Uptake of 18F-FDG in Acute Aortic Dissection: A Determinant of Unfavorable Outcome

The prognostic value of preoperative systemic inflammatory response index in predicting outcomes of acute type A aortic dissection patients underwent surgical treatment

Background

The systemic inflammatory response index (SIRI) is a novel inflammatory-immune biological marker that has prognostic value in various cardiovascular diseases. This study aims to investigate the relationship between SIRI and short-term and long-term prognosis in patients with acute type A aortic dissection (AAAD) underwent surgical treatment.

Methods

We conducted a retrospective analysis of patients with AAAD who underwent emergency surgical treatment at our center. Through multifactorial logistics regression analysis and cox proportional hazards regression analysis, we identified SIRI as an independent risk factor for major adverse events (MAEs) and long-term aorta-related adverse events (ARAEs) post-surgery. The optimal cutoff value of preoperative SIRI was determined using receiver operating characteristic (ROC) curve analysis, and patients were divided into low SIRI group and high SIRI group. The prognostic outcomes at different time points post-surgery for the two groups of patients were analyzed using Kaplan-Meier survival analysis, and the significance was determined by log-rank test.

Results

A total of 691 AAAD patients were included in this study. Among them, 50 patients (7.2%) died within 30 days post-surgery, and 175 patients (25.3%) experienced MAEs. A total of 641 patients were followed up, with an average follow-up time of 33.5 ± 17.5 months, during which 113 patients (17.6%) experienced ARAEs. The results of multifactorial logistics regression analysis and cox proportional hazards regression analysis showed that SIRI was an independent risk factor for postoperative MAEs (OR=3.148, 95%CI[1.650-6.006], p<0.001) and ARAEs (HR=2.248, 95%CI[1.050-4.809], p<0.037). Kaplan-Meier analysis demonstrated that the MAEs-free survival in the high SIRI group was significantly lower than that in the low SIRI group, and a similar trend was observed in the ARAEs-free survival during follow-up (log-rank test, p<0.001).

Conclusion

Preoperative SIRI is significantly associated with the short-term and long-term prognosis of AAAD patients underwent emergency open surgery, demonstrating its valuable prognostic value. Therefore, preoperative SIRI is a reliable biological marker that can serve as a valuable tool for preoperative risk stratification and decision management.

Systemic immune-inflammation index predicts the clinical outcomes in patients with acute uncomplicated type-B aortic dissection undergoing optimal medical therapy

BACKGROUND

Optimal medical therapy (OMT) for uncomplicated type B aortic dissection (uTBAD) provides excellent short-term outcomes during follow up; however, its long-term therapeutic effectiveness is unsatisfactory. This study evaluated the predictive value of systemic immune-inflammation index (SII) for adverse events among patients with acute uTBAD undergoing OMT.

METHODS

We performed a retrospective analysis of a prospectively maintained database between 2013 and 2020. The primary end point in this study was composite outcomes including aortic intervention, all-cause mortality, retrograde type A aortic dissection (rTAAD) and aortic diameter growth > 5 mm. The patients were divided into high and low SII groups according to the optimal cut-off value of SII as determined using the receiver operating characteristic curve. Cox proportional hazards models were constructed to estimate the hazards ratios and identify the predictors of composite outcomes.

RESULTS

A total of 124 patients with acute uTBAD who underwent OMT were enrolled. One patient died during hospitalisation. At the end of a mean follow-up duration of 51 ± 23 months, 53 (43.1%) patients experienced composite outcomes, 15 patients (12.2%) died, 31 (25.2%) underwent aortic intervention, 21 (17.1%) exhibited diameter growth of > 5 mm, and 2 developed rTAAD. The patients were divided into low SII group (n = 78, 62.9%) and high SII group (n = 46, 37.1%) as per the optimal cut-off SII value of 1449. The incidence of composite outcomes in high SII group was significantly higher than that in low SII (28 [60.9%] vs. 26[33.3%], p < 0.01). Patients with high SII demonstrated significantly higher mortality rate than those with a low SII (11 [23.9%] vs. 5 [6.4%], respectively; p < 0.01). In addition, the high SII group had significantly higher rate of aortic-related reinterventions than the low SII group (16 [34.8%] vs. 15 [19.2%], p = 0.03). Multivariable Cox analyses showed that a high SII score was independently associated with composite outcomes rate (hazard ratio, 2.15; 95% confidence interval, 1.22-3.78; p < 0.01).

CONCLUSIONS

The long-term therapeutic effectiveness of OMT alone in patients with acute uTBAD is unsatisfactory. An SII > 1449 at the time of diagnosis is an independent predictor of OMT failure.

Longitudinal Assessment of Inflammatory Activity in Acute Type B Aortic Dissection with Integrated Fluorodeoxyglucose Positron Emission Tomography/Magnetic Resonance Imaging

OBJECTIVE

The significance of the inflammatory response in the natural course of acute type B aortic dissection (ATBAD) is unknown. The aim was to characterise inflammation and its transformation over time in ATBAD using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) with contrast enhanced magnetic resonance imaging (MRI).

METHODS

Ten patients underwent FDG-PET/MRI within two weeks of ATBAD (acute phase), three to four months (subacute phase), nine to 12 months (early chronic phase), and 21 to 24 months (late chronic phase) after ATBAD. Target background ratios (TBRs) were measured in the ascending aorta, aortic arch, and descending aorta. MRI inflammatory markers were assessed in the descending aorta.

