Diastolic Heart Failure in Diabetics

摘要

In their study 'Impaired exercise capacity in diabetic patients after coronary bypass surgery: effects of diastolic and en-dothelial function', Wu et al. have demonstrated that diabetics after coronary artery bypass graft (CABG) had more advanced diastolic dysfunction and oxygen extraction impairment than non-diabetic patients.Can diabetic patients have diastolic failure even before their CABG? Hyperglycemiaitself is associated with cardiac dysfunction as seen in the United Kingdom Prospective Diabetic Study. In this study, a correlation was seen between the severity of hyperglycemia and the occurrence of heart failure - for each 1% increase in glycosylated hemoglobin, the risk of heart failure increased by 12%. Similarly, Iribarren et al. have shown that glycosylated hemoglobin levels >= 10 compared with a level <7 were associated with a 1.56-fold increase in risk of development of congestive heart failure (CHF) in diabetic subjects. It has been previously known that excessive diastolic left ventricular (LV) stiffness is an important contributor to heart failure in patients with diabetes mellitus. In patients with heart failure and normal LV ejection fraction (LVEF), cardiomyocyte resting tension (F_(passive)) isolated from LV endomyocardial biopsy samples was recently demonstrated to be elevated and to be an important determinant of LV stiffness. Diabetes ispresumed to increase stiffness through myocardial deposition of collagen and advanced glycation end products. Cardiomyocyte resting tension also elevates stiffness, especially in heart failure with normal LVEF.A recent study by van Heerebeek et al. has identified the mechanisms responsible for the increased diastolic stiffness of the diabetic heart. They have also demonstrated that diabetics show a major difference in pathogenesis of heart failure between patients with reduced and normal LVEF. Fibrosis and advanced glycation end products are more important when LVEF is reduced, whereas cardiomyocyte resting tension is more important when LVEF is normal. Therefore, there is a possibility that these patients can have diastolic failure even before CABG.