Cleveland Family Study

10.16.2 Videocassette Tape Evaluation

All videocassette tapes will be scanned to determine whether the images are technically adequate for interpretation. The technician will scan the videocassette tape to acquire the best quality baseline images of the artery and flow velocity as well as to identify the time point of maximum dilation achieved in response to hyperemia (defined by one minute post-cuff release) and NTG.

The image to be used in the analysis will be determined by _________. A paper copy of that image will be printed and used or measurements. The ________ will measure the diameter and velocity independently.

At the specified time points, end-diastolic (simultaneous with the R wave on the ECG recorded on the videocassette tape during the procedure) frames will be selected for analysis. When possible, arterial segments, a fixed distance from an anatomic marker, will be chosen for analysis at each time point to achieve consistency.

10.16.2.1 Arterial Diameter

The arterial diameter will be assessed perpendicular to the artery’s axis at 3-5 equally spaced, equivalently imaged (baseline and post-occlusion images) sites along the vessel’s axis depending on the extent of artery that will be adequately imaged. The near and far wall locations will be ideally determined at the blood-intima-media interface. Alternatively, acceptable measurements will be made at the blood-hard reflection interface. Only comparisons between similar interfaces will be employed. Absence of a consistent blood-vessel wall interface disqualifies the image for interpretation.

10.16.2.2 Flow-Mediated and NTG-Induced Vasodilation

Flow-mediated vasodilation will be calculated as the percent change in the mean diameter between the 1-minute post-cuff release diameter and the baseline image. NTG-induced vasodilation will be assessed as above at baseline and after 5 minutes, and will be calculated as the percent changed in the diameter between the post-NTG and pre-NTG diameters.

Pulse Wave Doppler measurements will be made using velocity time integral (VTI) or TAM velocity of the Doppler flow signal by averaging 3 consecutive beats. Heart rate will be recorded from the ECG. Flow-mediated vasodilation or NTG vasodilation will be expressed as the increase in diameter divided by the respective baseline diameter, multiplied by 100%.

10.16.2.3 Volume Flow

Volume flow at rest, peak hyperemia and pre and post NTG will be calculated by multiplying the VTI by the heart rate and the cross-sectional area of the vessel taken from the baseline diameter.

10.16.2.4 Diameter Measurements

Diameter measurements will be made off the hard-copy print out of the appropriately selected frames made __________________readers with a digital caliper (Mitutoyo Digimatic Caliper).

10.16.2.5 Doppler Velocity Analysis

Doppler velocity analysis will be made by the ultrasonographer at the study site with electronic tracing from the ultrasound system. Hard-copy prints from the videocassette tape typically contain the frame number on the videocassette tape and time. Time will always be recorded on the videocassette tape irrespective of ultrasound system tape.