RESULTS

Ten patients were included: median age 69 years, median clinical follow up 32 months. In the acute phase there was increased FDG uptake in the descending aorta (maximum TBR 5.8, SD [standard deviation] 1.3) compared with the ascending aorta (TBR 3.3, SD 0.8, p < .010) and arch (TBR 4.2, SD 0.6, p = .010). The maximum TBR of the descending aorta decreased from the acute to subacute phase (TBR 3.5, SD 0.6, p = .010) and further to the early chronic phase (TBR 2.9, SD 0.4, p = .030) but was stable thereafter. The acute phase maximum TBR in the ascending aorta (TBR 3.3) and arch (TBR 4.2) decreased to the subacute phase (ascending: TBR 2.8, SD 0.6, p = .020; arch: TBR 2.7, SD 0.4, p = .010) and was stable thereafter. Four patients underwent surgical aortic repair (three for aortic dilatation at one, five, and 28 months and one for visceral ischaemia at three weeks). MRI signs of inflammation were present in all surgically treated patients vs. two of six of medically treated patients (p= .048).

CONCLUSION

ATBAD is associated with increased FDG uptake in the acute phase primarily in the descending aorta, but also involving the aortic arch and ascending aorta, indicating an inflammatory response in the whole aorta. Inflammation subsides early in the ascending aorta and arch (three months), whereas it stabilised later in the descending aorta (nine to 12 months). MRI signs of inflammation were more frequent in patients who later needed surgical treatment and merit further investigation.

The mechanism and therapy of aortic aneurysms

Aortic aneurysm is a chronic aortic disease affected by many factors. Although it is generally asymptomatic, it poses a significant threat to human life due to a high risk of rupture. Because of its strong concealment, it is difficult to diagnose the disease in the early stage. At present, there are no effective drugs for the treatment of aneurysms. Surgical intervention and endovascular treatment are the only therapies. Although current studies have discovered that inflammatory responses as well as the production and activation of various proteases promote aortic aneurysm, the specific mechanisms remain unclear. Researchers are further exploring the pathogenesis of aneurysms to find new targets for diagnosis and treatment. To better understand aortic aneurysm, this review elaborates on the discovery history of aortic aneurysm, main classification and clinical manifestations, related molecular mechanisms, clinical cohort studies and animal models, with the ultimate goal of providing insights into the treatment of this devastating disease. The underlying problem with aneurysm disease is weakening of the aortic wall, leading to progressive dilation. If not treated in time, the aortic aneurysm eventually ruptures. An aortic aneurysm is a local enlargement of an artery caused by a weakening of the aortic wall. The disease is usually asymptomatic but leads to high mortality due to the risk of artery rupture.

Imaging surveillance for complications after primary surgery for type A aortic dissection

Acute type A aortic dissection (ATAAD) is a life-threatening condition that requires emergency surgery to avert fatal outcome. Conventional surgical procedures comprise excision of the entry tear and replacement of the proximal aorta with a synthetic vascular graft. In patients with DeBakey type I dissection, this approach leaves a chronically dissected distal aorta, putting them at risk for progressive dilatation, dissection propagation and aortic rupture. Therefore, ATAAD survivors should undergo serial imaging for evaluation of the aortic valve, proximal and distal anastomoses, and the aortic segments beyond the distal anastomosis. The current narrative review aims to describe potential complications in the early and late phases after ATAAD surgery, with focus on their specific imaging findings.

Usefulness of 18F-FDG PET/computed tomography in differentiating between subacute and chronic aortic dissection: initial investigation

OBJECTIVES

In the selection of thoracic endovascular repair for aortic dissection (AD), it is important to distinguish between the subacute and chronic phases, but there is no reliable way to distinguish between them in patients with unknown onset of AD. The purpose of this study was to assess the diagnostic performance of 2-[18F] fluoro-2-deoxy-d-glucose (18F-FDG)-PET/computed tomography (PET/CT) for discriminating subacute AD from chronic AD.

METHODS

Thirteen patients with AD who were medically treated and followed up for 6 months were studied. 18F-FDG PET/CT images were obtained for each patient in the subacute phase (the first scan) and at 6 months (the second scan) after the onset. Target-to-background ratio (TBR) was measured as the maximum standardized uptake value (SUV) in the dissected aortic wall divided by blood pool SUV.

RESULTS

TBR was significantly higher in the first scan (mean ± SD, 1.97 ± 0.32) than in the second scan (1.69 ± 0.29, P = 0.007). The area under the receiver operating characteristic curve of TBR for discriminating subacute AD from chronic AD was 0.76. With a threshold of 1.74, the TBR showed the sensitivity, specificity, and positive and negative predictive value of 85%, 69%, 73%, and 82%, respectively, for the discrimination of subacute AD from chronic AD.

CONCLUSION

Metabolic assessment of dissected aortic wall by 18F-FDG PET/CT is useful in differentiating between subacute and chronic AD and can provide important information in determining the appropriate indication for treatment for patients with AD of unknown onset.

Systemic immune-inflammation index predicted the clinical outcome in patients with type-B aortic dissection undergoing thoracic endovascular repair

BACKGROUND

The systemic immune-inflammation index (SII) has been reported to have prognostic ability in various cardiovascular diseases; however, it has not been studied in type-B aortic dissection (TBAD). We aimed to explore the relation of SII with short-term and long-term outcomes in TBAD patients undergoing thoracic endovascular repair (TEVAR).

METHODS

We performed a retrospective analysis of a prospectively maintained database from 2010 to 2017. The patients were divided into two groups (high SII and low SII) as per the optimal cut-off value determined using the receiver operating characteristic curve. Multivariate logistic and Cox regression analyses were performed to analyse the relationship between the SII and the short-term and long-term outcomes.

