Relation Between Microvascular Function and Large Artery Stiffness in African American Diabetic Patients.

Rationale: Diabetes is highly prevalent among African Americans and poses a higher risk for vascular complications in this population. Although socioeconomic factors are well known to influence outcomes, true biologic differences in risk factor vulnerability have been suggested. Vascular complications have been traditionally viewed as either macrovascular (myocardial infarction and stroke) or microvascular (retinopathy, nephropathy, and neuropathy). Better glycemic control is known to improve microvascular but not macrovascular complications. In recent years, there has been a growing appreciation that microvascular dysfunction may promote large artery disease and vice versa. Given this notion of vascular “cross-talk” and since subclinical dysfunction is known to precede target organ damage, the objective of this study was to determine whether subclinical microvascular dysfunction is related to large artery stiffness. Methods: A total of 141 patients with type II diabetes were recruited from our outpatient clinics over a 6 month period. Medical information was obtained via patient interview and electronic medical record review including laboratory results. Microvascular function was assessed by the vascular reactivity index (VRI), which assesses changes in digital temperature before and after release of arterial cuff occlusion (VENDYS 5000BC DTM system Endothelix, Inc.). Large artery stiffness was assessed by carotid-femoral pulse wave velocity (PWV) using applanation tonometry (Sphygmocor, Atcor Inc.). Results: Mean age was 60 + 8 years, 64% were female. 80% had hypertension and 90% had dyslipidemia. 15% had chronic kidney disease. Mean HbA1C levels were 8.1 + 2.2%. For the entire group, VRI was significantly correlated with PWV (r=.27, p=.002). On multivariate analysis, VRI was independently associated with PWV (β=-1.0, p=.001) and a trend towards an association with HbA1c (β =.07, p=.09) after adjusting for traditional cardiovascular risk factors. Conclusions: Among African Americans with diabetes, subclinical microvascular dysfunction is significantly correlated to large artery stiffness and possibly to glycemic control. Further study is needed to clarify mediating factors of these relationships.