Prediction of all-cause mortality in cardiovascular patients by using machine learning models

Background

Cardiovascular disease (CVD) is the leading cause of death worldwide. The prediction of all-cause death in patients with chronic cardiovascular risk will enable improved preventive strategies.

Purpose

This study aims to predict death of patients, who suffering from cardiovascular disease, within a follow-up period of 20 years. For this purpose was utilized the Ludwigshafen Risk and Cardiovascular Health (LURIC) study was utilized and employed machine learning models.

Methods

The Ludwigshafen Risk and Cardiovascular Health (LURIC) study was used in this analysis, which includes 3,316 patients (mean age 61.98 years, 69.2% male, 1722 deceased patients and 1594 alive or censored patients). After performing feature selection, 23 clinical and laboratory markers were included in our analysis. Pre-processing techniques such as SelectKbest and KNNImputer, were applied to the dataset and then it was splitted into a train and test (30%) set. The prediction of 20-year-risk of death was accomplished using the following machine learning algorithms: Logistic Regression (LR), Support Vector Machine (SVM), eXtreme Gradient Boosting (XGB) and Adaptive Boosting (AdaB). 10-fold cross validation was applied to verify the results of the models.

Results

The efficiency of each machine learning algorithm has been evaluated. XGB outperformed the others, achieving the highest accuracy (76.00%) and Area under (AUC) the Receiver Operating Characteristic Curve (ROC curve) value (0.776). The AUC value of the LR, SVM and AdaB are 0.761, 0.746 and 0.751, respectively. Figure 1 presents the ROC curve and AUC values for all models. Furthermore, the accuracy (ACC), precision, specificity, recall, F1-score and standard deviation were estimated for each classifier (Table 1).

Conclusion

We predicted all-cause mortality in patients with 20 years cardiovascular risk, using machine learning models and data of 3,316 patients. The most accurate predictive model was achieved by the eXtreme Gradient Boosting, with an accuracy equal to 76.00% and an AUC value of 0.776.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): HORIZON2020

Prediction of depression among patients with cardiovascular disease scheduled cardiac surgery using an AI-empowered pipeline

Introduction

Several studies have demonstrated, that one in three patients with cardiovascular disease (CVD) suffers from depression, and depression increases the likelihood for cardiac morbidity and mortality in the CVD population by 2–3-fold, independently of traditional risk factors or gender.

Purpose

The aim of this work is to predict depression in patients with CVD.

Methods

The clinical study was conducted in the cardiac surgical intensive care unit of The Central Clinical Hospital, the Medical University of Lodz in Poland, among patients scheduled for elective coronary artery bypass graft surgery (CABG). 224 patients signed an informed consent form, met the inclusion criteria and were enrolled in the study. All the patients had chronic coronary syndromes. The inclusion criteria were: consecutive adult patients scheduled for CABG surgery or CABG surgery with cardiac valve repair or replacement (CVR). The study population was examined by a psychiatrist the day prior to the scheduled operation, a diagnosis of major depressive disorder (MDD) was established on the basis of DSM-5 criteria.

A data curation pipeline was applied to automatically remove outliers and duplicated fields in the input dataset. An AI-empowered pipeline was developed to classify patients at higher risk for depression. Random downsampling with replacement was applied to deal with the increased class imbalance by taking into consideration two confound factors, namely the Mini Mental State Examination and Hemoglobin concentration <10mg/dl. The downsampling process was repeated K times. In each iteration, three bagging and boosting ML schemas were utilized for the classification task including the AdaBoost (adaptive boosting), Random Forests and Extreme Gradient boosting trees (XGBoost). To this end, a nested cross-validation process was applied for hyperparameter optimization and model validation, where: (i) a 3-fold cross-validation process was first applied to seek for the optimal set of hyperparameters based on the grid search approach by tuning core parameters, including the learning rate, number of estimators, and max depth, among others, and (ii) a stratified 5-fold cross-validation process was subsequently used to evaluate the performance of the best model from the previous stage by computing the classification accuracy, sensitivity, specificity, and area under the ROC curve (AUC). The performance evaluation results were averaged across the 5 folds and across the downsampling iterations. Shappley additive explanation analysis was finally applied to provide explainable risk factors for depression.

Results

sRAGE was significantly correlated with depression (r=0.32, p=0.038). The Random forests classifier presented the highest performance to predict depression (Accuracy: 0.71, Sensitivity: 0.71, Specificity: 0.75 and AUC: 0.74).

Conclusions

Depression can be predicted with 71% accuracy at patients with CVD and elevated sRAGE values.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): HORIZON2020

FEA of Drug-Eluting Stents and Sensitivity Analysis of a Continuum Damage Model for the Degradation of PLGA Coating

Drug-Eluting Stents (DES) are commonly used in coronary angioplasty operations as a solution against artery stenosis and restenosis. Computational Bioengineering allows for the in-silico analysis of their performance. The scope of this work is to develop a DES Digital Twin, focusing on the mechanical integrity of its biodegradable coating throughout the operational lifecycle. The implementation leverages the Finite Element Method (FEM) to compute the developed mechanical stress field on the DES during the inflation/deflation stage, followed by the degradation of the polymer-based coating. The simulation of the degradation process is based on a Continuum Damage Mechanics (CDM) model that considers bulk degradation. The CDM algorithm is implemented on the NX Nastran solver through a user-defined material (UMAT) subroutine. For benchmarking purposes and to compare with the baseline design of the BioCoStent project, this conceptual study implements an alternative stent design, to study the effect of the geometry on the developed stresses. Additionally, the effect of the degradation rate on the polymer-based coating's lifecycle is studied via sensitivity analysis.

Coupled FEA Model with Continuum Damage Mechanics for the Degradation of Polymer-based coatings on Drug-Eluting Stents

Drug-Eluting Stents (DES) are commonly used in Coronary angioplasty procedures to reduce the phenomenon of restenosis. Numerical simulations are proven to be a useful tool to the Bioengineering community in computing the mechanical performance of stents. BioCoStent is a research project aiming to develop a DES with retinoic acid (RA) coating, in the frame of which FEAC is responsible for the in silico numerical simulation of the coating's degradation in terms of Finite Element Analysis (FEA). The coatings under study are poly(lactic-co-glycolic acid) (PLGA) and polylactide (PLA). The FEA is based on the Continuum Damage Mechanics (CDM) theory and considers a mechanistic model for polymer bulk degradation of the coatings. The degradation algorithm is implemented on the NX Nastran solver through a user-defined material UMAT subroutine. This paper describes the developed numerical model to compute the degradation of biodegradable coatings on DES. The transient numerical model provides useful insight into the critical areas with regards to the scalar damage of the coatings. The FEA results present a complete degradation of polymers after several weeks.

POS0290 PREDICTING RISK FACTORS OF MALT LYMPHOMA IN SJÖGREN’S SYNDROME

Background:

Primary Sjögren Syndrome (SS) is a slowly progressive systemic autoimmune disease complicated by lymphoma, with mucosa associated lymphoid tissue (MALT) type being the most common lymphoma form. Several predictors related to pSS associated lymphomas have been described, but there are no studies focusing on specific risk factors for the MALT histologic subtype.

Objectives:

To identify predictors at SS diagnosis for MALT lymphoma development in pSS patients using simple clinical features.

Methods:

From 815 SS patients of a single center fulfilling the 2016 ACR/EULAR criteria, those with subsequent development of MALT lymphoma according to the 2016 WHO classification were identified and matched in 1:2 ratio, with non-lymphoma SS control patients according to age, disease duration from SS diagnosis and gender. Lymphoma patients diagnosed within a year from SS diagnosis were excluded from the current study. Clinical, laboratory, histologic data as well as the ESSDAI scores at the time of SS diagnosis were recorded and compared between lymphoma and non-lymphoma patients. Independent lymphoma predictors were identified by a data driven Fast Correlation Based Feature selection (FCBF)/Logistic Regression (LR) algorithm.