RESULTS

A total of 805 TBAD patients who underwent TEVAR were enrolled. Twenty-six (3.2%) patients died during hospitalisation. At the end of a median follow-up duration of 48.80 mon, 70 (9.8%) patients had died. The patients were divided into the high-SII group [n = 333 (41.4%%)] and the low-SII group [n = 472 (58.6%)] as per the optimal cut-off value of 1,062. Multivariable logistic analyses showed that a high-SII score was independently associated with major adverse cardiovascular events (MACEs) in-hospital (odd ratio [OR], 1.67; 95% confidence interval [CI], 1.13-2.47; p = .01). In addition, multivariable Cox analyses showed that a high-SII score could be an independent indicator for follow-up adverse events (hazard ratio [HR], 1.70; 95% CI, 1.14-2.56, p = .01).

CONCLUSIONS

Systemic immune-inflammation index is associated with both in-hospital and long-term outcomes in patients with TBAD undergoing TEVAR. Therefore, SII may serve as valuable tool for risk stratification before intervention.

Association Between Preoperative Monocyte to High-Density Lipoprotein Ratio on In-hospital and Long-Term Mortality in Patients Undergoing Endovascular Repair for Acute Type B Aortic Dissection

Aims: The monocyte to high-density lipoprotein ratio (MHR), a novel marker of inflammation and cardiovascular events, has recently been found to facilitate the diagnosis of acute aortic dissection. This study aimed to assess the association of preoperative MHR with in-hospital and long-term mortality after thoracic endovascular aortic repair (TEVAR) for acute type B aortic dissection (TBAD).

Methods: We retrospectively evaluated 637 patients with acute TBAD who underwent TEVAR from a prospectively maintained database. Multivariable logistic and cox regression analyses were conducted to assess the relationship between preoperative MHR and in-hospital as well as long-term mortality. For clinical use, MHR was modeled as a continuous variable and a categorical variable with the optimal cutoff evaluated by receiver operator characteristic curve for long-term mortality. Propensity score matching was used to diminish baseline differences and subgroups analyses were conducted to assess the robustness of the results.

Results: Twenty-one (3.3%) patients died during hospitalization and 52 deaths (8.4%) were documented after a median follow-up of 48.1 months. The optimal cutoff value was 1.13 selected according to the receiver operator characteristic curve (sensitivity 78.8%; specificity 58.9%). Multivariate analyses showed that MHR was independently associated with either in-hospital death [odds ratio (OR) 2.11, 95% confidence interval (CI) 1.16-3.85, P = 0.015] or long-term mortality [hazard ratio (HR) 1.78, 95% CI 1.31-2.41, P < 0.001). As a categorical variable, MHR > 1.13 remained an independent predictor of in-hospital death (OR 4.53, 95% CI 1.44-14.30, P = 0.010) and long-term mortality (HR 4.16, 95% CI 2.13-8.10, P < 0.001). Propensity score analyses demonstrated similar results for both in-hospital death and long-term mortality. The association was further confirmed by subgroup analyses.

Conclusions: MHR might be useful for identifying patients at high risk of in-hospital and long-term mortality, which could be integrated into risk stratification strategies for acute TBAD patients undergoing TEVAR.

Diagnostic value of monocyte to high-density lipoprotein ratio in acute aortic dissection in a Chinese han population

Background: Recently, considerable evidence pointed out monocyte to high-density lipoprotein ratio (MHR) is highly related to inflammatory related diseases. We aim to explore the level of MHR in acute aortic dissection (AAD) patients and determine whether MHR can be a novel diagnostic marker of AAD. Research design and methods: A total of 228 subjects including 128 AAD patients and 110 healthy control were enrolled. MHR levels and other serum samples were obtained at admission. Results: The baseline MHR levels were significantly higher in patients with AAD (p < 0.0001). A cutoff value of MHR >0.37 was associated with a sensitivity of 86.70% and a specificity of 93.60% for AAD. MHR levels were positively correlated with the time from symptom onset (R² = 0.0318, p = 0.0003). Additionally, the area under the curve (AUC) was increased to 0.979 in patients whose time from onset of symptoms >24 h, with a sensitivity of 98.04% and a specificity of 93.64%. Multivariate logistic regression demonstrated that MHR levels, history of hypertension, and coronary artery disease (CHD) emerged as independent predictors of AAD. Expert Opinion: MHR has a high diagnostic value in AAD patients, especially in those whose time from onset of symptoms >24 h.

Acute Aortic Dissection Initially Suspected on 18F-FDG PET/CT

A 64-year-old man with anal cancer underwent follow-up F-FDG PET/CT to evaluate chemoradiation therapy response 5 months after an initial PET/CT. The follow-up F-FDG PET/CT demonstrated new FDG-avid curvilinear soft tissue adjacent to the abdominal aorta, interpreted as an aortic dissection. Despite lack of clinical symptoms, the patient was directed to an emergency room the same day, where a contrast-enhanced CT confirmed an aortic aneurysm with dissection. The patient underwent endovascular surgical repair the following day. This case demonstrates that newly FDG-avid aortic soft tissue should be recognized and may need further evaluation to characterize clinically significant vascular pathology.

18F-FDG uptake as a predictive factor for progressive aortic enlargement in aortic dissection

OBJECTIVE

Progressive aortic enlargement (PAE) is a critical adverse event in patients with medically treated aortic dissection (AD). However, no reliable predictor of the PAE has been established. The purpose of this study was to evaluate the value of ¹⁸F-FDG PET/CT for the prediction of PAE in patients with medically treated AD.

METHODS

Sixteen patients with AD who underwent optimal medical therapy were enrolled. ¹⁸F-FDG PET/CT examinations were performed in subacute phase (2 weeks-3 months) after the onset of AD. Target-to-background ratio (TBR) was measured as the maximum standardized uptake value (SUV) in the dissected aortic wall divided by blood pool SUV. The relation between TBR and occurrence of PAE (> 10 mm/year) was evaluated.

