The function of the left ventricular myocardial segments assessed by velocity vector imaging in patients with a myocardial infarction before and after coronary artery bypass

Rationale: Velocity vector imaging is a non-invasive technique to analyze left ventricle (LV) fibers and determine the depth and area of an ischemic injury and the response to revascularization. Aim : To assess LV functional parameters in patients with non Q-wave myocardial infarction and Q-wave myocardial infarction using velocity vector imaging before and in the early postoperative period after coronary bypass grafting. Methods : We analyzed the strain (S) and strain rate (SR) of longitudinal, circular and radial fibers in 252 LV segments in 14 patients with non Q-wave myocardial infarction (group I) and in 252 segments in 14 patients with Q-wave myocardial infarction (group II) before and at day 12 after coronary bypass grafting. Results : General analysis of the fibers from all LV segments, as well as a detailed analysis of each segment was performed by velocity vector imaging. The general analysis showed the following: the function of longitudinal fibers in group I was characterized by a low S parameter (-15.2 ± 7.4%) and normal SR (-1.04 ± 0.6 s-1); in group II – a low S (-12.7 ± 6.4%) and SR (-0.80 ± 0.4 s-1). The deformation characteristics of the circular fibers were reduced in both groups (group I: S -17.1 ± 8.9%, SR 1.23 ± 0.7 s-1; group II: S -14.02 ± 8.3%, SR -0.98 ± 0.6 s-1). The radial fibers had normal S values (group I: 29.1 ± 19.9%, group II: 25.9 ± 19.7%), high SR value in group I (1.73 ± 1.0 s-1) and normal SR in group II (1.35 ± 0.6 s-1). After coronary bypass surgery, the group II demonstrated an improvement in the SR of longitudinal (-0.91 ± 0.5 s-1, p = 0.001) and circumferential (-1.11 ± 0.5 s-1, p = 0.001) fibers, whereas the S of radial fibers deteriorated (21.7 ± 8.9%, p = 0.0004). In group I, radial fiber SR became normal (1.39 ± 0.6 s-1, p = 0.0004). A detailed analysis of the LV identified 10 groups of segments depending on the changes S and/or SR. Revascularization had an impact on all segments in patients of both groups. The segments with combined changes in S and SR improved its function. The segments with changes only in S or only in SR reduce their function, which is considered as a step to harmonic contraction. Conclusion : General analysis of LV fibers shows the impact of myocardial infarction, and the detailed analysis helps to identify the impact of revascularization.