Metabolic Syndrome and Acute Myocardial Infarction

Prevalence of the metabolic syndrome in acute MI and impact of hyperglycaemia on hospital outcomes

Zeller M, Steg PG, Ravisy J, et al. Prevalence and impact of metabolic syndrome on hospital outcomes in acute myocardial infarction. Arch Intern Med 2005;165:1192-8

Metabolic syndrome was defined by the National Cholesterol Education Program Adult Treatment Panel [NCEP ATP III] in 2001, as the association of ≥3 of 5 of the following criteria: abdominal obesity, high blood pressure, high triglyceride levels, low high-density lipoprotein [HDL] cholesterol levels and hyperglycaemia. In patients at high risk of cardiovascular disease, the prevalence of metabolic syndrome is very high. Moreover, it has been demonstrated in patients with established symptomatic vascular disease (eg, coronary artery disease, stroke, and peripheral arterial disease) that the prevalence of metabolic syndrome correlates with the extent of vascular damage.

This prospective study, conducted in France, is a 4-year, population-based registry of 811 patients screened and 633 patients enrolled at 6 public or private hospitals around Dijon. All participants in the study had a confirmed diagnosis of acute myocardial infarction [MI]. Patients included in the study were 18 years or above and were admitted to hospitals within 24 hours of symptom onset with a suspected diagnosis of MI. Family history was defined by a history of premature coronary artery disease in first-degree relatives (occurrence at age <55 years for men and <65 years for women). Reference blood pressure values were those from the day before discharge or on the eve of death if patients died. Echocardiograms were performed on the day of admission and on day 3±1 following the Simpson method, using the apical views to calculate left ventricular ejection fraction [LVEF]. The waist circumference (abdominal obesity) was measured on the day of admission. Diabetes is an important risk factor for heart failure after MI therefore the impact of metabolic syndrome on the development of heart failure was assessed carefully and classified using the highest Killip reached class; others definitions were severe heart failure: Killip class >2; cardiogenic shock: systolic blood pressure <90 mm Hg, persisting for more than 1 hour despite fluid challenge with clinical symptoms of perfusion.

Among the 633 MI patients, 46% (n=290) fulfilled the criteria for metabolic syndrome according to the NCEP ATP III. Patients with metabolic syndrome were older and more likely to be women, at higher risk for cardiovascular disease and had a higher incidence of prior history of MI. Patients with metabolic syndrome had a longer delay from onset of symptoms to hospital admission and consequently the incidence of heart failure was higher (Killip class >1). When echography was performed (70% of patients), LVEF was similar for both groups (with or without metabolic syndrome). The probability of receiving thrombolytic therapy was lower in patients with metabolic syndrome. Additional observations for this group included significantly lower creatinine clearance and markedly abnormal glucose and lipid profiles with lower HDL cholesterol levels.

The multivariate analysis demonstrated that metabolic syndrome was not an independent predictor for fatal outcome when adjusted for age, female sex, creatinine clearance, ST-segment elevation MI, anterior wall MI, smoking, admission pulse, systolic and diastolic blood pressures, Killip class >I on admission and previous MI (P=0.41). However, using the same methodology, metabolic syndrome was a strong and independent predictor of severe heart failure (relative risk 2.13 with 95% confidence interval 1.28 to 3.57; P=0.003). Of note, hyperglycaemia and low HDL cholesterol level have the strongest association with severe heart failure. Hyperglycaemia is the only independent determinant for the prediction of cardiogenic shock, even after the same previous adjustments.

In this study, hypertension, low HDL cholesterol, abdominal obesity and elevated triglyceride levels had little impact on hospital outcomes. Hyperglycaemia on the contrary was strongly associated with poor hospital outcomes in patients with MI. Hyperglycaemia was an independent predictor of the worst prognosis after 1 year, whereas body mass index and blood lipid levels were not. Fasting hyperglycaemia is the most important risk factor for development of heart failure in patients with metabolic syndrome. Higher risk of congestive heart failure caused by severe pump failure in diabetic patients induces a higher in-hospital case fatality rate in these patients compared with non-diabetics. Hyperglycaemia is the most important criterion of metabolic syndrome in patients with MI given the association with increased incidence of congestive heart failure, and it is therefore vital to assess blood glucose during the acute phase of MI.