RESULTS

PAE was observed in four patients during the median follow-up period of 24 months. The TBR measured in the 4 patients showing PAE was significantly higher than that in the remaining 12 patients without PAE (2.44 ± 0.56 vs 1.87 ± 0.33, P = 0.025). The area under the receiver operating characteristic curve of TBR for predicting PAE was 0.82. With a threshold of 2.34, the TBR showed the sensitivity, specificity, and positive and negative predictive value of 75%, 92%, 75%, and 92%, respectively, for the prediction of PAE.

CONCLUSIONS

Higher ¹⁸F-FDG uptake in the dissected aortic wall as determined by TBR is associated with increased risk of PAE in patients with medically treated AD. TBR shows good specificity and negative predictive value for predicting PAE.

Prognostic Role of Admission C-Reactive Protein Level as a Predictor of In-Hospital Mortality in Type-A Acute Aortic Dissection: A Meta-Analysis

BACKGROUND

Acute aortic dissection (AD) is a lethal vascular disease, accounting for over 90% cases of acute aortic syndrome. Despite advances in understanding associated risk factors, the long-term prognosis for AD patients is still poor. Several prognostic biomarkers have been used for AD as per the IRAD, such as older age (>70 years), onset of chest pain and hypotension, but they are not effective in all patients. Instead, C-reactive protein (CRP) is a consistent inflammatory marker. CRP levels are abnormally increased in AD. However, the prognostic value of serum CRP level in AD remains unclear.

OBJECTIVE

To perform a systematic review and meta-analysis (registration no CRD42017056205) to evaluate whether CRP is a biomarker associated with in-hospital mortality in type-A AD.

METHODS

PubMed, Web of Science, CNKI, SciELO, and EMBASE were searched for papers published from January 2000 to October 2017 for studies on the prognostic role of CRP at admission in type-A AD patients. Outcome data were extracted and pooled hazard ratios (HRs) were calculated.

RESULTS

18 (N = 2875 patients) studies met the inclusion criteria. Elevated CRP level was associated with a significantly increased risk of in-hospital mortality in patients with type-A AD (HR = 1.15, 95% CI: 1.06-1.25, p = 0.001). The pooled sensitivity of CRP in type-A AD patients was 77% (95% CI 69%-84%, p < 0.001), and the specificity was 72% (95% CI 66%-78%, p < 0.001).

CONCLUSION

Elevated CRP level is significantly associated with increased risks of in-hospital mortality in patients with type-A AD. CRP is a convenient prognostic factor in type-A AD patients.

STAT3 Activation Correlates with Adventitial Neutrophil Infiltration in Human Aortic Dissection

Objective: Aortic dissection (AD) is a fatal disease that is caused by the rapid destruction of the aortic wall. Although recent studies in animal models indicate an important relationship between inflammation and tissue destruction, activation status of inflammatory signaling and its relation to the inflammatory cell infiltration are poorly characterized in human AD.

Materials and Methods: We examined the activation of inflammatory signaling molecules NFκB and STAT3, and neutrophil infiltration in AD tissue samples that were obtained during the surgical repair within 24 h after AD onset.

Results: Activation of NFκB was observed mainly in the intima both in AD samples and in aortic samples without AD. Activation of STAT3 was observed in AD samples, but not in the aortic sample without AD. Neutrophil infiltration was observed predominantly in the adventitial layer of AD samples. Histological analysis revealed that STAT3 was activated in cells other than neutrophils. Notably, STAT3 activation and neutrophil infiltration showed positive correlation in adventitial layer of AD tissue.

Conclusion: These findings demonstrated that adventitial STAT3 activation was associated with neutrophil infiltration, suggesting their importance in AD pathogenesis.

Predictive value of 18F-FDG PET/CT in patients with acute type B aortic intramural hematoma

BACKGROUND

The clinical course and predictors of adverse aortic events (AAE) in patients with acute Stanford type B intramural hematoma (IMH) remain controversial. This study aimed to investigate whether 18F-FDG PET/CT can predict risk in patients with acute type B IMH.

METHODS AND RESULTS

This study included 34 patients with acute type B IMH who underwent PET/CT within 14 days from the onset of symptoms. The maximal standardized uptake values (SUVmax) of 18F-FDG uptake was significantly different between patients with or without AAE (4.3 ± 0.6 vs 3.7 ± 1.0, P = 0.020), but not the target to blood ratio (TBR, SUVmax divided by SUV in the superior vena cava) (1.6 ± 0.2 vs 1.5 ± 0.5, P = 0.064). In patients with initial ulcer-like projection (ULP), a blood-filled pouch protruding into the IMH, which was seen in 25 patients(74%), both the SUVmax and TBR were significantly higher in patients who developed AAE, (4.3 ± 0.6 vs 3.3 ± 0.5, P = 0.001; 1.6 ± 0.2 vs 1.4 ± 0.2, P = 0.01); the TBR >1.5, which is determined from receiver-operating-characteristic curve, had a sensitivity of 73% and a specificity of 80% in predicting AAE.

CONCLUSION

Patients with ULP and high 18F-FDG uptake were more likely to develop AAE and may require closer surveillance with serial imaging.

