Design and data collection

Study design

    • Age in years
    • Sex
    • Presence of diabetes
    • History of cigarette smoking
    • Presence of peripheral vascular disease
    • Presence of cerebrovascular disease
    • Presence of hypercholesterolemia

  • (For details about the histopathology, see Background.)

    • Presence of intimal thickening
    • Presence of medial calcification or atherosclerosis
    • Type of atherosclerosis

  • (For details about the morphometric analysis, see Background.)

    • Percentage of luminal narrowing
    • Intimal thickness index
    • Intima-to-media ratio

    • Diameter of lumen + intima
    • Internal elastic lamina area
    • Intimal area
    • Medial area
    • Width of intima
    • Width of media

Statistician’s description of study design

Brian and Lek’s study used a clinical sample and made several measurements on two artery types for the same patients.

Protocol

Patient selection From time of study commencement, all eligible CABG patients seen by cardiac surgeons are invited to participate.
Informed consent Research nurse explains purpose of study and surgical procedures involved. If patient agrees to participate, provide with Informed Consent form and ask to sign. Forward Informed Consent form to administration.
Patient data collection Research nurse interviews patient and completes interview schedule. Missing information obtained from patient files when possible.
Specimen collection Collect the discarded segments of RA and ITA grafts from all participating patients. Collect the discarded segments for analysis.
Specimen treatment Fix artery segments in a 4% formaldehyde solution and store for histopathology and morphometric analysis.
Histopathology preparation Prepare multiple transverse slices of each artery, with 5µm sections, in paraffin wax. Record a unique identifier for each artery to ensure the pathologist is blind to the artery source, that is, does not know which type of artery is being examined.
Histopathology Pathologist records the presence of the following arterial abnormalities: intimal thickening; medial calcification; atherosclerosis. Also, record the type of atherosclerosis using the American Heart Association classification of vascular lesions.
Morphometric preparation Exclude specimens that have been distorted in surgery or by histopathology preparation.
Morphometric analysis Using colour image analysis, measure the following:
  • Circumference of the internal elastic lamina (IELC)
  • Width and area of the intima
  • Width and area of the media

Calculate the following:

  • Diameter internal to the media = IELC/ p
  • Internal elastic lamina area = IELC2/ 4 p
  • Percentage of luminal narrowing = 100 x (intimal area/ Internal elastic lamina area)
  • Intimal thickness index = intimal area/ medial area
  • Intima-to-media ratio = maximum width of intima/ width of media at maximal intima thickness