Impact of the Glycemic State on the in Hospital and Short Term Outcomes of Patients With ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Angioplasty

Reperfusion failure is attributed to different factors, including diabetes. Several mechanisms have been proposed for the harmful effects of hyperglycemia after acute myocardial infarction. Association of hyperglycemia with the activation of blood coagulation has been well studied; it could induce a shortening of the fibrinogen half-life, increase in fibrinopeptide A, fragments of pro-thrombin in factor VII, and platelet aggregation, all of which could lead to increased activation of thrombosis. Hyperglycemia at admission is associated with increased levels of inflammatory markers, enhanced expression of cytotoxic T-cells, and reduced expression of cytotoxic T-lymphocyte-associated protein 4, indicating its association with increased inflammatory immune process after acute myocardial infarction. It also could be associated with endothelial dysfunction, oxidative stress, and possibly, abolition of protective ischemic preconditioning. Other possible mechanism of harmful effects of acute hyperglycemia is microvascular dysfunction after coronary revascularization.

Studying the influence of diabetes mellitus on clinical outcome in the thrombolytic era of acute myocardial infarction, GUSTO-I trial showed that patients with diabetes mellitus have a significantly increased risk of both early and late mortality, which may be attributed to more advanced coronary artery disease and co-morbidities.

Results of the HORIZONS-AMI study showed that patients with newly diagnosed diabetes mellitus had similarly poor prognosis after primary percutaneous coronary intervention in ST-elevation myocardial infarction patients as those with previously established diabetes mellitus, newly diagnosed diabetes mellitus was based on HgbA1c levels following admission and did not assess for blood glucose levels at admission or during hospital stay.

Regarding the effect of diabetes mellitus on left ventricular systolic function, diabetic patients with first ST-elevation myocardial infarction had reduced left ventricular systolic function, measured with speckle-tracking strain, compared with non-diabetic patients at baseline and at 6-month follow up, despite similar left ventricular ejection fraction in both groups. Similarly, according to the ischemic cascade, diastolic function is expected to be affected with variable degrees among diabetic, prediabetic and non-diabetic ST-elevation myocardial infarction patients.

Timmer et al, studied the effect of admission stress hyperglycemia and that of chronic hyperglycemia (elevated levels of HbA1c in patients with undiagnosed diabetes mellitus) on ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention; both elevated glucose and HbA1c levels were associated with adverse outcomes. However elevated glucose but not elevated HbA1c was associated with larger enzymatic infarct size and high early mortality.