Results:

A unified dataset of 57 MALT lymphoma patients and 114 non lymphoma controls along with 39 features/variables was generated. The median age of SS diagnosis and the disease duration from SS diagnosis to lymphoma diagnosis (lymphoma group) or last follow up (control group) was 50,5 years old (range 25-77) and 7 years (range 0- 30) for the control group and 50 years old (range 24-70) and 8 years (range 1 -30) for the lymphoma group, respectively. MALT lymphoma patients presented more frequently with palpable purpura (23,2% vs 5,3% p=0,001), cryoglobulinemia (30,2% vs 1,6% p<0,0001), low C4 serum levels (62,9% vs 32,1% p=0,0003), rheumatoid factor (76,9% vs 56,1% p=0,01), anti La/SSB antibodies (33,9% vs 50,8% p=0,049) and higher median ESSDAI score (5 vs 2, p<0,0001). In contrast, autoimmune thyroiditis was more prevalent in controls (48,2% vs 18,6%, p=0,004). The FCBF/LR model revealed cryoglobulinemia (p=0,03) and ESSDAI at SS Diagnosis (p<0,001) as the only independent lymphoma predictors.

Conclusion:

MALT is the predominant pSS related lymphoproliferative histologic type, associated with systemic disease activity and vasculitic manifestations at SS diagnosis. Cryoglobulinemia and ESSDAI score were proven independent risk factors for MALT lymphoma development.

Table 1.

An FCBF-based multivariable logistic regression analysis results for investigating risk factors for MALT lymphoma development

Prominent featureRegression coefficientOdds ratiop-valueCI lowCI upperCryoglobulinemia1.675.3420.033*1.1824.327Total ESSDAI at diagnosis0.281.318<0.001*1.2081.439Kidney involvement0.071.0690.50.1010.351

•< 0.05 (95% confidence interval). The rest of the features that participated in the analysis include the following: Palpable purpura, Low C4, Salivary gland enlargement, Lacrimal gland enlargement, ANA Titers, RF, Focus score at Sjögren diagnosis, PNS involvement, Anti-La, Disease duration from SS onset to SS diagnosis, Neutrophils<1500, Autoimmune thyroiditis, Lung involvement – interstitial disease Type, Lymphocytes<1000, Lymphadenopathy fixed, Arthralgias, Dry eyes, Raynaud, Gender, Age at Sjögren diagnosis, Dry mouth, Aca, Hb<12.5 g/dL, ANA, Disease duration from SS Diagnosis to Lymphoma diagnosis or last follow up, Anti-Ro, Arthritis, WBC<4000/μL, Lung involvement bronchocentric disease, Interstitial renal disease, PLTs<100.000/μL, Liver involvement-PBC, Liver involvement–autoimmune hepatitis, CNS involvement.

•AUC=0.78

Disclosure of Interests:

None declared

OP0294 SJÖGREN’S SYNDROME ASSOCIATED LYMPHOMAS: CLINICAL DESCRIPTION AND 10-YEAR SURVIVAL

Background:

Sjögren’s Syndrome (SS) is a chronic systemic autoimmune disease of unknown etiology, carrying the highest lymphoma risk among autoimmune diseases, with significant impact on mortality and morbidity of patients.

Objectives:

To describe: i) the clinical phenotype of SS, ii) the histologic type, stage, treatment options regarding lymphomas and iii) the prognosis of patients with SS related lymphoproliferative disorders.

Methods:

Eight hundred and fifteen consecutive SS patients’ records from a single center fulfilling the 2016 ACR/EULAR were reviewed retrospectively for the purpose of this study. One hundred twenty-one patients with a diagnosis of non-Hodgkin Lymphoma (NHL) were identified and enrolled in the study population. Cumulative clinical, laboratory and histologic data were recorded and overall survival as well as event free survival curves were constructed using the Kaplan-Meier method. An event was defined as a disease progression, lymphoma relapse, treatment failure, histologic transformation, development of a 2nd lymphoma or death from any cause.

Results:

From 121 pSS patients with lymphoma the most common histologic type encountered was MALT lymphoma (92/121, 76,0%) followed by DLBCL (11/121, 9.0%) and NMZL (8/119, 6.6%). The remaining 10 patients had various lymphomas of B (follicular, lymphoplasmacytic, chronic lymphocytic leukemia} and T cell origin (peripheral T cell lymphoma not otherwise specified, primary cutaneous T cell lymphoma, angioimmunoblastic t-cell lymphoma). Permanent salivary gland enlargement (66.1%, 80/121), palpable purpura (34,7% 42/121), peripheral nervous involvement (9,9%, 12/121), interstitial lung disease (8,2%, 10/121) presence of serum cryoglobulins (38,7%, 43/111) and C4 hypocomplementemia (69,8% 81/116) present at least 1 year before the development of lymphoma were the main pSS related features. The median age at lymphoma diagnosis was 58 years old (range 29-82) while MALT lymphomas developed earlier compared to DLBCL from pSS diagnosis (8 vs 3 OR= 3.84, 95%CI: 0.29 to 10.46; p=0.0266). The commonest biopsy proven extranodal sites included the labial minor salivary (43,8% patients) and parotid glands (30,5%) while 11% of patients had more than 1 extranodal sites affected. Bone marrow involvement was evident in 24,3% of patients (29/119) while nodal involvement in 35,5% (42/118). The majority of patients (65%) had limited disease (stage I or II). A watch and wait therapeutic policy was chosen in 40 patients while the rest received rituximab with or without chemotherapy. The 10-year survival and event free rates were 79% and 45,5% for MALT lymphomas, 40,9% and 24,2% for DLBCL and 46% and 31% for NMZL respectively (Figure 1). The Mantel-Cox log-rank comparison of the overall survival curves revealed a statistically significant difference (p=0.0016) among lymphoma subtypes.

Figure 1.

Overall and event free survival of SS-associated lymphoma patients. A. Kaplan-Meier overall survival analysis. B. A Kaplan-Meier event free survival analysis.

Conclusion:

This is the largest single center series of SS- associated lymphoma patients, providing a detailed description of SS and lymphoma related features, combined with a 10-year survival and event free curves for the first time in the literature.

Disclosure of Interests:

None declared.

OP0291 SEVERITY OF LABIAL MINOR SALIVARY GLAND FOCUS SCORE AND FUTURE LYMPHOMA DEVELOPMENT IN SJÖGREN’S SYNDROME

Background:

The typical histologic picture of focal sialadenitis in the labial minor salivary gland (LMSG) tissues has been incorporated as a parameter in the majority of Sjögren’s syndrome (SS) classification criteria, with focus score (FS) being the most widely used (1). In previous studies, higher FS has been associated with the presence of autoantibodies and extra-glandular manifestations including lymphoma, implying that FS can predict severe disease (2,3). However, there are no studies exploring the association of FS with lymphoma development along with the time interval from SS diagnosis to lymphoma diagnosis.

Objectives:

To investigate an association of focus score grading with lymphoma development and time to lymphoma occurrence.

Methods:

From a total population 1998 consecutive patients fulfilling the 2016 ACR-EULAR criteria for SS who were followed-up in 5 Rheumatology centers from Greece and Italy (Universities of Athens, Pisa, Udine, Harokopio and Ioannina) (UPAHI group), those with positive (LMSG) (FS ≥1) were identified. (1). Patients who had not been subjected to an LMSG biopsy or had a negative biopsy (FS<1) or the biopsy was evaluated using other histologic classifications were excluded from the present study. Lymphoma patients with diagnostic LMSG biopsy performed within a year from lymphoma diagnosis as well as non-lymphoma patients with less than 1 year between SS diagnosis and their last follow up, were also excluded. Cumulative clinical and histologic data attributed to SS as defined by ESSDAI and/or ESSPRI, up to lymphoma diagnosis or last follow up, were recorded. A combined data driven Fast Correlation Based Feature selection (FCBF)/Logistic Regression (LR) model was applied on the unified dataset to identify independent lymphoma associated risk factors. A correlation between FS and time interval until lymphoma diagnosis was performed using the Pearson formula.