LNK deficiency promotes acute aortic dissection and rupture

Aortic dissection (AD) is a life-threatening vascular disease with limited treatment strategies. Here, we show that loss of the GWAS-identified SH2B3 gene, encoding lymphocyte adaptor protein LNK, markedly increases susceptibility to acute AD and rupture in response to angiotensin (Ang) II infusion. As early as day 3 following Ang II infusion, prior to the development of AD, Lnk-/- aortas display altered mechanical properties, increased elastin breaks, collagen thinning, enhanced neutrophil accumulation, and increased MMP-9 activity compared with WT mice. Adoptive transfer of Lnk-/- leukocytes into Rag1-/- mice induces AD and rupture in response to Ang II, demonstrating that LNK deficiency in hematopoietic cells plays a key role in this disease. Interestingly, treatment with doxycycline prevents the early accumulation of aortic neutrophils and significantly reduces the incidence of AD and rupture. PrediXcan analysis in a biobank of more than 23,000 individuals reveals that decreased expression of SH2B3 is significantly associated with increased frequency of AD-related phenotypes (odds ratio 0.81). Thus, we identified a role for LNK in the pathology of AD in experimental animals and humans and describe a new model that can be used to inform both inherited and acquired forms of this disease.

Role of PET/CT in the Evaluation of Aortic Disease

Positron emission tomography (PET) /computed tomography (CT) has been established as a standard imaging modality in the evaluation of malignancy. Although PET/CT has played a major role in the management of oncology patients, its clinical use has also increased for various disorders other than malignancy. Growing evidence shows that PET/CT images have many advantages in aortic disease as well. This review article addresses the potential role of PET/CT in diseases involving the aorta, emphasizing its usefulness with regard to acute thoracic aortic syndromes, aortic aneurysm, atherosclerotic lesions, aortitis and aortic tumors.

Update on the Therapeutic Strategy of Type B Aortic Dissection

Stanford type B aortic dissection (TBAD) is a life-threatening disease. Current therapeutic guidelines recommend medical therapy with aggressive blood pressure lowering for patients with acute TBAD unless they have fatal complications. Although patients with uncomplicated TBAD have relatively low early mortality, aorta-related adverse events during the chronic phase worsen the long-term clinical outcome. Recent advances in thoracic endovascular aortic repair (TEVAR) can improve clinical outcomes in patients with both complicated and uncomplicated TBAD. According to present guidelines, complicated TBAD patients are recommended for TEVAR. However, the indication in uncomplicated TBAD remains controversial. Recent results of randomized trials, which compared the clinical outcome in patients treated with optimal medical therapy and those treated with TEVAR, suggest that preemptive TEVAR should be considered in uncomplicated TBAD with suitable aortic anatomy. However, these trials failed to show improvement in early mortality in patients treated with TEVAR compared with patients treated with optimal medical therapy, which suggest the importance of patient selection for TEVAR. Several clinical and imaging-related risk factors have been shown to be associated with early disease progression. Preemptive TEVAR might be beneficial and should be considered for high-risk patients with uncomplicated TBAD. However, an interdisciplinary consensus has not been established for the definition of patients at high-risk of TBAD, and it should be confirmed by experts including physicians, radiologists, interventionalists, and vascular surgeons. This review summarizes the current understanding of the therapeutic strategy in patients with TBAD based on evidence and expert consensus.

Molecular targets in aortic aneurysm for establishing novel management paradigms

Aortic aneurysm (AA) is a lethal disease and presents a large challenge for surgeons in the clinic. Although surgical management remains the major choice of AA, operative mortality remains high. With advances in understanding of the mechanisms of AAs, molecular targets, such as matrix metalloproteinases (MMPs), D-dimer, and inflammation markers, including C-reactive protein, interleukins and phagocytes, are important in the pathology of development of AA. These markers may become important for improving the diagnostic quality and provide more therapeutic choices for treatment of AA. Although these new markers require long-term trials before they can be translated into the clinic, they can still be helpful in determining new directions. The main aim of this review is to discuss the current findings of molecular targets in progression of AA and discuss the potential application of these new targets for managing this disease.

Increased risk of aortic aneurysm (AA) in relation to the severity of psoriasis: A national population-based matched-cohort study

BACKGROUND

Inflammation of systemic and vascular tissues besides the skin in psoriasis is associated with cardiovascular morbidity and mortality.

OBJECTIVE

We sought to investigate whether or not patients with psoriasis have an increased risk of aortic aneurysm (AA).

METHODS

This population-based cohort study identified 34,301 patients with psoriasis in the Taiwan National Health Insurance Research Database during 2004 to 2006, who were matched for age and sex with 137,204 control subjects without psoriasis from the Taiwan Longitudinal Health Insurance Database 2000. Each individual was individually followed up for 5 years to identify those who subsequently developed AA.

RESULTS

After adjusting for medical history and medication use, patients with psoriasis were at increased overall risk of AA (adjusted hazard ratio [HR] 1.80; 95% confidence interval 1.25-2.61). The risk for AA increased with the severity of psoriasis. The adjusted HRs were higher for male than female patients (adjusted HR 1.84 vs 1.56), and for patients younger than 50 years versus older patients (adjusted HR 2.81 vs 1.64).

LIMITATIONS

There is a lack of information regarding patients' Psoriasis Area and Severity Index score, daily tobacco use, or alcohol consumption.

CONCLUSION

Patients with psoriasis are predisposed to developing AA: this risk increases with psoriasis severity and is independent of established cardiovascular risk factors.

Modern diagnostics for type B aortic dissection

Background

Undifferentiated chest pain is one of the most common complaints in the acute care setting. Type B aortic dissection is an important cause of chest pain and a complex clinical entity, which carries significant morbidity and mortality and requires accurate clinical and radiological evaluation.

Methods

Imaging technologies have become an irreplaceable tool to establish the diagnosis of aortic dissection and to plan treatment strategies. Computed tomography is an important component in this process, replacing catheter-based angiography as the most commonly used preoperative and postoperative imaging modality for the thoracic aorta. The use of functional imaging methods, such as magnetic resonance imaging and echocardiography is evolving. These methods are able to provide the clinically relevant anatomical, hemodynamic and biomechanical information that is necessary for accurate diagnosis, risk stratification and patient selection for treatment.

