Coronary Artery Plaque Burden in Asymptomatic Danish Men Aged 65-75 Years and the Relation to Glycemic Status.
Condition: Coronary Artery Disease; Dysglycemia
MeSH terms: Coronary Artery Disease
Study type: Observational

Summary: 
      Cardiovascular disease (CVD) is one of the leading causes of death in the Western Society.
      Patients with type 2 diabetes mellitus (T2DM) or dysglycemia have an increased risk of
      developing CVD. Furthermore, T2DM have an increased risk of developing heart failure,
      especially non-systolic, whether or not this is correlated to stepwise abnormal glycemic
      status is not fully investigated.

      The aims of this study are to investigate association between 1) Coronary plaque burden and
      morphology to glycemic status (normal glucose tolerance (NGT), dysglycemia (impaired fasting
      glucose (IFG) or impaired glucose tolerance (IGT)) and diabetic oral glucose tolerance test
      (OGTT) in participants without known T2DM), 2) Coronary plaque burden and morphology to
      diastolic and systolic function of the left ventricle including 2D speckle-tracking
      assessments, 3) Glycemic status to diastolic and systolic function of the left ventricle
      including 2D speckle-tracking assessments

      In this descriptive study, 500-800 asymptomatic men aged 65-75 without known diabetes will be
      included and divided into three subpopulations according to glycemic status. Blood sample,
      oral glucose tolerance test (OGTT), echocardiography and Coronary CT Angiography (CCTA) will
      be performed at inclusion
    

Detailed description: 
      Background

      Cardiovascular disease: Cardiovascular disease (CVD) is still one of the leading causes of
      death in the Western Society. Despite extensive research, risk estimation based on
      traditional risk factors predicts risk in the general population but may not give an adequate
      individual risk, and can thereby under- or overestimate the risk of future cardiovascular
      event and therefore lead to either over- or undertreatment of a not ignorable part of the
      population.

      T2DM/dysglycemia and atherosclerosis: The prevalence of type 2 diabetes mellitus (T2DM) is
      rising rapidly. Furthermore, one study has reported that the prevalence of dysglycemia or
      undiagnosed diabetes were as high as 43.8% among 60-year-old men. T2DM is known to be
      strongly associated with an increased risk of CVD, but also dysglycemia has been associated
      with an increased risk of CVD. Thus, it is possible that there is a linear relationship
      between stepwise dysregulated glycemic status and increased coronary plaque burden, but the
      relationship has not been fully explored.

      CCTA: Coronary CT Angiography (CCTA) can be performed with or without contrast. Contrast
      enhanced CCTA has been found to be a valid and reproducible method of evaluation of both
      extent and characteristics of atherosclerotic plaques. Motoyama et al. reported spotty
      calcification, positive remodeling, and LAP (non-calcified plaque) to be associated with an
      increased risk of development of AMI, especially when two or more patterns were co-localized
      in the plaques. Thus, it might be possible that this type of plaque morphology is associated
      with vulnerable plaques.

      Echocardiography and T2DM/Dysglycemia: T2DM is correlated to a higher incidence of diastolic
      dysfunction, which is thought to predispose to diabetic cardiomyopathy. In addition, subtle
      left ventricular systolic dysfunction assessed by 2D speckle-tracking (also termed impaired
      strain) was found in patients with diabetes and normal systolic function. To our knowledge
      only few studies have investigated diastolic dysfunction and 2D speckle-tracking in patients
      with dysglycemia and their results were mostly diverging.

      To our knowledge no studies have investigated coronary artery plaque burden and morphology in
      asymptomatic men aged 65-75 years with focus on the influence of glycemic status in
      individuals without known T2DM. Due to the expectance of increasing number of patients with
      T2DM and dysglycemia the coming years, it must be foreseen that the number of patients with
      CVD will increase in this group of patients. It is mandatory that we increase our knowledge,
      especially about the development of coronary atherosclerosis and left ventricular function.
      We expect that this study will bring further light on these important aspects of dysglycemia
      and hopefully give information to improve treatment and prophylaxis.

      Methods

      Study population: We plan to recruit 500-800 participants from the DANCAVAS study. More
      detailed description of the Study population can bee read in "Eligibility". Based on one oral
      glucose tolerance test (OGTT) per participant, this population will be divided into three
      groups; normal glucose tolerance (NGT), dysglycemia (impaired fasting glucose (IFG) or
      impaired glucose tolerance (IGT)) and diabetic OGTT without known T2DM. We use the WHO
      definitions in dividing the participants into the mentioned three groups of different
      glycemic status. To date the use of OGTT in diagnosing T2DM, demands two measurements at two
      separate days. Because of the measurement of only one OGTT in this study, the participants
      with diabetic OGTT does not per se fulfil the criteria for diabetes.