Results:

A unified dataset of 618 SS patients with FS≥1 and at least one year of disease duration from SS diagnosis to lymphoma diagnosis or last follow up, with 30 clinical, laboratory and histologic features, was constructed. The median age at SS diagnosis was 53 (range: 15 – 80) years old, the female to male ratio was 20:1 and the median disease duration was 6 years (range: 1-35). Half (49%) of the study population had focus score between one and two (1≤FS<2), followed by a declining proportion of patients accounted for every subsequent escalating FS group. No statistically significant difference was found regarding disease duration among the various FS escalating groups (p= 0.1603, Kruskal-Wallis test). Fifty eight patients had lymphoma with no statistically significant difference in disease duration compared to non-lymphoma controls. The data driven FCBF/LR algorithm with lymphoma on the whole dataset revealed that cryoglobulinemia (p=0.021), salivary gland enlargement (p=0.008) and FS (p=0,049) are independent lymphoma associated risk factors. A statistically significant negative correlation was found using a Pearson formula (R=-0.32 and p=0.015) regarding the focus score and the time to lymphoma diagnosis.

Conclusion:

This is the largest study of SS patients’ histologic analysis exploring the association of LMSG FS grading with lymphoma development and the time interval until its diagnosis. Higher FS values correlate with increased lymphoma risk and early lymphoma occurrence.

Figure 1.

Pearson correlation between FS and time interval until lymphoma diagnosis

References:

[1]Shiboski et al. Arhtritis Rheumatol. 2017

[2]Carrubi et al. Lupus 2015

[3]Risselada AP et al. Ann Rheum Dis 2014

Disclosure of Interests:

None declared

CCTA-derived functional and morphological features and their comparative performance in predicting impaired coronary vasodilatation by PET-myocardial perfusion imaging

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported in part from European Regional Development Fund, Operational Programme “Competitiveness, Entrepreneurship and Innovation 2014-2020 (EPAnEK)”, titled: The Greek Research Infrastructure for Personalized Medicine (pMED-GR) , no. GR 5002802 ,and by Greece and the European Union (European Social Fund-ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014-2020» in the context of the project “Assessment of coronary atherosclerosis: a new complete, anatomo-functional, morphological and biomechanical approach”, Project no. 504776

onbehalf

EVINCI-SMARTOOL

Background/Objectives: The relationship between biomechanical characteristics of a coronary lesion with myocardial blood flow has not been studied. We investigated the relationship between local endothelial shear stress (ESS) and computed tomography coronary angiography (CTCA)-derived anatomical and plaque characteristics data with impaired vasodilating capability assessed by positron emission tomography myocardial perfusion imaging (PET-MPI).

Methods

A total of 92 coronary vessels of 53 patients who have undergone both CTCA and PET-MPI with 15O-water or 13N-ammonia were analysed. PET was considered abnormal when &gt; 1 contiguous segments showed both stress Myocardial Blood Flow (MBF) ≤2.3mL/g/min and Myocardial Flow Reserve (MFR) ≤2.5 for 15O-water or &lt;1.79 mL/g/min and ≤2.0 for 13N-ammonia respectively.  CTCA images were used to assess stenosis severity, lesion specific total plaque volume (PV), non-calcified PV and calcified PV as well as plaque phenotype. ESS was calculated for the full length of a lesion (total), as well as in the proximal, minimum lumen area and distal lesion segments.

Results

ESS was weakly correlated with total PV (rho = 0.273, p = 0.008), non-calcified PV (rho = 0.247, p = 0.017) and the volume of necrotic core (rho = 0.242, p = 0.02). ESS increased progressively with stenosis severity (p ≤ 0.001). ΕSS was also higher in functionally significant vs. non-significant lesions (10.4 [8.04-54.4] Pa vs. 3.9 [2.32-7.29] Pa, p ≤0.001). Addition of ESS to stenosis severity improved prediction (Δ[AUC]:0.113, 95% CI: 0.055 to 0.171, p = 0.0001) of functionally significant lesions.

Conclusion

There is a weak positive association between lesion-specific ESS and plaque volume. ESS increases progressively with stenosis severity and is higher in functionally significant lesions by PET-MPI. The addition of ESS to CTCA-anatomical information improves prediction of an abnormal PET-MPI result.

Prediction of impaired myocardial blood flow (MBF) with the use of machine learning techniques on CTCA based parameters

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported in part from European Regional Development Fund, Operational Programme “Competitiveness, Entrepreneurship and Innovation 2014-2020 (EPAnEK)”, titled: The Greek Research Infrastructure for Personalized Medicine (pMED-GR) , no. GR 5002802 ,and by Greece and the European Union (European Social Fund-ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014-2020» in the context of the project “Assessment of coronary atherosclerosis: a new complete, anatomo-functional, morphological and biomechanical approach”, Project no. 504776

Background

Computed Tomography Coronary Angiography (CTCA) is a non-invasive imaging modality, used effectively for anatomo-functional assessment of coronary artery disease (CAD). Machine learning (ML) processes can effectively allow the extraction of useful information from multidimensional feature spaces for evaluation of coronary lesions.

Purpose

To investigate the ability of ML for predicting impaired myocardial blood flow (MBF) by combining computational fluid dynamics (CFD) derived parameters with quantitative plaque burden, plaque morphology and anatomical characteristics obtained from CTCA.

Methods

53 patients (31 male, mean age 64.7 ± 7.1 years) with intermediate pre-test likelihood of CAD who underwent CTCA and PET-MPI were included. PET was considered positive when &gt; 1 contiguous segment demonstrated MBF ≤ 2.3 mL/g/min for 15O-water or ≤ 1.79 for 13N-ammonia respectively. CFD derived parameters such as a previously validated, virtual functional assessment index (vFAI), segmental endothelial shear stress (ESS), as well as anatomical and plaque characteristics were assessed. Seven classifiers were implemented and internally validated using 5-fold cross validation, repeated 1000 times. Using sequential forward selection (SFS), the highest rank features combination, based on appearances in the highest mean area under curve (AUC) classification scheme, was selected and features performance was evaluated following exhaustive search (ES).

Results

92 coronary segments were analyzed and 34 features derived from CTCA were extracted. Classifiers performance are depicted in Figure A. k-NN was the best classifier with AUCmean = 0.791 (SENSmean= 0.622, SPECmean = 0.840, p &lt; 0.05). Clusters of features and number of appearances are presented in Figure B. The combination of vFAI, stenosis severity and lumen area demonstrated the highest AUC (1473 times). ES results are depicted in Figure C. The combination of vFAI and lumen area was the best predictor among all the combinations (AUCmean = 0.830, SENSmean =0.61, SPECmean =0.83, p &lt; 0.05) followed by vFAI and stenosis severity (AUCmean = 0.81, SENSmean =0.72, SPECmean = 0.87, p &lt; 0.05) and vFAI alone (AUCmean = 0.806, SENSmean =0.61, SPECmean =0.87, p &lt; 0.05).

Conclusion

ML analysis is feasible for predicting with reasonable specificity abnormal MBF by PET, using a combination of CFD derived parameters and anatomical features. vFAI as a single characteristic was a specific predictor of impaired MBF, whilst in combination with stenosis severity, maintained almost the same AUC and specificity values and resulted in improved sensitivity. On the other hand, addition of lumen area to vFAI, increases the AUC and provides a relatively good specificity but low  sensitivity.

Abstract Figure 1

Coronary CT angiography derived features for predicting an abnormal pet myocardial perfusion imaging: a machine learning approach

Background

Computed Tomography Coronary Angiography (CTCA) is an effective non-invasive imaging modality for anatomo-functional assessment of coronary artery disease (CAD). Machine learning (ML) algorithms allow extraction and process of useful information from multidimensional spaces for evaluation of coronary lesions.

Purpose

To investigate the ability of ML to integrate computational fluid dynamics (CFD) derived parameters with quantitative plaque burden, plaque morphology and anatomical characteristics for predicting impaired myocardial flow reserve by PET myocardial perfusion imaging (MPI).

