Matrix metalloproteinase levels in chronic thoracic aortic dissection

BACKGROUND

Imbalance between matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) can lead to aortic wall failure. We hypothesized that patients with aneurysms resulting from chronic descending thoracic aortic dissection have elevated tissue and plasma levels of specific MMPs and decreased tissue levels of TIMPs.

MATERIALS AND METHODS

Aortic tissue was obtained from 25 patients who required surgical repair of descending thoracic aortic aneurysm due to chronic aortic dissection and from 17 organ-donor controls without aortic disease. Tissue levels of MMP-1, -2, -3, -9, -12, and -13 and TIMP-1 and -2 were measured by colorimetric activity assay or enzyme-linked immunosorbent assay and confirmed by Western blot and immunohistochemistry. Blood obtained from the 25 patients and 15 controls without aortic diseases was used to compare plasma levels of MMP-3, -9, and -12.

RESULTS

Total MMP-1, total MMP-9, and active MMP-9 levels were higher and total MMP-2 levels were lower in dissection tissue than in control tissue. Additionally, the MMP-9 to TIMP-1 and active to total MMP-2 ratios were higher and the MMP-2 to TIMP-2 ratio was lower in dissection tissue. Furthermore, patients had higher plasma active to total MMP-9 ratios than the controls. Age and hypertension were associated with increased MMP levels.

CONCLUSIONS

Increased levels of several MMPs and increased MMP to TIMP ratios in aortic tissue from patients suggest an environment that favors proteolysis, which may promote progressive extracellular matrix destruction and medial degeneration after aortic dissection. An elevated active to total MMP-9 ratio in plasma may be a biomarker for end-stage aneurysm development in patients with chronic thoracic aortic disease.

Valve-sparing aortic root replacement: early and midterm outcomes in 83 patients

BACKGROUND

Valve-sparing aortic root replacement (VSARR) is an alternative to traditional composite valve graft (CVG) root replacement. We examined early and midterm outcomes after VSARR.

METHODS

A combined retrospective/prospective study was performed in 83 patients who underwent VSARR (16%) among 515 patients who underwent aortic root replacement during a nearly 12-year period. Thirty-six patients (43%) had a connective tissue disorder, 3 patients (4%) had acute aortic dissection, and 40 (48%) patients had at least moderate aortic regurgitation (AR). Twenty-eight patients (34%) had left ventricular hypertrophy or dilatation. The reimplantation VSARR technique was used in 82 patients (99%), and the Florida sleeve technique was used in 1 patient. Thirty-two patients (39%) underwent concomitant aortic arch replacement. For early survivors, the median duration of follow-up was 3.5 years (range, 5 days-12.2 years).

RESULTS

One patient had severe AR after VSARR that necessitated intraoperative conversion to a mechanical CVG. The 1 operative death and 1 stroke occurred in a patient with acute dissection. Actuarial survival was 96.4%±2.0% at 2 years and 86.9%±5.6% at 8 years. Six patients (7%) had late valve-related complications: 1 died of endocarditis, 4 underwent reoperation for severe AR and received replacement valves, and 1 had severe AR and is being monitored. Freedom from repair failure (reoperation, endocarditis, or severe AR) was 94.8%±2.6% at 2 years and 87.3%±5.7% at 8 years.

CONCLUSIONS

Valve-sparing aortic root replacement can have excellent early and respectable midterm outcomes, even when combined with arch repair. Further follow-up remains necessary to evaluate the long-term durability of VSARR.

Inflammatory Cell Infiltrates in Acute and Chronic Thoracic Aortic Dissection

BACKGROUND

Thoracic aortic dissection (TAD) is a highly lethal cardiovascular disease. Injury to the intima and media allows pulsatile blood to enter the media, leading to dissection formation. Inflammatory cells then infiltrate the site of aortic injury to clear dead cells and damaged tissue. This excessive inflammation may play a role in aneurysm formation after dissection.

