The Changes of Tissue Velocity and Strain Rate after Exercise in Patients with Coronary Artery Disease

ABSTRACT

BACKGROUND AND OBJECTIVES: Tissue Doppler imaging (TDI)-derived tissue velocity (TV) and strain rate (SR) are new ultrasonic parameters for assessing the regional myocardial function by quantitatively measuring the myocardial velocity. The aim of this study was to investigate the changes of these indices after exercise, in patients with coronary artery disease (CAD), for comparison with the wall motion score index (WMSI). SUBJECTS AND MEHTODS Twenty-one patients with CAD and 21 normal subjects were studied, before and after an exercise stress test, using the Bruce protocol. TDI data were obtained, and analyzed offline, for peak systolic TV (PSTV) and peak systolic SR (PSSR), using a 16 segment-model. The segmental PSTV and PSSR were compared with the WMSI. RESULTS: The number of segments with a significant increase in the PSTV or PSSR, after exercise (p<0.05), was less in the CAD patients than the normal subjects (9 vs. 14 segments, 7 vs. 10 segments, respectively). The PSTV, after exercise, progressively decreased from the base to the apex in both the normal and CAD groups, but the absolute values were significantly lower in the CAD group (base 8.44+/-1.28 vs. 6.56+/-1.6, mid 6.31+/-1.18 vs. 4.26+/-1.25 and apex 3.48+/-0.83 vs. 1.25+/-1.27 cm/sec, p<0.05, respectively). In the normal subjects, the PSSRs, after exercise, were uniform in all segments, whereas this was not the cases in the CAD group (p<0.05). The PSSR showed a negative correlation with the WMSI (r=-0.45, p<0.05). CONCLUSION: This study has shown that TV and SR can detect the ischemic myocardium with exercise stress, and objectively measure the systolic function in patients with CAD. The quantification of stress echocardiography may overcome the training requirement, and subjective nature, of conventional wall motion scoring.