Methods

49 patients (29 male, mean age 65.3±6.3 years) with intermediate pre-test likelihood of CAD who underwent CTCA and PET-MPI were included. PET was considered positive when &gt;1 contiguous segment demonstrated Myocardial flow reserve (MFR) ≤2.5 mL/g/min for 15O-water or ≤2.0 for 13N-ammonia respectively. CDF derived parameters such as a previously validated CT-FFR surrogate, virtual functional assessment index (vFAI), segmental endothelial shear stress (ESS), as well as anatomical and plaque characteristics were assessed. k-nearest neighbor (k-NN), support vector machines (SVM) and feedforward neural networks (FF-NN) were implemented. ML was internally validated using 5-fold cross validation, repeated 100 times. Using sequential forward selection (SFS), the 5 highest rank features based on appearances in each classification scheme were selected and following exhaustive search (ES) the best features combinations were identified. Each classifier's performance was evaluated using an area-under-receiver operating characteristic curve (AUC) analysis.

Results

85 coronary segments were analyzed and 28 features derived from CTCA were extracted. The features ranking for every classifier are depicted in Figure 1. k-NN using a combination only of ESS in the proximal (ESSprox) and distal segment achieved an AUC=0.78 (Sens=0.71, Spec=0.77, p&lt;0.05) for predicting a positive PET result. Combining ESSprox with burden fibrofatty tissue and non-calcified plaque burden, SVM achieved an AUC=0.75 (Sens=0.74, Spec=0.67, p&lt;0.05) whilst for FF-NN, the corresponding AUC was 0.79 (Sens=0.76, Spec=0.7, p&lt;0.05) using ESSprox, vFAI and % Fibrofatty volume. Among the best features combinations, ESSprox was the most consistent one achieving an AUC=0.75 (Sens=0.66, Spec=0.73, p&lt;0.05) for k-NN, AUC=0.73 (Sens=0.58, Spec=0.59, p&lt;0.05), for SVM and an AUC=0.73 (Sens=0.63, Spec=0.62, p&lt;0.05) for FF-NN respectively.

Conclusion

ML analysis is feasible for predicting abnormal MFR by PET using a combination of CFD derived parameters, anatomical and morphological features. ESSprox was present in every combination of best features. As a single characteristic was a moderate predictor of impaired MFR, whilst in combination with plaque characteristics and CFD derived features resulted in improved sensitivity and specificity.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): This research is co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme “Human, Resources Development, Education and Lifelong Learning 2014-2020” in the context of the project “Assessment of coronary atherosclerosis: a new complete, anatomo-functional, morphological and biomechanical approach” and from p-Med GR 5002802

Relationship between endothelial shear stress, plaque burden and stenosis severity and their comparative performance in predicting impaired coronary vasodilation by pet myocardial perfusion imaging

Background

Advances in CTCA imaging enable assessment of coronary plaque burden, a predictor of myocardial perfusion abnormalities and more recently, with the use of computational fluid dynamics (CFD) of endothelial shear stress (ESS), an established contributor to atherosclerotic plaque development and progression.

Purpose

To investigate the relationship of local endothelial shear stress (ESS) and plaque burden (PB) between them and with stenosis severity as well as their comparative performance in predicting impaired coronary vasodilating capability assessed by PET myocardial perfusion imaging (MPI).

Methods

49 patients (29 males, mean age 65.3±6.3 years, intermediate pre-test likelihood of coronary artery disease, CAD), who underwent PET-MPI with 15O-water or 13N-ammonia and CTCA were included. PET was considered abnormal when &gt;1 contiguous segment showed both stress Myocardial Blood Flow ≤2.3 mL/g/min and Myocardial Flow Reserve ≤2.5 for 15O-water or &lt;1.79 mL/g/min and ≤2.0 for 13N-ammonia respectively. On CTCA, stenosis (sten) severity was classified as: &lt;30%, 31–50%, 51–70% and 71–90%. CFD were applied to every vessel, assuming a mean pressure of 100 mmHg as the inlet boundary condition and a coronary velocity profile of 1 ml/sec as the outlet. ESS was calculated for the full length of a stenosis (total), as well as in the proximal (prox), minimum lumen area (MLA) and distal (dist) stenotic segments. Atherosclerotic PB was defined as lesion plaque volume/lesion vessel volume ×100.

Results

85 coronary vessels were evaluated. There was a positive correlation between ESS and PB (r(total)=0.544, r(prox)=0.528, r(MLA)=0.529, r(dist)=0.474, p&lt;0.001 for all). All ESS indices and PB increased progressively with stenosis severity compared to segments with a &lt;30% stenosis (p≤0.004 for all comparisons). ESS indices and PB were also higher in lesions demonstrating impaired vasodilating capacity compared to those without (p≤0.02 for all comparisons, figure 1). All ESS indices performed equally with PB and sten &gt;50% in predicting an abnormal PET MPI, (AUC: from 0.682 to 0.780, p-diff &gt;0.5 for all comparisons). The pairwise combination of sten &gt;50% with the ESS segments, except the distal one, increased the predictive ability of the model over stenosis alone (AUC (sten &gt;50% + ESS(total)) = 0.80, AUC (sten &gt;50% + ESS(prox)) = 0.797, AUC (sten &gt;50% + ESS(MLA)) = 0.822, p-diff ≤0.01 for all comparisons, AUC (sten &gt;50% + ESS(dist)) = 0.768, p-diff=0.07).

Conclusion

There is a low to moderate positive association between lesion plaque burden and ESS indices. Like PB, ESS increases progressively with stenosis severity and is higher in lesions paired with abnormal PET results. ESS is a moderate predictor of impaired vasodilating capability, performing equally with PB and stenosis severity. The addition of ESS to stenosis severity can improve prediction of an abnormal PET result.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): This study is co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning 2014-2020” in the context of the project “Assessment of coronary atherosclerosis: a new complete, anatomo-functional, morphological and biomechanical approach” and from p-Med GR 5002802

OP0096 THE DIFFERENCES BETWEEN SJÖGREN’S SYNDROME PATIENTS WITH COMBINED SERONEGATIVITY AND ANTI-RO/SSA SEROPOSITIVITY

Background:

Sjögren’s syndrome (SS) is characterized by B cell hyperactivity reflected by hypergammaglobulinemia as well as a plethora of autoantibodies including antinuclear antibodies (ANA), anti-Ro/SSA, anti-La/SSB and rheumatoid factors (RF). Previous studies have focused on the phenotype of single positive (ANA or anti-Ro/SSA or anti-La/SSB) or double positive (anti-Ro/SSA and anti-La/SSB positive) SS patients, showing differences regarding the age of diagnosis, sicca manifestations and specific extraglandular manifestations. To our knowledge, no study has ever explored the clinical spectrum of triple seronegative (anti-Ro/SSA + anti-La/SSB + RF negative) and quadruple seronegative (ANA +anti-Ro/SSA + anti-La/SSB + RF negative) SS patients.

Objectives:

To study the differences in the clinical phenotype of triple and quadruple seronegative (SS) patients in a large cohort of well characterized patients, after comparison with anti-Ro/SSA positive patients.

Methods:

From a total cohort of 1723 consecutive SS patients who fulfill the 2016 EULAR/ACR criteria and are followed up in 4 clinical centers ([Universities of Pisa and Athens, Harokopio and Ioannina, (PAHI)], those who have been found triple or quadruple seronegative were identified and compared with matched anti-Ro/SSA positive SS patients according to age of SS onset, disease duration and gender, in 1:1 and 1:2 ratio respectively. Glandular (dry mouth, dry eyes, parotid gland enlargement) and extra-glandular manifestations (Raynaud’s phenomenon, chronic fatigue arthralgias/myalgias, arthritis, palpable purpura, liver involvement, kidney involvement, lung involvement, neurologic involvement, long standing lymphadenopathy and lymphoma) were compared between the 2 seronegative groups and the anti-Ro/SSA positive control group. Statistical analysis for categorical variables was performed by Fisher exact or chi-square tests and for continuous variables with t test or Mann-Whitney accordingly.