METHODS

Using immunohistochemistry, we compared aortic tissues from patients with acute TAD (n = 11), patients with chronic TAD (n = 35), and donor controls (n = 20) for the presence of CD68+ macrophages, neutrophils, mast cells, and CD3+ T lymphocytes.

RESULTS

Tissue samples from patients with acute or chronic TAD generally had significantly more inflammatory cells in both the medial and adventitial layers than did the control samples. In tissues from patients with acute TAD, the adventitia had more of the inflammatory cells studied than did the media. The pattern of increase in inflammatory cells was similar in chronic and acute TAD tissues, except for macrophages, which were seen more frequently in the adventitial layer of acute TAD tissue than in the adventitia of chronic TAD tissue.

CONCLUSIONS

The inflammatory cell content of both acute and chronic TAD tissue was significantly different from that of control tissue. However, the inflammatory cell profile of aneurysmal chronic TAD was similar to that of acute TAD. This may reflect a sustained injury response that contributes to medial degeneration and aneurysm formation.

Mitral valve disease in patients with Marfan syndrome undergoing aortic root replacement

BACKGROUND

Cardiac manifestations of Marfan syndrome include aortic root dilation and mitral valve prolapse (MVP). Only scant data exist describing MVP in patients with Marfan syndrome undergoing aortic root replacement.

METHODS AND RESULTS

We retrospectively analyzed data from 166 MFS patients with MVP who were enrolled in a prospective multicenter registry of patients who underwent aortic root aneurysm repair. Of these 166 patients, 9% had mitral regurgitation (MR) grade >2, and 10% had MR grade 2. The severity of MVP and MR was evaluated by echocardiography preoperatively and ≤ 3 years postoperatively. Forty-one patients (25%) underwent composite graft aortic valve replacement, and 125 patients (75%) underwent aortic valve-sparing procedures; both groups had similar prevalences of MR grade >2 (P=0.7). Thirty-three patients (20%) underwent concomitant mitral valve (MV) intervention (repair, n=29; replacement, n=4), including all 15 patients with MR grade >2. Only 1 patient required MV reintervention during follow-up (mean clinical follow-up, 31 ± 10 months). Echocardiography performed 21 ± 13 months postoperatively revealed MR >2 in only 3 patients (2%). One early death and 2 late deaths occurred.

CONCLUSIONS

Although the majority of patients with Marfan syndrome who undergo elective aortic root replacement have MVP, only 20% have concomitant MV procedures. These concomitant procedures do not seem to increase operative risk. In patients with MR grade ≤ 2 who do not undergo a concomitant MV procedure, the short-term incidence of progressive MR is low; however, more follow-up is needed to determine whether patients with MVP and MR grade ≤ 2 would benefit from prophylactic MV intervention.

Advanced atherosclerosis is associated with increased medial degeneration in sporadic ascending aortic aneurysms

OBJECTIVE

The pathogenesis of non-familial, sporadic ascending aortic aneurysms (SAAA) is poorly understood, and the relationship between ascending aortic atherosclerosis and medial degeneration is unclear. We evaluated the prevalence and severity of aortic atherosclerosis and its association with medial degeneration in SAAA.

METHODS AND RESULTS

Atherosclerosis was characterized in ascending aortic tissues collected from 68 SAAA patients (mean age, 62.9 ± 12.0 years) and 15 controls (mean age, 56.6 ± 11.4 years [P = 0.07]) by using a modified American Heart Association classification system. Upon histologic examination, 97% of SAAA patients and 73% of controls showed atherosclerotic changes. Most SAAA samples had intermediate (types 2 and 3, 35%) or advanced atherosclerosis (types ≥ 4; 40%), whereas most control samples showed minimal atherosclerosis (none or type 1, 80%; P < 0.001 after adjusting for age). In a separate analysis, we examined the total incidence and grade distribution of medial degenerative changes among SAAA samples according to atherosclerosis grade. Advanced atherosclerosis was associated with higher grades of smooth muscle cell depletion (P < 0.001), elastic fiber depletion (P = 0.02), elastic fiber fragmentation (P < 0.001), and mucopolysaccharide accumulation (P = 0.04). Aortic diameter was larger in SAAA patients with advanced atherosclerosis than in patients with minimal (P = 0.04) or intermediate atherosclerosis (P = 0.04). Immunostaining showed marked CD3+ T-cell and CD68+ macrophage infiltration, MMP-2 and MMP-9 production, and cryopyrin expression in the medial layer adjacent to atherosclerotic plaque.

