NLRP3 (Nucleotide Oligomerization Domain-Like Receptor Family, Pyrin Domain Containing 3)-Caspase-1 Inflammasome Degrades Contractile Proteins: Implications for Aortic Biomechanical Dysfunction and Aneurysm and Dissection Formation

OBJECTIVE

Increasing evidence suggests that contractile dysfunction in smooth muscle cells (SMCs) plays a critical role in aortic biomechanical dysfunction and aortic aneurysm and dissection (AAD) development. However, the mechanisms underlying SMC contractile dysfunction in sporadic AAD are poorly understood. In this study, we examined the role of the NLRP3 (nucleotide oligomerization domain-like receptor family, pyrin domain containing 3)-caspase-1 inflammasome, a key inflammatory cascade, in SMC contractile dysfunction in AAD.

APPROACH AND RESULTS

We observed significant SMC contractile protein degradation in aortas from patients with sporadic thoracic AAD. The contractile protein degradation was associated with activation of the NLRP3-caspase-1 inflammasome cascade. In SMCs, caspase-1 bound and directly cleaved and degraded contractile proteins, leading to contractile dysfunction. Furthermore, Nlrp3 or caspase-1 deficiency in mice significantly reduced angiotensin II-induced contractile protein degradation, biomechanical dysfunction, and AAD formation in both thoracic and abdominal aortas. Finally, blocking this cascade with the inflammasome inhibitor, glyburide (an antidiabetic medication), reduced angiotensin II-induced AAD formation.

CONCLUSIONS

Inflammasome-caspase-1-mediated degradation of SMC contractile proteins may contribute to aortic biomechanical dysfunction and AAD development. This cascade may be a therapeutic target in AAD formation. In addition, glyburide may have protective effects against AAD development.

Incidence, Predictors, and Impact of Postoperative Atrial Fibrillation after Coronary Artery Bypass Grafting in Military Veterans

Little is known about the frequency and clinical implications of postoperative atrial fibrillation in military veterans who undergo coronary artery bypass grafting (CABG). We examined long-term survival data, clinical outcomes, and associated risk factors in this population. We retrospectively reviewed baseline, intraoperative, and postoperative data from 1,248 consecutive patients with similar baseline risk profiles who underwent primary isolated CABG at a Veterans Affairs hospital from October 2006 through March 2013. Multivariable logistic regression identified predictors of postoperative atrial fibrillation. Kaplan-Meier analysis was used to evaluate long-term survival (the primary outcome measure), morbidity, and length of hospital stay. Postoperative atrial fibrillation occurred in 215 patients (17.2%). Independent predictors of this sequela were age ≥65 years (odds ratios [95% confidence intervals], 1.7 [1.3-2.4] for patients of age 65-75 yr and 2.6 [1.4-4.8] for patients >75 yr) and body mass index ≥30 kg/m² (2.0 [1.2-3.2]). Length of stay was longer for patients with postoperative atrial fibrillation than for those without (12.7 ± 6.6 vs 10.3 ± 8.9 d; P ≤0.0001), and the respective 30-day mortality rate was higher (1.9% vs 0.4%; P=0.014). Seven-year survival rates did not differ significantly. Older and obese patients are particularly at risk of postoperative atrial fibrillation after CABG. Patients who develop the sequela have longer hospital stays than, but similar long-term survival rates to, patients who do not.

Organ Protection During Thoracoabdominal Aortic Surgery: Rationale for a Multimodality Approach

Surgical repair of thoracoabdominal aortic aneurysms (TAAAs) remains a technically challenging operation that requires a systematic approach to prevent ischemic complications and achieve excellent clinical outcomes. Techniques for organ protection have evolved substantially over the past 20 years. This review describes our current multimodality approach to organ protection during TAAA repair.

Aortic Complications Associated With Pregnancy in Marfan Syndrome: The NHLBI National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC)

BACKGROUND

The risk of aortic complications associated with pregnancy in women with Marfan syndrome (MFS) is not fully understood.

