Diabetic retinopathy is accompanied by disturbances in retinal blood flow, which is assumed to be related to the diabetic metabolic dysregulation. It has previously been shown that normoinsulinemic hyperglycemia has no effect on the diameter of retinal arterioles at rest and during an increase in the arterial blood pressure induced by isometric exercise. However, the influence of hyperinsulinemia on this response has not been studied in detail. In seven normal persons, the diameter response of retinal arterioles to an increased blood pressure induced by isometric exercise, to stimulation with flickering light, and to the combination of these stimuli was studied during euglycemic normoinsulinemia (protocol N) on one examination day, and euglycemic hyperinsulinemia (protocol H) on another examination day. Isometric exercise induced significant contraction of retinal arterioles at all examinations, but during a repeated examination the diameter response was significantly reduced in the test persons following the N protocol and increased in the persons following the H protocol. Flicker stimulation induced a significant dilatation of retinal arterioles at all examinations, and the response was significantly higher during a repeated examination, irrespective of the insulin level. Repeated exposure to isometric exercise reduces contraction, whereas repeated exposure to flickering light increases dilatation of retinal arterioles in vivo. Hyperinsulinemia increases contraction of retinal arterioles induced by isometric exercise.
Central blood pressure (BP) has attracted increasing interest because of a potential superiority over brachial BP in predicting cardiovascular morbidity and mortality. Several devices estimating central BP noninvasively are now available. The aim of our study was to determine the validity of the Arteriograph, a brachial cuff-based, oscillometric device, in patients with type 2 diabetes.
We measured central BP invasively and compared it with the Arteriograph-estimated values in 22 type 2 diabetic patients referred to elective coronary angiography.
The difference (invasively measured BP minus Arteriograph-estimated BP) in central systolic BP (SBP) was 4.4±8.7 mm Hg (P = 0.03). The limits of agreement were ±17.1 mm Hg.
Compared with invasively measured central SBP, we found a systematic underestimation by the Arteriograph. However, the limits of agreement were similar to the previous Arteriograph validation study and to the invasive validation studies of other brachial cuff-based, oscillometric devices. A limitation in our study was the large number of patients (n = 14 of 36) in which the Arteriograph was unable to analyze the pressure curves. In a research setting, the Arteriograph seems applicable in patients with type 2 diabetes.