Microvascular capillary assessment in relation to forearm blood flow.

OBJECTIVE: To study whether vascular reactivity as assessed by the methods forearm blood flow (FBF) and postocclusive reactive hyperaemia (PRH) in the nail fold was related as a measure of endothelium-dependent vasodilation in the microcirculation. METHODS: Microvascular reactivity was assessed in forearm blood flow and in the nail fold by vital capillaroscopy of individual microvessels as postocclusive reactive hyperaemia. Vascular reactivity was assessed at baseline (n = 25) as well as after infusion of acetylcholine and of sodium nitroprusside (n = 13). We also performed a multivariate regression analysis to assess whether forearm blood flow or flow-mediated dilatation related to postocclusive reactive hyperaemia. RESULTS: This study showed a distinct microvascular response to both acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (endothelium-independent vasodilation) during forearm blood flow assessment and postocclusive reactive hyperaemia assessment in the nail fold (n = 13). These changes were inversely related (r- = -0·57; P<0·05). CONCLUSIONS: Forearm blood flow was inversely correlated to postocclusive reactive hyperaemia. Postocclusive reactive hyperaemia was shortened after infusion with both acetylcholine and sodium nitroprusside. This occurred in parallel with the expected increase in forearm blood flow, conceivably reflecting that both methods can be used to assess endothelium-dependent vasodilation in the microcirculation.

Cardiogenic shock triggered by phaeochromocytoma crisis after an oral glucose tolerance test: a case report.

BACKGROUND: Phaeochromocytomas are rare catecholamine-producing tumours which typically present with comparatively benign symptoms such as headache, palpitations, sweating, hypertension, and insulin resistance. In rare cases, severe cardiac manifestations have been reported. We describe a patient who developed severe hypoglycaemia after an oral glucose tolerance test (OGTT), potentially triggering a phaeochromocytoma crisis and cardiogenic shock. To the best of our knowledge, only four other cases of hypoglycaemia after OGTT have been reported in patients with phaeochromocytoma, of which none developed a phaeochromocytoma crisis. CASE SUMMARY: A 53-year-old woman with hypertension, dyslipidaemia, and prediabetes presented to the Emergency Department with hypoxia, hyperglycaemia, lactic acidosis, severe left ventricular dysfunction, and pulmonary oedema followed by cardiogenic shock. Onset of symptoms was only few hours after an OGTT during which she had developed severe transient hypoglycaemia. Angiography was performed due to elevated troponin levels and showed a midventricular contraction pattern typical of takotsubo. This was subsequently confirmed by cardiac magnetic resonance imaging. The patient's condition improved during the first 36 h and she was discharged home on Day 7. A positive catecholamine test prompted readmission to the Endocrinology Unit, where computer tomography confirmed the diagnosis of phaeochromocytoma. An adrenalectomy was performed, and the diagnosis was verified histopathologically. DISCUSSION: The possibility of a phaeochromocytoma must be considered as a potential triggering factor in patients presenting with takotsubo cardiomyopathy, in particular, when blood glucose levels fluctuate between severe hypo- and hyperglycaemia.

Immediate effect of passive smoking on microcirculatory flow.

OBJECTIVE: Exposure to SHS, as by passive smoking, seems to increase the incidence of cardiovascular events. It has been shown that active smoking of a single cigarette causes an immediate and significant decrease in microcirculatory blood flow velocity, whereas the acute effects of exposure to SHS on microcirculatory flow have as yet not been demonstrated. METHODS: Healthy nonsmoking volunteers of both genders were studied during acute exposure to SHS of two cigarettes burning up to 10 minutes. Microvessels were examined by in vivo vital capillaroscopy (Capiflow(®)), allowing continuous assessment of CBV. RESULTS: CBV decreased from 514 mm/sec (CI 383-646) at baseline to 306 mm/sec (CI 191-420) at end of SHS exposure with a further decrease to a nadir of 240 mm/sec (CI 155-325) four minutes after the end of this exposure (p < 0.0001; ANOVA). CONCLUSIONS: The result of this study shows that passive inhalation of secondhand cigarette smoke induces an immediate and prolonged marked reduction in CBV in nonsmoking healthy volunteers.

Microvascular reactivity in response to smoking and oral antioxidants in humans.

