Worldwide survey of thoracic endografts: Practical clinical application

Article Outline

• Introduction
• Survey advantages and limitations
• Variety of diseases treated
• Conclusion
• Copyright

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Introduction 

This survey was conducted between June 2003 and June 2004 during personal visits with expert physicians at several centers of excellence in thoracic endovascular aortic repair (TEVAR) around the world. They and their colleagues deserve specific credit for graciously opening their labs and sharing their clinical experience in the field.

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Survey advantages and limitations 

Peer-reviewed scientific publications are the gold standard of evidence for medical decision-making. However, in rapidly emerging technologies, early experiences are dominated by prototype devices, single-site series, and initial learning periods. Data from United States clinical trials are useful because of the well-defined protocol, regulatory oversight, and generally more diligent follow-up and core lab review. On the other hand, practical clinical use often does not comply with the rigid entry criteria of these studies, which were initially designed to evaluate TEVAR for primarily descending thoracic aneurysms. To get a grasp of the general clinical practice experience with thoracic endografts, eight physicians were surveyed (Table I). Their reflections inform the pooled data on 1180 patients, which is one of the largest series so far in TEVAR. Limitations of this compilation are the lack of uniformity in surveillance protocols, definitions, follow-up intervals, and compliance, as well as overlap with existing publications.

Table I. Expert physicians and institutions by TEVAR volume

TEVAR, Endovascular repair of thoracic pathology; UCLA, University of California, Los Angeles.

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Variety of diseases treated 

Table II summarizes the types of thoracic pathology that have been treated and the 30-day mortality for patients in each of these categories. The impression of most of the eight physicians is that endovascular treatment is equivalent to or better than conventional treatment in each of these categories except for thoracoabdominal aneurysm, chronic dissection, and aortic stenosis. There was no consensus on the relative benefits of TEVAR vs standard therapy for these three disease states. Most of the patients (64.2%) have been treated for degenerative descending thoracic aortic aneurysms, and a wide variety of endografts have been used in treatment (Table III).

Table II. Various aortic pathologies treated by endovascular thoracic repair and periprocedural mortality

Primary aortic pathology	Percent of total cases	30-day mortality (%)
Degenerative aneurysm
Descending thoracic aneurysm	64.2	4.1
Thoracoabdominal aneurysm	1.6	5.0
Post-traumatic
Acute traumatic disruption	10.0	5.5⁎
Pseudoaneurysm	3.3	2.7
Dissection
Acute dissection	7.8	9.9
Intramural hematoma with ulcer	2.2	7.2
Giant penetrating ulcer	1.0	0
Chronic dissection	8.4	3.3
Miscellaneous
Aortic fistula	0.9	2.6
Embolizing lesion	0.3	0
Stenosis/coarctation	0.1	0

Table III. Distribution of endovascular grafts in this compilation

Most patients (70.3%) have been treated in an operating room environment and 49.2% in fixed unit fluoroscopy units. Intravascular ultrasound was used in 12%, and transesophageal echocardiography in 38.1%. Primary access was in the femoral artery in 84.4% (percutaneous in 1.1%), iliac in 7.5%, conduit or aortofemoral graft limb in 6.5%, infrarenal aorta in 1.1%, and other sites in 0.4%. It is interesting that the busiest center routinely used a right brachial-femoral wire and relied upon a portable C-arm with infrequent use of ultrasound.

The left subclavian artery was covered in 29.8%, the left common carotid in 8.0%, the innominate in 3.7%, celiac artery in 3.1%, and superior mesenteric artery in 0.8%. With more experience, debranching procedures, fenestrations, scallops, and branches are being performed. The option to revascularize these major branches is exercised at different rates: most centers revascularize the carotid, innominate, and visceral arteries when they are covered. In contrast, revascularization is performed before or concurrently with TEVAR in only 36.7% of patients who have coverage of the left subclavian artery. Many centers have decreased use of routine subclavian revascularization except when there are diseased or hypoplastic right vertebral arteries or fistulas/reconstructions based on left subclavian branches. Most patients are managed expectantly; when symptoms develop after left subclavian coverage, which is unusual, delayed revascularization is performed.

Spinal cord drainage was used sparingly in 1.0% but in up to 6.8% of patients with extensive descending aortic coverage or history of abdominal aortic aneurysm. Utilization of spinal cord drainage, arterial line pressure monitoring, and aggressive blood pressure support may be on the increase as TEVAR is applied to more diffuse pathology. Adenosine (2.1%) and high-dose β-blocker (0.1%) were used rarely to arrest or slow the heart for deployment and are becoming obsolete with newer device delivery technologies.

The 30-day morbidity rates reflect stroke in 2.8%, renal failure in 1.6%, and paraplegia in 2.5%. As the stroke rate is higher than the paraplegia rate, extensive deairing is practiced at some high-volume centers. It is noteworthy that 43% of the paraplegia complications were delayed in onset and reversible in a significant portion of patients.

Later outcomes are best described by time-dependent intervals; unequal or unknown lengths of follow-up make precision impossible in this compilation. Nevertheless, general estimates are useful to characterize TEVAR. Endoleak was noted in 10.5% of patients, sac expansion in 4.0%, proximal neck dilation or dissection in 2.7%, distal neck dilation in 2.1%, intercomponent migration in 1.7%, proximal migration in 1.3%, distal migration in 0.4%, asymptomatic device failure such as fracture in 6.3%, symptomatic device failure in 0.1%, and aneurysm rupture in 0.9%. Although these rates are low, some of the complications are catastrophic, such as proximal aortic dissections and perforations.

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Conclusion 

The treatment of thoracic aortic disease is rapidly evolving following United States Food and Drug Administration approval of one device for treatment of descending thoracic aneurysms. Alternatives to the traditional open surgical approach to dissection, transection, and other less common pathology are being developed and applied in centers of excellence. Mortality rates for open surgical repair of the thoracic aorta have decreased with experience, but early reports of thoracic aortic endografts support TEVAR as a less-invasive option with lower morbidity and periprocedural mortality rates.

Several engineering advancements are being pursued to address shortcomings in earlier devices for thoracic endovascular repair. These include endografts that conform to the individual aortic anatomy, more flexible and accurate delivery systems, more robust construction to accommodate higher thoracic aortic forces, and mechanisms to treat pathology close to or involving the aortic arch and visceral side branches. As these technologies mature, it is quite possible that TEVAR will become the preferred initial therapy for many thoracic aortic diseases.