      Data acquisition

        1. OGTT: Patients will be instructed in 8-12 hours fasting before the OGTT. Fasting plasma
           glucose (FPG) will be measured. Thereafter, 75 gram glucose will be ingested over five
           minutes. 120 minutes later plasma glucose (120-PG) will be measured and patients will be
           categorized according to mentioned definitions.

        2. Echocardiography: Echocardiography standard measurements of left ventricular (LV)
           systolic and diastolic function:

             -  LV and left atrial volumes will be estimated using Simpson's biplane method of
                discs in the 4 and 2-chamber views, and LV ejection fraction will be calculated.

             -  The mitral inflow pattern will be estimated in the apical 4-chamber view, and the
                peak early (E) and peak atrial(A) velocities will be measured. Peak early mitral
                annular velocities (e') will be estimated using tissue Doppler imaging. The
                E/e´ratio will be obtained by dividing E by average value of e´.

           Global left ventricular longitudinal strain (GLS):

             -  Longitudinal systolic strain will be measured using 2D speckle tracking
                echocardiography. This measurement will be obtained from views with an optimized
                focus on the LV and a frame rate of about 60-80 frames/sec. Subsequently LV will be
                divided into 18 segments. GLS will be calculated by the software as the mean value
                of the peak systolic longitudinal strain of the 18 segments.

        3. CCTA: The CCTA scan GE revolution will be used. CAC score will be evaluated using non
           contrast scans from the DANCAVAS study. In our study, contrast enhanced scans using
           256-slice, ECG-gated, will be performed. In order to regain optimal results, patients
           with pulse >60 beat/min will be given intravenous Beta-blockers and sublingual
           Nitroglycerin spray just before the examination if not contraindicated. Depending on
           BMI, tube voltage will be 120 or 100 kV and tube current 350-650 mAs. The collimation is
           256×0,23mm with a gantry rotation time of 280 ms with 16 centimeters axial coverage per
           rotation. The estimated total radiation dose for one contrast enhanced CCTA is 1-6 mS.
           To reduce risk of contrast related affection of the kidney function a recent eGFR must
           be obtained before scanning and patients will be sufficiently hydrated.

           CCTA analysis:

           Plaque burden The major proximal coronary segments; 1,2,3-5,6,7-11,12,13 are analyzed.

           Per vessel analysis of:

             -  Percent atheroma volume (PAV):(Total vessel volume-total lumen volume/total vessel
                volume×100%)

             -  Total atheroma volume (TAV):(Total vessel volume-total lumen volume)

             -  Normalized atheroma volume (NAV):(Total vessel volume-total lumen volume/mean
                segment length)

           Plaque morphology

           Per plaque analysis of:

             -  LAP: defined as a non-calcified plaque (HU<150) with a lipid core of <30 HU.

             -  Remolding indices (RI): calculated by lesion diameter/reference diameter, where the
                reference diameter is from a normal appearing proximal segment.

             -  Spotty calcifications (SC): defined as small calcified nodules <3mm in length and
                <=90 degrees of the coronary arch.

             -  Degree of stenosis: a significant stenosis is defining as >70% of the luminal area.

           All CTTA scans will be assessed by an observer blinded to patient characteristics. Semi
           quantitative method using dedicated plaque software (QAngioCT Research Edition version
           2.0, Medis Medical Imaging Systems, Leiden, Holland) will be used to assess the plaque
           analysis.

        4. Population characteristics: Baseline data will be collected from journal system and
           questionnaires and includes demographic, former CVD disease, presence of T2DM and
           information regarding the traditional risk factors (e.g. hypertension,
           hypercholesterolemia, obesity and smoking).

        5. Blood sample: Blood sample includes e.g.cholesterol profile, HbA1c, Creatinine,
           C-Peptide, Insulin etc. Additionally, totally 30 ml blood will be collected to form a
           biobank for future research on the influence of inflammatory markers on atherosclerosis
           and glycemic status.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        We will recruit participants from the DANCAVAS study. The DANCAVAS study will include
        45.000 men aged 65-74 years. 15.000 of the participants will be randomly selected to CCTA
        (non-contrast) and the resulting 30.000 constitutes the control group. The CCTA will be
        performed in four Danish cities. Our study will include 500-800 of those DANCAVAS
        participants who will undergo CCTA in OUH Svendborg Hospital. In our study we will perform
        following examination in addition to the examinations in the DANCAVAS study: one CCTA
        (contrast enhanched), one echocardiography and one OGTT.
      
Biospecimen description: 
      Storage in biobank (-80° C):

      5 x 2 ml (serum). 4 x 2 ml (ethylenediaminetetraacetic acid). 2 x 2 ml (sodium citrate)

      1 x 2 ml (erythrocyte sedimentation rate)