While percutaneous coronary intervention (PCI) is an effective treatment strategy in patients with diabetes mellitus (DM)， it is however associated with higher rate of in-hospital complications， repeat revascularisation procedures， in-stent restenosis and lower event-free survival when compared to non-diabetics. The reasons for this include more diffuse and severe coronary artery disease， small-calibre vessels， rapid progression of new disease， and altered platelet and endothelial function.

Before the stent era， the rate of coronary restenosis was high in diabetics undergoing balloon angioplasty. The Bypass angioplasty Revascularisation Investigation (BARI) trial showed that diabetic patients with multivessel disease had lower 5-year survival rate undergoing angioplasty compared to coronary bypass surgery (66% vs 81%). These may be attributed to increased frequency of restenosis and incomplete revascularisation achieved with angioplasty procedures.
 
The development of bare metal stent (BMS) and more recently of the drug eluting stents (DES) has changed dramatically the prognosis of PCI in this population. The angiographic benefit observed with the use of BMS was correlated with clinical improvement with a reduction in clinical end points， such as cardiac death， non-fatal myocardial infarction， and need for repeated revascularisation， in the diabetic stenting group compared with the diabetic balloon angioplasty group. However the rate of event-free survival of diabetic patients remains better in the CABG group despite a systematic use of bare metal stenting in the PCI group in the Arterial Revascularisation Therapy Study (ARTS 1) study.

Many studies have demonstrated drug-eluting stents to have superior clinical and angiographic benefits compared with bare metal stents in the general population. Only one randomized study has been designed specifically to address diabetic patients (the DIABETES trial). In that study， there was a clear efficacy of the sirolimus eluting stent in reducing both angiographic and clinical parameters of restenosis in both insulin dependent and non-insulin dependent diabetic patients. The relative efficacy of sirolimus vs paclitaxel eluting stents in diabetic patients is still unclear. Only one study， the ISAR-DIABETES， enrolled diabetic patients in a direct non-inferiority trial comparing the two types of DESs. The primary endpoint was in-segment late luminal loss， and the results showed that there was less late loss with the sirolimus than the paclitaxel DES (0.43mm vs 0.67mm). The study was however not powered to assess difference in clinical events of ischemia-driven revascularisation and major adverse cardiac events (MACE). Further meta-analysis comparing indirectly the two DES by Stettler et al showed no difference in terms of MACE. There is also a lack of data regarding the rate of acute and late stent thrombosis in diabetic patients as DM is a known significant predictor of stent thrombosis.

In conclusion， there is a clear need for a large multicentre trial comparing the efficacy of the different types of DESs with a clinical primary end point at an adequate power， in diabetic patients. Studies comparing PCI with DES and CABG in diabetics with multivessel disease are ongoing which will shed light on the eventual role of percutaneous coronary revacularisation in this high-risk subgroup of patients. It is also imperative to note that local stent-based therapy should still be combined with metabolic normalization to provide optimal control of diabetic coronary disease.