Labeling Of Red Blood Cells Research Articles

Vascular Supply of the Cerebral Cortex is Specialized for Cell Layers but Not Columns

The vascular supply to layers and columns was compared in macaque primary visual cortex (V1) by labeling red blood cells via their endogenous peroxidase activity. Alternate sections were processed for cytochrome oxidase to reveal "patches" or "blobs," which anchor the interdigitated column systems of striate cortex. More densely populated cell layers received the most profuse blood supply. In the superficial layers the blood supply was organized into microvascular lobules, consisting of a central venule surrounded by arterioles. Each vessel was identified as an arteriole or venule by matching it with the penetration site where it entered the cortex from a parent arteriole or venule in the pial circulation. Although microvascular lobules and cytochrome oxidase patches had a similar periodicity, they bore no mutual relationship. The size and density of penetrating arterioles and venules did not differ between patches and interpatches. The red blood cell labeling in patches and interpatches was equal. Moreover, patches and interpatches were supplied by an anastomotic pial arteriole system, with no segregation of blood supply to the two compartments. Often a focal constriction was present at the origin of pial arterial branches, indicating that local control of cortical perfusion may be accomplished by vascular sphincters.

A Study on Analysis of Labeling Efficiency Depending on Mixing Time in Asan Medical Center Red Blood Cell Labeling Method

ABSTRACT The aim of this study was to overcome the shortcomings of technetium-99m red blood cell labeling, such as the requirement of additional time, and to maintain a stable labeling efficiency by reducing the mixing time for technetium-99m red blood cell labeling in the Asan Medical Center red blood cell labeling method developed by this hospital. Thirty patients, who underwent an examination using technetium-99m red blood cell labeling in the nuclear medicine department from April to September 2012, were selected randomly. Blood samples (5 mL per patient) were mixed with acid citrate dextrose, and 1-mL aliquots were taken to make four blood samples. The Asan Medical Center red blood cell labeling method was used for labeling. In this case, the mixing time was set to 5, 10, 15, and 20 min before calculating the efficiency of each labeling. The difference depending on the mixing time was compared. According to the technetium-99m red blood cell labeling efficiency depending on the mixing time in the Asan Medical Center red blood cell labeling method, the efficiency of each labeling was 92 ± 5%, 96 ± 5%, 97 ± 5%, and 98 ± 5% for 5, 10, 15, and 20 min, respectively. Overall, the labeling efficiency was relatively low when the mixing time was 5 min, whereas there was no significant difference in labeling efficiency when the mixing time was longer than 5 min. In conclusion, the Asan Medical Center red blood cell labeling method can provide an environment that is more conducive to the combination of red blood cell with technetium-99m pertechnetate than the previous modified labeling method because the Asan Medical Center red blood cell labeling method removes blood plasma in an additional centrifugation process.

Comparative Physiology of Mice and Rats: Radiometric Measurement of Vascular Parameters in Rodent Tissues

A solid understanding of physiology is beneficial in optimizing drug delivery and in the development of clinically predictive models of drug disposition kinetics. Although an abundance of data exists in the literature, it is often confounded by the use of various experimental methods and a lack of consensus in values from different sources. To help address this deficiency, we sought to directly compare three important vascular parameters at the tissue level using the same experimental approach in both mice and rats. Interstitial volume, vascular volume, and blood flow were radiometrically measured in selected harvested tissues of both species by extracellular marker infusion, red blood cell labeling, and rubidium chloride bolus distribution, respectively. The latter two parameters were further compared by whole-body autoradiographic imaging. An overall good interspecies agreement was observed for interstitial volume and blood flow on a weight-normalized basis in most tissues. In contrast, the measured vascular volumes of most rat tissues were higher than for mouse. Mice and rats, the two most commonly utilized rodent species in translational drug development, should not be considered as interchangeable in terms of vascular volume per gram of tissue. This will be particularly critical in biodistribution studies of drugs, as the amount of drug in the residual blood of tissues is often not negligible, especially for biologic drugs (e.g., antibodies) having long circulation half-lives. Physiologically based models of drug pharmacokinetics and/or pharmacodynamics also rely on accurate knowledge of biological parameters in tissues. For tissue parameters with poor interspecies agreement, the significance and possible drivers are discussed.

