of Work: The purpose of this intra-agency agreement (Y02-AG-5-0282) is to support the measurement of arterial pulse wave velocity (APWV) as a measure of arterial stiffness in the NHLBI Activity Counseling Trial (ACT). The trial is designed to test the hypothesis that increases in physical activity resulting from educational interventions will reduce arterial stiffness. The setting is appropriate for this hypothesis testing because of the prospective nature of the study and the range of interventions which will be adopted. The measurements will be taken at three points in time when other physiologic measures are taken. This will allow assessment of intra-individual variability as well as the possibility of examining change over time in these measures in relation to the level of compliance with the physical activity intervention. The study is taking place in three geographic locations to assure adequate sample size for subgroup analysis: Memphis, TN, Dallas, TX and Palo Alto, CA. Pulse wave velocity is being measured by two Doppler flow velocity probes simultaneously measuring the carotid and femoral arteries. A computer algorithm calculates average flow velocity tracings on a beat-to-beat basis. The time needed for the pressure wave to travel from the proximal to distal sampling site is calculated from the foot of the pressure wave. The baseline examinations have now been completed, with approximately 500 APW tracings available for analysis. Quality control reports from the Coordinating Center indicate that a very high proportion of the tracings are of acceptable quality and will be useful for analysis. Personnel from the Reading Center in Baltimore and the Coordinating Center at Bowman Gray conducted a validation study at the three sites in March of this year. Records produced by measurement teams at the sites were compared to measurements made on the same individuals by the team of investigators from the reading center. Results of the study suggest that the protocol is valid and reproducible and measurements taken by the local site teams are highly correlated with those made by the visiting teams, with only slightly higher variability among the local site teams' readings. Presently the clinics are approximately two-thirds of the way through the process of making 6-month follow-up APWV measurements, and the quality of the readings appears to remain at a high level. Plans are under way for analysis of the baseline data and preparation of manuscripts. The final measurement of APWV will be conducted at 24 months subsequent to baseline.
| Havlik, R J; Brock, D; Lohman, K et al. (2001) High-density lipoprotein cholesterol and vascular stiffness at baseline in the activity counseling trial. Am J Cardiol 87:104-7, A9 |