CONCLUSIONS

SAAA tissues exhibited advanced atherosclerosis that was associated with severe medial degeneration and increased aortic diameter. Our findings suggest a role for atherosclerosis in the progression of sporadic ascending aortic aneurysms.

Molecular mechanisms of thoracic aortic dissection

Thoracic aortic dissection (TAD) is a highly lethal vascular disease. In many patients with TAD, the aorta progressively dilates and ultimately ruptures. Dissection formation, progression, and rupture cannot be reliably prevented pharmacologically because the molecular mechanisms of aortic wall degeneration are poorly understood. The key histopathologic feature of TAD is medial degeneration, a process characterized by smooth muscle cell depletion and extracellular matrix degradation. These structural changes have a profound impact on the functional properties of the aortic wall and can result from excessive protease-mediated destruction of the extracellular matrix, altered signaling pathways, and altered gene expression. Review of the literature reveals differences in the processes that lead to ascending versus descending and sporadic versus hereditary TAD. These differences add to the complexity of this disease. Although tremendous progress has been made in diagnosing and treating TAD, a better understanding of the molecular, cellular, and genetic mechanisms that cause this disease is necessary to developing more effective preventative and therapeutic treatment strategies.

A meta-analysis of deep hypothermic circulatory arrest versus moderate hypothermic circulatory arrest with selective antegrade cerebral perfusion

INTRODUCTION

A recent concern of deep hypothermic circulatory arrest (DHCA) in aortic arch surgery has been its potential association with increased risk of coagulopathy, elevated inflammatory response and end-organ dysfunction. Recently, moderate hypothermic circulatory arrest (MHCA) with selective antegrade circulatory arrest (SACP) seeks to negate potential hypothermia-related morbidities, while maintaining adequate neuroprotection. The present meta-analysis aims to compare postoperative outcomes in arch surgery using DHCA or MHCA+SACP as neuroprotective strategies.

METHODS

Electronic searches were performed using six databases from their inception to January 2013. Two reviewers independently identified all relevant studies comparing DHCA with MHCA+SACP, as defined by a recent hypothermia temperature consensus. Data were extracted and meta-analyzed according to pre-defined clinical endpoints.

RESULTS

Nine comparative studies were identified for inclusion in the present meta-analysis. Stroke rates were significantly lower in patients undergoing MHCA+SACP (P=0.0007, I(2)=0%), while comparable results were observed with temporary neurological deficit, mortality, renal failure or bleeding. Infrequent and inconsistent reporting of systemic outcomes precluded analysis of other systemic outcomes.

CONCLUSIONS

The present meta-analysis indicated the superiority of MHCA+SACP in terms of stroke risk.

Consensus on hypothermia in aortic arch surgery

Considered a standard part of aortic arch surgery, hypothermia can sufficiently reduce cerebral metabolic demand to permit reasonable periods of circulatory arrest. Yet despite its ubiquitous application and critical importance, temperature classification in hypothermic circulatory arrest is still without clear definition. The following Consensus from experts in high-volume aortic institutions defines 'profound', 'deep', 'moderate', and 'mild' hypothermia and recommends standardized monitoring sites, so as to facilitate more consistent reporting and robust analysis.

