The present study represents an assessment of LV myocardial deformation changes by traditional standard echocardiography and speckle tracking echocardiography of the 3VD patients with and without DM. The standard echocardiography demonstrated no significant difference of parameters between the 3VD-DM and the 3VD-non-DM groups. By the 2D STE, it indicates that the GLS and segmental PSLSs of 3VD patients are significantly lower than the normal subjects, and much lower longitudinal strain values are found in the 3VD-DM patients than the 3VD-non-DM patients. As to evaluate the effect of the duration of DM on the 3VD patients, it is observed that the significantly worse GLS is found in the 3VD patients with the duration of DM ≥5 years than with the duration of DM<5 year. However, as to the effect of the glucose control level on the 3VD patients, it is found that there is no significant difference of GLS and segmental PSLSs are observed between the patients with HbA1C≥7 or HbA1C<7.
4.1 LV longitudinal function in T2DM
In the past three decades, a number of experimental, pathological, epidemiological and clinical data confirmed the association of DM with myocardial dysfunction. According to the standard echocardiography in our study, it demonstrated the diastolic dysfunction of the 3VD-DM and the 3VD-non-DM patients, compared with the control group. However, these differences weren’t been found between the 3VD-DM and the 3VD-non-DM patients.
Echocardiography-based speckle-tracking strain imaging is an emerging modality to assess LV function. The use of noninvasive strain imaging may provide added information to aid in perioperative risk stratify caption and management for these high-risk patients，such as DM  . LV longitudinal myocardial systolic dysfunction, as assessed in terms of lower GLS, has been identified decreased in DM patients . It has been reported that DM patients have lower longitudinal myocardial mechanics, circumferential and rotational mechanics . And diabetic patients might have dysfunction apparent in the longitudinal direction . Several studies have confirmed that the LV function in diabetic patients gradually develop to dysfunction, and eventually develop symptoms of heart failure . Nakai et al. reported that GLS in T2DM patients was significantly lower than that in age-matched normal subjects in spite of similar LVEF . While, Zoroufian et al. also found that segmental and global systolic longitudinal strains were decreased in diabetic patients with normal coronary artery and EF value . Therefore, the speckle tracking echocardiography could be more sensitive to detect the changes of DM for impaired LV function.
4.2 LV longitudinal function in 3VD patients with T2DM
The diffuse multi-vessel atherosclerosis is frequently present in the T2DM patients，before symptoms of ischemia occur . The frequency of 3VD in patients with DM comorbidity was much higher. Sometimes, the CAD in diabetic patients is missed or delayed since the typical symptoms of myocardial ischemia are often masked. The speckle-tracking strain was further used to evaluate the features of these patients.
Previously studies reported that the patients with both CAD and DM had more impaired PSLSs than patients with either condition alone. Limited data was collected to focus on the 3VD patients and to differentiate between the 3VD-DM patients and the 3VD-non-DM patients. Interesting, the findings of our present study extend the available knowledge, in which the global and apical PSLSs of the 3VD-DM patients was significantly lower than the 3VD-non-DM patients. Our study showed that the patients with 3VD-DM had significantly lower longitudinal strain values (global and segmental PSLSs) compared with the normal subjects.
The reasons of the worse GLS in 3VD-DM patients were prone to impaired cardiac systolic and diastolic function. A number of mechanisms have been reported to play an important role in DM patients’ LV longitudinal dysfunction . These changes are observed as changes in free acid metabolism, increased apoptosis, activation of the renin angiotensin system, autonomic neuropathy and increased oxidative stress among others  . All these underlying pathogenetic conditions change the cardiac structure and lead to myocardial ischemia . Since the 3VD lead to the more seriously myocardial ischemia, the damaged longitudinal strain could be observed more obviously in both 3VD and DM patients.
4.3 The effect of the duration and the glucose control level of DM on the GLS of 3VD patients
Several other studies found that the impairment of the GLS in asymptomatic DM patients was progressed with time. The effect of the DM duration on the 3VD patients is unknown. Our study investigated the GLS changes in 3VD patients with different DM duration. It showed the 3VD patients with DM ≥5 years had significantly lower longitudinal strain values compared with the duration of DM <5 years, especially in global, mid and apical PSLSs. Other researches demonstrated the duration of diabetic disease was the only independent predictor for the decrease in GLS , similar with our results. It seems that the longer DM duration cause worse GLS, even in the 3VD patients. It is postulated that prolonged exposure to hyperglycemia can epigenetically modify gene expression profiles in human cells and that hyperglycemic memory is sustained even after hyperglycemic control is therapeutically achieved . That is why the longer DM duration cause worse GLS in the 3VD patients.
Then, the effect of the glucose control level on the 3VD patients with DM was evaluated. A study showed that diabetes with poor blood glucose control, as defined by HbA1c ≥ 7%, leads to reductions of LV systolic strain . Other clinical trials have shown that normalization of blood glucose failed to reduce cardiovascular outcomes in the diabetic population . In our study, we found that there was no significant difference between the 3VD patients with HbA1C≥7 or HbA1C<7. This result demonstrates the glucose control has limited effect on the GLS in the 3VD patients. It may come from that myocardial ischemia was severe because of 3VD, in which it can cause the decreased GLS. Relatively, the damage of uncontrolled glucose level on the LV strain in the 3VD-DM patients maybe limited.
There are several limitations to our study. First, the LV strain in the radial and circumferential directions was not evaluated. The automated algorithm used in the present study only permits the assessment of longitudinal LV strain. Then, patients with and without DM differed with respect to some clinical characteristics, including age, con-founding comorbid conditions such as hypertension and some medications treatment as out lined inTable1. Although these differences were due mostly to DM, it is also possible that the differences observed in longitudinal strain might be due to the aforementioned differences in clinical characteristics. In our study, patients in the DM group had a higher incidence of hypertension than those in the non-DM group, which may influence the strain difference between groups with and without DM . However, exclusion of hypertensive patients from the study is unlikely because the incidence of hypertension is very high in patients with CAD. Therefore, the impairment of strains may not be specific to CAD or DM, and further investigations are needed to validate our findings.