography using a suprasternal notch view generally affords a more reliable Doppler assessment of aortic coarctation compared with TEE.
- In this case, insertion of an endovascular stent across a coarctation resulted in a decline in the peak gradient and a reduction in the diastolic/systolic velocity ratio. While stent placement is typically performed under fluoroscopic guidance, immediate postdeployment TEE imaging can be used to detect aortic dissection or stent malposition with inadvertent occlusion of the left subclavian artery.
- By using 2-dimensional, color-flow and spectral Doppler imaging, TEE can assist in the assessment of patients with aortic coarctation. In patients treated with endovascular stent placement, TEE can document relief of obstruction and exclude procedural complications.
Name: Hiroshi Inoue, MD.
Contribution: This author helped design and conduct the study, analyze the data, write the manuscript, and obtain transesophageal echocardiographic images.
Attestation: Hiroshi Inoue approved the final manuscript.
Name: Takaharu Tokita, MD.
Contribution: This author helped write the manuscript.
Attestation: Takaharu Tokita approved the final manuscript.
Name: Yasuaki Tohi, MD.
Contribution: This author helped write the manuscript.
Attestation: Yasuaki Tohi approved the final manuscript
Name: Jun Ito, MD.
Contribution: This author helped write the manuscript.
Attestation: Jun Ito approved the final manuscript.
Name: Hiroaki Uchida, MD.
Contribution This author helped write the manuscript.
Attestation: Hiroaki Uchida approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
The authors would like to thank Associate Professor Jeremy Williams, Tokyo Dental College, for his assistance with the English of the manuscript.
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