Conclusion

Advanced image acquisition equipment and expertise are increasingly available in a growing number of institutions and as a consequence, existing strategies for the management of type B dissection are rapidly evolving.

Management of acute aortic dissection

A new appraisal of the management of acute aortic dissection is timely because of recent developments in diagnostic strategies (including biomarkers and imaging), endograft design, and surgical treatment, which have led to a better understanding of the epidemiology, risk factors, and molecular nature of aortic dissection. Although open surgery is the main treatment for proximal aortic repair, use of endovascular management is now established for complicated distal dissection and distal arch repair, and has recently been discussed as a pre-emptive measure to avoid late complications by inducing aortic remodelling.

Adventitial CXCL1/G-CSF expression in response to acute aortic dissection triggers local neutrophil recruitment and activation leading to aortic rupture

RATIONALE

In-hospital outcomes are generally acceptable in patients with type B dissection; however, some patients present with undesirable complications, such as aortic expansion and rupture. Excessive inflammation is an independent predictor of adverse clinical outcomes.

OBJECTIVE

We have investigated the underlying mechanisms of catastrophic complications after acute aortic dissection (AAD) in mice.

METHODS AND RESULTS

When angiotensin II was administered in lysyl oxidase inhibitor-preconditioned mice, AAD emerged within 24 hours. The dissection was initiated at the proximal site of the descending thoracic aorta and propagated distally into an abdominal site. Dissection of the aorta caused dilatation, and ≈70% of the mice died of aortic rupture. AAD triggered CXCL1 and granulocyte-colony stimulating factor expression in the tunica adventitia of the dissected aorta, leading to elevation of circulating CXCL1/granulocyte-colony stimulating factor levels. Bone marrow CXCL12 was reduced. These chemokine changes facilitated neutrophil egress from bone marrow and infiltration into the aortic adventitia. Interference of CXCL1 function using an anti-CXCR2 antibody reduced neutrophil accumulation and limited aortic rupture post AAD. The tunica adventitia of the expanded dissected aorta demonstrated high levels of interleukin-6 (IL-6) expression. Neutrophils were the major sources of IL-6, and CXCR2 neutralization significantly reduced local and systemic levels of IL-6. Furthermore, disruption of IL-6 effectively suppressed dilatation and rupture of the dissected aorta without any influence on the incidence of AAD and neutrophil mobilization.

CONCLUSIONS

Adventitial CXCL1/granulocyte-colony stimulating factor expression in response to AAD triggers local neutrophil recruitment and activation. This leads to adventitial inflammation via IL-6 and results in aortic expansion and rupture.

[Risk evaluation of type B aortic dissection: importance for treatment of acute aortic syndrome]

Acute aortic syndrome (AAS) is a modern term used to describe interrelated emergency aortic conditions with similar clinical characteristics and challenges including aortic dissection, intramural hematoma (IMH) and penetrating aortic ulcer (PAU). Population-based studies suggest that the incidence of aortic dissection ranges from 2.6 to 3.5 cases per 100,000 inhabitants per year; hypertension and a variety of genetic disorders with altered connective tissue are the most prevalent risk conditions. In general, open surgical repair is recommended when dissection involves the ascending aorta, whereas medical management and endovascular stent graft repair is the best option when the ascending aorta is spared. Pathological conditions involving the aortic arch may be treated using a hybrid approach combining debranching of supra-aortic vessels and stent graft placement. Stent graft-induced remodeling of a dissected aorta seems to have long-term benefits in complicated and so-called uncomplicated type B dissections as almost every case reveals a risk profile and one in eight patients diagnosed with acute type B aortic dissection has either an IMH or a PAU. Pain is the most commonly presenting symptom of AAS and should prompt immediate attention including diagnostic imaging modalities, such as multislice computed tomography, transesophageal ultrasound and magnetic resonance imaging. A specific therapeutic approach is necessary for IMH and PAU because without treatment they have a very poor outcome, are unpredictable in evolution and can be more severe than acute aortic dissection. All patients must receive the best medical treatment available at admission. High-risk but asymptomatic patients with IMH and PAU can probably be monitored without interventions. All symptomatic patients will need treatment. In many of these patients a direct surgical approach is often prohibitive due to age and multiple comorbidities. Endovascular treatment offers superior results and is becoming a recognized indication for such patients. Irrespective of the treatment modality close surveillance is mandatory in order to monitor disease progression.

Emergence of molecular imaging of aortic aneurysm: implications for risk stratification and management

Imaging cellular and molecular processes associated with aneurysm expansion, dissection, and rupture can potentially transform the management of patients with thoracic and abdominal aortic aneurysm. Here, we review recent advances in molecular imaging of aortic aneurysm, focusing on imaging modalities with the greatest potential for clinical translation and application, PET, SPECT, and MRI. Inflammation (e.g., with (18)F-FDG, nanoparticles) and matrix remodeling (e.g., with matrix metalloproteinase-targeted tracers) are highlighted as promising targets for molecular imaging of aneurysm. Potential alternative or complementary approaches to molecular imaging for aneurysm risk stratification are briefly discussed.

Thorax: normal and benign pathologic patterns in FDG-PET/CT imaging

This article describes the normal patterns of thoracic (18)F-fluorodeoxyglucose (FDG) biodistribution, and expands on the role of FDG-PET/computed tomography (CT) for the evaluation of patients suffering from a spectrum of benign pathologic conditions that affect the chest. The discussion addresses the applications of FDG-PET/CT imaging in a wide variety of chest-related disorders. Familiarity with the normal thoracic biodistribution of FDG, coupled with knowledge of the potential nonmalignant causes of increased FDG uptake in the chest, is essential to minimize the incidence of incorrect interpretation of FDG-PET images in daily clinical practice.

