Endovascular stent-graft placement in aortic dissection: a meta-analysis

Real-time vascular interventional magnetic resonance imaging

Endovascular stent-graft placement is emerging as a promising alternative to medical and surgical treatment of patients with diseases of the descending thoracic and abdominal aorta. Precise placement of the stentgraft, which is currently performed under x-ray control, remains, however, challenging as there are several shortcomings to fluoroscopic guidance beyond that related to the harmful effect of radiation exposure and nephrotoxic contrast media. While transesophageal echocardiography and intravascular ultrasound have been used as adjunct imaging modalities during endovascular stent-graft procedures to overcome the limitations of angiography, these techniques have not mitigated the need for fluoroscopy. Magnetic resonance imaging (MRI) guidance of vascular interventional procedures offers several potential advantages over fluoroscopy-guided techniques, including image acquisition in any desired orientation, superior 3D soft-tissue contrast with simultaneous visualization of the interventional device, absence of ionizing radiation, and avoidance of nephrotoxic contrast media. Magnetic resonance imaging is often used for pre-operative diagnosis of aortic disease and can provide all relevant information for the planning of endovascular stent-graft procedures as well as for accurate and immediate post-interventional evaluation. However, visualization of interventional instruments by MRI has proven to be the chief obstacle. This article will review current approaches that have been developed for depicting vascular instruments by MRI and will also discuss the first experimental experiences with MRI-guided endovascular stent-graft placement in a swine model of aortic dissection.

Acute aortic dissection

Acute aortic dissection is an uncommon but lethal cause of acute chest, back, and abdominal pain. Establishing a timely diagnosis is paramount, as mortality from acute aortic dissection rises by the hour. Physical findings are protean and may include acute aortic valve insufficiency, peripheral pulse deficits, a variety of neurologic deficits, or end-organ ischemia. The keys to establishing a timely diagnosis are maintaining a high index of suspicion and quickly obtaining a diagnostic study. CT angiography, magnetic resonance imaging, transesophageal echocardiography, and, to a lesser extent, aortography are all highly accurate imaging modalities. The choice of study should be driven by the clinical stability of the patient, the information required and the resources available at presentation. Proximal dissections are surgical emergencies, but distal dissections are generally treated medically. Endovascular stents are gaining favor for use in the repair of both acute and chronic distal dissections. Long-term outcome data for endovascular stenting are still limited, and it remains unclear when stenting should be favored over surgery or medical therapy.

Thoracic aorta endografts: Variations in practice among medical specialists

BACKGROUND

Endovascular stent-graft placement is emerging as a novel treatment option for patients with diseases of the descending thoracic aorta. However, currently no consensus guidelines exist to direct uniformity in stent-graft procedures as well as for pre- and postprocedural patient management, unlike that for the management of other cardiovascular disorder. Accordingly, the aim of the present survey was to assess variations in thoracic aortic stent-graft practice among different subspecialties in Germany.

METHODS

An interdisciplinary questionnaire survey was conducted among 206 departments of vascular surgery, radiology, cardiology, and cardiothoracic surgery in Germany that actively performed aortic stent-graft placement. Data on preoperative procedure planning, logistics, practical/technical issues of stent-graft placement, and postoperative patient management were evaluated using a standardized, self-administered questionnaire comprising 29 items. Responses were tabulated for analysis.

RESULTS

Of a total of 206 questionnaires, 184 (89.3%) were returned with 71 (38.5%) centers reporting to have performed thoracic aortic stent-graft placement (total number of procedures 2,267) through 1997 and 2003. The average number of stent-graft procedures per year was 7.4 (25-75% percentile, 2.05-10.75) at participating sites, with 49% of the respondents reporting <5 procedures per year. Treatment of thoracic aortic aneurysms was the predominant indication for stent-graft placement, followed by type B-dissection. As anticipated, marked variability existed among the different medical specialties performing stent-graft procedures with respect to all aspects of the procedures including indication for treatment, choice of preoperative and intraoperative imaging modalities, technical equipment and perioperative management. The only consistent agreement was on the need for lifelong follow-up after stent-graft placement, with CT being the preferred imaging technique (90% of centers).

CONCLUSION

The present survey documents an increasing adoption of endovascular stent-graft placement for patients with diseases of the descending thoracic aorta in Germany. Despite this, there is a lack of consensus among the different medical specialties performing stent-graft placement with respect to indications and technical execution of stent-grafting. Our data supports the need for consensus practice guidelines endorsed by medical professional societies for stent-graft procedure to standardize the growing number of thoracic stent graft procedures.