Imaging of vascular remodeling after simulated thoracoabdominal aneurysm repair

ObjectiveA better understanding of the response of the spinal cord blood supply to segmental artery (SA) sacrifice should help minimize the risk of paraplegia after both open and endovascular repair of thoracoabdominal aortic (TAA) aneurysms.MethodsTwelve female juvenile Yorkshire pigs were randomized into 3 groups and perfused with a barium–latex solution. Pigs in group 1 (control) had infusion without previous intervention. Pigs in group 2 were infused 48 hours after ligation of all SAs (T4-L5) and those in group 3 at 120 hours after ligation. Postmortem computed tomographic scanning of the entire pig enabled overall comparisons and measurement of vessel diameters in the spinal cord circulation.ResultsWe ligated 14.5 ± 0.8 SAs: all filled retrograde to the ligature. Paraplegia occurred in 38% of operated pigs. A significant increase in the mean diameter of the anterior spinal artery (ASA) was evident after SA sacrifice (P < .0001 for 48 hours and 120 hours). The internal thoracic and intercostal arteries also increased in diameter. Quantitative assessment showed an increase in vessel density 48 hours after ligation of SAs, reflected by an obvious increase in small collateral vessels seen on 3-dimensional reconstructions of computed tomographic scans at 120 hours.ConclusionsRemodeling of the spinal cord blood supply—including dilatation of the ASA and proliferation of small collateral vessels—is evident at 48 and 120 hours after extensive SA sacrifice. It is likely that exploitation of this process will prove valuable in the quest to eliminate paraplegia after TAA aneurysm repair

The collateral network concept: Remodeling of the arterial collateral network after experimental segmental artery sacrifice

ObjectiveA comprehensive strategy to prevent paraplegia after open surgical or endovascular repair of thoracoabdominal aortic aneurysms requires a thorough understanding of the response of the collateral network to extensive segmental artery sacrifice.MethodsTen Yorkshire pigs underwent perfusion with a low-viscosity acrylic resin. With the use of cardiopulmonary bypass, 2 animals each were perfused in the native state and immediately, 6 hours, 24 hours, and 5 days after sacrifice of all segmental arteries (T4–L5). After digestion of surrounding tissue, the vascular cast of the collateral network underwent analysis of arterial and arteriolar diameters and the density and spatial orientation of the vasculature using light and scanning electron microscopy.ResultsWithin 24 hours, the diameter of the anterior spinal artery had increased significantly, and within 5 days the anterior spinal artery and the epidural arterial network had enlarged in diameter by 80% to 100% (P < .0001). By 5 days, the density of the intramuscular paraspinous vessels had increased (P < .0001), a shift of size distribution from small to larger arterioles was seen (P = .0002), and a significant realignment of arterioles parallel to the spinal cord had occurred (P = .0005).ConclusionsWithin 5 days after segmental artery occlusion, profound anatomic alterations in the intraspinal and paraspinous arteries and arterioles occurred, providing the anatomic substrate for preservation of spinal cord blood flow via collateral pathways

The fate of the distal aorta after repair of acute type A aortic dissection

ObjectivesThe residual aorta’s behavior after repair of acute type A dissection is incompletely understood. We analyzed segmental growth rates, distal reoperation, and factors influencing long-term survival.MethodsOne hundred seventy-nine consecutive patients (70% male; mean age, 60 years) with acute type A dissection underwent aggressive resection of the intimal tear and open distal anastomosis (1986-2003). Hospital mortality was 13.4%. Survivors had serial computed tomographic scans: digitization yielded distal segmental dimensions. Segment-specific average rates of enlargement and factors influencing faster growth were analyzed. Distal reoperations and patient survival were examined.ResultsEighty-nine (57%) patients had imaging data sufficient for growth rate calculations. The median diameters after repair were as follows: aortic arch, 3.6 cm; descending aorta, 3.7 cm; and abdominal aorta, 3.2 cm. Subsequent growth rates were 0.8, 1.0, and 0.8 mm/y, respectively. Initial size of greater than 4 cm (P = .005) and initial diameter of less than 4 cm with a patent false lumen (P = .004) predicted greater growth in the descending aorta, and male sex (P = .05) significantly affected growth in the abdominal aorta. No significant factors were found for the aortic arch. There were 25 distal aortic reoperations (16 patients), and risk of reoperation was 16% at 10 years. Risk factors reducing long-term survival after repair of acute type A dissection included age (P < .0001), new neurological deficit at presentation (P = .04), absence of preoperative thrombus in the false lumen of the ascending aorta (P = .03), and a patent distal false lumen postoperatively (P = .06) but not distal reoperation.ConclusionsGrowth of the distal aorta after repair of acute type A dissection is typically slow and linear. Distal reoperation is uncommon, and late risk of death is approximately twice that of a healthy population

Reoperative aortic root and transverse arch procedures: A comparison with contemporaneous primary operations

ObjectivesLong-term survival and risk factors affecting outcome after reoperative root/ascending aorta and transverse arch procedures have not been clearly described.MethodsTwo hundred patients (138 male patients; age, 60 ± 15 years) underwent reoperative root/ascending aorta (n = 100) or transverse arch (n = 100) procedures at our institution from January 1998 to December 2004 and were compared with 480 consecutive contemporaneous patients with primary procedures (323 male patients; age, 62 ± 16 years; 335 proximal aorta and 145 transverse arch procedures).ResultsReoperative proximal aorta procedures had a higher hospital mortality (7%) than primary root/ascending aorta procedures (3%), but there was a less dramatic difference in operative mortality after primary and reoperative arch procedures (9% vs 10%). Separate multivariable analyses of root/ascending aorta procedures and arch procedures revealed chronic obstructive pulmonary disease and age to be significant risk factors for death after either procedure. In addition, an ejection fraction of less than 30% posed a significant risk for proximal aortic surgery, and diabetes and nonelective operations predicted poorer outcome after arch operations. For survivors of root/ascending aorta operations, there was no significant difference in long-term outcome between reoperations and primary procedures, with both restoring longevity to expected levels for an age- and sex-matched normal population. Patients undergoing arch operations, however, continued to have a poorer long-term outlook than their normal peers.ConclusionsIn this series, reoperations in the transverse arch carry the same risk as primary arch procedures, but a higher operative mortality is seen with reoperative than with primary root/ascending aorta procedures. The long-term outlook is better for patients undergoing root/ascending operations than for patients undergoing aortic arch operations, with no difference in the longevity of patients undergoing primary procedures versus reoperations

The ARCH Projects: design and rationale (IAASSG 001)

OBJECTIVE A number of factors limit the effectiveness of current aortic arch studies in assessing optimal neuroprotection strategies, including insufficient patient numbers, heterogenous definitions of clinical variables, multiple technical strategies, inadequate reporting of surgical outcomes and a lack of collaborative effort. We have formed an international coalition of centres to provide more robust investigations into this topic. METHODS High-volume aortic arch centres were identified from the literature and contacted for recruitment. A Research Steering Committee of expert arch surgeons was convened to oversee the direction of the research. RESULTS The International Aortic Arch Surgery Study Group has been formed by 41 arch surgeons from 10 countries to better evaluate patient outcomes after aortic arch surgery. Several projects, including the establishment of a multi-institutional retrospective database, randomized controlled trials and a prospectively collected database, are currently underway. CONCLUSIONS Such a collaborative effort will herald a turning point in the surgical management of aortic arch pathologies and will provide better powered analyses to assess the impact of varying surgical techniques on mortality and morbidity, identify predictors for neurological and operative risk, formulate and validate risk predictor models and review long-term survival outcomes and quality-of-life after arch surger