**1. Introduction**

The prevalence of diabetes mellitus has increased exponentially, from 108 million in 1980 to 422 million worldwide in 2014 [1]. Cardiovascular diseases (CVDs) constitute the number one cause of mortality globally, representing 30% of all global deaths [2]. Cardiovascular disease is the leading cause of morbidity and premature mortality in patients with diabetes mellitus (DM) [3–6]. A meta-analysis of 102 prospective studies (The Emerging Risk Factor Collaboration) showed that DM in general, confers an increased risk for developing vascular disease compared to non-diabetic patients [7]. DM increases the risk of coronary heart disease, stroke, and peripheral arterial disease by between two and four-fold. The increased risk is independent of, and additional to other cardiovascular risk factors [7–10].

It has been reported that between 20 and 30% of patients with coronary artery disease have known DM, and up to 70% have newly detected DM or impaired glucose tolerance [11]. Importantly, the risk of myocardial infarction (MI) is three to five times higher in type 2 DM. A diabetic patient with no history of MI has the same long-term risk as a non-DM subject with a past history of MI [12]. For these reasons, DM is considered to be a "coronary heart disease equivalent" [13]. The anatomical pattern of coronary artery disease (CAD) in patients with DM influences the prognosis [11]. The extension of CAD in diabetic patients exhibits distinctive characteristics that infer an increased risk. Likewise, CAD in diabetics is characterised by being diffuse, affecting the left main stem more frequently, involving multiple vessels, and also affecting the distal coronary tree [14]. CAD typically progresses more rapidly in diabetic compared with non-diabetics [15]. Furthermore, patients with DM have more associated comorbidities, such as peripheral artery disease, cerebrovascular disease or chronic kidney disease, which influence outcomes after coronary revascularisation [11].

The indications for myocardial revascularisation, for both symptomatic and prognostic reasons, were the same in patients with or without DM [16]. The anatomical pattern in which diabetes affects patients, combined with an increased risk of stent failure (restenosis and stent thrombosis), in conjunction with the "Prothrombotic State" that characterised these patients, resulted in poorer outcomes following revascularisation in general. However, it is particularly evident following percutaneous revascularisation.

Three randomised clinical trials compared percutaneous coronary intervention (PCI) vs. coronary artery bypass graft surgery in patients with DM, using mainly first-generation drug-eluting stents (DES) [11]. With this in mind, safety concerns following PCI have surfaced, specifically with the use of first-generation DES, as diabetes has emerged as an independent predictor of stent thrombosis (ST) [17]. Recently, new generation DES platforms were designed and have demonstrated improved safety outcomes, compared to the first generation. Thus, coronary artery bypass grafting has been the revascularisation treatment recommended in diabetics with multivessel disease.

Although the advent of drug-eluting stents has narrowed the gap between surgery and the percutaneous treatment, the former remains the gold standard in diabetics with diffuse coronary artery disease.

One of the main determinants of poor outcomes in DM is the progression of atherosclerosis, which is more pronounced in diabetics and remains the main cause of cardiac events at one year follow up, after percutaneous revascularisation. This review focuses on all the aforementioned issues, which affect diabetic patients, as well as any updates to the current evidence regarding the different modalities of revascularisation in this special population.