Results:

Two hundred and four SS patients (11,8%) were identified as triple negatives and 53 (3,0%) as quadruple, with a median disease duration of 6 years (range: 0-41) and 5 years (range: 0-32) respectively. The matched anti-Ro/SSA controls were 204 for the triple and 103 for the quadruple negatives. Triple negatives had lower frequency of monoclonal gammopathy (5,5% vs 12,1% p=0,04), low C4 serum levels (23% vs 36%, p=0,009) and lymphoma (3,4% vs 9,8%, OR= 3,06, 95% CI =1,27-7,85) while quadruple negatives exhibited higher prevalence of dry eyes (100% vs 90%) and lower prevalence of long standing lymphadenopathy (2,7% vs 19,5%, p=0,001) and lymphoma (0% vs 15%, p=0,001) compared to anti-Ro/SSA matched controls.

Conclusion:

Combined seronegativity account for more than 10% of SS population and is associated with lower prevalence of lymphoma compared to anti-Ro/SSA positive patients.

Disclosure of Interests:

Loukas Chatzis: None declared, Vasileios Pezoulas: None declared, Francesco Ferro: None declared, Valentina Donati: None declared, Aliki Venetsanopoulou: None declared, Evangelia Zampeli: None declared, Maria Mavromati: None declared, Paraskevi Voulgari: None declared, Clio Mavragani: None declared, Dimitris Fotiadis: None declared, Fotini Skopouli: None declared, Salvatore De Vita Consultant of: Roche, Human Genome Science, Glaxo Smith Kline and Novartis, Chiara Baldini: None declared, Haralampos M. Moutsopoulos: None declared, Athanasios Tzioufas: None declared, Andreas Goules: None declared

FRI0149 THE CLINICAL FEATURES OF SJÖGREN’S SYNDROME PATIENTS WITH EARLY AND LATE DISEASE ONSET

Background:

Sjögren’s syndrome (SS) affects mainly individuals of the 4thor 5thdecade of life, although patients with early (≤35 years old) or late (≥65 years old) disease onset have been described in the literature. The clinical spectrum of the disease extends from mild dryness to severe systemic vasculitis and lymphoproliferative disorders. The phenotypic diversity of SS is defined by many factors, including age, since many parameters related to age may affect the clinical expression of the disease. Few studies have been conducted to study the effect of age on the clinical phenotype of SS, though with limited number of patients. Large and well-defined groups of SS are required to address such questions.

Objectives:

To study the clinical phenotype of SS patients with early and late disease onset and to explore the association of age with lymphoma development in a unified multicenter cohort.

Methods:

From a total cohort of 1997 consecutive SS patients who fulfill the 2016 EULAR/ACR criteria and are followed up in 5 clinical centers ([Universities ofUdine,Pisa andAthens,Harokopio andIoannina, (UPAHI)], those with either early (≤35 years) or late (≥65 years) disease onset were identified and matched according to gender and disease duration with middle aged controls whose disease onset was at the 4thor 5thdecade of life. Glandular manifestations, extra-glandular manifestations, serologic characteristics and histologic features were compared between the 2 age groups and the middle-aged control groups. Statistical analysis for categorical variables was performed by Fisher exact or chi-square tests and for continuous variables with t test or Mann-Whitney accordingly.

Results:

Three hundred seventy-nine (19%) SS patients with early and 293 (15%) with late disease onset were identified and compared with 353 and 285 middle aged SS controls respectively. The median disease duration of patients with early onset was 12 years (range:0-68) and for those with late disease onset was 5 years (range: 0-27). SS patients with early disease onset had statistically significant higher frequency of Raynaud’s phenomenon, lymphadenopathy, hypergammaglobulinemia, anti-Ro/SSA, anti-La/SSB, rheumatoid factor, salivary gland enlargement, low C4 complement levels, leukopenia and lymphoma (10,3% vs 5,7%, p= 0.03, OR= 1,91, 95% CI: 1,11-3,27) while SS patients with late disease onset had more frequently dry mouth, interstitial lung disease and lymphoma (6,8% vs 2,1%, p=0,01, OR= 3,4. 95%CI: 1,35-1,81).

Conclusion:

In a multicenter cohort of 1997 consecutive SS patients, those with early and late disease onset comprise more than one third of the total SS population. Patients with early disease onset, exhibit robust B cell responses with traditional risk factors for lymphoma as opposed to patients with late disease onset. Both age groups have increased lymphoma prevalence but presumably for different reasons, since late onset patients lack classical predictors of lymphoma. Therefore, these predictors deserve further study in different disease subsets.

Disclosure of Interests:

Andreas Goules: None declared, Ourania Argyropoulou: None declared, Vasileios Pezoulas: None declared, Francesco Ferro: None declared, Saviana Gandolfo: None declared, Valentina Donati: None declared, Marco Binutti: None declared, Sara Zandonella Callegher: None declared, Loukas Chatzis: None declared, Aliki Venetsanopoulou: None declared, Evangelia Zampeli: None declared, Maria Mavromati: None declared, Paraskevi Voulgari: None declared, Clio Mavragani: None declared, Chiara Baldini: None declared, Fotini Skopouli: None declared, Dimitris Fotiadis: None declared, Salvatore De Vita Consultant of: Roche, Human Genome Science, Glaxo Smith Kline and Novartis, Haralampos M. Moutsopoulos: None declared, Athanasios Tzioufas: None declared

THU0294 THE DIFFERENCES IN THE CLINICAL SPECTRUM OF CRYOGLOBULINEMIC VASCULITIS BETWEEN SJÖGREN’S SYNDROME AND HCV HEPATITIS

Background:

Cryoglobulinemic vasculitis (CV) is a serious complication of Sjögren’s syndrome (SS) and is closely associated with type II IgMk cryoglobulins. CV has been well documented in HCV patients without SS, and shares common features with CV in SS. So far, few studies have described the clinical picture of CV in HCV negative SS, but the number of studied patients was rather small and CV was not well defined. To better describe the clinical spectrum of CV in SS and explore the differences compared to HCV-related CV, a large cohort of well characterized patients is required.

Objectives:

To study the clinical phenotype of CV in HCV-negative SS patients, in a large cohort of well characterized patients, after applying stringent classification CV criteria and in comparison with the classical CV of HCV patients.

Methods:

From a total cohort of 1997 consecutive SS patients who fulfill the 2016 EULAR/ACR criteria and are followed up in 5 clinical centers ([Universities ofUdine,Pisa andAthens,Harokopio andIoannina, (UPAHI)], those who fulfil the 2011 classification criteria for CV were identified and compared with matched HCV-CV patients according to age and gender. Glandular, extra-glandular manifestations and serologic features were compared between the 2 CV groups. Statistical analysis for categorical variables was performed by Fisher exact or chi-square tests and for continuous variables with t test or Mann-Whitney accordingly.

Results:

Among the 1083 SS patients who have been evaluated for cryoglobulins, 114 (9,8%) were found positive. Seventy-one (6,5%) SS patients met the 2011 CV criteria while 44 patients presented with type II IgMk cryoglobulinemia without CV. Sixty nine of 71 (97%) SS related CV patients were females and 2 of 71 (3%) males. Forty eight of 71 (68%) had SS disease onset >35 and <65 years old while 14/71 (19,7%) and 9/71 (12,7%) had SS disease onset <35 and >65 years old respectively. The most common clinical manifestations of CV among SS patients were purpura (90%) followed by arthralgias (70%), fatigue (59%), Raynaud’s phenomenon (48%), lymphadenopathy (31%), peripheral neuropathy (22,3%), vasculitic ulcer (11,3%) and glomerulonephritis (11,3%). Interestingly, almost 50% of SS related CV patients developed lymphoma and displayed high frequency of strong predictors including purpura, low C4 complement (88,6%) and salivary gland enlargement (SGE). Compared to HCV-CV patients, SS-CV patients had higher frequency of sicca manifestations, SGE, fatigue, arthritis, Raynaud’s phenomenon, lymphadenopathy, type II IgMk cryoglobulins and lymphoma.

Conclusion:

The prevalence of cryoglobulinemia and CV among SS patients is about 10% and 6-7% respectively. SS-CV patients are mainly middle-aged females with purpura as the main clinical manifestation, and up to one half of them may develop lymphoma, which is rarer in HCV-CV. Compared to HCV-CV patients, SS patients with CV have more frequently sicca symptoms, SGE and type II IgMk cryoglobulins.

