Clinical Hemorheology and Microcirculation

Purpose: Indocyanine green (ICG) fluorescence angiography is used to evaluate tissue perfusion in many different medical fields. This study aims to evaluate the value of ICG angiography in the determination of tissue perfusion in the PAD lower extremities. Material and methods: In a prospective clinical study, ICG angiography was used to evaluate tissue perfusion and collateralization in 30 PAD patients. The perfusion index and maximum fluorescence intensity (MPI) were calculated as arterial perfusion parameters. Results: Significant differences in the perfusion index were found for the different PAD stages (p < 0.001). Poor collateralization was associated with a significantly lower perfusion index than good collateralization (p = 0.003). A ROC analysis for the perfusion index showed a positive likelihood ratio of 6.00 and a negative likelihood ratio of 0.00 with an area under the curve of 0.949 to discriminate critical and non-critical PAD. Conclusion: ICG angiography is a promising diagnostic tool to quantify tissue perfusion and demonstrate critical limb ischemia and collateralization in lower extremities affected by PAD.

Objective: We studied the protective effects of postconditioning (PS) in healthy and hypercholesterolemic rats after renal ischaemia-reperfusion (IR) injury. We aimed to examine cytokine expression and apoptosis in tissue damage after revascularisation (TNF-α levels in serum and tissue). Methods: Male Wistar rats (n = 32) were divided into four groups. The animals of normal feed groups (NF) were fed with normal rat chow and the cholesterol feed groups (CF) were fed with 1.5% cholesterol containing diet for 8 weeks. Anaesthetized rats underwent a 45-min cross-clamping in both kidney pedicles. Ischaemia was followed by 120-min reperfusion with or without PS protocol (group PS vs. IR). Postconditioning was induced by four intermittent periods of ischaemia-reperfusion of 15-s duration each. Serum cholesterol, triglyceride, urea and creatinine levels were determined. Proinflammation was characterized by the measurement of serum TNF-α. Tissue injury in kidney was determined by formaline-fixed, paraffin-embedded tissue sections. Tissue TNF-α levels were determined by immunohistochemistry. Results: Significant elevation was observed in serum TNF-α level after IR injury in normal feed groups, which was reduced by PS. In CF group neither the elevation nor the postconditioning induced reduction were as significant as in the NF groups. In normal feed group PS caused a significant reduction in tissue TNF-α level which was significantly higher in CF. Conclusions: Ischaemic postconditioning proved to be an effective defense against IR in NF groups, but it was ineffective in CF groups in kidney tissue.

Several beneficial effects of resveratrol (RES), a natural antioxidant present in red wine have already been described. The aim of our study was to investigate if RES had a clinically measurable cardioprotective effect in patients after myocardial infarction. In this double-blind, placebo controlled trial 40 post-infarction Caucasian patients were randomized into two groups. One group received 10 mg RES capsule daily for 3 months. Systolic and diastolic left ventricular function, flow-mediated vasodilation (FMD), several laboratory and hemorheological parameters were measured before and after the treatment. Left ventricular ejection fraction showed an increasing tendency (ns) by RES treatment. However, left ventricular diastolic function was improved significantly (p < 0.01) by RES. A significant improvement in endothelial function measured by FMD was also observed (p < 0.05). Low-density lipoprotein (LDL) level significantly decreased (p < 0.05) in the RES treated group. Red blood cell deformability decreased and platelet aggregation increased significantly in the placebo group (p < 0.05), while resveratrol treatment has prevented these unfavourable changes. Concerning other measured parameters no significant changes were observed neither in placebo nor in RES group. Our results show that resveratrol improved left ventricle diastolic function, endothelial function, lowered LDL-cholesterol level and protected against unfavourable hemorheological changes measured in patients with coronary artery disease (CAD).

