The Effect of Type 2 Diabetes And Low Aerobic Fitness On Diastolic Function

Abstract

Individuals with type 2 diabetes are at greater risk of developing heart failure as a consequence of diabetic cardiomyopathy. Diabetic cardiomyopathy is characterized by diastolic dysfunction. Despite the prevalence of impaired diastolic filling in type 2 diabetic subjects, evidence implicating hyperglycemia as a specific cause is equivocal. A reduced aerobic capacity could also contribute to the diastolic dysfunction in individuals with type 2 diabetes. PURPOSE To determine whether low aerobic fitness or glycemic control was associated with diastolic dysfunction in a group of type 2 diabetic subjects. METHODS Subjects aged from 40 to 60 years old were divided into three groups: 13 sedentary type 2 diabetic subjects, 15 sedentary nondiabetic subjects and 10 trained nondiabetic athletes. Mitral valve pulsed Doppler and tissue Doppler imaging (TDI), which is relatively preload independent, were used to assess left ventricular diastolic function. RESULTS Peak early mitral inflow velocity (E), peak late mitral inflow velocity (A) and E/A were not different between type 2 diabetic and sedentary control groups, however A was lower in the trained athletes compared to type 2 diabetic and sedentary control groups (p<0.01). As a result, the E/A ratio was higher in athletes (p<0.05). TDI showed that peak early mitral annular velocity (E') and the ratio of E' and peak late mitral annular velocity (E'/A') were lower and E/E', an estimate of left ventricular pressure, was higher in type 2 diabetic compared to the trained athletes and sedentary control subjects. TDI variables were similar among the sedentary controls and athletes. Multiple regression of the type 2 diabetic and sedentary control groups showed that HbA1c, but not VO2max was inversely correlated with E'/A' and positively correlated with E/E'. Moreover, 69% of the type 2 diabetic subjects had impaired diastolic filling patterns vs. 40% of sedentary control subjects. None of the trained athletes had an impaired diastolic filling pattern. CONCLUSIONS This study demonstrates that diastolic filling is impaired in individuals with type 2 diabetes, even when compared with similarly sedentary non-diabetic subjects. The results suggest that the abnormalities of diastolic filling may be associated with the diabetes per se rather than impaired exercise capacity although this requires confirmation in other studies.