METHODS AND RESULTS

MFS women participating in the large National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) were evaluated. Among 184 women with MFS in whom pregnancy information was available, 94 (51%) had a total of 227 pregnancies. Among the women with pregnancies, 10 (10.6%) experienced a pregnancy-related aortic complication (4 type A and 3 type B dissections, 1 coronary artery dissection, and 2 with significant [≥3 mm] aortic growth). Five of 7 aortic dissections, including all 3 type B, and the coronary dissection (75% of all dissections) occurred in the postpartum period. Only 5 of 8 women with pregnancy-associated dissection were aware of their MFS diagnosis. The rate of aortic dissection was higher during the pregnancy and postpartum period (5.4 per 100 person-years vs 0.6 per 100 person-years of nonpregnancy; rate ratio, 8.4 [95% CI=3.9, 18.4]; P<0.0001).

CONCLUSIONS

Pregnancy in MFS is associated with an increased risk of aortic dissection, both types A and B, particularly in the immediate postpartum period. Lack of knowledge of underlying MFS diagnosis before aortic dissection is a major contributing factor. These findings underscore the need for early diagnosis, prepregnancy risk counseling, and multidisciplinary peripartum management.

Extent II Thoracoabdominal Aortic Aneurysm Repair: How I Do It

The primary risks associated with thoracoabdominal aortic aneurysm (TAAA) repair-namely operative death, paraplegia, and renal failure necessitating dialysis-are commonly related to the distal ischemia that occurs during aortic clamping and the disruption of vital branching arteries. Our technique for open TAAA repair has evolved over the course of 3 decades, from the unheparinized, simple "clamp-and-sew" approach learned directly from E. Stanley Crawford himself to a contemporary, multimodal strategy that uses an array of surgical adjuncts. Today, our approach to TAAA repair is largely standardized and based on the Crawford extents of TAAA repair, but we have maintained flexibility to explore new techniques and to adapt to the specific needs of patients. To protect the spinal cord, we routinely use mild passive hypothermia, cerebrospinal fluid drainage, left heart bypass, and reimplantation of crucial intercostal or lumbar arteries. The renal arteries are perfused with cold solution to protect the kidneys from ischemic damage, and the celiac axis and superior mesenteric artery are perfused with isothermic blood from the left heart bypass circuit, which minimizes the duration of abdominal-organ ischemia. The most extensive repair, Crawford extent II repair, typically replaces the aorta from just beyond the left subclavian artery to the aortic bifurcation; unsurprisingly, it commonly poses greater operative risk than do less extensive TAAA repairs (extent I, III, and IV). Subsequently, most surgical adjuncts used today were developed to ameliorate risk in extent II repair. Here, we provide a detailed description of our approach to open extent II TAAA repair.

Shared Genetic Risk Factors of Intracranial, Abdominal, and Thoracic Aneurysms

BACKGROUND

Intracranial aneurysms (IAs), abdominal aortic aneurysms (AAAs), and thoracic aortic aneurysms (TAAs) all have a familial predisposition. Given that aneurysm types are known to co-occur, we hypothesized that there may be shared genetic risk factors for IAs, AAAs, and TAAs.