We evaluated the erythrocyte deformability in a group of subjects with polycythemia vera (PV) using a Rheodyn-SSD Laser Diffractometer, at the shear stresses of 6, 12, 30 and 60 Pa. Our data showed a significant decrease of red cell deformability, expressed as elongation index (EI), in PV subjects compared with normal controls. These results suggest that the hyperviscosity syndrome accompanying this myeloproliferative disease may be considered a mixed form, resulting from the association of a polycythemic condition with a sclerocythemic disorder.

It is known that hemorheological parameters show gender differences that might be altered by gonadectomy (GoE). Since micro-rheological parameters (erythrocyte deformability and aggregation) sensitively change during and after ischemia-reperfusion (I/R), the question arises whether the hemorheological effects of I/R may show gender differences and further changes might be expected when GoE and I/R are additive. Sprague-Dawley rats were divided into six groups: Control males and females, I/R males and females with 1-hour hind limb ischemia, GoE + I//R males and females when 3 months after bilateral gonadectomy the I/R was induced. Before and just after ischemia, and on the 1st-3rd-5th-7th postoperative days blood samples were taken (lateral tail vein, 0.3–0.5 mL) for analyzing hematological parameters, erythrocyte's deformability (slit-flow ektacytometer) and aggregation (light-transmission aggregometer). Leukocyte and platelet counts raised markedly in gonadectomized animals during the investigated days. Hemorheological changes of I/R showed gender differences: significant impairment of erythrocyte deformability was found on the 1st–3rd postoperative days, expressed mostly in females. In gonadectomized females the postischemic deformability values were impaired. Erythrocyte aggregation index significantly raised by the 1st postoperative day, dominantly in males. It is suggested that gonadectomy may act as an additional rheological ‘risk factor’ related to blood micro-rheological parameters in ischemia-reperfusion.

Recent evidence has shown that plasma fibrinogen, a major cardiovascular risk factor, interacts with the erythrocyte membrane and acts to influence blood flow via erythrocyte nitric oxide (NO) modulation. In the present in-vitro study, whole blood samples were harvested from healthy subjects and aliquots were incubated in the absence (control aliquots) and presence of fibrinogen at different degrees of band 3 phosphorylation, and the erythrocyte deformability was determined. The present study shows that in the presence of higher fibrinogen concentrations, similar to those found in inflammatory conditions, erythrocyte deformability is increased only when band 3 is dephosphorylated by the presence of syk inhibitor and at low shear stress. On the contrary, no changes were verified in the presence of fibrinogen when band 3 is allowed to be phosphorylated by inhibiting the phosphotyrosine phosphatase enzyme activity with calpeptin. We also observed that the presence of fibrinogen at higher concentration does not induce changes in erythrocyte deformability in the absence of modulators of the band 3 phosphorylation degree. However, the mechanisms by which fibrinogen signalling modulates erythrocyte function remain to be clarified and are currently under study.

In patients with acute myocardial infarction (AMI), high red blood cell distribution width (RDW) seems to predict further cardiovascular events, although the mechanism and its possible relation with anaemia and inflammation remains uncertain. We determined in 119 AMI patients before hospital discharge RDW, along with haemoglobin, haematimetric indices and inflammatory parameters (fibrinogen, C-reactive protein, plasma viscosity, neutrophil count). In the follow-up period (21 ± 11 months), 30 patients (25%) developed a recurrent cardiovascular event. In the lineal regression analysis, MCH and neutrophil count were independent determinants for RDW (beta coefficient = −0.544 p < 0.001; beta coefficient: 0.279 p = 0.001, respectively). The logistic regression analysis showed that RDW >14% increases the risk of future events by 6 times; OR 6.19 IC 95% (2.1–18.5); even after adjusting for anaemia, mean corpuscular haemoglobin (MCH) <27 pg/L, fibrinogen >400 mg/dL and neutrophil count >5.7 (10³/μL). Our results confirm that RDW, an available and inexpensive measurement reported in routine blood cell counts, seems to be an independent predictor for recurrent cardiovascular events in AMI patients. As we found no association of RDW with either anaemia or inflammatory parameters, the mechanism responsible for increased RDW deserves further research.