Measurement of posttransfusion red cell survival with the biotin label.

The goal of this review is to summarize and critically assess information concerning the biotin method to label red blood cells (RBC) for use in studies of RBC and transfusion biology-information that will prove useful to a broad audience of clinicians and scientists. A review of RBC biology, with emphasis on RBC senescence and in vivo survival, is included, followed by an analysis of the advantages and disadvantages of biotin-labeled RBC (BioRBC) for measuring circulating RBC volume, posttransfusion RBC recovery, RBC life span, and RBC age-dependent properties. The advantages of BioRBC over (51)Cr RBC labeling, the current reference method, are discussed. Because the biotin method is straightforward and robust, including the ability to follow the entire life spans of multiple RBC populations concurrently in the same subject, BioRBC offers distinct advantages for studying RBC biology and physiology, particularly RBC survival. The method for biotin labeling, validation of the method, and application of BioRBCs to studies of sickle cell disease, diabetes, and anemia of prematurity are reviewed. Studies documenting the safe use of BioRBC are reviewed; unanswered questions requiring future studies, remaining concerns, and regulatory barriers to broader application of BioRBC including adoption as a new reference method are also presented.

Preclinical evaluation of carbon-11 and fluorine-18 sulfonamide derivatives for in vivo radiolabeling of erythrocytes.

BackgroundTo date, few PET tracers for in vivo labeling of red blood cells (RBCs) are available. In this study, we report the radiosynthesis and in vitro and in vivo evaluation of 11C and 18F sulfonamide derivatives targeting carbonic anhydrase II (CA II), a metallo-enzyme expressed in RBCs, as potential blood pool tracers. A proof-of-concept in vivo imaging study was performed to demonstrate the feasibility to assess cardiac function and volumes using electrocardiogram (ECG)-gated positron emission tomography (PET) acquisition in comparison with cine magnetic resonance imaging (cMRI) in rats and a pig model of myocardial infarction.MethodsThe inhibition constants (Ki) of CA II were determined in vitro for the different compounds by assaying CA-catalyzed CO2 hydration activity. Binding to human RBCs was estimated after in vitro incubation of the compounds with whole blood. Biodistribution studies were performed to evaluate tracer kinetics in NMRI mice. ECG-gated PET acquisition was performed in Wistar rats at rest and during pharmacological stress by infusing dobutamine at 10 μg/kg/min and in a pig model of myocardial infarction. Left ventricular ejection fraction (LVEF) and volumes were compared with values from cMRI.ResultsThe Ki of the investigated compounds for human CA II was found to be in the range of 8 to 422 nM. The fraction of radioactivity associated with RBCs was found to be ≥90% at 10- and 60-min incubation of tracers with heparinized human blood at room temperature for all tracers studied. Biodistribution studies in mice indicated that 30% to 67% of the injected dose was retained in the blood pool at 60 min post injection. A rapid and sustained tracer uptake in the heart region with an average standardized uptake value of 2.5 was observed from micro-PET images. The LVEF values obtained after pharmacological stress in rats closely matched between the cMRI and micro-PET values, whereas at rest, a larger variation between LVEF values obtained by both techniques was observed. In the pig model, a good agreement was observed between PET and MRI for quantification of left ventricular volumes and ejection fraction.ConclusionsThe 11C and 18F sulfonamide derivatives can be used for efficient in vivo radiolabeling of RBCs, and proof-of-concept in vivo imaging studies have shown the feasibility and potential of these novel tracers to assess cardiac function.

