2380Mechanisms of myocardial ischemia during exercise in microvascular angina

Background

Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a vasodilator, the pathophysiological basis of which is unclear. This study sought to address two major gaps in our understanding of MVD: firstly, whether diminished flow reserve is due to structural changes within the microvasculature or potentially reversible dysfunction and secondly to unravel the mechanism of exercise-induced ischemia in the absence of obstructive disease.

Methods

Simultaneous intracoronary pressure and flow velocity recordings were made in the left anterior descending artery of patients with angina and no obstructive epicardial disease (Fractional Flow Reserve >0.80). Measurements were made at rest, during adenosine-mediated hyperaemia and supine bicycle exercise. Wave intensity analysis was used to quantify waves that accelerate and decelerate coronary blood flow, coronary perfusion efficiency being defined as the proportion of total wave energy that accelerates blood flow. Patients were prospectively classified into MVD (coronary flow reserve <2.5) and controls with researchers blinded to the classification throughout the protocol. Myocardial perfusion and vascular function were assessed by 3T cardiac MRI and venous occlusion plethysmography with forearm blood flow (FBF) assessment during serial infusions of acetylcholine, adenosine and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).

Results

78 patients were enrolled (42 patients had MVD and 36 were controls), with no differences in cardiovascular risk factors between groups. The MVD group had elevated coronary blood flow (21.3±6.4 vs. 15.1±4.5cm s–1; p<0.001) and global myocardial perfusion (1.36±0.37 vs. 1.13±0.22ml/min/g; p=0.01) at rest. Maximum coronary and myocardial blood flow during hyperaemia was similar in both groups. During exercise, MVD patients achieved similar peak flow (30.5±10.0 vs. 26.3±7.7cm s–1; p=0.07) despite a higher rate-pressure product (20777±5205 vs. 17450±4710bpm.mmHg; p=0.01). Coronary perfusion efficiency, decreased with exercise in the MVD group (61±11% vs. 44±10% p<0.001) but was unchanged in controls. On MRI, MVD had lower hyperaemic endo-epicardial perfusion ratio than controls (0.94±0.08 vs. 1.04±0.13; p=0.001). Augmentation of FBF with acetylcholine was attenuated in MVD patients compared to controls (p=0.02) but the response to adenosine was similar (p=0.13). Infusion of L-NMMA caused a significantly greater reduction in FBF in MVD patients compared to controls (p<0.001).

Exercise Physiology in MVD

Conclusion

Impaired flow reserve in MVD represents a dysfunctional state, characterised by inappropriately elevated resting flow due to increased nitric-oxide synthase mediated vasodilatation. There is abnormal flow distribution in the myocardium predisposing to subendocardial ischaemia, associated with and exacerbated by impaired cardiac-coronary coupling during exercise. These novel findings may represent distinct therapeutic targets.

Acknowledgement/Funding

British Heart Foundation

3043Endotrophin, a fragment of collagen type VI, is correlated to IMT and associated with cardiovascular events in patients with atherosclerosis and diabetes: the IMI-SUMMIT cohort

Background/Introduction

Patients with micro- and macrovascular diseases, including atherosclerosis, have increased risk of cardiovascular events and early mortality. The atherosclerotic disease is characterised by accumulation of lipids, cells and proteins in the arterial wall, which includes remodelling of the extracellular matrix (ECM). Collagen type VI (COL6) is known to be over-expressed in patients with atherosclerosis. The biomarker PRO-C6, known as endotrophin, is a COL6 fragment that reflects formation of collagen type VI, and possess pro-inflammatory and pro-fibrotic activities.

Purpose

We explored whether increased endotrophin levels, measured by PRO-C6, were associated with intima-media thickness (IMT) and mortality in the IMI-SUMMIT cohort.

Methods

Circulating protein levels of PRO-C6 were measured in EDTA plasma from 1500 patients enrolled at four European University Hospitals, using an enzyme-linked immunosorbent assay. Follow-up data were available up to three years after sample collection. Associations between PRO-C6 and incidence of cardiovascular (CV) events and all-cause mortality were assessed by Kaplan-Meier curves and Cox proportional hazard regression analyses. Pearson correlation was performed to explore the association of PRO-C6, IMT and clinical variables. Known confounders defined by the Framingham Heart study (age, gender and diabetes) were included in the Cox proportional hazard regression analysis.

