Patient characteristics and laboratory examination results between normal controls and obese patients are shown in Table 1 Table 1 Clinical parameters of normal controls and obese patients

There were significant differences in weight, BMI, BSA, SBP, DBP and HR between normal controls and obese patients (P < 0.001). The values of weight, BMI, BSA, SBP, DBP and HR in obese patients were significantly larger than those in normal controls. There were no significant differences in age or sex (P > 0.05).

The values of HbA1c, TC, TG, LDL-C and FPG in obese patients were significantly larger than those in normal controls (P < 0.05), and there were no significant differences in BUN and SCR (P > 0.05).

Echocardiographic parameters and GLS between normal controls and obese patients (Table 2)Table 2 Echocardiographic parameters between normal controls and obese patients

There were significant differences in LAD, IVSd, LVPWd, LVd, LVEDV, LVESV, LVEF, E, A, E/A, e′, and E/e′ between normal controls and obese patients (P < 0.001). The values of IVSd, LVPWd, LVd, LVEDV, LVESV, A, and E/e′ in obese patients were significantly larger than those in normal controls; however, the values of LVEF, E, E/A, and e′ were significantly lower than those in normal controls. There were no significant differences in the LAV index or MAPSE among normal controls, T2DM patients and T2DM patients with HT (P > 0.05).

The absolute value of GLS in obese patients was significantly lower than that in normal controls (P < 0.001).

Global MW between normal controls and obese patients (Table 3; Fig. 1)Table 3 Global myocardial work index between normal controls and obese patientsFig. 1

Global myocardial work between normal controls and obese patients

There were significant differences in GWI, GCW, GWW, GWE and GCW/GWW between normal controls and obese patients (P < 0.005). The values of GWI, GCW, GWE and GCW/GWW in obese patients were significantly lower than those in normal controls, while GWW was significantly larger than that in normal controls. The GWI, GCW, and GWW of obese patients with normal GLS were significantly increased compared to the normal controls (P < 0.05), but GWE and GCW/GWW were significantly reduced compared to the normal controls (P < 0.05). The GWI, GCW, GWE, and GCW/GWW of obese patients with abnormal GLS were significantly reduced compared to the normal controls and obese patients with normal GLS (P < 0.05), while GWW was significantly increased compared to the normal controls and obese patients with normal GLS (P < 0.05).

Subgroup analysis of global MW in obese patients (Table 4; Fig. 2)Table 4 Global myocardial work index among patients with mild, moderate and severe obesityFig. 2

Global myocardial work index among Mild, Moderate and Severe obese patients

There were significant differences in GWI, GCW, GWW, GWE and GCW/GWW among mild, moderate and severe obese patients (P < 0.001). Trend analysis showed that the values of GWI, GCW, GWE and GCW/GWW in severe obese patients were lower than those in moderate obese patients and lower than those in mild obese patients (P < 0.01), while GWW in severe obese patients was larger than that in moderate obese patients and larger than that in mild obese patients (P < 0.05).

Univariable and multivariate regression for GWI and GCW in obese patients (Tables 5 and 6)Table 5 Relationship between GWI and different clinical and echocardiographic parameters in obese patientsTable 6 Relationship between GCW and different clinical and echocardiographic parameters in obese patients

Univariable linear regression analysis showed that GWI and GCW were associated with sex, age, BMI, SBP and LVEF in obese patients, so these variables were incorporated into the multivariate linear regression model of GWI and GCW by means of stepwise selection based on the univariate linear regression analysis results.

Female sex, BMI and SBP were independent influencing factors of impaired GWI (β = 0.15, P < 0.001) (β=-0.18, P < 0.001) (β = 0.50, P < 0.001) and GCW (β = 0.17, P < 0.001) (β=-0.19, P < 0.001) (β = 0.57, P < 0.001).

ROC analysis to confirm the diagnostic value of LV dysfunction by global MW (Table 7; Fig. 3)Table 7 Receiver operating characteristic curve analysis for detecting subclinical LV myocardial systolic dysfunction in obese patientsFig. 3

ROC analysis was performed to determine the performance of MW to detect subclinical LV systolic dysfunction in obese patients

The AUC of GWI was 0.809 (0.774 to 0.840), and the cut-off value was 2163.00mmHg%, with a sensitivity of 80.73% and specificity of 69.47%. The AUC of GCW was 0.820 (0.786 to 0.850), and the cut-off value was 2442.00 mmHg%, with a sensitivity of 67.89% and specificity of 84.35%. The AUC of GWW was 0.603 (0.562 to 0.643), and the cut-off value was 109.00 mmHg%, with a sensitivity of 43.12% and specificity of 72.90%. The AUC of GWE was 0.696 (0.657 to 0.733), and the cut-off value was 94.00%, with a sensitivity of 39.76% and specificity of 88.17%. The AUC of GCW/GWW was 0.684 (0.645 to 0.721), and the cut-off value was 29.78, with a sensitivity of 65.75% and specificity of 60.69%.

The AUC of the combination of GWI, GCW, GWW, and GWE was 0.872 (0.842 to 0.897), and the cut-off value was 0.55, with a sensitivity of 80.43% and specificity of 80.92%. The AUC value was significantly higher than the AUCs of the individual indices (P < 0.001).

Intraobserver and interobserver variability are presented in Table 8 Table 8 ICCs for intra- and interobserver variability for MW parameters

Intraobserver and interobserver variabilities were calculated by the intraclass correlation coefficient (ICC). All global MW parameters exhibited excellent intra- and interobserver correlations with ICC values > 0.94.