This study was performed in 17 post-myocardial infarction patients with regional wall motion abnormalities. Exclusion criteria included inadequate echocardiographic visualization, presence of a left bundle branch block on the electrocardiogram, and severe valvular heart disease. Clinical information was retrieved from past medical records.

Echocardiography was performed using an iE33 ultrasound system and 2.5 MHz transducers (Philips Ultrasound Company, USA). Standard M-mode, 2-dimensional (2D), and pulsed wave echocardiography were performed according to 2005 American Society of Echocardiography recommendations.9) Interventricular septal wall thickness, posterior wall thickness, and LV end diastolic dimension were measured at the chordae tendinae level. LV ejection fraction was measured using the modified Simpson method. LV regional wall motion was assessed according to the conventional 16-segment model and classified as normal, hypokinetic, and akinetic based on visual analysis. The conventional Tei index was calculated from the sum of isovolumetric contraction time (IVCT) and isovolumetric relaxation time (IVRT), divided by ejection time (ET). For conventional Tei index calculation, IVCT, IVRT, and ET were measured from pulsed wave Doppler imaging of the trans-mitral inflow and LV outflow tracts. Using tissue Doppler, we measured the systolic (Sm), early (Em), and late diastolic myocardial velocities (Am) of each segment. For TDI-Tei index calculation, IVCT, IVRT, and ET were measured from tissue Doppler myocardial velocity images. IVCT was defined as the duration of the bidirectional spike between Am and Sm in the tissue Doppler tracing. IVRT was defined as the duration of the bidirectional spike between Sm and Em. ET was defined as the duration of Sm. The TDI-Tei index was calculated from the same equation used for the conventional Tei index (Fig. 1). TDI-velocities and TDI-Tei index were measured at the basal and mid segments of the LV walls from standard apical 4-, 2-, and 5-chamber views. Velocities and time interval measurements were obtained from one cardiac cycle. Myocardial segments of patients with LV regional wall motion abnormalities were subdivided into 3 groups: normal, hypokinetic, and akinetic segment groups. Average values of TDI-velocities and TDI-Tei indices were obtained in normal, hypokinetic, and akinetic segments, and results from each group were compared.

Continuous data were expressed as mean values±2 SD and categorical data were expressed as percentages. One-way analysis of variance (ANOVA) was applied to assess statistical significance of differences of the Sm, Em, Am, and TDI-Tei indices among the three subgroups, i.e., the normal, hypokinetic, and akinetic segments. Pearson's correlation analysis was performed to examine the association between the TDI-Tei and conventional Tei indices. Inter-observer variability was calculated as the SD of the differences between 2 observers, expressed as a percent of the average value. Measurements for TDI-Tei index calculation were performed twice on 5 patients for assessment of reproducibility.

Clinical characteristics of the study population are summarized in Table 1. All patients had sinus rhythm.

Echocardiographic measurements are summarized in Table 2. The TDI-Tei index, Sm, Em, and Am were measured at a total of 203 segments. Both the conventional Tei and TDI-Tei indices were 0.661±0.095 and 0.679±0.095, respectively. Fig. 2 shows the strong correlation between the conventional and TDI-Tei indices (r=0.811, p<0.001). Sm, Em, and Am were 5.3±0.9, 5.9±1.6, and 6.6±2.0 cm/s, respectively. Average values of TDI-Tei indices of dysfunctional segments (akinetic or hypokinetic segments, n=62) were significantly higher than those of normal segments (n=141) (0.714±0.169 vs. 0.669±0.135, p=0.041, respectively) (Table 3). TDI-Tei indices from akinetic segments of the anterior wall were not significantly different from those from of akinetic segments of the inferior wall (0.777±0.111 vs. 0.751±0.272, p=0.771, respectively) (Table 3). Average values of TDI-Tei indices were 0.742±0.201, 0.677±0.101, and 0.669±0.135 in akinetic, hypokinetic, and normal segments, respectively (Table 3). Average values of Sm, Em, and Am were 4.2±1.3, 5.3±1.9, and 5.6±2.4 cm/s in akinetic segments; 4.9±1.6, 5.4±2.1, and 5.5±2.5 in hypokinetic segments; and 5.4±1.5, 6.1±2.4, and 6.7±2.5 in normal segments, respectively (Table 3). ANOVA analysis showed that the TDI-Tei index and Sm were significantly different between akinetic and normal segments (p=0.020, p<0.001, respectively) (Fig. 3). A weak, but statistically significant negative correlation was observed between the TDI-Tei index and Sm in the patient group (r=-0.302, p<0.001) (Fig. 4). Inter-observer variability for the TDI-Tei index was 8±6%. Reproducibility for the TDI-Tei index was 95±4%.