Introduction
The prevalence of diabetes mellitus (DM) in patients requiring cardiac surgery is significantly increasing and achieving tight perioperative glycemic control in DM patients could decrease perioperative morbidity and improve survival [1-3] . Regarding aortic diseases, current studies have demonstrated a negative correlation between DM and the occurrence of aortic diseases [4-7] . However, previous studies are contradictory in that patients with DM were found to have poorer outcomes after abdominal aortic aneurysm repair [8],whereas mortality and clinical complications in type B aortic dissection patients after thoracic endovascular aortic repair (TEVAR) were significantly reduced in DM patients [9] . Whether patients with aortic diseases may benefit from the tight glycemic control remains unclear [10-11] .
DM has been shown to reduce the progression of aortic disease and the pathophysiological explanation of these phenomena include: 1) increasing the matrix of the aortic wall (suppression of plasmin and decreased levels/activity of matrix metalloproteinase [MMP]) and 2) reducing aortic mural macrophage infiltration and neovascularization[12] . The anti-inflammatory effect of oral antidiabetic medication drugs (including metformin, sulfonylurea, and thiazolidinedione) can also lower the risk of aortic aneurysm development [13] . However, insulin treatment may diminish this protective effect of hyperglycemia in preventing the aortic aneurysm development process [14] . Therefore, it seems that tight glycemic control (especially insulin treatment) is probably unnecessary and harmful for DM patients with aortic diseases.
Acute aortic syndromes consist of three interrelated diseases: aortic dissection, penetrating aortic ulcer and intramural hematoma (IMH). According to the analysis from the International Registry of Acute Aortic Dissection, fewer than 10% IMHA cases will resolve spontaneously whereas 16% to 47% will progress to aortic dissection[15] . Complicated IMHA is defined as the presence of rapid aortic expansion, signs of aortic rupture, fatal organ ischemia, recurrent or refractory pain, and refractory hypertension despite adequate medical therapy in the acute phase (≤14 days); immediate open surgery is the first choice for these patients. However, for uncomplicated IMHA patients, the ‘wait-and-watch strategy’ (optimal medical therapy with blood pressure and pain control, serial imaging and necessary TEVAR/surgery) is appropriate, particularly in the absence of aortic dilation (>50 mm) and hematoma thickness less than 11 mm [16-17] . In Asian countries, the “wait-and-watch strategy” is the first-line treatment for uncomplicated IMHA patients with a maximum aortic diameter less than 50 mm and a hematoma thickness less than 11 mm [18-20] . However, adverse clinical events (development of aortic dissection, delayed surgery or death) that develop within 6 months after medical treatment of uncomplicated IMHA can reach a prevalence of 36.5% [18] which means that not all uncomplicated IMHA patients may benefit from the “wait-and-watch strategy”.
In sum, we hypothesized that in uncomplicated type A IMH patients who received the “wait-and-watch strategy” (combined with tight glucose management), patients with DM (compared with patients without DM) would not benefit from such a treatment strategy because the anti-hyperglycemia treatment would probably diminish the protective effect of hyperglycemia in preventing aortic disease progression and the obviously high adverse clinical events that develop within 6 months after medical treatment of uncomplicated IMHA [1][18] . To answer this question, we compared the clinical outcomes in uncomplicated IMHA patients who received the “wait-and-watch strategy” (with and without DM) during the first hospitalization and later follow-up period.