Disclosure of Interests:

Ourania Argyropoulou: None declared, Vasileios Pezoulas: None declared, Luca Quartuccio: None declared, Francesco Ferro: None declared, Saviana Gandolfo: None declared, Valentina Donati: None declared, Aliki Venetsanopoulou: None declared, Loukas Chatzis: None declared, Evangelia Zampeli: None declared, Maria Mavromati: None declared, Paraskevi Voulgari: None declared, Clio Mavragani: None declared, Chiara Baldini: None declared, Fotini Skopouli: None declared, Dimitris Fotiadis: None declared, Massimo Galli: None declared, Salvatore De Vita Consultant of: Roche, Human Genome Science, Glaxo Smith Kline and Novartis, Haralampos M. Moutsopoulos: None declared, Andreas Goules: None declared, Athanasios Tzioufas: None declared

FRI0161 PHENOTYPIC DIFFERENCES BETWEEN SJÖGREN’S SYNDROME PATIENTS WITH LOW AND HIGH-GRADE INFLAMMATION BASED ON SALIVARY GLAND FOCUS SCORE

Background:

Sjögren’s syndrome (SS) is characterized by the presence of lymphocytic infiltration around the ductal epithelium of the salivary and lachrymal glands. The periepithelial inflammatory lesions and the enclosed B cell component are responsible for the glandular and extraglandular manifestations of the disease. Previous studies have shown that the severity of inflammation observed within the salivary glands is correlated with the occurrence of extraglandular manifestations. However, in these studies either the number of patients is small or the SS criteria are not well defined. To explore the association between the degree of inflammation within the salivary glands and the phenotype of the disease, large and well characterized cohorts of SS patients is required.

Objectives:

To compare the phenotypic features of SS patients with low and high degree of inflammation within the minor salivary glands as reflected by the focus score (FS).

Methods:

From a total cohort of 1723 consecutive SS patients who fulfill the 2016 EULAR/ACR criteria and are followed up in 4 clinical centers ([Universities ofPisa,Athens,Harokopio andIoannina, (PAHI)], those who had performed a lip biopsy and the focused score was available, were classified into low grade (FS<3) or high grade (FS≥3). Glandular (dry mouth, dry eyes, parotid gland enlargement) and extra-glandular manifestations (Raynaud’s phenomenon, arthralgias/myalgias, arthritis, palpable purpura, liver involvement, kidney involvement, lung involvement, neurologic involvement, long standing lymphadenopathy and lymphoma) as well as serologic features (ANA, RF, anti-Ro/SSA, anti-La/SSB) were compared between the 2 groups. Statistical analysis for categorical variables was performed by Fisher exact or chi-square tests and for continuous variables with t test or Mann-Whitney accordingly.

Results:

Eight hundred and eight minor salivary gland biopsies were available and evaluated based on focus score at the initial evaluation of SS patients, of whom 753 had low grade (FS<3) and 153 high grade (≥3) inflammation. The median disease duration after SS diagnosis was not statistically significant different for the 2 groups (median: 4 years, range: 0-36 years). SS patients with high grade inflammation displayed higher prevalence of salivary gland enlargement (SGE) (40% vs 25%, p=0,0002), long standing lymphadenopathy (22% vs 14%, p=0,02), ANA (97% vs 88%, p=0,0001), anti-La/SSB (52% vs 32%, p<0,0001), RF (61,5% vs 48%, p=0,003), peripheral neuropathy (PN) (5,3% vs 1,5, p=0,01) and of lymphoma (26% vs 8%, p<0,0001, OR=4,142, 95%CI=2,65 to 6,47) compared to those with low grade inflammation.

Conclusion:

SS patients with FS ≥3 at the initial evaluation, display higher prevalence of lymphoma as well as higher B cell hyperactivity and certain clinical manifestations (SGE, PNS, lymphadenopathy) that constitute risk factors for lymphoma development.

Disclosure of Interests:

Loukas Chatzis: None declared, Vasileios Pezoulas: None declared, Francesco Ferro: None declared, Valentina Donati: None declared, Aliki Venetsanopoulou: None declared, Evangelia Zampeli: None declared, Maria Mavromati: None declared, Paraskevi Voulgari: None declared, Clio Mavragani: None declared, Dimitris Fotiadis: None declared, Fotini Skopouli: None declared, Salvatore De Vita Consultant of: Roche, Human Genome Science, Glaxo Smith Kline and Novartis, Gorgoulis Vassilis: None declared, Chiara Baldini: None declared, Haralampos M. Moutsopoulos: None declared, Andreas Goules: None declared, Athanasios Tzioufas: None declared

Designing a mHealth clinical decision support system for Parkinson's disease: a theoretically grounded user needs approach

Background

Despite the established evidence and theoretical advances explaining human judgments under uncertainty, developments of mobile health (mHealth) Clinical Decision Support Systems (CDSS) have not explicitly applied the psychology of decision making to the study of user needs. We report on a user needs approach to develop a prototype of a mHealth CDSS for Parkinson’s disease (PD), which is theoretically grounded in the psychological literature about expert decision making and judgement under uncertainty.

Methods

A suite of user needs studies was conducted in 4 European countries (Greece, Italy, Slovenia, the UK) prior to the development of PD_Manager, a mHealth-based CDSS designed for Parkinson’s disease, using wireless technology. Study 1 undertook Hierarchical Task Analysis (HTA) including elicitation of user needs, cognitive demands and perceived risks/benefits (ethical considerations) associated with the proposed CDSS, through structured interviews of prescribing clinicians (N = 47). Study 2 carried out computational modelling of prescribing clinicians’ (N = 12) decision strategies based on social judgment theory. Study 3 was a vignette study of prescribing clinicians’ (N = 18) willingness to change treatment based on either self-reported symptoms data, devices-generated symptoms data or combinations of both.

Results

Study 1 indicated that system development should move away from the traditional silos of ‘motor’ and ‘non-motor’ symptom evaluations and suggest that presenting data on symptoms according to goal-based domains would be the most beneficial approach, the most important being patients’ overall Quality of Life (QoL). The computational modelling in Study 2 extrapolated different factor combinations when making judgements about different questions. Study 3 indicated that the clinicians were equally likely to change the care plan based on information about the change in the patient’s condition from the patient’s self-report and the wearable devices.

Conclusions

Based on our approach, we could formulate the following principles of mHealth design: 1) enabling shared decision making between the clinician, patient and the carer; 2) flexibility that accounts for diagnostic and treatment variation among clinicians; 3) monitoring of information integration from multiple sources. Our approach highlighted the central importance of the patient-clinician relationship in clinical decision making and the relevance of theoretical as opposed to algorithm (technology)-based modelling of human judgment.

P2702Assessment of endothelial shear stress and functional significance of coronary lesions by computed tomography coronary angiography (CTCA) and computational fluid dynamics: a comparison with PET

Background

The feasibility of assessing endothelial shear stress (ESS) in coronary lesions by non-invasive imaging and its potential role in different clinical settings has been recently explored. However, the relationship of ESS with functional indices derived by computed tomography coronary angiography (CTCA) and its value in predicting perfusion changes by quantitative positron emission tomography (PET) downstream stenotic vessels has not been assessed.

Purpose

To investigate the feasibility of calculating local ESS, its relationship with stenosis severity as well as with virtual functional assessment index (vFAI), and the comparative performance of the two parameters for predicting impaired coronary vasodilating capability in terms both of stress myocardial blood flow (MBF) and myocardial flow reserve (MFR) in patients submitted to CTCA.

Methods

Thirty-two patients (23 male-9 female, mean age 65.6±7.2 years) with intermediate pre-test likelihood of coronary artery disease (CAD), who were enrolled in the EVINCI and SMARTool projects, and had undergone CTCA with vFAI and PET myocardial perfusion imaging with 15 O-water or 13 N-ammonia were included in the study. PET was considered positive when >1 contiguous segments showed both stress MBF ≤2.3 mL/g/min and MFR ≤2.5 for 15 O-water or ≤1.79 mL/g/min and ≤2.0, for 13 N-ammonia respectively. A vFAI threshold of 0.85 was used as predictor of impaired vasodilating capability. ESS computation was based on a mean aortic pressure of 100 mmHg for the inlet and a mean blood flow at rest of 0.00105 kg/s for the outlet. ESS was calculated (Pa) in the full length of the stenosis and the mean value was obtained.

