Diabetes and PCI
Waqar Ahmed presented compelling statistics about the explosive epidemic of diabetes. Between 2000 and 2030, the worldwide prevalence is likely to increase from 2.8% to 4.4%. The Euro Heart Survey revealed a prevalence of 31% diabetes in patients with coronary disease. This increased to a remarkable 46% when those without known diabetes were tested and a further 25% were found to have newly diagnosed impaired glucose tolerance (IGT).
Renu Virmani reviewed diabetes pathology to explain why patients with diabetes are at greater risk from CAD. Insulin resistance is associated with smooth muscle proliferation, excessive matrix deposition, endothelial dysfunction, and delayed wound healing; the result is an abnormal response to vascular injury. The clinical consequences are greater plaque burden, diffuse long lesions and small vessel disease.
Pieter Kappetein illustrated the controversy in the management of stable three vessel disease by the case of a patient with angina, multivessel disease and diabetes. Her EuroSCORE was 5 and SYNTAX score was 30. Although the relatively high EuroSCORE increased the mortality risk of surgery, this nevertheless is similar with PCI and in view of the superior outcome regarding repeat revascularisation with surgery, he felt this case would be better served by CABG. In subsequent discussion it was agreed that other factors such as patient preference might weigh in favour of PCI which remained an acceptable option in these circumstances, emphasising the importance of the multidisciplinary meeting in reaching a consensus.
Tony Gershlick put the case for PCI. Whilst the BARI trial suggested surgery as a better option for reducing mortality, there are some important limitations of the study, which retrospectively analysed a relatively small number of diabetics in the pre-stent, pre-Glycoprotein (Gp) IIb/IIIa era. BARI findings suggest CABG is more advantageous in diabetics with complex disease (=4 lesions). Nevertheless following a review of existing data, he indicated that in his opinion patients with diabetes should be seriously considered by a multidisciplinary team (MDT) for PCI if the SYNTAX score is <32, with the proviso of employing both optimal PCI technique with an optimal DES whilst maintaining good glucose control.
Robbert De Winter considered the relative merits of EuroSCORE and SYNTAX. Interestingly the EuroSCORE does not account for diabetes. There is agreement that PCI is more appropriate in patients with low SYNTAX scores (despite the EuroSCORE) and surgery is better in patients with high SYNTAX and low EuroSCORE. Particular difficulty arises when a patient scores highly with both systems.
Olivier Varenne proposed a strategy to optimise outcomes in the diabetic patient undergoing PCI. This relies upon the early detection of diabetes or IGT and all patients with CAD should be screened with an oral glucose tolerance test. Optimum antiplatelet treatment should include Gp IIb/IIIa inhibitors in patients presenting with acute disease. Early indications point to a possible benefit of prasugrel use to reduce the incidence of MACE and stent thrombosis in diabetic patients presenting with ACS undergoing intervention. A multifactorial strategy should address all cardiovascular risk factors.
Pieter Kappetein discussed peri-operative strategy, which should where possible involve total arterial revascularisation. Skeletonisation of the IMA arteries may reduce the risk of sternal infection in diabetics treated with bilateral mammary grafts and the radial artery should be used for grafting highly stenotic arteries where vasoconstrictors are not likely to be required.
Ulf Stenestrand suggested that RCTs involving revascularisation in diabetics are limited to subgroup analyses and/or small numbers. Most trial outcomes are dominated by angiographic rather than clinical end points and most recent trials test technical aspects of PCI rather than revascularisation strategy. Registries can be useful to follow long-term outcome and high quality registries with extensive variables can compensate for their non-randomised design. Charanjit Rihal discussed two ongoing RCTs. Results of the BARI II trial will be available next month, which tests the "coronary revascularisation hypothesis" (initial elective CABG or PCI vs. initial medical treatment) and a "method of glycaemic control hypothesis" in 2,300 type II diabetics with stable CAD. The FREEDOM trial compares CABG with PCI (with DES) in 2000 diabetics with multivessel CAD. The results of both trials will be useful in refining our management strategies.
Peter Kearney summarised the session with some important messages. Diabetes is surprisingly common, has increased in prevalence and has an important impact on cardiovascular outcomes. Optimal medical management is mandatory to improve long-term outcomes and specific rigorous targets apply to this population. Patients with multivessel and/or left main disease, particularly those with diabetes, should be discussed at a MDT meeting. This should include experienced surgeons, interventionalists and non-invasive cardiologists, as well as imaging specialists. All patients with multivessel and/or left main disease should be risk stratified according to their SYNTAX score and EuroSCORE. Other risk factors, such as left ventricular function also play an important role in decision making. Whichever revascularisation option is appropriate, an optimal peri-procedural approach is mandatory. This will include the use of evidence-based pharmacotherapy, drugeluting stents and in surgical cases complete arterial revascularisation. There are important deficiencies in the evidence base which may be addressed by upcoming randomised controlled trials. Further randomised studies and highquality registries will be necessary to answer specific questions.