Metabolic and hematologic consequences of colectomy associated to hepatectomy in rats

To investigate the influence of partial colectomy associated with hepatectomy on the biodistribution of the (99m)Tc-phytate, on metabolic parameters, as well as labeling and morphology of red blood cells. Wistar rats were distributed into three groups (each with six), nominated as colectomy, colectomy+hepatectomy and sham. In the 30(th) postoperative day all rats were injected with (99m)Tc-phytate 0.1mL i.v. (radioactivity 0.66 MBq). After 15 minutes, liver sample was harvested and weighed. Percentage radioactivity per gram of tissue (%ATI/g) was determined using an automatic gamma-counter. Serum AST, ALT, alkaline phosphatase and red blood cells labeling were determined. The liver %ATI/g and red blood cells labeling were lower in colectomy and colectomy+hepatectomy rats than in sham rats (p <0.05), and no difference was detected comparing the colectomy and colectomy+hepatectomy groups. Red blood cells morphology did not differ among groups. Serum levels of AST, ALT and alkaline fosfatase were significantly higher in colectomy+hepatectomy than in colectomy rats (p<0.001). Hepatectomy associated with colectomy lowered the uptake of radiopharmaceutical in liver and in red blood cells in rats, coinciding with changes in liver enzymatic activity.

Abstract A138: Evaluation of neonatal Fc receptor (FcRn) expression and function in tumor cell lines and their potential effect on IgG disposition in solid tumors.

Abstract The human neonatal Fc receptor, hFcRn, is a trafficking receptor for human IgG expressed by various cell types such as vascular endothelial cells, antigen presenting cells, and colorectal, mammary, and pulmonary epithelial cells. Binding of FcRn by monomeric IgG occurs in a pH-restricted manner and, depending on the interacting cell type, can lead to IgG recycling or transcytosis. The recycling pathway is predominant in the vascular endothelium and it traffics IgG away from lysosomal degradation; transcytotic IgG transport, on the other hand, has been more commonly observed in intestinal, breast, and lung epithelium. We hypothesize that solid tumors originating from FcRn-expressing epithelia maintain FcRn expression and that functional expression of FcRn in tumors may affect IgG subcellular trafficking, metabolism, and overall tumor disposition. In the investigations presented herein, we provide quantitative evidence of robust FcRn expression by colorectal and breast tumor cell lines as examined by Flow-Assisted Cell Sorting (FACS) and Western Blotting. Furthermore, we show by Fluorescence Microscopy in selected cell lines that FcRn is localized in both early and recycling endosomes and that its localization in recycling endosomes supports its function in these cells, which is also shown by FACS to be predominantly that of a recycling receptor. To evaluate our hypothesis in vivo, we have developed and characterized an hFcRn mouse tumor model in which hFcRn expression is conditional on doxycycline dosing. Briefly, hFcRn-transduced HM7 colorectal tumor cells (HM7-hFcRn+) implanted into athymic nude mice were evaluated as a function of growth kinetics, vascular volume, and hFcRn expression for up to 14 days following cell inoculation. We show by immunohistochemical staining and FACS substantial hFcRn expression in HM7-FcRn+ tumors relative to parental HM7 tumors during the course of study. Tumor growth and tumor vascular volumes were similar to the parental model as shown by caliper measurements and indirect (99m)Tc red blood cell labeling, respectively, suggesting that this model is appropriate for our purpose. These results provide evidence of hFcRn expression in colorectal and breast cancer cell lines commonly used in xenograft studies and suggest that such expression may lead to IgG recycling in these cell types. Furthermore, we have developed a mouse tumor model that will allow us to determine whether the recycling function of hFcRn observed in vitro translates to an in vivo setting and its effect on IgG tumor distribution, metabolism, and ultimately, anti-tumor efficacy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A138.

Evaluation of red blood cell labelling methods based on a statistical model for red blood cell survival

The aim of this work is to compare different labelling methods that are commonly used to estimate the lifespan of red blood cells (RBCs), e.g. in anaemia of renal failure, where the effect of treatment with erythropoietin depends on the lifespan of RBCs. A previously developed model for the survival time of RBCs that accounts for plausible physiological processes of RBC destruction was used to simulate ideal random and cohort labelling methods for RBCs, as well as the flaws associated with these methods (e.g. reuse of label and loss of the label from the surviving RBCs). Random labelling with radioactive chromium and cohort labelling using heavy nitrogen were considered. Blood sampling times were determined for RBC survival studies using both labelling methods by applying the theory of optimal design. It was assessed whether the underlying parameter values of the model are estimable from these studies, and the precision of the parameter estimates were calculated. In theory, parameter estimation would be possible for both types of ideal labelling methods without flaws. However, flaws associated with random labelling are significant and not all parameters controlling RBC survival in the model can be estimated with good precision. In contrast, cohort labelling shows good precision in the parameter estimates even in the presence of reuse and prolonged incorporation of the label. A model based analysis of RBC survival studies is recommended in future to account for limitations in methodology as well as likely causes of RBC destruction.