Extent of preoperative false lumen thrombosis does not influence long-term survival in patients with acute type A aortic dissection

Background

Partial thrombosis of the false lumen has been related to aortic growth, reoperations, and death in the chronic phase of type B and repaired type A aortic dissections. The impact of preoperative false lumen thrombosis has not been studied previously. We used data from a contemporary, multinational database on aortic dissections to evaluate whether different degrees of preoperative false lumen thrombosis influenced long‐term prognosis.

Methods and Results

We examined the records of 522 patients with surgically treated acute type A aortic dissections who survived to discharge between 1996 and 2011. At the preoperative imaging, 414 (79.3%) patients had patent false lumens, 84 (16.1%) had partial thrombosis of the false lumen, and 24 (4.6%) had complete thrombosis of the false lumen. The annual median (interquartile range) aortic growth rates were 0.5 (−0.3 to 2.0) mm in the aortic arch, 2.0 (0.2 to 4.0) mm in the descending thoracic aorta, and similar regardless of the degree of false lumen thrombosis. The overall 5‐year survival rate was 84.7%, and it was not influenced by false lumen thrombosis (P=0.86 by the log‐rank test). Independent predictors of long‐term mortality were age >70 years (hazard ratio [HR], 2.34; 95% confidence interval [CI], 1.20 to 4.56, P=0.012) and postoperative cerebrovascular accident, coma, and/or renal failure (HR, 2.62; 95% CI, 1.40 to 4.92, P=0.003).

Conclusions

Patients with acute type A aortic dissection who survive to discharge have a favorable prognosis. Preoperative false lumen thrombosis does not influence long‐term mortality, reintervention rates, or aortic growth.

Molecular imaging in atherosclerosis: FDG PET

18F-FDG PET is a new noninvasive tool for inflammation functional imaging. Low spatial resolution is now compensated by coregistration with CT or MRI. New mechanistic insights have emerged from animal and histology to explain the obtained signals by hypoxia, macrophage infiltration, and differentiation. Mixed results have been found in biomarkers studies. Interesting data have come recently linking plaque anatomy and function in carotids and in aortic aneurysms as well as inflammation and events. In coronary arteries, plaque assessment is still hampered by myocardium uptake but developments are being made. 18-FDG PET has been able to monitor inflammation before and after several therapies in animals and humans but to date the lack of standardization and the absence of prospective event-driven studies prevent this promising technique to be used in clinical practice.

Correlation of biomechanics to tissue reaction in aortic aneurysms assessed by finite elements and [18F]-fluorodeoxyglucose-PET/CT

Mechanobiological interactions are essential for the adaption of the cardiovascular system to altered environmental and internal conditions, but are poorly understood with regard to abdominal aortic aneurysm (AAA) pathogenesis, growth and rupture. In the present study, we therefore calculated mechanical AAA quantities using nonlinear finite element methods and correlated these to [18F]-fluorodeoxyglucose (FDG)-metabolic activity in the AAA wall detected by positron emission tomography/computed tomography (PET/CT). The interplay between mechanics and FDG-metabolic activity was analyzed in terms of maximum values and the three-dimensional spatial relationship, respectively. Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) data sets of n = 18 AAA patients were studied. Maximum FDG-uptake (SUV max ) in the AAA wall varied from 1.32 to 4.60 (average SUV max 3.31 ± 0.87). Maximum wall stresses and strains ranged from 10.0 to 64.0 N∕cm(2) (38.2 ± 13.8  N∕cm(2)) and from 0.190 to 0.260 (0.222 ± 0.023), respectively. SUV max was significantly correlated to maximum wall stress and strain (SUV max to stress: r = 0.71, p = 0.0005; SUV max to strain: r = 0.66, p = 0.0013). To evaluate the three-dimensional spatial interaction between FDG-uptake and acting wall stress, element-wise correlations were performed. In all but 2 AAAs, positive element-wise correlation of FDG-uptake to wall stress was obtained, with the Pearson's correlation coefficient ranging from -0.168 to 0.738 ( 0.372 ± 0.263). The results indicate that mechanical stresses are correlated quantitatively and spatially to FDG-uptake in the AAA wall. It is hypothesized that unphysiologically increased loading in the AAA wall triggers biological tissue reaction, such as inflammation or regenerative processes, causing elevated FDG-metabolic activity. These findings strongly support experimental hypotheses of mechanotransduction mechanisms in vivo.

[State of the art: new developments in cardiac imaging]

Cardiac imaging continues to reveal new anatomical and functional insights into heart disease. In echocardiography, both transesophageal and transthoracic three-dimensional imaging have been fully developed and optimized, and the value of the techniques that have increased our understanding of cardiac mechanics and ventricular function is well established. At the same time, the healthcare industry has released new devices onto the market which, although they are easier to use, have limitations that restrict their use for routine assessment. Tomography's diagnostic and prognostic value in coronary artery disease continues to increase while radiation exposure becomes progressively lower. With cardiac magnetic resonance imaging, myocardial injury and recovery in ischemic heart disease and following acute coronary syndrome can be monitored in exquisite detail. The emergence of new combined tomographic and gamma camera techniques, exclusively developed for nuclear cardiology, have improved the quality of investigations and reduced radiation exposure. The hybrid or fusion images produced by combining different techniques, such as nuclear cardiology techniques and tomography, promise an exciting future.