Total aortic arch replacement: current approach using the trifurcated graft technique

Since the pioneering work of DeBakey, Cooley, and colleagues more than 50 years ago, surgical treatment of aneurysms involving the transverse aortic arch has been associated with substantial morbidity and mortality. Over the past 15 years, techniques for replacing the diseased aortic arch have evolved substantially. Previously, our approach to these operations involved femoral cannulation, profound-to-deep hypothermic circulatory arrest and retrograde cerebral perfusion, and the island technique for reattaching the brachiocephalic vessels. In contrast, we currently use innominate artery cannulation, deep-to-moderate hypothermic circulatory arrest with antegrade cerebral perfusion, bilateral cerebral monitoring with near-infrared spectroscopy, and the trifurcated graft (Y-graft) technique for reattaching the arch branches. Cannulating the innominate artery to provide an inflow site for cardiopulmonary bypass has facilitated the use of antegrade cerebral perfusion as a cerebral protection strategy; the left common carotid artery is additionally perfused to provide bilateral cerebral perfusion. Despite having a systemic circulatory arrest time that often exceeds 60 minutes, these improved perfusion strategies make it possible to consistently avoid cerebral circulatory arrest all together. A moderate temperature target of between 18 and 23 °C is now used; this appears to reduce the risk of hypothermic coagulopathy and improve hemostasis. Y-graft techniques, such as the trifurcated graft approach, have the advantages of eliminating residual aortic arch tissue and being easily tailored to the needs of the individual patient. This report describes total aortic arch replacement in patients with aneurysms that are confined to the ascending aorta and transverse aortic arch.

Results of open thoracoabdominal aortic aneurysm repair

BACKGROUND

Open surgical repair of thoracoabdominal aortic aneurysms (TAAAs) enables the effective replacement of the diseased aortic segment and reliably prevents aneurysm rupture. However, these operations also carry substantial risk of perioperative morbidity and mortality, principally caused by the associated ischemic insult involving the spinal cord, kidneys, and other abdominal viscera. Here, we describe the early outcomes of a contemporary series of open TAAA repairs.

METHODS

We reviewed the outcomes of 823 open TAAA repairs performed between January 2005 and May 2012. Of these, 209 (25.4%) were Crawford extent I repairs, 264 (32.1%) were extent II, 157 (19.1%) were extent III, and 193 (23.5%) were extent IV. Aortic dissection was present in 350 (42.5%) cases, and aneurysm rupture was present in 37 (4.5%). Adjuncts used during the procedures included cerebrospinal fluid drainage in 639 (77.6%) cases, left heart bypass in 430 (52.2%), and cold renal perfusion in 674 (81.9%).

RESULTS

The composite endpoint, adverse outcome-defined as operative death, renal failure that necessitated dialysis at discharge, stroke, or permanent paraplegia or paraparesis-occurred after 131 (15.9%) procedures. There were 69 (8.4%) operative deaths. Permanent paraplegia or paraparesis occurred after 42 (5.1%) cases, stroke occurred after 27 (3.3%), and renal failure necessitating permanent dialysis occurred after 45 (5.5%).

CONCLUSIONS

Although open surgical repair of the thoracoabdominal aorta can be life-saving to patients at risk for fatal aneurysm rupture, these operations remain challenging and are associated with substantial risk of early death and major complications. Additional improvements are needed to further reduce the risks associated with TAAA repair, particularly as increasing numbers of patients with advanced age and multiple or severe comorbidities present for treatment.

A meta-analysis of deep hypothermic circulatory arrest alone versus with adjunctive selective antegrade cerebral perfusion

INTRODUCTION

Recognizing the importance of neuroprotection in aortic arch surgery, deep hypothermic circulatory arrest (DHCA) now underpins operative practice as it minimizes cerebral metabolic activity. When prolonged periods of circulatory arrest are required, selective antegrade cerebral perfusion (SACP) is supplemented as an adjunct. However, concerns exist over the risks of SACP in introducing embolism and hypo- and hyper-perfusing the brain. The present meta-analysis aims to compare postoperative outcomes in arch surgery using DHCA alone or DHCA + SACP as neuroprotection strategies.