Results

Hybrid imaging analysis was performed in CTCA and PET datasets. 51 coronary segments were assessed. There were 27 lesions with stenosis 31–50% and 24 lesions with stenosis 51–70%. ESS was higher in the latter (20.4, IQ: 11.4–32.1 vs. 10.4, IQ: 5.5–15.7, p=0.04). Similarly, ESS was higher in stenoses with impaired vasodilating capacity compared to those without, although this difference did not reach statistical significance (22.8, IQ: 13.2–35.1 vs. 10.6, IQ: 5.7–22.1, p=0.10). The ROC curve analysis for prediction of both abnormal stress MBF and MFR followed the same pattern (AUC=0.668, 95% confidence interval (CI): 0.490–0.810, p=0.11).On the other hand, there was a moderate negative correlation (r=−0.41, p=0.004) between ESS and vFAI and the former was lower in stenoses with vFAI >0.85 compared to those below this threshold (7.35, IQ: 3.2–13.9 vs. 19.1, IQ: 14.1–32.8, p=0.012). vFAI was a good predictor of coronary flow capacity (AUC=0.737, CI: 0.58–0.85, p=0.02).

Conclusion

Calculation of ESS is feasible in CTCA datasets. ESS was related with stenosis severity and there was a trend to be higher in lesions with impaired coronary vasodilating capability. ESS is modestly related with vFAI and may also be an additional predictor of impaired regional myocardial flow obtained by PET imaging.

Acknowledgement/Funding

This study has received funding from the EU H2020 research and innovation programme under grant agreement No 689068 and from p-Med GR 5002802

Design and assembly of a chemically switchable and fluorescently traceable light-driven proton pump system for bionanotechnological applications

Energy-supplying modules are essential building blocks for the assembly of functional multicomponent nanoreactors in synthetic biology. Proteorhodopsin, a light-driven proton pump, is an ideal candidate to provide the required energy in form of an electrochemical proton gradient. Here we present an advanced proteoliposome system equipped with a chemically on-off switchable proteorhodopsin variant. The proton pump was engineered to optimize the specificity and efficiency of chemical deactivation and reactivation. To optically track and characterize the proteoliposome system using fluorescence microscopy and nanoparticle tracking analysis, fluorescenlty labelled lipids were implemented. Fluorescence is a highly valuable feature that enables detection and tracking of nanoreactors in complex media. Cryo-transmission electron microscopy, and correlative atomic force and confocal microscopy revealed that our procedure yields polylamellar proteoliposomes, which exhibit enhanced mechanical stability. The combination of these features makes the presented energizing system a promising foundation for the engineering of complex nanoreactors.

Biclustering strategies for genetic marker selection in gynecologic tumor cell lines

Over the past few decades great interest has been focused on cell lines derived from tumors, because of their usability as models to understand the biology of cancer. At the same time, advanced technologies such as DNA-microarrays have been broadly used to study the expression level of thousands of genes in primary tumors or cancer cell lines in a single experiment. Results from microarray analysis approaches have provided valuable insights into the underlying biology and proven useful for tumor classification, prognostication and prediction. Our approach utilizes biclustering methods for the discovery of genes with coherent expression across a subset of conditions (cell lines of a tumor type). More specifically, we present a novel modification on Cheng & Church's algorithm that searches for differences across the studied conditions, but also enforces consistent intensity characteristics of each cluster within each condition. The application of this approach on a gynecologic panel of cell lines succeeds to derive discriminant groups of compact bi-clusters across four types of tumor cell lines. In this form, the proposed approach is proven efficient for the derivation of tumor-specific markers.

Potential of interferometric cantilever detection and its application for SFM/AFM in liquids

We have developed an optical cantilever deflection detector with a spot size <3 µm and fm Hz(-1/2) sensitivity over a>10 MHz bandwidth. In this work, we demonstrate its potential for detecting small-amplitude oscillations of various flexural and torsional oscillation modes of cantilevers. The high deflection sensitivity of the interferometer is particularly useful for detecting cantilever oscillations in aqueous solutions, enabling us to reach the thermal noise limit in scanning or atomic force microscopy experiments with stiff cantilevers. This has resulted in atomic-resolution images of solid-liquid interfaces and submolecular-resolution images of native membranes.

The 5A structure of heterologously expressed plant aquaporin SoPIP2;1

SoPIP2;1 is one of the major integral proteins in spinach leaf plasma membranes. In the Xenopus oocyte expression system its water channel activity is regulated by phosphorylation at the C terminus and in the first cytosolic loop. To assess its structure, SoPIP2;1 was heterologously expressed in Pichia pastoris as a His-tagged protein and in the non-tagged form. Both forms were reconstituted into 2D crystals in the presence of lipids. Tubular crystals and double-layered crystalline sheets of non-tagged SoPIP2;1 were observed and analyzed by cryo-electron microscopy. Crystalline sheets were highly ordered and diffracted electrons to a resolution of 2.96A. High-resolution projection maps of tilted specimens provided a 3D structure at 5A resolution. Superposition of the SoPIP2;1 potential map with the atomic model of AQP1 demonstrates the generally well conserved overall structure of water channels. Differences concerning the extracellular loop A explain the particular crystal contacts between oppositely oriented membrane sheets of SoPIP2;1 2D crystals, and may have a function in rapid volume changes observed in stomatal guard cells or mesophyll protoplasts. This crystal packing arrangement provides access to the phosphorylated C terminus as well as the loop B phosphorylation site for studies of channel gating.

Atomic force bio-analytics

The atomic force microscope (AFM) allows biomolecules to be observed and manipulated under native conditions. It operates in buffer solution, produces molecular images with outstanding signal-to-noise ratio, and addresses single molecules. Progress in sample preparation and instrumentation has led to topographs that reveal sub-nanometer details and surface dynamics of biomolecules. Antibodies or oligonucleotides immobilized on cantilevers induce bending upon binding of the cognate biomolecule, allowing sub-picomolar concentrations to be measured. Biomolecules tethered between support and retracting AFM-tip produce force extension curves that reflect the mechanical stability of secondary structure elements. Furthermore, multifunctional tips may activate single molecules to observe them at work. In all cases, the cantilever is critical: its mechanical properties dictate the force-sensitivity and the scanning speed.

Progress in the analysis of membrane protein structure and function

Structural information on membrane proteins is sparse, yet they represent an important class of proteins that is encoded by about 30% of all genes. Progress has primarily been achieved with bacterial proteins, but efforts to solve the structure of eukaryotic membrane proteins are also increasing. Most of the structures currently available have been obtained by exploiting the power of X-ray crystallography. Recent results, however, have demonstrated the accuracy of electron crystallography and the imaging power of the atomic force microscope. These instruments allow membrane proteins to be studied while embedded in the bi-layer, and thus in a functional state. The low signal-to-noise ratio of cryo-electron microscopy is overcome by crystallizing membrane proteins in a two-dimensional protein-lipid membrane, allowing its atomic structure to be determined. In contrast, the high signal-to-noise ratio of atomic force microscopy allows individual protein surfaces to be imaged at sub-nanometer resolution, and their conformational states to be sampled. This review summarizes the steps in membrane protein structure determination and illuminates recent progress.

Two-dimensional crystals: a powerful approach to assess structure, function and dynamics of membrane proteins

Electron crystallography and atomic force microscopy allow the study of two-dimensional membrane protein crystals. While electron crystallography provides atomic scale three-dimensional density maps, atomic force microscopy gives insight into the surface structure and dynamics at sub-nanometer resolution. Importantly, the membrane protein studied is in its native environment and its function can be assessed directly. The approach allows both the atomic structure of the membrane protein and the dynamics of its surface to be analyzed. In this way, the function-related conformational changes can be assessed, thus providing a detailed insight on the molecular mechanisms of essential biological processes.

