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

The alpha angle α (degrees) is a thrombelastographic measure of clot propagation. A parametric measurement of clot propagation [maximum rate of thrombus generation (MRTG), dynes/cm per s], however, has recently been utilized. Thus, the relationship of changes in α with changes in MRTG were determined. α and MRTG values obtained from 859 thrombelastograms was collected from nine studies. Data were analyzed and the relationship between α 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 α (R = 0.88, P < 0.001). Whole-blood α values were in the range 66.7-74.7 whereas MRTG values were 5.5-10.8, and plasma α 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 α. While normal α 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.