Gu et al. [11] reported, that in US population, survival of diabetic subjects was lower than that of non-diabetic subjects in all age, sex, and race groups. Also, type 2 DM is associated with reduced life expectancy at almost all ages in the Scotland [12]. Adults with type 2 DM, especially those with cardiovascular comorbidity, did not live as long than their non-diabetic people in South Korea [13]. Patients with diabetes mellitus (DM) are at increased risk of infection. Movahed et al. [14] studied Veterans Health Administration hospitals database and reported presence of IE in 1340 (0.5%) DM patients versus 1412 (0.3%) non-DM, control group patients (relative increase of 40%), and concluded, that patients with type II DM have significantly higher prevalence of IE. Also, Abe et al. [4] identified 76385 patients with native valve IE during 2004 -14 years, from the US National Inpatient Sample, of which 22284 (28%) had DM, and found, that proportion of DM among patients with IE increased from in 22% in 2004 to 30% in 2014 (p < 0.0001). Miguel-Yanes et al. [3] identified 16,626 patients with IE in Spain, and found, that incidence of IE, among population with and without diabetes, have increased during the period 2001–2015 with significantly higher incidence rates in the diabetic population. However, it is not clear whether this is a true increase in the incidence of IE, or a better diagnosis.
Kourany et al. [15] compare outcomes between 150 diabetic and 905 non-diabetic patients with IE, from the International Collaboration on Endocarditis Merged Database. Diabetic patients underwent surgical intervention less frequently (32.0% vs. 44.9%, p = 0.003), and had higher overall in-hospital mortality (30.3% vs. 18.6%, p = 0.001). Olmos et al. [16] reported, that in-hospital mortality (43.5% vs. 30.0%; p = 0.008) were more common among patients with DM than in those without, but not described treatment modality, surgical or conservative. Farag et al. [17] studied 360 patients with IE, operated between 1993 and 2012, and reported, that non-survivors had higher rates of preoperative diabetes mellitus (p = 0.005), but not found diabetes as independent predictors of 30-day mortality. Yoshioka et al. [5] described 470 patients underwent valve surgery for left-sided active IE, 374 non-DM and 96 with DM. In-hospital mortality was 8% in patients without DM and 13% in patients with DM (p = 0.187). The overall survival rate at 1 and 5 years was 87% and 81% in patients without DM and 72% and 59% in patients with DM (p < 0.001). Wei et al. [18] studied of 866 people, who had been diagnosed with IE. They were divided into three groups: 469 patients in the normoglycaemia group, 246 patients in prediabetes group and 151 patients in diabetes group. Surgery was performed in 72.3% ,68.7% and 55.6% of cases respectively (p = 0.001). During median follow-up of 2.4 year, 126 (14.5%) died. Compared with those in the normoglycaemia group, higher long-term mortality was seen among people with prediabetes or diabetes (9.7% vs. 22.0% vs. 28.1%, P < 0.001). Lin et al. [19] described 412 patients with IE divided into 2 groups: group 1, patients with DM (n = 72) and group 2, patients without DM (n = 340) and concluded, that overall in-hospital mortality rate for both groups was 20.2% and was higher in group 1 than in group 2 (41.7% vs. 16.5%, p < 0.01).
Among the entire cohort of patients in our study, the percentage of the diabetic patients was 22% and those with DM were older. These data are comparable with other studies [5, 15, 16, 18, 19]. The possible explanation for this fact is that the long-term course of diabetes is associated with a sharp increase in the frequency of IE. Østergaard et al. [20] identified 300,000 patients with DM through the Danish Prescription Registry and investigated the association between the duration of DM and the incidence of IE. In patients with DM duration of 0–5 years, 5–10 years, 10–15 years, and more than 15 years, the incidence rates of IE were 0.24, 0.33, 0.58, and 0.96 cases of IE/1000 person years, respectively. Patients with DM duration 5–10 years, 10–15 years, and > 15 years were associated with a higher risk of IE compared with DM duration 0–5 years. Another study from the above mention Danish Registry [21], included 1767 patients with IE undergoing surgery, 735 patients < 60 years (24.1% female), 766 patients 60–75 years (25.8% female), and 266 patients ≥ 75 years (36.1% female). The proportions of patients undergoing surgery were 35.3, 26.9, and 9.1% for patients < 60 years, 60–75 years, and > 75 years, respectively. Mortality at 90 days was 7.5, 13.9, and 22.3% (p < 0.001) for three age groups. In adjusted analyses, patients 60–75 years and patients ≥ 75 years were associated with a higher mortality, HR = 1.84 (95% CI: 1.48–2.29) and HR = 2.47 (95% CI: 1.88–3.24) as compared with patients < 60 years. In addition, the diabetic patients had more co-morbidities, higher operation risk and longer operation time.
Our study carried out in a contemporary cohort of Israeli patients, who underwent surgery due to IE, demonstrates several important implications regarding the impact of type 2 DM on short-, mid- and long-term mortality. Our results are very similar to previously reported: 30-day mortality 11.7% vs. 7.7%, 1- and 5-years mortality was 86.8% vs. 79.8% and 84.4% vs. 69.1% for diabetic and non-diabetic patients respectively. Diabetic patients have trend to increasing mortality at the short- and intermediate period post-surgery for IE, but this is not statistically significant. Statistically significant difference was observed only for 5-years survival (p = 0.003).
There are a few limitations in our study. First, our study is retrospective in design. Second, our study was conducted in a single-center cardiac surgery department. Third, very high-risk patients are not candidate for surgery, there might be an option, that non-operated IE patients would change the survival results, Forth, we have limited microbiologic data.