OBJECTIVE: To investigate whether a daily intake of a moderate dose of antioxidants modifies the microcirculatory response to smoking, assuming a major influence of oxidative stress on microcirculation. METHODS: The microvascular response to smoking was assessed in individual capillaries by capillaroscopy before and after two weeks of treatment with oral antioxidants. RESULTS: Smoking prolonged time to peak (TtP) capillary blood flow velocity in all subjects. When the subjects were pre-treated with ascorbate, TtP was comparable to baseline values of untreated subjects. No significant effect of vitamin E was observed either before or after smoking. Capillary blood flow velocity increased after treatment with ascorbate as well as after vitamin E. However, significant reductions in velocity were still observed in response to smoking even after subjects consumed ascorbate and vitamin E (p<0.0004 and p<0.000008 respectively). CONCLUSIONS: This study focused on individual capillaries, and confirms that smoking has a very pronounced, direct and reproducible microvascular effect possible to demonstrate in vivo in human capillaries. Moderate intake of the antioxidant ascorbate clearly mitigated the effects induced by smoking. TtP after smoking in subjects treated with ascorbate was similar to that observed in untreated subjects before smoking a cigarette. Thus, oxidative stress could be assumed to play a role in the effects of smoking on microcirculation.

Preserved microcirculatory response to acute estrogen not reflected by exercise capacity.

BACKGROUND: To assess the acute effect of a single dose of 10 mg oral micronized 17beta-estradiol on microcirculation in postmenopausal women with and without coronary artery disease and its potential influence on exercise capacity. METHODS: Postmenopausal women (n=11) with coronary artery disease had symptoms of ischemic heart disease and at least 1 mm ST depression at exercise. Microcirculation was examined by vital microscopy, with and without the acute administration of estrogen in a placebo-controlled cross-over design. Exercise test was performed on bicycle. The microcirculatory findings were contrasted to those in 14 healthy postmenopausal women. RESULTS: 17Beta-estradiol in serum and blood flow velocity increased significantly after acute oral estrogen administration both in women with coronary artery disease (p<0.001) and in healthy women (p<0.0001), with no significant difference between the two groups. No effect on exercise capacity or ST depression at exercise was detected. CONCLUSIONS: Previously reported data that a single dose of estrogen administered to postmenopausal women results in positive effects on exercise was not reproduced. An increased peripheral microvascular flow velocity was detected in women with coronary artery disease and this increase was not accompanied by an increased exercise capacity.

Effect of ascorbic acid on microcirculation in patients with Type II diabetes: a randomized placebo-controlled cross-over study.

Manifestations of vascular disease, including microvascular changes, constitute the major part of the morbidity and mortality in diabetic patients. Oxidative stress has been suggested to play an important role in the vascular dysfunction of diabetic patients. Furthermore, epidemiological observations indicate a beneficial effect of an increased dietary intake of antioxidants. The present study tested the hypothesis that the antioxidant ascorbic acid influences microcirculatory function in patients with Type II diabetes. Patients with Type II diabetes were treated with 1 g of ascorbic acid three times a day for 2 weeks in a randomized placebo-controlled double-blind cross-over design. Microvascular reactivity was assessed by vital capillaroscopy and PRH (post-occlusive reactive hyperaemia). hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-1ra (interleukin-1 receptor antagonist) and ox-LDL (oxidized low-density lipoprotein) were analysed. The results showed no significant change in microvascular reactivity assessed after 2 weeks of ascorbic acid treatment. TtP (time to peak) was 12.0+/-3.3 s before and 11.2+/-3.5 s after ascorbic acid (n=17). In comparison, TtP was 11.5+/-2.9 s before and 10.6+/-2.8 s after placebo (not significant). IL-1ra, IL-6, hs-CRP and ox-LDL did not change significantly after ascorbic acid, neither as absolute or relative values. In conclusion, in contrast with some studies reported previously, we could not demonstrate an effect of continuous oral treatment with ascorbic acid on microvascular reactivity assessed at the level of individual capillaries. Furthermore, we found no indication of an effect on inflammatory cytokines or ox-LDL.

Micro- and macrocirculatory effects of apheresis in patients with familial hyperlipidemia.

High lipid levels have been shown to coexist with a disturbed vascular endothelial function. Thus, acute lipid lowering could be expected to improve vascular reactivity. Patients with familial hyperlipidemia (FH) have substantial and rapid decreases in lipid levels after low-density lipoprotein apheresis. Thus, an opportunity exists to study acute effects of lipid lowering on vascular reactivity. Flow mediated vasodilation (FMD) is commonly used to assess endothelial function in conduit vessels, whereas vital capillary microscopy during the post-reactive hyperemia (PRH) phase is used to assess response at the microvascular level. It is not known whether endothelial dysfunction is a general phenomenon in all kinds of vessels or if there are differences between micro- and macrovessels. In the present study, we were not able to demonstrate an improved vascular response after acute lipid lowering in FH patients. This was true both in the microcirculation (PRH) and in the conduit vessels (FMD). However, the two methods gave concordant results, demonstrating disturbed vascular reactivity in the patients as compared with healthy subjects. We have found no previous report with parallel assessments at the microcirculatory and macrocirculatory levels.