To our knowledge, this is the first study addressing the relevance of post-stress LVEF drop in a large cohort of patients with type-2 diabetes. The results show that stress-induced ischemia is an independent predictor of a post-stress LVEF drop, but LVEF fall is also detectable in the absence of myocardial perfusion abnormalities. In contrast, neither clinical variables nor infarct size were associated with a post-stress LVEF drop.
It has been demonstrated that the post-stress LVEF drop in patients with CAD is linked to regional perfusion defects and predicts the presence of severe disease [3, 22]. In diabetic patients an abnormal LVEF response to exercise has been documented by echocardiography or radionuclide angiography also in the absence of CAD [23–25]. Accumulating data showed that diabetes mellitus leads to cardiac functional and structural changes, independent on hypertension, CAD, or any other known cardiac disease, supporting the existence of a diabetic cardiomyopathy .
In the present study performed in diabetic patients, although severe ischemia was more frequent in patients with post-stress LVEF drop, the distribution of the number of diseased vessels was similar in patients with and without of post-stress LVEF drop. Noteworthy, post-stress LVEF drop was present in a substantial number of subjects (37%) without ischemia. Abnormality in the contractile response during stress might explain this finding, suggesting loss of contractile reserve . An important epidemiological evidence of the independent effect of diabetes on LV systolic function is given by the results of the Strong Heart Study . Compared with non-diabetics, patients with diabetes had greater LV mass, and lower LV fractional shortening after adjusting for confounding covariables . In addition, the presence of post-stress LVEF drop in diabetic patients with normal perfusion may be also related to coronary vascular dysfunction in the absence of significant coronary artery stenosis [28–30]. This hypothesis is supported by the observation that in the subgroup of patients who underwent coronary angiography, the distribution of the number of vessels with a significant coronary stenosis was similar in patients with and without post-stress LVEF drop.
As expected, summed difference score was an independent predictor of post-stress LVEF drop. In particular, severe myocardial ischemia was found in 46% of patients with and in 27% of those without post-stress LVEF drop. Several studies reported that in patients with suspected or known CAD stress-induced transient LV dysfunction is associated with severe and extensive ischemia [3–7, 31, 32]. However, these studies evaluated post-stress LVEF drop in unselected patients population. The finding of a higher LVEF at rest in patients with post-stress LVEF drop is in agreement with previous studies. In particular, Guenancia et al.  in patients with recent myocardial infarction found high LVEF resting values as independent predictor of post-stress LVEF drop. In our study, patients with post-stress LVEF drop had a poorer outcome than those without. However, when only patients with normal myocardial perfusion were considered, event-free survival was comparable in patients with and without post-stress drop in LVEF, confirming the prognostic role of stress-induced ischemia.
This study has some potential limitations. First, perfusion patterns might influence the decrease of post-stress LVEF [34, 35]. However, it has been demonstrated that gated MPS provides an accurate assessment of LVEF even in the presence of large perfusion defects as compared to equilibrium radionuclide angiography and echocardiography . Another limitation of this study is the lack of hemoglobin A1c levels, which was not available in all patients. In addition, coronary angiography was not performed in all patients.