Metabolic syndrome and diabetes in post-acute myocardial infarction patients

The metabolic syndrome (MetS) is characterised by the co-occurrence of multiple metabolic disorders that are risk factors for both type 2 diabetes and atherosclerotic cardiovascular disease (CVD). Many studies have shown that obesity, hypertension, impaired glucose tolerance, hypertriglyceridemia, and low levels of high-density lipoprotein (HDL)-cholesterol appear together more often than expected by chance alone. However, the MetS is an ill-defined concept with many unanswered questions. The term MetS was first used by Haller1 in 1977 when he described its association with atherosclerosis. This description was preceded by several others, including one by Morgagni about 250 years ago, who also included in the syndrome obstructive sleep apnoea.2 The term MetS started to be widely clinical used after 1988 when Reaven3 proposed insulin resistance as the underlying mechanism, although he did not included obesity in his definition of ‘syndrome X’ as he denominated it. Later in 1991, Ferranini et al.4 proposed the term ‘insulin resistance syndrome’. Since then there has been a long-standing debate about how to define this syndrome,5–9 definitions being based on components and cut-off points based on expert consensus rather than on evidence-based outcomes. A common feature of the World Health Organization (WHO),5 the National Heart, Lung, and Blood Institute/American Heart Association (NHLB/AHA),6 and the International Diabetes Federation (IDF)7 definitions is that all include subjects with diabetes, while the European Groups for the Study of Insulin Resistance (EGIR)8 definition is based on hyperinsulinemia. Comparing epidemiological and clinical studies on the MetS is thus difficult because of the many definitions involved. Nevertheless, a few meta-analyses were attempted which revealed that, in the general population, persons with MetS have about twice the risk of CVD,10,11 regardless of which definition is used,12 between three to five-fold risk of type 2 diabetes13,14 and one and a half times the risk of mortality from all causes.11