Development and Evaluation of a Novel Method for Preclinical Measurement of Tissue Vascular Volume

Identification of clinically predictive models of disposition kinetics for antibody therapeutics is an ongoing pursuit in drug development. To encourage translation of drug candidates from early research to clinical trials, clinical diagnostic agents may be used to characterize antibody disposition in physiologically relevant preclinical models. TechneScan PYP was employed to measure tissue vascular volumes (V(v)) in healthy mice. Two methods of red blood cell (RBC) labeling were compared: a direct in vivo method that is analogous to a clinical blood pool imaging protocol, and an indirect method in which radiolabeled blood was transfused from donor mice into recipient mice. The indirect method gave higher precision in RBC labeling yields, lower V(v) values in most tissues, and lower (99m)Tc uptake in kidneys and bladder by single photon emission computed tomographic (SPECT) imaging relative to the direct method. Furthermore, the relative influence of each method on the calculated area under the first 7 days of the concentration-time curve (AUC(0-7)) of an IgG in nude mice was assessed using a physiologically based pharmacokinetic model. The model was sensitive to the source of V(v) values, whether obtained from the literature or measured by either method, when used to predict experimental AUC(0-7) values for radiolabeled trastuzumab in healthy murine tissues. In summary, a novel indirect method for preclinical determination of V(v) offered higher precision in RBC labeling efficiency and lower renal uptake of (99m)Tc than the direct method. In addition, these observations emphasize the importance of obtaining accurate physiological parameter values for modeling antibody uptake.

Assessment of the effect of Bacopa monnieri (L.) Wettst. extract on the labeling of blood elements with technetium-99m and on the morphology of red blood cells

Bacopa monnieri (L.) Wettst. (BM), a traditional Ayurvedic medicine, used for centuries as a memory enhancing, anti-inflammatory, antipyretic, sedative and antiepileptic agent. BM extract have been extensively investigated by several authors for their neuropharmacological effects. In nuclear medicine, red blood cells (RBC) labeled with technetium-99m (99mTc) have several clinical applications. However, data have demonstrated that synthetic or natural drugs could modify the labeling of RBC with 99mTc. As Bacopa monnieri is extensively used in medicine, we evaluated its influence on the labeling of RBC and plasma proteins using technetium-99m (99mTc). This labeling procedure depends on a reducing agent and usually stannous chloride is used. Blood was incubated with BM extracts. Stannous chloride solution and 99mTc were added. Blood was centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P or BC were also precipitated, centrifuged and insoluble fraction (IF) and soluble fraction (SF) were separated. The percentage of radioactivity (%ATI) in BC, IF-BC and IF-P were calculated. The %ATI significantly decreased on BC from 95.53±0.45 to 35.41±0.44, on IF-P from 80.20±1.16 to 7.40±0.69 and on IF-BC from 73.31±1.76 to 21.26±1.40. The morphology study of RBC revealed important morphological alterations due to treatment with BM extracts. We suggest that the BM extract effect could be explained by an inhibition of the stannous and pertechnetate ions or oxidation of the stannous ion or by damages induced in the plasma membrane.

Avaliação do controle radioquímico do Ricinus communis L. e Tc-99m na marcação de hemácias

O Ricinus communis L. pertence à família das Euforbiáceas, possui frutos típicos de onde é extraído o óleo de rícino, altamente tóxico. Neste estudo foi analisado o efeito do extrato de Ricinus communis L na marcação de hemácias com Tc-99m através do controle radioquímico. Os resultados mostraram que no controle radioquímico por meio da cromatografia, foi observado que o extrato marcado com Tc-99m mostrou duas frações com 130.007 e 494.592 cpm, e na marcação de hemácias, com %ATI de 61.88 e 41.32% nas frações 1 e 2. Foi concluído que o extrato de R. communis L. altera a captação do Tc-99m in vitro, competindo com o material radioativo em possíveis sítios de ligação nas células vermelhas do sangue, como a capacidade de oxidação do íon estanoso ou por competição com o íon pertecnetato.

