Diabetes, revascularization and CABG: When there is smoke, there is a fire!

In the current issue of SCVJ Dr. Mölstad presents data from the registry of coronary angiography at the Feiring Heart Clinic, Norway 1. In this very impressive registry, data from 13 511 patients who underwent coronary angiography confirm results from randomised trials that indicate that coronary by-pass surgery (CABG) is the preferred mode of revascularization for patients with diabetes and coronary artery disease. The current data do lend support for surgery being better than angioplasty, at least for multi-vessel disease, albeit the data are not overwhelmingly strong. They do clearly demonstrate an increased risk for patients with diabetes undergoing any kind of revascularization, although this may at least partly be explained by diabetics having more triple-vessel disease as well as more advanced symptoms. This is similar to several studies in patients with acute coronary syndromes where diabetes in general comes out as an independent risk factor 2.

Since the presentation of the BARI-trial, this issue has been debated, and current practise does not always reflect current knowledge; there are very little data to support the widespread preferential use of angioplasty in patients with diabetes and coronary artery disease. In the BARI-study, CABG was associated with a higher in-hospital mortality, 1.2 vs. 0.6%, a lower 5 year rate of death (19.4 vs. 34.5%) and a higher rate of survival free of myocardial infarct (MI) and free of recurrent revascularization, as compared to diabetic patients initially treated by angioplasty 3, 4. The benefit of CABG was mainly confined to patients receiving arterial grafts. The original BARI-data were presented more than 10 years ago, and since then improvements in angioplasty technique, stents, glycoprotein IIb/IIIa inhibitors, clopidogrel and patient preferences have frequently, and probably not always erroneously, been cited as reasons to perform angioplasty instead of CABG. However, also more recent data from ARTS and SoS still indicate a benefit of CABG over PCI 5, 6. It must be pointed out that diabetic patients in all of these studies are subgroups of just a couple of hundred patients, and thus underpowered to detect anything but very large differences in outcome.

The resolution to this issue may lie in the near future when we will have much more data coming in from several large ongoing randomised trials such as FREEDOM, CARDia and BARI2D. Until then, evidence-based medicine indicates that bypass surgery is the preferred method of revascularization in patients with multi-vessel coronary artery disease.

There are a few other notable data in this report: 25% of patients are still smokers, and even 20% of diabetics are smoking when being referred for revascularization, a stunningly large figure. Smoking in patients with coronary artery disease is obviously negative for the outcome and for the long-term results, and it is almost absurd that we accept this addiction to go on, and still spend thousands of euros on revascularization.

Almost one third of the patients in the present registry are NOT revascularized, which either reflects a very thoughtful process of assessment, avoiding the pitfalls of the increasingly popular practise of “ad hoc” PCI, or it may reflect a modest overuse of coronary angiography, without documented myocardial ischemia. The concept of very early angiography without clear demonstration of myocardial ischemia has been shown to be beneficial in the setting of acute coronary syndrome in patients with several markers of risk, i.e. elevated troponins, ST-segment depression, advanced age and diabetes. Such high-risk patients also tend to be preferentially treated with CABG 7. Recent studies indicate that with aggressive use of statins and clopidogrel, a more semi-selective approach may provide similar results 8.

In summary, current data reinforce two key messages: a) patients with diabetes and coronary artery disease should be offered bypass surgery as the primary method of revascularization, and b) basic medical treatment, including smoking cessation, must not be forgotten.