Thrombelastographic measures of clot propagation: a comparison of alpha with the maximum rate of thrombus generation.

The alpha angle alpha (degrees) is a thrombelastographic measure of clot propagation. A parametric measurement of clot propagation [maximum rate of thrombus generation (MRTG), dynes/cm2 per s], however, has recently been utilized. Thus, the relationship of changes in alpha with changes in MRTG were determined. alpha and MRTG values obtained from 859 thrombelastograms was collected from nine studies. Data were analyzed and the relationship between alpha and MRTG defined with commercially available software. Additional comparisons were made retrospectively from whole-blood and plasma data obtained from 33 normal individuals. Data from the nine studies demonstrated that MRTG increased in an exponential fashion compared with increases in alpha (R2 = 0.88, P < 0.001). Whole-blood alpha values were in the range 66.7-74.7 whereas MRTG values were 5.5-10.8, and plasma alpha values were 65.1-77.9 with corresponding MRTG values of 3.5-12.0. Assessment of clot propagation utilizing MRTG provides a more parametric evaluation than the determination of alpha. While normal alpha values may vary by only 12-20%, MRTG values vary by approximately 200-300%. The MRTG should be progressively utilized to a greater extent in both laboratory and clinical settings to parametrically quantify clot growth kinetics with thrombelastography.