Chocolate Intake Associated with Failed Labeling of 99mTc Red Blood Cells

Red blood cells (RBC) labeled in vivo with (99m)Tc-pertechnetate are used worldwide in nuclear medicine departments. Here, we present a case of (99m)Tc-RBC labeling failure associated with chocolate intake in a 25-y-old woman, resulting in uninterpretable images. Because of this clinical observation, we performed in vitro RBC labeling on blood samples from volunteers after they consumed chocolate. Chocolate intake inhibited the labeling rate, compared with the control condition, and significantly increased the (99m)Tc free fraction (34.1% +/- 11.3% vs. 14.0% +/- 1.2%). We cannot explain how this interaction could occur, but cacao components are known to modulate red cell and plasma oxidoreductive status and to modify red cell membrane permeability and plasticity. Therefore, for patients who can be considered likely to consume chocolate, such as young patients, we recommend that they limit their consumption of chocolate for 12 h before RBC labeling.

Complement fraction 3 binding on erythrocytes as additional mechanism of disease in paroxysmal nocturnal hemoglobinuria patients treated by eculizumab

AbstractIn paroxysmal nocturnal hemoglobinuria (PNH) hemolytic anemia is due mainly to deficiency of the complement regulator CD59 on the surface of red blood cells (RBCs). Eculizumab, an antibody that targets complement fraction 5 (C5), has proven highly effective in abolishing complement-mediated intravascular hemolysis in PNH; however, the hematologic benefit varies considerably among patients. In the aim to understand the basis for this variable response, we have investigated by flow cytometry the binding of complement fraction 3 (C3) on RBCs from PNH patients before and during eculizumab treatment. There was no evidence of C3 on RBCs of untreated PNH patients; by contrast, in all patients on eculizumab (n = 41) a substantial fraction of RBCs had C3 bound on their surface, and this was entirely restricted to RBCs with the PNH phenotype (CD59−). The proportion of C3+ RBCs correlated significantly with the reticulocyte count and with the hematologic response to eculizumab. In 3 patients in whom 51Cr labeling of RBCs was carried out while on eculizumab, we have demonstrated reduced RBC half-life in vivo, with excess 51Cr uptake in spleen and in liver. Binding of C3 by PNH RBCs may constitute an additional disease mechanism in PNH, strongly enhanced by eculizumab treatment and producing a variable degree of extravascular hemolysis.

Uncaria tomentosa extract: evaluation of effects on the in vitro and in vivo labeling of blood constituents with technetium-99m

The influence (in vivo and in vitro) of an Uncaria tomentosa extract (Cats claw) on the labeling of red blood cells (RBCs) and plasma and cellular proteins with technetium-99m (Tc-99m) was evaluated. For the in vivo treatment, animals were treated with Cats claw. For the in vitro treatment, heparinized blood was incubated with Cats claw before the addition of stannous chloride (SnCl2) and Tc-99m. Samples of plasma (P) and RBCs were separated and also precipitated with trichloroacetic acid. The soluble and insoluble fractions of P and RBCs were isolated. The analysis of the results of the in vivo study, indicates that there is no significant alteration on the uptake of Tc-99m by the blood constituents, but it significantly decrease (p&lt;0.05) the labeling of blood constituents by in vitro methods. These effects could be due to chelation of stannous and /or pertechnetate ions and blockage of the Tc-99m bindings sites.

