Non-invasive assessment of vascular function - Paradoxical vascular response to intravenous glucose in coronary heart disease

Background In healthy individuals, insulin administration causes an increas e in forearm blood flow which is dependent on the effects of insulin on the vascular endothelium. Glucose, administered as an intravenous bolus, produ ces a transient hyperinsulinaemic response. We hypothesized that the insuli n response to an intravenous glucose challenge during the intravenous gluco se tolerance test might lead to increases in forearm blood flow in healthy individuals, and that such a response might be altered in patients with cor onary heart disease. Methods and Results Healthy individuals (n=10, aged 41.6 +/- 3.0 years, mea n+/-SEM) and patients with angiographically proven coronary heart disease ( n=13, aged 65.5+/-2.4 years) underwent an intravenous glucose tolerance tes t with simultaneous measurement of right forearm blood flow at 28 time poin ts, using mercury-in-silastic venous occlusion plethysmography. In controls , forearm blood flow increased to a mean of 31.7% above baseline values at 7 min and remained above baseline up to 180 min after intravenous glucose. In contrast, patients with coronary heart disease exhibited an opposite res ponse. with forearm blood flow decreasing to a mean of - 16.2% below baseli ne values at 7 min and - 25.8% at 180 min. Marked group differences emerged in net changes from baseline in forearm blood flow throughout the intra ve nous glucose tolerance test, expressed as incremental areas under the forea rm blood flow profiles (controls: +351.3 +/- 121.7; coronary heart disease patients: - 244.3 +/- 72.4 min ml(-1) . 100 ml(-1), P=0.001). Conclusions We have demonstrated for the first time that in healthy individ uals forearm blood flow increases after an intravenous bolus of glucose, an d that paradoxically, this response is reduced below baseline forearm blood flow in patients with coronary heart disease. Further studies are needed t o determine whether plethysmographic measurement of Forearm blood flow afte r an intravenous bolus of glucose could provide a clinically useful non-inv asive test for the diagnosis of occult coronary heart disease. (Eur Heart J 2000; 21: 39-44) (C) 2000 The European Society of Cardiology.