Results

Plasma PRO-C6 was significantly correlated with IMT in both the common carotid artery and the carotid bulb (r=0.09, p=0.002 and r=0.11, p=0.0003, respectively), HbA1c (r=0.11, p<0.0001) and C-reactive protein (r=0.14, p<0.0001). A total of 145 patients suffered from fatal or non-fatal cardiovascular events during the three-year follow-up period. Patients in the highest PRO-C6 tertile had a two-fold increased risk of experiencing a CV event during follow-up (p=0.002), independently of age, presence of CVD at baseline, type 2 diabetes, smoking and statin treatment in a regression model.

Conclusion

The present findings demonstrate that circulating levels of PRO-C6 are associated with atherosclerosis severity and increased incidence of cardiovascular events. Since PRO-C6 detects the signaling molecule endotrophin, the results may indicate that endotrophin is not only a biomarker of atherosclerotic disease, but may have a role in promoting disease progression.

Acknowledgement/Funding

This work was supported by the Danish Research Foundation, The Danish innovation foundation and the IMI-SUMMIT participants

Difference in the frequency of pouchitis between ulcerative colitis and familial adenomatous polyposis: is the explanation in peripouch fat?

AIM

Patients with ulcerative colitis (UC) have an unexplained higher incidence of pouchitis and a greater amount of peripouch fat compared with patients with familial adenomatous polyposis (FAP). The aims of this study were to compare the peripouch fat areas between patients with UC and patients with FAP, and to explore relationship between peripouch fat and pouchitis or chronic antibiotic-refractory pouchitis (CARP).

METHOD

Patients with an abdominal CT image from our prospectively maintained Pouch Database were included. Abdominal fat and peripouch fat were measured on CT images at different levels or planes. Comparisons of peripouch fat and CARP were performed before and after propensity score matching.

RESULTS

A total of 277 patients with UC and 40 patients with FAP were included. Compared with patients with FAP, patients with UC were found to have a higher incidence of pouchitis (58.5% vs 15.0%, P < 0.001) and CARP (24.5% vs 2.5%, P = 0.002) and a higher total peripouch fat area (P = 0.030) and mesenteric peripouch fat area (P = 0.022) at Level-3. Univariate and multivariate analyses showed that diagnosis (UC vs FAP) and peripouch fat areas at Level-3 and Level-5 were independent risk factors for CARP. With propensity score matching, 38 pairs of patients with UC and FAP were matched successfully. After matching, patients with UC were found to have higher total peripouch fat area and higher mesenteric peripouch fat area at Level-3, and a higher incidence of pouchitis (57.9% vs 13.2%, P < 0.001) and CARP (23.7% vs 2.6%, P = 0.007).

CONCLUSION

Our study demonstrates that patients with UC have more peripouch fat than those with FAP, which may explain the difference in the frequency of pouchitis and CARP between these groups of patients.

FM1-7 Cranio-cervical instability in ehlers-danlos syndrome employing upright, dynamic MR imaging; a comparative study

Objectives

Ehlers-Danlos syndrome (EDS) is a hereditary connective tissue disorder leading to hypemobile joints including the craniocervical junction. Neck pain is a prominent feature. Structural abnormalities may have a dynamic element and thus may not be captured in a recumbent MRI. There is currently a lack of evidence1 assessing the use and diagnostic impact of positional MRI in Ehlers-Danlos syndrome. We aim to evaluate structural features and dynamic instability in an EDS cohort employing dynamic MR imaging against a non EDS symptomatic cohort.

Design

Comparative Study.

Subjects

Patients diagnosed with Ehlers-Danlos syndrome and control subjects (non EDS with cervical spondylosis) were included in this study.

Methods

Cranio – cervical spine global and segmental movement parameters in the neutral, extension and flexion positions were measured from T2-weighted images in the midline sagittal plane. These parameters included the clivo axial angle, grabb oakes line, C2 sagittal vertical axis, C0-C1 angle, C1-2 angle, cervical lordosis and T1 slope.

Results

The clivo- axial angle measured in neutral was 139.7±10.4 degrees in the EDS group vs 148.9±8.4 in the control group (p<0.01) The cervical range of movement between flexion and extension was 74.6±24.4 in the EDS group vs 39.4±11.3 in the controls (p<0.0001).

Conclusions

EDS patients with neck symptoms exhibit different static as well as dynamic craniocervical structural features compared to a general population control.

Reference

Ont Health Technol Assess Ser [Internet]2015July;15(13):1–24.

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A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.