Effect of the extract of Ricinus communis L. on the osmotic fragility, labeling of red blood cells with Technetium-99m and morphology of the cells

The aim of this study was to evaluate the influence of the proteic extract of R. communis on the cell physiology by the osmotic fragility, labeling of the blood elements with the 99mTc and cell morphology. To evaluate the osmotic fragility, the blood samples of the Wistar rats were incubated with the concentrations of R. communis and with the solutions of NaCl (0.4; 0.7; 0.9%). In the labeling of the blood elements procedure, the rat blood was treated with a solution of Tc-99m and TCA at 5%, determining the rate of radioactivity (%ATI) in the plasma (P) and in the red blood cells (RBC). The soluble and insoluble fractions of the plasma were also evaluated. The cells morphology submitted to the extract was evaluated by the optical microscopy (x40). The results indicated that the rate of the hemolysis increased in the presence of 0.125 mg/mL of the extract. There was a decay of 49.69% in the rate of ATI in the insoluble fraction of the cells, with the morphological alterations in the red blood cells. These results suggested that the extract changed the capability of binding of the red blood cells due to the stannous ion oxidation, modifying the cells structure.

Preparation and evaluation of [201Tl](III)-DTPA complex for cell labeling

Due to interesting physical properties and wide availability of 201Tl as a SPECT radionuclide, the incorporation of this nuclide into DTPA for cell labeling was targeted. Thallium-201 (T1/2 = 3.04 d) in Tl+ form was converted to Tl3+ cation in the presence of O3/6M HCl and di-isopropyl ether, controlled by RTLC/gel electrophoresis methods. The final evaporated activity reacted with cDTPA in normal saline to yield [201Tl](III)DTPA at room temperature after 0.5 hour, followed by solid phase extraction purification using C18 Sep-Pak column (radiochemical yield >95%). Radiochemical purity of more than 99% was obtained using RTLC with specific activity of about 260 GBq/mmol. The stability of the tracer was checked in the final product in the presence of human serum at 37 °C up to 3 days. The partition coefficient was also measured. The labeled compound was used in red blood cell (RBC) labeling. The cell uptake ratio was determined at 4, 25 and 37 °C up to 3 hours.

Effect of an extract of Artemisia vulgaris L. (Mugwort) on the in vitro labeling of red blood cells and plasma proteins with technetium-99m

The aim of this work was to evaluate the effect of an extract of the Artemisia vulgaris L. (mugwort) on the labeling of blood constituents with technetium-99m (99mTc). Blood samples from Wistar rats were incubated with a mugwort extract and the radiolabeling of blood constituents was carried out. Plasma and blood cells were separated by centrifugation. Aliquots of plasma and blood cells were also precipitated with trichloroacetic acid and centrifuged to isolate soluble and insoluble fractions of plasma and blood cells. Radioactivity in each fraction was counted and the percentages of radioactivity (%ATI) was calculated. Mugwort extract decreased significantly (p&lt;0.05) the %ATI on the blood compartments and on the blood cells proteins (insoluble fraction). The analysis of the results indicates that the extract could have substances that could interfere on the transport of stannous through the erythrocyte membrane alterating the labeling of blood cells with 99mTc.

Influence of biflorin on the labelling of red blood cells, plasma protein, cell protein, and lymphocytes with technetium-99m: in vitro study

In this paper we report the results of an in vitro study involving the influence of biflorin (an o-quinone isolated from Capraria biflora L. that has potent antimicrobial activity) on the Tc-99m labeling of red blood cells, plasma protein, cells protein, and lymphocytes. Blood was withdrawn from Wistar rats and incubated with various concentrations of biflorin, and solutions of stannous chloride and Tc-99m were added. Plasma (P) and red blood cells (RBC) were isolated, precipitated, and centrifuged, and soluble (SF) and insoluble (IF) fractions were isolated. The results show that the highest concentration (100%) of biflorin is able to reduce the uptake of Tc-99m (%ATI) on RBC and the fixation on IF-P. To study the influence of biflorin on 99mTc lymphocyte labeling, human blood was submitted to a technique with Ficoll-Hypac and centrifuged, and white cells were isolated. Lymphocytes (2.5 mL; 1.0 x 106 cells/mL) were obtained and a 0.2 mL solution was incubated with biflorin (0.1 mL). Solutions of stannous chloride and 99mTc were added. Lymphocytes were separated and the %ATI bound in these cells was evaluated. A reduction in %ATI (from 97.85 ± 0.99 to 88.86 ± 5) was observed for RBC and for IF-P (73.24 ± 5.51 to 20.72 ± 6.95). In this case the results showed no decrease in %ATI for the lymphocytes with biflorin.