METHODS

Electronic searches were performed using six databases from their inception to January 2013. Two reviewers independently identified all relevant studies comparing DHCA alone with DHCA + SACP. Data were extracted and meta-analyzed according to pre-defined clinical endpoints.

RESULTS

Nine comparative studies were identified in the present meta-analysis, with 648 patients employing DHCA alone and 370 utilizing DHCA + SACP. No significant differences in temporary or permanent neurological outcomes were identified. DHCA + SACP was associated with significantly better survival outcomes (P=0.008, I(2)=0%), despite longer cardiopulmonary bypass time. Infrequent and inconsistent reporting of other clinical results precluded analysis of systemic outcomes.

CONCLUSIONS

The present meta-analysis indicate the superiority of DHCA + SACP in terms of mortality outcomes.

GenTAC registry report: gender differences among individuals with genetically triggered thoracic aortic aneurysm and dissection

Previous data suggest women are at increased risk of death from aortic dissection. Therefore, we analyzed data from the GenTAC registry, the NIH-sponsored program that collects information about individuals with genetically triggered thoracic aortic aneurysms and cardiovascular conditions. We performed cross-sectional analyses in adults with Marfan syndrome (MFS), familial thoracic aortic aneurysm or dissection (FTAAD), bicuspid aortic valve (BAV) with thoracic aortic aneurysm or dissection, and subjects under 50 years of age with thoracic aortic aneurysm or dissection (TAAD <50 years). Women comprised 32% of 1,449 subjects and were 21% of subjects with BAV, 34% with FTAAD, 22% with TAAD <50 years, and 47% with MFS. Thoracic aortic dissections occurred with equal gender frequency yet women with BAV had more extensive dissections. Aortic size was smaller in women but was similar after controlling for BSA. Age at operation for aortic valve dysfunction, aneurysm or dissection did not differ by gender. Multivariate analysis (adjusting for age, BSA, hypertension, study site, diabetes, and subgroup diagnoses) showed that women had fewer total aortic surgeries (OR = 0.65, P < 0.01) and were less likely to receive angiotensin converting enzyme inhibitors (ACEi; OR = 0.68, P < 0.05). As in BAV, other genetically triggered aortic diseases such as FTAAD and TAAD <50 are more common in males. In women, decreased prevalence of aortic operations and less treatment with ACEi may be due to their smaller absolute aortic diameters. Longitudinal studies are needed to determine if women are at higher risk for adverse events.

AKT2 confers protection against aortic aneurysms and dissections

RATIONALE

Aortic aneurysm and dissection (AAD) are major diseases of the adult aorta caused by progressive medial degeneration of the aortic wall. Although the overproduction of destructive factors promotes tissue damage and disease progression, the role of protective pathways is unknown.

OBJECTIVE

In this study, we examined the role of AKT2 in protecting the aorta from developing AAD.

METHODS AND RESULTS

AKT2 and phospho-AKT levels were significantly downregulated in human thoracic AAD tissues, especially within the degenerative medial layer. Akt2-deficient mice showed abnormal elastic fibers and reduced medial thickness in the aortic wall. When challenged with angiotensin II, these mice developed aortic aneurysm, dissection, and rupture with features similar to those in humans, in both thoracic and abdominal segments. Aortas from Akt2-deficient mice displayed profound tissue destruction, apoptotic cell death, and inflammatory cell infiltration that were not observed in aortas from wild-type mice. In addition, angiotensin II-infused Akt2-deficient mice showed significantly elevated expression of matrix metalloproteinase-9 (MMP-9) and reduced expression of tissue inhibitor of metalloproteinase-1 (TIMP-1). In cultured human aortic vascular smooth muscle cells, AKT2 inhibited the expression of MMP-9 and stimulated the expression of TIMP-1 by preventing the binding of transcription factor forkhead box protein O1 to the MMP-9 and TIMP-1 promoters.

