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Conditions during coronary artery bypass grafting (CABG) performed on beating heart (off-pump) are more physiological than using extracorporeal perfusion (on-pump). The present study aims to examine the hemorheological aspects of the two techniques. Blood samples were taken from patients undergoing on-pump (n = 25) and off-pump (n = 22) CABG, upon arrival to the operating theatre, after 20 and 40 minutes during the operation, after closing the thorax, on the 1st and 2nd postoperative days, and during the 2nd and 6th month control check-ups. Hematocrit (Hct), plasma and whole blood viscosity (PV, WBV; Hevimet 40 capillary viscometer), red blood cell (RBC) aggregation (Myrenne RBC aggregometer, LORCA) and deformability (LORCA, Carat FT-1 filtrometer), and platelet aggregation (Carat TX4 aggregometer) were determined. The morphology of red blood cells was investigated by scanning electron microscopy (SEM). Hct, PV, WBV and RBC aggregation decreased significantly during the early phase of the surgery, they started to recover during the postoperative period, and reached the baseline values by the 2nd and 6th month control check-ups. These parameters were significantly lower in samples taken after 20 and 40 minutes in the on-pump group. SEM showed rather damaged and malformed cells in case of on-pump surgery. Ektacytometry showed no significant difference, but RBC deformability was impaired during on-pump surgery when measured by filtrometry. The decrease in platelet aggregation was more pronounced by the end of surgery in case of on-pump technique. During CABG rheological parameters change less when using the off-pump method, and mechanical damage of RBCs are also smaller. The off-pump technique seems to be favorable from a hemorhelogical point of view. [ABSTRACT FROM AUTHOR]

Increased blood viscosity has not been associated with mortality risk in coronary heart disease (CHD). We aimed to investigate the predictive power of hematocrit per blood viscosity (Hct/BV) ratio as a marker of rheological oxygen carrying capacity of the blood to assess mortality risk of CHD. Elective coronary angiography was performed and CHD was proved in 109 patients in 1996 and 1997. In 78 cases (72%) complete follow up information was obtained in February 2006. During the follow up time (mean 8.9 years) 10 patients died due to cardiac cause (group C). Two patients died due to non-cardiac cause and 66 were still alive at the end of the follow up period (group NC, n=68). Mean hematocrit per blood viscosity (Hct/BV) ratio was significantly lower in group C comparing to NC (87±5; 93±9 Pa-1s-1, SD, respectively, p=0.022). Other factors (body mass index, serum cholesterol, fibrinogen, hematocrit, plasma and blood viscosity, cardiac index, left ventricular ejection fraction) provided no statistical differences. Kaplan–Meier survival analysis showed only the impact of fibrinogen and Hct/BV ratio on cardiac mortality (p=0.029 and 0.009, respectively). Receiver operating characteristic curves proved only Hct/BV ratio to be able to differentiate between groups (area under curve: 0.716, p=0.028). Hct/BV ratio showed significant negative correlation with the frequency of hospital admissions (r=-0.377, p=0.03). Low Hct/BV ratio can be regarded as a risk factor of cardiac death in CHD. [ABSTRACT FROM AUTHOR]

Plasma fibrinogen concentration, plasma and whole blood viscosity (WBV) are independent risk factors of coronary artery disease (CAD). Fibrinogen seems to be a relatively stronger risk factor for women than for men, but men are more endangered by higher hematocrit (Hct) and WBV than women are. We have previously reported that a theoretically optimal Hct value can be determined using Hct/WBV ratio in healthy subjects, hyperlipidemic and Raynaud's disease patients. Our aim was to examine whether Hct/WBV ratio is differently correlated with Hct in men and women with proven CAD. In a retrospective study we analysed the hemorheological data of 162 CAD outpatients (107 men and 55 women). Coronary angiography, echocardiography and impedance cardiography were performed. Hemorheological parameters (Hct, fibrinogen level, plasma viscosity, WBV), blood picture, serum lipid concentrations were determined and Hct/WBV ratio was calculated. Mean ages of male and female patients were similar (54.9 and 55.4 years, respectively), but men had significantly higher coronary angiography score than women. Mean left ventricular ejection fraction, stroke volume index and cardiac index showed no significant differences in men and women. Similarly, lipid concentrations, fibrinogen levels and plasma viscosities demonstrated no statistical differences. However, Hct, WBV and Hct/WBV ratios were significantly higher in male than in female patients (p<0.00001; p<0.00001 and p<0.005, respectively). The most striking gender difference was found in the correlation between Hct/WBV ratio and cardiac index. Men older than 56 years showed negative, women positive correlation (r=-0.485, p=0.01; r=0.468, p=0.006, respectively). This study demonstrates that Hct/WBV ratio as a rheological oxygen carrying capacity parameter is positively correlated with the cardiac index as it can be expected. However, the correlation is negative in elder men indicating an unhealthy relation between hemodynamic and hemorheologic parameters. [ABSTRACT FROM AUTHOR]