METHODS AND RESULTS

We performed a mega-analysis of 1000 Genomes Project-imputed genome-wide association study (GWAS) data of 4 previously published aneurysm cohorts: 2 IA cohorts (in total 1516 cases, 4305 controls), 1 AAA cohort (818 cases, 3004 controls), and 1 TAA cohort (760 cases, 2212 controls), and observed associations of 4 known IA, AAA, and/or TAA risk loci (9p21, 18q11, 15q21, and 2q33) with consistent effect directions in all 4 cohorts. We calculated polygenic scores based on IA-, AAA-, and TAA-associated SNPs and tested these scores for association to case-control status in the other aneurysm cohorts; this revealed no shared polygenic effects. Similarly, linkage disequilibrium-score regression analyses did not show significant correlations between any pair of aneurysm subtypes. Last, we evaluated the evidence for 14 previously published aneurysm risk single-nucleotide polymorphisms through collaboration in extended aneurysm cohorts, with a total of 6548 cases and 16 843 controls (IA) and 4391 cases and 37 904 controls (AAA), and found nominally significant associations for IA risk locus 18q11 near RBBP8 to AAA (odds ratio [OR]=1.11; P=4.1×10(-5)) and for TAA risk locus 15q21 near FBN1 to AAA (OR=1.07; P=1.1×10(-3)).

CONCLUSIONS

Although there was no evidence for polygenic overlap between IAs, AAAs, and TAAs, we found nominally significant effects of two established risk loci for IAs and TAAs in AAAs. These two loci will require further replication.

Endovascular Repair of Thoracic Aortic Disease: Overview of Current Devices and Clinical Results

Endovascular repair of thoracic aortic aneurysm has become an important treatment modality in patients who are at increased risk for open surgical repair. Since the US Food and Drug Administration (FDA) approved the clinical application of this technology in the thoracic aorta in 2005, there has been a rapid growth in this treatment modality as numerous endovascular devices have been introduced in the application of thoracic aortic pathology. Although thoracic aortic aneurysm is the only FDA-approved treatment indication for endovascular repair, this technology may lead to a broader clinical applicability in other thoracic pathologies. This article reviews the current endovascular devices designed for the treatment of thoracic aortic pathology. These devices are described, and the current clinical results are discussed.

Aortic Dissection in Patients With Genetically Mediated Aneurysms: Incidence and Predictors in the GenTAC Registry

BACKGROUND

Aortic dissection (AoD) is a serious complication of thoracic aortic aneurysm (TAA). Relative risk for AoD in relation to TAA etiology, incidence, and pattern after prophylactic TAA surgery are poorly understood.

OBJECTIVES

This study sought to determine the incidence, pattern, and relative risk for AoD among patients with genetically associated TAA.

METHODS

The population included adult GenTAC participants without AoD at baseline. Standardized core laboratory tests classified TAA etiology and measured aortic size. Follow-up was performed for AoD.

RESULTS

Bicuspid aortic valve (BAV) (39%) and Marfan syndrome (MFS) (22%) were the leading diagnoses in the studied GenTAC participants (n = 1,991). AoD occurred in 1.6% over 3.6 ± 2.0 years; 61% of AoD occurred in patients with MFS. Cumulative AoD incidence was 6-fold higher among patients with MFS (4.5%) versus others (0.7%; p < 0.001). MFS event rates were similarly elevated versus those in patients with BAV (0.3%; p < 0.001). AoD originated in the distal arch or descending aorta in 71%; 52% of affected patients, including 68% with MFS, had previously undergone aortic grafting. In patients with proximal aortic surgery, distal aortic size (descending thoracic, abdominal aorta) was larger among patients with AoD versus those without AoD (both p < 0.05), whereas the ascending aorta size was similar. Conversely, in patients without previous surgery, aortic root size was greater in patients with subsequent AoD (p < 0.05), whereas distal aortic segments were of similar size. MFS (odds ratio: 7.42; 95% confidence interval: 3.43 to 16.82; p < 0.001) and maximal aortic size (1.86 per cm; 95% confidence interval: 1.26 to 2.67; p = 0.001) were independently associated with AoD. Only 4 of 31 (13%) patients with AoD had pre-dissection images that fulfilled size criteria for prophylactic TAA surgery at a subsequent AoD site.

CONCLUSIONS

Among patients with genetically associated TAA, MFS augments risk for AoD even after TAA grafting. Although increased aortic size is a risk factor for subsequent AoD, events typically occur below established thresholds for prophylactic TAA repair.