Bacterial Na(+)-ATP synthase has an undecameric rotor

Synthesis of adenosine triphosphate (ATP) by the F(1)F(0) ATP synthase involves a membrane-embedded rotary engine, the F(0) domain, which drives the extra-membranous catalytic F(1) domain. The F(0) domain consists of subunits a(1)b(2) and a cylindrical rotor assembled from 9-14 alpha-helical hairpin-shaped c-subunits. According to structural analyses, rotors contain 10 c-subunits in yeast and 14 in chloroplast ATP synthases. We determined the rotor stoichiometry of Ilyobacter tartaricus ATP synthase by atomic force microscopy and cryo-electron microscopy, and show the cylindrical sodium-driven rotor to comprise 11 c-subunits.

Structural characterization of two aquaporins isolated from native spinach leaf plasma membranes

Two members of the aquaporin family, PM28A and a new one, PM28C, were isolated and shown to be the major constituents of spinach leaf plasma membranes. These two isoforms were identified and characterized by matrix-assisted laser desorption ionization-mass spectrometry. Edman degradation yielded the amino acid sequence of two domains belonging to the new isoform. PM28B, a previously described isoform, was not found in our preparations. Scanning transmission electron microscopy mass analysis revealed both PM28 isoforms to be tetrameric. Two types of particles, a larger and a smaller one, were found by transmission electron microscopy of negatively stained solubilized proteins and by atomic force microscopy of PM28 two-dimensional crystals. The ratio of larger to smaller particles observed by transmission electron microscopy and single particle analysis correlated with the ratio of PM28A to PM28C determined by matrix-assisted laser desorption ionization-mass spectrometry. The absence of PM28B and the ratio of PM28A to PM28C indicate that these plasma membrane intrinsic proteins are differentially expressed in spinach leaves. These findings suggest that differential expression of the various aquaporin isoforms may regulate the water flux across the plasma membrane, in addition to the known mechanism of regulation by phosphorylation.

Surface tongue-and-groove contours on lens MIP facilitate cell-to-cell adherence

The lens major intrinsic protein (MIP, AQP0) is known to function as a water and solute channel. However, MIP has also been reported to occur in close membrane contacts between lens fiber cells, indicating that it has adhesive properties in addition to its channel function. Using atomic force and cryo-electron microscopy we document that crystalline sheets reconstituted from purified ovine lens MIP mostly consisted of two layers. MIP lattices in the apposing membranes were in precise register, and determination of the membrane sidedness demonstrated that MIP molecules bound to each other via their extracellular surfaces. The surface structure of the latter was resolved to 0.61 nm and revealed two protruding domains providing a tight "tongue-and-groove" fit between apposing MIP molecules. Cryo-electron crystallography produced a projection map at 0.69 nm resolution with a mirror symmetry axis at 45 degrees to the lattice which was consistent with the double-layered nature of the reconstituted sheets. These data strongly suggest an adhesive function of MIP, and strengthen the view that MIP serves dual roles in the lens.

Conformations of the rhodopsin third cytoplasmic loop grafted onto bacteriorhodopsin

BACKGROUND

The third cytoplasmic loop of rhodopsin (Rho EF) is important in signal transduction from the retinal in rhodopsin to its G protein, transducin. This loop also interacts with rhodopsin kinase, which phosphorylates light-activated rhodopsin, and arrestin, which displaces transducin from light-activated phosphorylated rhodopsin.

RESULTS

We replaced eight residues of the EF loop of bacteriorhodopsin (BR) with 24 residues from the third cytoplasmic loop of bovine Rho EF. The surfaces of purple membrane containing the mutant BR (called IIIN) were imaged by atomic force microscopy (AFM) under physiological conditions to a resolution of 0.5-0.7 nm. The crystallinity and extracellular surface of IIIN were not perturbed, and the cytoplasmic surface of IIIN increased in height compared with BR, consistent with the larger loop. Ten residues of Rho EF were excised by V8 protease, revealing helices E and F in the AFM topographs. Rho EF was modeled onto the BR structure, and the envelope derived from the AFM data of IIIN was used to select probable models.

CONCLUSIONS

A likely conformation of Rho EF involves some extension of helices E and F, with the tip of the loop lying over helix C and projecting towards the C terminus. This is consistent with mutagenesis data showing the TTQ transducin-binding motif close to loop CD, and cysteine cross-linking data indicating the C-terminal part of Rho EF to be close to the CD loop.

The reaction center complex from the green sulfur bacterium Chlorobium tepidum: a structural analysis by scanning transmission electron microscopy

The three-dimensional (3D) structure of the reaction center (RC) complex isolated from the green sulfur bacterium Chlorobium tepidum was determined from projections of negatively stained preparations by angular reconstitution. The purified complex contained the PscA, PscC, PscB, PscD subunits and the Fenna-Matthews-Olson (FMO) protein. Its mass was found to be 454 kDa by scanning transmission electron microscopy (STEM), indicating the presence of two copies of the PscA subunit, one copy of the PscB and PscD subunits, three FMO proteins and at least one copy of the PscC subunit. An additional mass peak at 183 kDa suggested that FMO trimers copurify with the RC complexes. Images of negatively stained RC complexes were recorded by STEM and aligned and classified by multivariate statistical analysis. Averages of the major classes indicated that different morphologies of the elongated particles (length=19 nm, width=8 nm) resulted from a rotation around the long axis. The 3D map reconstructed from these projections allowed visualization of the RC complex associated with one FMO trimer. A second FMO trimer could be correspondingly accommodated to yield a symmetric complex, a structure observed in a small number of side views and proposed to be the intact form of the RC complex.

Electrostatically balanced subnanometer imaging of biological specimens by atomic force microscope

To achieve high-resolution topographs of native biological macromolecules in aqueous solution with the atomic force microscope (AFM) interactions between AFM tip and sample need to be considered. Short-range forces produce the submolecular information of high-resolution topographs. In contrast, no significant high-resolution information is provided by the long-range electrostatic double-layer force. However, this force can be adjusted by pH and electrolytes to distribute the force applied to the AFM tip over a large sample area. As demonstrated on fragile biological samples, adjustment of the electrolyte solution results in a local reduction of both vertical and lateral forces between the AFM tip and proteinous substructures. Under such electrostatically balanced conditions, the deformation of the native protein is minimized and the sample surface can be reproducibly contoured at a lateral resolution of 0.6 nm.

Surface analysis of the photosystem I complex by electron and atomic force microscopy

Two-dimensional (2D) crystals of the photosystem I (PSI) reaction center from Synechococcus sp. OD24 were analyzed by electron and atomic force microscopy. Surface relief reconstructions from electron micrographs of freeze-dried unidirectionally shadowed samples and topographs recorded with the atomic force microscope (AFM) provided a precise definition of the lumenal and stromal PSI surfaces. The lumenal surface was composed of four protrusions that surrounded an indentation. One of the protrusions, the PsaF subunit, was often missing. Removal of the extrinsic proteins with the AFM stylus exposed the stromal side of the PSI core, whose surface structure could then be imaged at a resolution better than 1.4 nm. This interfacial surface between core and extrinsic subunits, had a pseudo-2-fold symmetry and protrusions that correlated with the surface helices e and e' or were at the sites of putative alpha-helix-connecting loops estimated from the 4 A map of the complex. The molecular dissection achieved with the AFM, opens new possibilities to unveil the interfaces between subunits of supramolecular assemblies.

Mapping flexible protein domains at subnanometer resolution with the atomic force microscope

The mapping of flexible protein domains with the atomic force microscope is reviewed. Examples discussed are the bacteriorhodopsin from Halobacterium salinarum, the head-tail-connector from phage phi29, and the hexagonally packed intermediate layer from Deinococcus radiodurans which all were recorded in physiological buffer solution. All three proteins undergo reversible structural changes that are reflected in standard deviation maps calculated from aligned topographs of individual protein complexes. Depending on the lateral resolution (up to 0.8 nm) flexible surface regions can ultimately be correlated with individual polypeptide loops. In addition, multivariate statistical classification revealed the major conformations of the protein surface.