Left ventricular function during arm exercise: influence of leg cycling and lower body positive pressure

The purpose of this study was to characterize left ventricular (LV) diastolic filling and systolic performance during graded arm exercise and to examine the effects of lower body positive pressure (LBPP) or concomitant leg exercise as means to enhance LV preload in aerobically trained individuals. Subjects were eight men with a mean age (+/-SE) of 26.8 +/- 1.2 yr. Peak exercise testing was first performed for both legs [maximal oxygen uptake (Vo(2)) = 4.21 +/- 0.19 l/min] and arms (2.56 +/- 0.16 l/min). On a separate occasion, LV filling and ejection parameters were acquired using non-imaging scintography using in vivo red blood cell labeling with technetium 99(m) first during leg exercise performed in succession for 2 min at increasing grades to peak effort. Graded arm exercise (at 30, 60, 80, and 100% peak Vo(2)) was performed during three randomly assigned conditions: control (no intervention), with concurrent leg cycling (at a constant 15% leg maximal Vo(2)) or with 60 mmHg of LBPP using an Anti G suit. Peak leg exercise LV ejection fraction was higher than arm exercise (60.9 +/- 1.7% vs. 55.9 +/- 2.7%; P < 0.05) as was peak LV end-diastolic volume was reported as % of resting value (110.3 +/- 4.4% vs. 97 +/- 3.7%; P < 0.05) and peak filling rate (end-diastolic volume/s; 6.4 +/- 0.28% vs. 5.2 +/- 0.25%). Concomitant use of either low-intensity leg exercise or LBPP during arm exercise failed to significantly increase LV filling or ejection parameters. These observations suggest that perturbations in preload fail to overcome the inherent hemodynamic conditions present during arm exercise that attenuate LV performance.

Clinical validation of the gated blood pool SPECT QBS® processing software in congestive heart failure patients: correlation with MUGA, first-pass RNV and 2D-echocardiography

Left (LVEF) and right ventricular ejection fraction (RVEF) as well as LV regional wall motion at rest are valuable tools to monitor and tailor treatment of congestive heart failure (CHF) patients. Gated blood pool SPECT (GBPS) is under evaluation as an "all-in-one" technique, providing information on LVEF, RVEF, and wall motion derived from a single examination. Aim of the study was to evaluate a commercially available automated GBPS processing software for EF measurements and wall motion analysis in heart failure patients. Thirty-two patients (12 female; mean age+/-SD: 53+/-13 years), suffering from dilated (63%), ischemic (25%) or hypertrophic (13%) cardiomyopathy, were studied. First-pass radionuclide ventriculography (FP-RNV), planar multigated radionuclide angiography (MUGA), and GBPS were performed at rest after in vivo labeling of red blood cells, and LVEF and RVEF was calculated with each method. Later on the same day LVEF was calculated by echocardiography. LV wall motion (summed motion score and wall motion index) was derived from GBPS and echocardiography using the standard 16-segment model. Mean LVEF measured by GBPS, echocardiography, MUGA and FP-RNV was 33+/-13%, 37+/-15%, 41+/-14% and 45+/-13%, respectively. LVEF values calculated from GBPS showed moderate to good correlation with FP-RNV (r=0.61), MUGA (r=0.65) and ECHO (r=0.74; all p<0.01). Mean RVEF calculated by GBPS, FP-RNV and MUGA was 45+/-14%, 46+/-9% and 38+/-9%, respectively. RVEF values calculated from GBPS showed weak correlation with FP-RNV (r=0.33) and MUGA (r=0.26; all p=n.s.). Assessment of GBPS wall motion was qualitatively possible in all patients. The agreement between GBPS and ECHO was 82% (kappa=0.73). The wall motion index showed good correlation between both methods (r=0.88; p<0.001). An automated algorithm for LVEF calculation and wall motion analysis using GBPS is feasible for clinical routine diagnostic in CHF patients. The RVEF calculation method needs to be improved before routine clinical application can be recommended.