Vascular imaging with positron emission tomography

Atherosclerosis is an inflammatory disease that causes most myocardial infarctions, strokes and acute coronary syndromes. Despite the identification of multiple risk factors and widespread use of drug therapies, it still remains a global health concern with associated costs. Although angiography is established as the gold standard means of detecting coronary artery stenosis, it does not image the vessel wall itself, reporting only on its consequences such as luminal narrowing and obstruction. MRI and computed tomography provide more information about the plaque structure, but recently positron emission tomography (PET) imaging using [(18) F]-fluorodeoxyglucose (FDG) has been advocated as a means of measuring arterial inflammation. This results from the ability of FDG-PET to highlight areas of high glucose metabolism, a feature of macrophages within atherosclerosis, particularly in high-risk plaques. It is suggested that the degree of FDG accumulation in the vessel wall reflects underlying inflammation levels and that tracking any changes in FDG uptake over time or with drug therapy might be a way of getting an early efficacy readout for novel anti-atherosclerotic drugs. Early reports also demonstrate that FDG uptake is correlated with the number of cardiovascular risk factors and possibly even the risk of future cardiovascular events. This review will outline the evidence base, shortcomings and emerging applications for FDG-PET in vascular imaging. Alternative PET tracers and other candidate imaging modalities for measuring vascular inflammation will also be discussed.

Vessel Wall Inflammation in Spontaneous Cervical Artery Dissection

Background and Purpose—

Vessel wall inflammation (VWI) may be a pathogenetic factor in cervical artery dissection (CAD). We used contrast-enhanced high-resolution MRI (hrMRI) and positron emission tomography CT (PET-CT) to systematically investigate VWI in spontaneous CAD.

Methods—

In this monocentric, prospective, observational study, all consecutive patients with acute, MRI-confirmed, spontaneous CAD admitted to our center between August 2007 and August 2009 were included. VWI was defined as perivascular contrast enhancement in hrMRI and increased perivascular [18F]-fluorodesoxyglucose uptake in PET-CT. VWI was further differentiated between local (restricted to the site of dissection) and generalized (exceeding the site of dissection).

Results—

A total of 37 patients were included. Multiple dissections were seen in 10 patients (27%). Twenty-five patients received both modalities as planned, 8 received only PET-CT, and 4 received only hrMRI. A subset of patients showed signs of a generalized VWI in hrMRI (4/29 patients, 14%) and PET-CT (8/33 patients, 24%). In patients who received both modalities, all with hrMRI signs of generalized VWI were PET-CT positive (3/3), whereas some PET-CT–positive patients were hrMRI-negative (4/7). If present, generalized VWI in hrMRI completely resolved within 6 months. The presence of >2 simultaneous dissections (seen in 2 patients) was significantly associated with generalized VWI in hrMRI ( P =0.015) but marginally not in PET-CT ( P =0.053).

Conclusions—

A subset of patients with spontaneous CAD showed signs of a generalized transient inflammatory arteriopathy in contrast-enhanced hrMRI and PET-CT. This subset of patients may be more prone to multiple dissections.

What is the relationship between ¹⁸F-FDG aortic aneurysm uptake on PET/CT and future growth rate?

PURPOSE

In this study we investigate the relationship between (18)F-fluorodeoxyglucose (FDG) metabolism and future aneurysm expansion measured by serial duplex ultrasound. Current screening programmes are increasing the identification of patients with abdominal aortic aneurysm (AAA). The management of these patients remains challenging and methods of risk stratification are sought.

METHODS

Thirty-four consecutive patients [31 men, 3 women, median age 75 years, interquartile range (IQR) 71-78] with aortic aneurysms under routine surveillance with serial ultrasound were prospectively recruited for (18)F-FDG positron emission tomography (PET)/CT. A whole vessel type analysis was performed measuring the highest aortic wall (18)F-FDG uptake (standardized uptake value or SUV(max)), and target to background ratio (TBR) for each axial image and median SUV(max) and TBR value were calculated. Institutional Review Board permission and informed patient consent were obtained.

RESULTS

Nine patients failed to undergo 12-month follow-up study (deceased n = 2, withdrew n = 1, failed to attend ultrasound scan n = 5, emergency aneurysm repair n = 1) leaving 25 patients for analysis. The median whole vessel SUV(max) was 1.70 (IQR 1.45-2.08). The median whole vessel TBR was 1.15 (IQR 1.00-1.40). The median aneurysm expansion at 12 months was 2.0 mm (IQR 0.5-5.0). The correlation (r) between (18)F-FDG SUV(max) and ultrasound expansion at 1 year was -0.501 (p = 0.011).

CONCLUSION

The preliminary findings from this observational longitudinal pilot study suggest that there is an inverse trend between (18)F-FDG uptake on PET and future AAA expansion. Aortic aneurysms with lower metabolic activity may therefore be more likely to expand.

PET/CT and vascular disease: current concepts

Since its introduction in 2001, positron emission tomography associated to computed tomography (PET/CT) has been established as a standard tool in cancer evaluation. Being a multimodality imaging method, it combines in a single session the sensitivity granted by PET for detection of molecular targets within the picomolar range, with an underlying submilimetric resolution inherent to CT, that can precisely localize the PET findings. In this last decade, there have been new insights regarding the pathophysiology of atherosclerosis, particularly about plaque rupture and vascular remodeling. This has increased the interest for research on PET/CT in vascular diseases as a potential new diagnostic tool, since some PET molecular targets could identify diseases before the manifestation of gross anatomic features. In this review, we will describe the current applications of PET/CT in vascular diseases, emphasizing its usefulness in the settings of vasculitis, aneurysms, vascular graft infection, aortic dissection, and atherosclerosis/plaque vulnerability. Although not being properly peripheral vascular conditions, ischemic cardiovascular disease and cerebrovascular disease will be briefly addressed as well, due to their widespread prevalence and importance.