International Circulation: Professor Tan， you have published an article entitled Stent thrombosis after percutaneous coronary intervention for bifurcation lesions in the Journal of interventional cardiology， can you tell us what we should we be paying more attention to in order to prevent this complication?
 
Prof. Tan: Stent thrombosis (ST) following PCI is a catastrophic event associated with a very high mortality in the range of 40~50%， and patients almost universally suffer myocardial infarction when it occur acutely. So the prevention of ST is of the utmost concern for all operators. When we are treating bifurcation lesions， we are actually dealing with a subset of complex lesion well known to be associated with higher incidence of major cardiac events including stent thrombosis. So it is important that we address these high risk lesions in a careful manner which will hopefully not increase the risk of ST. From the literature， we learned that ST is no different whether bare metal stents (BMS) or drug eluting stents (DES) are used. What this means is that DES has not increased the risk of ST in treating bifurcation lesions， wether it is early or ST. Stent thrombosis is a multifactorial condition and its occurrence may be contributed by procedural， lesion and patient factors. Meticulous techniques employed by the operators when treating complex bifurcation stenosis and the use of appropriate duration of dual anti-platelet therapy are imperative in preventing ST.

International Circulation: Is it not true that there has been an increased incidence of late stent thrombosis early in the use of drug eluting stents in bifurcation lesion? Could you help clarify this?

Prof. Tan: Yes， stent thrombosis is a real phenomenon but it is fortunately a low event occurring one. Bifurcation lesion is known to be an important predictor of ST in the DES era. However in many studies comparing the one-stent and two-stent bifurcation treatment strategy， there is no evidence to suggest that the two-stent strategy is associated with a higher incidence of ST. So we can be reassured that the risk of stent thrombosis is low if an operator adopts a two-stent strategy， provided that he deploys the stents well. 

International Circulation: Stent thrombosis remains a critical problem after percutaneous coronary intervention. Could you tell us about the effects of anti-platelet drugs on the prevention of stent thrombosis?

Prof. Tan: There is no question that the use of dual anti-platelet therapy can lessen the risk of stent thrombosis. The current guidelines recommended the use of dual anti-platelet therapy (aspirin and clopidogrel) for 1 year in patients who receive DES. Perhaps we should give dual antiplatelet drugs even longer in those who receives DES in left main or multi-vessel disease PCI if they have low bleeding risk. The duration of anti-platelet therapy remains to be 1 month for patients undergoing elective stenting with bare metal stents. It is important to mention that patient’s compliance with dual anti-platelet therapy must be sought before considering putting in a DES. Any risk of patients’ non-compliance or premature termination of antiplatelet therapy will dissuade me from implanting a DES.

International Circulation: It is evident that diabetes mellitus is a significant coronary risk factor and there is an increasing number of diabetic patients undergoing PCI. Is there any difference among the different kinds of DES for treatment of diabetic patients?

Prof. Tan: We know that diabetes mellitus (DM) is a major cardiovascular risk factor and up to about 40% of patients undergoing PCI have this condition. The question is whether there is any difference between the use of various DES in diabetic patients? The data has been rather inconclusive. I will say at this point， there is no real solid evidence to suggest that one DES is better than the other in treating diabetic patients. From our own institutional experience reported in TCT 2005， we did not see a difference between the use of sirolimus- and paclitaxel- DES in diabetic patients undergoing PCI.

International Circulation: You have published an article entitled Time-dependent dynamic mobilization of circulating progenitor cells during percutaneous coronary intervention in diabetics on International journal of cardiology. According to the article， we know the levels and function of circulating progenitor cells (CPC)， especially endothelial progenitor cells (EPC)， are attenuated in diabetic patients. Could you introduce the mechanism of this phenomenon?

Prof. Tan: I’m afraid we still do not know the exact mechanism of this attenuated effect， but it goes along with the conventional knowledge that diabetic patients are at a higher risk for thrombotic events and have poorer outcomes following PCI. It is certainly an area that interests us a great deal and we are doing more research on it.

International Circulation: You have published an article entitled Clinical experience of StarClose vascular closure device in patients with first and recurrent femoral punctures in the Journal of interventional cardiology， could you tell us the prevalence of complication rates among the different closure devices?

Prof. Tan: We have been evaluating various types of vascular closure devices in our laboratory， ranging from Perclose suture device， Angio-Seal collagen plug and StarClose. The complication rate is low at less than 1% for all. We have found very little difference in terms of the risk of complications with the different types of closure devices. The operators’ experience and comfort level with the device is imperative. There are obviously some operators who prefer one device to another. But I think in good hands and with good training， there is little difference to choose between the different types of closure devices.