Which stent for diabetic patients: the glass half-full or half-empty?

Diabetes, as we are becoming keenly aware, is growing to epidemic proportions, and it is incumbent on cardiologists to consider the ‘comparative effectiveness’ of our treatments for its cardiovascular complications. The incidence of death or myocardial infarction (MI) has been found to be five times higher in patients with diabetes compared with those without. In 2001, the National Cholesterol Education Program’s Adult Treatment Panel 3 classified diabetes as a risk equivalent to established coronary artery disease. The relative impact of revascularization strategies for multivessel diabetic patients with ischaemic heart disease has been extensively studied, with evidence favouring more complete revascularization with surgery over percutaneous methods. A meta-analysis of 10 percutaneous coronary intervention (PCI) vs. coronary atery bypass graft (CABG) trials conducted before drug-eluting stents (DESs) were introduced confirmed that in multivessel disease patients with diabetes, survival was better with surgery (Figure 1). The question of revascularization choice is being revisited now that DESs are widely used. Another pertinent question relates to whether revascularization is needed for stable diabetic patients with ischaemic heart disease. The recently completed BARI 2D Trial showed that there was little to be gained by stenting patients with mild-to-moderate degrees of coronary obstruction and ischaemia. However, for patients requiring revascularization, several trials have been performed and are underway to test the question of whether DESs have levelled the playing field with surgery. The CARDia Trial and the diabetic patients in the SYNTAX Trial had similar survival rates treated with DESs or surgery. The 1-year follow-up is too short to engender confidence, but the early results were encouraging. The FREEDOM Trial, nearing enrolment completion, will be the largest study of diabetic multivessel disease patients randomized to a DES or CABG. Will the use of DESs in these diabetic patients change the results first seen in the EAST and BARI trials and the meta-analyses of the pre-DES trials favouring CABG? Trials of DESs vs. bare metal stents (BMSs) have not been powered for clinical events, and much of what we know so far has been gleaned from registries. Some registries, including the Swedish Registry, raised a red flag about the long-term safety issues regarding DESs. Fortunately, further experience of that registry and others (NY and Massachusetts) has not shown excess mortality or MI events but has confirmed a significant reduction in revascularization events. As we pointed out 7 years ago, the problem of restenosis, although a significant inconvenience, was not often associated with death or MI. Our prediction of the number needed to treat by using DESs to prevent one revascularization event was .20. This seems borne out by these more recent registries. Because of the organized health system in Sweden and the ability to carry out near complete follow-up for hard events, this experience is especially instructive. Stenestrand et al. have examined the outcome of diabetic patients treated in the SCAAR/SWEDEHEART Registry. All consecutive patients with diabetes who underwent stenting with a BMS or a DES during 2003–2006 were followed from 1 to 4 years (median 2.5). The size of the study provided an opportunity to evaluate important subgroups, especially those with or without ST-segement elevation myocardial infarction (STEMI). The patients receiving a DES or a BMS were enrolled concurrently during a period of increasing use of DESs. This method risks selection bias and the authors have attempted to mitigate that bias with propensity score methods. Nonetheless, other registries have been handicapped by unadjustable selection bias. For example, selecting patients for a BMS who are poorly insured and in whom chronic double antiplatelet therapy compliance is judged to be unreliable presents a problem. This may be less of a problem in the Swedish Registry because of the national health system with universal coverage. Also there seems to be a significant heterogeneity in selection based on geography (apparently related to physician preference rather than patient variables).