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ORIGINAL ARTICLE |
Department of Cardiovascular and Endovascular Surgery, Arizona Heart Institute, Phoenix, AZ, USA
Ourania Preventza, MD Tel: +832 355 9910 Email: opsmile01{at}aol.com, Division of Cardiothoracic Surgery, Texas Heart Hospital at St Luke’s Episcopal Hospital, Baylor College of Medicine, MS:BCM 390, One Baylor Plaza, Houston, TX 77030, USA.
ABSTRACT
Endografting, like open surgical repair of the thoracic aorta, can be complicated by paraplegia. We reviewed our thoracic endografting experience regarding the incidence and treatment of spinal cord neurologic events. Between February 2000 and July 2008, 346 patients underwent endoluminal grafting of the descending thoracic aorta. Indications for intervention included atherosclerotic aneurysms (45.9%), acute and chronic dissections (31.5%), miscellaneous lesions (13.6%), and penetrating aortic ulcers (8.9%). Ten women and 4 men (4.0%), with a mean age of 71.3 years, developed either paraparesis (1.7%) or paraplegia (2.3%). Nine (64.3%) of these patients had an aneurysm, 4 (28.6%) had acute or chronic type B aortic dissection, and 1 (7.1%) had a penetrating aortic ulcer; 3 (21.4%) of them had previously undergone open abdominal aortic aneurysm repair, and 13 (92.9%) required coverage of more than 20 cm of the aorta. Cerebrospinal fluid drainage was instituted in 7/8 paraplegic patients. Eight (57.1%) of the 14 patients recovered fully, 2 (14.3%) experienced partial recovery, and 4 (28.6%) had significant neurological deficits. Paraplegia following thoracic endografting appears to be associated with female sex, long-segment coverage of the thoracic aorta, and aneurysmal disease.
Key Words: Aortic Aneurysm • Thoracic • Blood Vessel Prosthesis Implantation • Paraplegia • Spinal Cord Ischemia • Stroke
INTRODUCTION
Postoperative paraplegia is a devastating consequence of thoracic endovascular aortic repair (TEVAR). The mechanism of spinal cord ischemia has yet to be completely understood, and reducing the risk of paraplegia is an important goal in the development of TEVAR. The incidence of both immediate and delayed paraplegia in patients undergoing TEVAR is 2.4%–10%, and the incidence of stroke may be as high as 7%.1–4,8,9 Recent studies on open repair of thoracic and thoracoabdominal aortic aneurysms found a 2%–14% risk of paraplegia.5–9 Because overall experience with TEVAR is limited compared to that of open repair, documenting the complications and outcomes is essential. We reviewed our comprehensive TEVAR experience to determine the incidence and treatment outcomes of spinal cord complications.
PATIENTS AND METHODS
This study reviewed the results of TEVAR at the Arizona Heart Institute between February 2000 and August 2008. Patients were treated as part of a single-site investigational device-exemption protocol approved by the institutional review board of the Arizona Heart Hospital. The feasibility of endografting was determined by preoperative computed tomography (CT). The sizing of the graft was based on preoperative CT and intraoperative ultrasound and aortography. A Gore TAG graft (WL Gore and Associates, Flagstaff AZ, USA) was used in 314 patients, and a Talent graft (Medtronic, Inc., Santa Rosa, CA, USA) in 32. Data were prospectively entered into our clinical database. Demographics, lesion characteristics, indications for TEVAR, preoperative revascularization of the left subclavian artery, and prophylactic use of cerebrospinal fluid (CSF) drainage in all 346 patients is given in Table 1
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Paraplegia was defined as no lower extremity movement or motion without gravity or against gravity. Paraparesis was incomplete paraplegia or weakness in a lower extremity muscle group, with the patient able to stand or walk with assistance. A neurologic event observed upon waking was defined as an immediate deficit. A neurologic event evident after a period of normal neurologic function was termed a delayed deficit. When paralysis or paraparesis was recognized, the mean arterial pressure was increased and steroids were administered. Lumbar CSF was drained promptly if no immediate improvement was noticed with increased mean arterial pressure or steroid administration.
The following factors were assessed for an association with postoperative spinal cord ischemia: age, sex, cardiac history, hypertension, diabetes mellitus, previous surgical repair of an abdominal aortic aneurysm (AAA), and cerebrovascular disease with history of stroke or transient ischemic attack. In addition, the indications for endografting, coverage of the left subclavian artery, and extent of coverage of the descending thoracic aorta were reviewed.
RESULTS
CSF drainage was instituted prophylactically in 4 patients with thoracic aneurysms and history of AAA repair; graft coverage of the descending thoracic aorta extended >20 cm in all 4, and the left subclavian artery was also covered in 1 of them. Spinal pressure was maintained at 12 mm Hg postoperatively. None of these 4 patients developed a neurologic deficit, and the lumbar drains were removed 48 h after the procedure. The incidence of paraparesis or paraplegia and the characteristics of patients with paraplegia are given in Table 2. Of these 14 patients, 8 (57.1%) recovered fully, 2 (14.3%) experienced partial recovery, and 4 (28.6%) had significant residual neurologic deficits. Paralysis was detected in 8 (2.3%) patients; (Table 3) it was noted on the 1st postoperative day in 7 cases, and 3 days after the procedure due to hypotension secondary to retroperitoneal bleeding in the other. Five of these patients had descending thoracic aneurysms and 3 had acute complicated type IIIA (above the diaphragm) or IIIB (below the diaphragm) aortic dissection. Blood pressure augmentation and steroid administration were used in all patients with paraplegia or paraparesis (Table 3). CSF drainage was instituted for 48–72 h in 7 paraplegic patients, with spinal pressure kept <12 mm Hg; the patient with intracranial bleeding did not receive a drain. Four paraplegic patients had significant permanent neurologic deficits; one of them died after 22 days from respiratory failure. Paraparesis was seen in 6 (1.7%) patients, with symptoms first appearing on days 1–31; 4 of them had atherosclerotic aneurysms, 1 had aneurysmal dilatation secondary to chronic dissection, and 1 had a penetrating ulcer. All 6 patients with paraparesis recovered (Table 3). Other neurologic complications are shown in Table 4. Seven patients suffered a cerebrovascular accident within 30 days of the procedure; 3 of them had history of a previous cerebrovascular accident.