CONCLUSIONS

Impaired AKT2 signaling may contribute to increased susceptibility to the development of AAD. Our findings provide evidence of a mechanism that underlies the protective effects of AKT2 on the aortic wall and that may serve as a therapeutic target in the prevention of AAD.

Scientific impact of Association for Academic Surgery and Society of University Surgeons plenary session abstracts increases in the era of the Academic Surgical Congress from 2006 to 2010

BACKGROUND

The objective of our study was to analyze plenary abstracts since 2006, when the Association for Academic Surgery (AAS) and Society of University Surgeons (SUS) began hosting the combined annual Academic Surgical Congress (ASC). Plenary session abstracts from the separate AAS and SUS meetings from 2002 to 2004 had previously revealed no significant difference in the scientific impact of published manuscripts.

MATERIALS AND METHODS

In total, 76 abstracts from the AAS (n = 40) and SUS (n = 36) plenary sessions at the annual ASC meetings (2006-2010) were reviewed. Publication rate, citation number, 2010 impact factor (IF), and 5-y IF were obtained. Statistical analysis was conducted using Fisher exact and Student t-tests.

RESULTS

Overall, 60 (79%) of 76 ASC plenary abstracts presented between 2006 and 2010 were published in peer-reviewed journals. Analysis revealed a higher publication rate for AAS (90%) compared with SUS (67%) plenary abstracts (P = 0.02). Among the articles published, the overall mean number of total citations was 6.7, with no difference between AAS and SUS (5.9 versus 7.8, P = 0.46). The mean 2010 five-year IF for all publications was 4.6 (AAS, 4.3 versus SUS, 5.0; P = 0.54). Compared with a previous analysis from the separate meetings, the mean IF has increased for both societies at an equivalent rate of 0.4.

CONCLUSIONS

After the initiation of the joint ASC meeting in 2006, the SUS and AAS plenary presentations continue to exhibit high-quality research. This study supports the benefit of a joint meeting for the AAS and SUS, as it has been associated with an increasing overall scientific impact for plenary abstracts.

The natural history of moderate aortic stenosis in a veteran population

OBJECTIVE

Our objective was to evaluate the natural history of moderate aortic stenosis in veterans--a unique patient population with significant comorbidities.

METHODS

We retrospectively reviewed the records of all patients who underwent echocardiography at a single veterans affairs hospital during 2006. We identified consecutive patients who had moderate aortic stenosis as indicated by a mean transaortic gradient of 25 to 40 mm Hg, peak aortic jet velocity of 3 to 4 m/s, or aortic valve area of 1.0 to 1.5 cm(2). The primary end point was defined as survival without aortic valve replacement.

RESULTS

Of the 104 patients (mean age, 74 ± 10 years), 49% had diabetes, 21% had peripheral vascular disease, 21% were current smokers, 18% had chronic obstructive pulmonary disease, 60% had coronary artery disease, 89% had hypertension, and 31% had a body mass index of 30 kg/m(2) or more. Mean ejection fraction was 49% ± 12%. During the mean follow-up period of 22 months (range, 1-67 months), 30% of patients underwent aortic valve replacement--26% for symptomatic severe aortic stenosis and 4% concomitantly with coronary artery bypass grafting as the primary indicated operation--and 61% died. Event-free survivals were 48%, 24%, and 15% at 1, 3, and 5 years, respectively.

CONCLUSIONS

Our cohort of military veteran patients had significant comorbidities. Event-free survival for such patients who have moderate aortic stenosis is significantly lower than previously reported data suggest. Within this unique group of patients, identifying factors that accelerate the progression of moderate aortic stenosis would help surgeons select patients who may benefit from early aortic valve replacement for moderate aortic stenosis.