Background: Viscosity measurement is challenging due to the internal properties of blood and the artifacts deriving from the various viscometer systems., Objective: We aimed to determine the pitfalls of a cone-plate viscometer (Brookfield DV-III Ultra LV) before starting measurements and compare it to our capillary type model (Hemorex Hevimet 40). Effects of sample storage and thermal calibration were assessed as well., Methods and Results: Intra-observer variability was studied by 10 replicate measurements of 7 blood samples, mean coefficients of variation were less than 5%. Instruments were compared by measuring 26 blood samples, an average difference of 7% in WBV and 10% in PV was observed. 9 blood samples were stored at 4°C, 22°C and 37°C up to 48 hours to study the effect of storage on viscosity values. WBV at 50 and 100 s-1 became significantly lower after 3 hours at 37°C (p < 0.05). WBV at higher shear rates and PV remained constant at all temperatures. To evaluate the possibility of measuring one sample at different temperatures, 8 blood samples were measured at 40°C with the device calibrated both at 20°C and 40°C; no significant difference was observed., Conclusions: Thorough validation studies are required before starting experimental and routine viscosity measurements.

Purpose: The prognostic scoring systems for mortality of intensive care patients estimate clinical outcome using several physiological and biochemical parameters. In altered hemodynamic conditions of critically ill patients, hemorheological variables may play a significant role in appropriate tissue perfusion. We investigated if hemorheological parameters are altered in critical status and if they could be markers of mortality., Methods: 112 patients (67.8 ± 12 years, 58 males, 54 females) treated in intensive care unit with different non-surgical diseases were investigated. Routine laboratory parameters and prognostic scores were determined and hemorheological variables (hematocrit, plasma and whole blood viscosity, red blood cell aggregation and deformability) were measured on the 1st and the 2nd day after admission., Results: ICU scores predicted 35.2-41.3% mortality rate, real mortality in intensive care unit was 37.5%, while 30-day mortality was 46.6%. Whole blood viscosity (WBV) and red blood cell (RBC) deformability were lower, red blood cell aggregation was higher in septic than in nonseptic patients (p < 0.05). In septic patients calcium was increased, osmolality was decreased, while in nonseptic patients WBV and RBC aggregation were higher in nonsurvivors compared to survivors (p < 0.05). Worsening of RBC deformability from day 1 to day 2 predicted higher mortality (p < 0.05)., Conclusion: Calcium and osmolality level were associated with outcome in sepsis. Whole blood viscosity, red blood cell aggregation and change in red blood cell deformability could predict mortality in nonseptic patients and they may add prognostic information over the ICU scores. Further investigations are needed to evaluate the benefit of our findings in clinical practice.

Background: Carotid artery stenosis (CAS) is not only an important risk factor of cerebrovascular events but it can also indicate generalized atherosclerosis. Hemorheological parameters are altered in CAS and in chronic cerebrovascular disorders as well, but it is controversial if hemorheological parameters could be markers of stenosis or atherosclerosis., Methods: 107 patients were investigated, 40% of them had stroke or TIA in case history and 48% had CAS. Routine lab parameters were determined and hemorheological variables were measured: hematocrit, plasma viscosity, whole blood viscosity, red blood cell aggregation, and deformability., Results: In the stenotic group whole blood viscosity and red blood cell aggregation were deteriorated (p < 0.05). Whole blood and plasma viscosity were higher and red blood cell deformability was lower in the symptomatic group (p < 0.05). Plasma viscosity and red blood cell deformability were altered in the evolving atherosclerosis group and the CAS groups compared to patients having no signs of stenosis (p < 0.05), but there was no difference among the CAS groups., Conclusion: Although hemorheological parameters are impaired both in CAS and chronic cerebrovascular disorders, the severity of stenosis cannot be detected based on hemorheological parameters. Our investigation suggests that alteration of hemorheological parameters could indicate carotid atherosclerosis.

Background: Sex-specific response to antiplatelet medications have been reported in several previous studies., Objective: We investigated a possible connection between gender differences in hemorheological parameters and in vitro platelet aggregation in vascular patients treated with widely used antiplatelet agents., Methods: In vitro platelet aggregation was assessed in 2687 patients treated with 100 mg acetylsalicylic acid (ASA), 1047 patients treated with 75 mg clopidogrel and 311 patients on dual antiplatelet therapy (100 mg aspirin and 75 mg clopidogrel) according to the method of Born. In subgroups of patients fibrinogen concentration, whole blood and plasma viscosity, red blood cell aggregation and hematocrit were simultaneously measured. The subjects were divided into groups according to their gender., Results: ADP induced platelet aggregation was significantly higher in women in the case of ASA treatment (p<0.001). No gender differences could be observed in platelet function in patients treated with clopidogrel or on dual antiplatelet therapy. Hematocrit and whole blood viscosity were significantly higher in men in all groups (p<0.001), while no significant gender differences were observed in red blood cell aggregation indices in either group. Fibrinogen concentration was significantly higher in women than in men among patients treated with 100 mg ASA (p<0.05), but not in the other groups., Conclusions: Significantly higher fibrinogen concentration found in aspirin treated women than men may play a role in higher ADP induced platelet aggregation. Gender differences in response to monotherapy suggest that benefits from combination therapy may be greater in females. The clinical relevance of higher ADP induced platelet aggregation in women treated with ASA needs further investigation.