AKT2 Promotes Bone Marrow Cell-Mediated Aortic Protection in Mice

BACKGROUND

Insufficient aortic protection and repair may contribute to the development of aortic aneurysms and dissections (AAD). However, mechanisms of aortic protection and repair are poorly understood. We have shown that the multifunctional kinase AKT2 plays an important role in protecting the aortic wall. Here, we examined whether AKT2 protects against AAD by promoting bone marrow cell (BMC)-mediated aortic protection.

METHODS

Irradiated wild-type mice received green fluorescent protein-expressing BMCs from wild-type mice or Akt2(-/-) mice, followed by challenge with angiotensin II (1000 ng/kg/min) infusion for 4 weeks. We compared BMC recruitment, aortic destruction, and AAD development between groups. The direct effects of wild-type and Akt2(-/-) BMCs on smooth muscle cell survival were examined in coculture experiments.

RESULTS

After angiotensin II infusion, no (0 of 14) wild-type BMC recipients had AAD; in contrast, 64% (9 of 14) of Akt2(-/-) BMC recipients had AAD (p = 0.002) with severe aortic destruction. Compared with aortas from challenged wild-type BMC recipients, aortas from challenged Akt2(-/-) BMC recipients showed significantly less BMC recruitment, NG2 (neuron-glial antigen 2) progenitor activation, and FSP1 (fibroblast-specific protein 1) fibroblast activation. In addition, aortas from challenged Akt2(-/-) BMC recipients showed increased apoptosis and inflammation. In coculture experiments, wild-type but not Akt2(-/-) BMCs prevented smooth muscle cells from undergoing oxidative stress-induced apoptosis.

CONCLUSIONS

After aortic challenge, BMCs are recruited to the aortic wall and provide protection by activating progenitors and fibroblasts and by promoting aortic cell survival. Our findings indicate that AKT2 is involved in these processes and that defects in this pathway may promote progressive degeneration during AAD development.

Asprosin, a Fasting-Induced Glucogenic Protein Hormone

Hepatic glucose release into the circulation is vital for brain function and survival during periods of fasting and is modulated by an array of hormones that precisely regulate plasma glucose levels. We have identified a fasting-induced protein hormone that modulates hepatic glucose release. It is the C-terminal cleavage product of profibrillin, and we name it Asprosin. Asprosin is secreted by white adipose, circulates at nanomolar levels, and is recruited to the liver, where it activates the G protein-cAMP-PKA pathway, resulting in rapid glucose release into the circulation. Humans and mice with insulin resistance show pathologically elevated plasma asprosin, and its loss of function via immunologic or genetic means has a profound glucose- and insulin-lowering effect secondary to reduced hepatic glucose release. Asprosin represents a glucogenic protein hormone, and therapeutically targeting it may be beneficial in type II diabetes and metabolic syndrome.

Hepatopancreaticobiliary Values after Thoracoabdominal Aneurysm Repair

BACKGROUND

After thoracoabdominal aortic aneurysm (TAAA) repair, blood tests assessing hepatopancreaticobiliary (HPB) organs commonly have abnormal results. The clinical significance of such abnormalities is difficult to determine because the expected postoperative levels have not been characterized. Therefore, we sought to establish expected trends in HPB laboratory values after TAAA repair.

METHODS

This 5-year study comprised 155 patients undergoing elective Crawford extent II TAAA repair. In accordance with a prospective study protocol, all repairs involved left-sided heart bypass, selective visceral perfusion, and cold renal perfusion. Blood levels of aspartate transaminase (AST), alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH), total bilirubin, amylase, and lipase were measured before TAAA repair and for 7 days afterward. Ratios between postoperative and baseline levels were compared for each time point with 95% confidence intervals.