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Preventing spinal cord ischemia remains a challenge in TEVAR and open aortic repair. Our incidence of neurologic events and 2.3% rate of paraplegia are comparable to those of other studies on TEVAR and open repair of isolated descending thoracic aneurysms.1–9 Eliminating thoracic or thoracoabdominal incisions, avoiding general anesthesia, and expanding the pool of patients who can be offered treatment are the benefits highlighted by proponents of TEVAR. Eliminating the need for aortic crossclamping and the consequent decrease in distal arterial pressure and spinal cord perfusion is another potential benefit. Nevertheless, as we and others have found, endoluminal grafting does not eliminate the risk of neurologic events, and the patients offered minimally invasive intervention are often considered to be at high risk for an open procedure.10 Indeed, 5 of our patients with neurologic complications had a history of cardiac events including myocardial infarction, coronary artery bypass surgery, and angioplasty. Although there is no proven causal association of these comorbidities with spinal cord ischemia, they might have placed these patients at higher risk of complications.
Certain risk factors are known to be associated with spinal cord ischemia in TEVAR. Exclusion of critical intercostal arteries (T7–L1) supplying the anterior spinal artery is likely to result in neurologic events, and long-segment coverage of the thoracic aorta poses a significant risk of spinal cord complications.11,13 Using a segment of normal aorta proximal and distal to the aneurysm for fixation of the graft may also impair flow to the intercostal arteries. In our study, 13/14 patients with neurologic complications required >20 cm coverage of the descending thoracic aorta. Occlusion of the left subclavian artery may also jeopardize proximal collateral circulation to the spinal cord, and previous AAA repair can compromise pelvic and hypogastric collaterals that supply the anterior spinal artery.10,12,13 Among our patients with neurologic symptoms, the left subclavian artery was covered in 2 and 1 had previous open AAA repair and required more than 20 cm of his aorta lined, and another presented with contained ruptured (acute complicated type III dissection) and had the left subclavian artery covered. We believe that sacrificing lumbar or iliolumbar arteries during open abdominal aortic surgery may increase the risk of neurologic complications in patients who later undergo TEVAR. According to this study and our previous results, coverage of the left subclavian alone has no impact on spinal cord ischemia.14 Hypotension in the postoperative period is one of the most important factors in both immediate and delayed paraplegia.11–13 Spinal cord perfusion is very dependent on collaterals rather than single segmental arteries, and collaterals are vulnerable to abrupt hemodynamic changes.15 Hypotension after retroperitoneal bleeding was associated with the onset of paraplegia 3 days after the procedure in one of our patients; we believe that hypotension and exploration for retroperitoneal hematoma may have triggered the spinal cord ischemia.
A number of techniques have been used to prevent paraplegia during open and endovascular thoracic aortic repair, such as distal aortic perfusion, CSF drainage, local hypothermia, steroids, hypothermic circulatory arrest, and spinal cord monitoring, but none has been completely successful.7,9,16,17 Augmentation of blood pressure to maintain spinal cord pressure >70 mm Hg, either by vasopressors or by volume expansion, is our goal. The strategy of increasing mean arterial pressure to >90 mm Hg and steroid therapy resolved paraparesis in our patients. The use of CSF drainage as a prophylactic or salvage technique in cases of postoperative paraplegia has been reported by others.1 We used prophylactic CSF drainage sucessfully in 2 patients with previous AAA repair because we anticipated coverage of a long segment of the descending thoracic aorta. CSF drainage in combination with steroid administration and increased blood pressure was employed in 7 paraplegic patients, with complete recovery in 2 of them. It is our practice to continue CSF drainage for 48 h. Prophylactic drainage has been recommended in patients deemed at high risk of spinal cord ischemia, such as those with prior AAA repair.10 When there is a need to treat both abdominal and thoracic aortic pathologies, we propose a waiting period between the procedures for the development of collaterals for spinal cord blood supply.
In this series, the incidence of spinal cord ischemia was higher in woman than men, although sex has not been implicated as a risk factor in other reports.10–12 Poor functional outcomes have been associated with female sex in open surgical repair of thoracoabdominal aortic aneurysms.18
Regarding neurologic events other than paraplegia, our incidence of stroke was 2%, and 3/7 patients had history of cerebrovascular accidents. Patients with history of stroke are more prone to a new cerebrovascular accident. Aggresive manipulation of catheters and guidewires in the aortic arch might predispose patients to this complication. The combination of prior stroke together with high-grade atheroma of the aortic arch predicts a high probability of cerebral embolization.19 We believe that careful asssessment of the aortic arch using intravascular ultrasound and CT, combined with minimal device manipulation, can limit the stroke risk. All patients who experienced transient ischemic attacks recovered completely.
It was concluded that female sex, long-segment coverage of the descending aorta, and aneurysmal disease were associated with spinal cord ischemia in this study. Elective procedures that include prophylactic CSF drainage, augmentation of blood pressure, and steroid administration may help prevent or reverse neurologic complications in some patients.
REFERENCES
Asian Cardiovasc Thorac Ann 2009;
17:568-572
© 2009 by SAGE Publications
DOI: 10.1177/0218492309349813
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