In our prospective study the effect of Sclerovit (0.8 mg folic acid, 20 mug vitamin B12,5 mg vitamin B6,100 mg vitamin E) on inflammatory markers, hemorheological parameters, platelet aggregation, von Willebrand factor activity as a marker of endothelium dysfunction, plasma lipids, plasma levels of folic acid, vitamin B12 and homocysteine (hcy), flow mediated vasodilatation (FMD) and thickness of carotis intima-media after 1 and 6 months of treatment in patients with vascular diseases (10 patients took 1 capsule, 10 patients 2 capsules of Sclerovit and 10 patients placebo) was determined.Plasma level of vitamin B12, folic acid and elongation index of red blood cells (RBC) increased significantly (p<0.05-0.001), hcy and triglyceride concentrations decreased significantly (p<0.05-0.001) in patients taking Sclerovit. HDL-cholesterol, RBC count, hematocrit, plasma and whole blood viscosity increased significantly (p<0.05-0.001) both in patients taking placebo or vitamins. Fibrinogen and CRP showed a significant (p<0.05-0.01) increase in patients on placebo, but did not change in patients on Sclerovit therapy. FMD showed a significant (p<0.05) amelioration in patients on 1 capsule of Sclerovit.Beside the favorable effects of Sclerovit on some of the measured parameters, the observed deterioration in hemorheological parameters can correlate with the contradictory results of large prospective studies with vitamins.

Evaluation of plasma viscosity has been underutilized in the clinical practice. Plasma viscosity is determined by water-content and macromolecular components. Plasma is a highly concentrated protein solution, therefore weak protein-protein interactions can play a role that is not characterized by electrophoresis. The effect of a protein on plasma viscosity depends on its molecular weight and structure. The less spheroid shape, the higher molecular weight, the higher aggregating capacity, and the higher temperature or pH sensitivity a protein has, the higher plasma viscosity results. Plasma is a Newtonian fluid, its viscosity does not depend on flow characteristics, therefore it is simple to measure, especially in capillary viscosimeters. Its normal value is 1.10-1.30 mPa s at 37 degrees C and independent of age and gender. The measurement has high stability and accuracy, thus little alterations may be pathologically important. Inflammations, tissue injuries resulting in plasma protein changes can increase its value with high sensitivity, though low specificity. It can increase in parallel with erythrocyte sedimentation rate (ESR), but it is not influenced by hematocrit (anemia, polycytemia), or time to analysis. Based on these favorable features, in 1942 plasma viscosity was recommended to substitute ESR. In hyperviscosity syndromes plasma viscosity is better in follow-up than ESR. In rheumatoid arthritis, its sensitivity and specificity are better than that of ESR or C-reactive protein. Plasma fibrinogen concentration and plasma viscosity are elevated in unstable angina pectoris and stroke and their higher values are associated with higher rate of major adverse clinical events. Elevation of plasma viscosity correlates to the progression of coronary and peripheral artery diseases. In conclusion, plasma viscosity should be measured routinely in medical practice.

In our present study we investigated the association between platelet aggregation in patients treated with the most widely used antiplatelet agents (100 and 300-325 mg acetylsalicylic acid (ASA), 75 mg clopidogrel, 500 mg ticlopidine and the combination of 100 mg aspirin and 75 mg clopidogrel), fibrinogen levels and aging. Between 2001 and 2005 we measured in vitro platelet aggregation in 5026 vascular patients according to the method of Born. Platelet aggregation was tested with 5 and 10 microM adenosine-diphosphate, 2 microg/ml collagen and 10 microM epinephrine stimulants. Fibrinogen level was simultaneously measured in a subgroup of 3243 patients. The subjects were divided by age into decades. Platelet aggregation increased significantly with advancing age in the case of 100 and 300-325 mg ASA-treated patients (p<0.001). In aspirin-treated patients also fibrinogen levels increased with aging (p<0.001). There was no association between platelet aggregation or fibrinogen levels and aging either in patients treated with 75 mg clopidogrel or with 500 mg ticlopidine. Thienopyridine-treated patients exhibited significantly lower fibrinogen levels than ASA-treated individuals (p<0.001). Our results suggest that advancing age is associated with elevated platelet aggregability in widely used antiplatelet regimens that might contribute to higher risk of cardiovascular events in the elderly.