RESULTS

Temporal patterns for the laboratory values varied greatly. Amylase, lipase, and AST underwent significant early increases before decreasing to preoperative levels. LDH increased immediately and remained significantly elevated, whereas ALT increased more gradually. GGT remained near baseline through postoperative day 4, and then increased to more than twice baseline. Total bilirubin never differed significantly from baseline. After adjusted analysis, the ischemic time predicted the maximum AST, lipase, GGT, and LDH values.

CONCLUSIONS

Although most HPB laboratory values increase significantly after elective TAAA repair, the temporal trends for different values vary substantially. The ischemic time predicts the maximum AST, lipase, GGT, and LDH levels. These trends should be considered when laboratory values are assessed after TAAA repair.

Open aortic arch repair: state-of-the-art and future perspectives

Surgical procedures for the treatment of complex aortic arch pathology remain among the most challenging cardiovascular operations, incurring considerable risk for death and stroke. The purpose of this article is to describe the evolution of our approach to open repair of the aortic arch. Our arterial cannulation strategy has shifted from femoral and direct aortic to right axillary and more recently innominate artery cannulation. This transition has facilitated the administration of continuous antegrade cerebral perfusion and more moderate levels of hypothermia during complex repairs. Modifications in surgical technique, including arch reconstruction with the trifurcated graft, and the classical and frozen elephant trunk techniques have simplified the conduct of the operation. Experimental and clinical research supporting the evolution of our approach is discussed in this paper.

Valve-sparing aortic root replacement in patients with Marfan syndrome enrolled in the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions

BACKGROUND AND AIM OF THE STUDY

The long-term outcomes of aortic valve-sparing (AVS) root replacement in Marfan syndrome (MFS) patients remain uncertain. The study aim was to determine the utilization and outcomes of AVS root replacement in MFS patients enrolled in the Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC).

METHODS

At the time of this analysis, 788 patients with MFS were enrolled in the GenTAC Registry, of whom 288 had undergone aortic root replacement. Patients who had undergone AVS procedures were compared to those who had undergone aortic valve replacement (AVR).

RESULTS

AVS root replacement was performed in 43.5% of MFS patients, and the frequency of AVS was increased over the past five years. AVS patients were younger at the time of surgery (31.0 versus 36.3 years, p = 0.006) and more likely to have had elective rather than emergency surgery compared to AVR patients, in whom aortic valve dysfunction and aortic dissection was the more likely primary indication for surgery. After a mean follow up of 6.2 +/- 3.6 years, none of the 87 AVS patients had required reoperation; in contrast, after a mean follow up of 10.5 +/- 7.6 years, 11.5% of AVR patients required aortic root reoperation. Aortic valve function has been durable, with 95.8% of AVS patients having aortic insufficiency that was graded as mild or less.

CONCLUSION

AVS root replacement is performed commonly among the MFS population, and the durability of the aortic repair and aortic valve function have been excellent to date. These results justify a continued use of the procedure in an elective setting. The GenTAC Registry will be a useful resource to assess the long-term durability of AVS root replacement in the future.

Endovascular repair as a bridge to surgical repair of an aortobronchial fistula complicating chronic residual aortic dissection

Endovascular and open surgical repair have been used in patients with descending thoracic aortic dissection; however, the appropriate treatment is debated. We describe the case of a 60-year-old woman who had a symptomatic, chronic, residual, descending thoracic aortic dissection that was complicated by an aortobronchial fistula. She underwent emergent thoracic endovascular stent-grafting but remained symptomatic. Computed tomographic angiograms showed a contained rupture into the lower lobe of the left lung. The patient underwent definitive surgery to remove the stents, reconstruct the aorta, and resect the nonviable lung tissue. The remainder of her postoperative course was uneventful, and she was discharged from the hospital 13 days after the 2nd operation. Results of genetic testing confirmed an earlier presumptive diagnosis of Marfan syndrome. In an emergency, the best initial option for patients with a complicated descending thoracic aortic dissection might be thoracic endovascular aortic repair, which could serve as a bridge to definitive open repair.