Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation

The current thesis was divided into two parts. Basic platelet research is the topic of the first section. The subsequent clinical part examines platelet reactivity in stable angina pectoris (AP) and in atrial fibrillation. Platelet heterogeneity was investigated in the first section (papers 1 and 2)...

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Main Author: Milovanovic, Micha
Format: Doctoral Thesis
Language:English
Published: Linköpings universitet, Hälsa, Aktivitet, Vård (HAV) 2010
Subjects:
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-62630
http://nbn-resolving.de/urn:isbn:978-91-7393-272-1
id ndltd-UPSALLA1-oai-DiVA.org-liu-62630
record_format oai_dc
collection NDLTD
language English
format Doctoral Thesis
sources NDLTD
topic MEDICINE
MEDICIN
spellingShingle MEDICINE
MEDICIN
Milovanovic, Micha
Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
description The current thesis was divided into two parts. Basic platelet research is the topic of the first section. The subsequent clinical part examines platelet reactivity in stable angina pectoris (AP) and in atrial fibrillation. Platelet heterogeneity was investigated in the first section (papers 1 and 2). The cells were separated according to density using linear Percoll™ (a density medium) gradients. The latter contained EDTA, prostaglandin E1 and theophylline to prevent platelet in vitro activity. The platelet population was then divided into density subpopulations (n = 16 - 20). Membrane attached fibrinogen was determined with a flow cytometer technique and used as a marker reflecting platelet in vivo activity. Platelet P-Selectin content was employed to estimate the quantity of platelet α-granules. Paper I examined healthy blood donors (n = 3). The second report (paper II) compared healthy volunteers (n = 2) and subjects with essential thrombocythemia (ET) (n = 2). The latter is a clonal disease being characterized by an excessive platelet production. Platelet counts were determined in all fractions. In manuscripts I and II determination of surface bound fibrinogen and intracellular P-Selectin was carried out in 12 and 16 platelet density fractions, respectively. High density platelets displayed more surface bound fibrinogen indicating in vivo activity. They also contained less P-Selectin. The latter finding implies platelet in vivo release reactions. Low density platelets circulated with more surface bound fibrinogen as well. Compared with peak density platelets, lighter cells contained more P-Selectin. ET was characterized by a similar platelet density pattern in that high and low density platelets displayed more surface bound fibrinogen. The similarity may explain why severe bleedings do not occur more frequently in ET. It is also obvious from the current thesis that the significance of platelet heterogeneity remains unclear and stimulates to further research. In particular, future work must involve more patients. The second part (papers III-VI) of the thesis was devoted to stable AP and atrial fibrillation. Determination of platelet reactivity i.e. platelet bound fibrinogen after stimulation was carried out in whole blood. A flow cytometer technique was employed (papers III-VI). Adenosine diphosphate (ADP) (1.7 and 8.5 μmol/L) and a thrombin-receptor activating peptide (TRAP-6) (57 and 74 μmol/L) were used as stimulating agents. Determination of peak platelet density (kg/L) was utilized as a further measure reflecting platelet reactivity (paper V). Surface bound and soluble P-Selectin were employed as platelet activity markers (paper VI). Gender differences with respect to platelet reactivity were investigated in paper III. Paper IV examined platelets in stable AP without significant coronary flow obstruction(s) as determined by coronary angiography. In a following study platelet reactivity was analysed in diabetes type II complicated by stable AP (paper V). Finally, long-term (more than 2 years) outcome of atrial fibrillation was related to platelet reactivity and activity (paper VI). In this study the subjects were investigated at the initial electrical cardioversion and the analysis were repeated after more than 2 years. Postmenopausal women with stable AP demonstrated more reactive platelets when stimulating with TRAP-6. They had higher platelet counts (paper III) as well. Stable AP without significant coronary flow obstruction(s) was associated with elevated platelet reactivity (paper IV). Diabetes type II was linked to higher peak platelet density and elevated platelet reactivity (paper V). Augmented platelet reactivity proved to be a feature of subjects remaining in atrial fibrillation more than 2 years after the electrical cardioversion (paper VI). In contrast, the irregular heart rhythm did not affect platelet activity. It is to assume that platelets at least partly are responsible for the sometimes atypical symptoms of females with stable AP. It is also conceivable to speculate that platelets contribute to chest pain in AP free from significant coronary flow obstruction(s). Theoretically, enhanced platelet reactivity could at least partly explain why diabetes type II affects the prognosis of coronary heart disease. The thesis further shows a possible theoretical link between atrial fibrillation, increased platelet reactivity and clot formation.
author Milovanovic, Micha
author_facet Milovanovic, Micha
author_sort Milovanovic, Micha
title Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
title_short Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
title_full Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
title_fullStr Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
title_full_unstemmed Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
title_sort platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
publisher Linköpings universitet, Hälsa, Aktivitet, Vård (HAV)
publishDate 2010
url http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-62630
http://nbn-resolving.de/urn:isbn:978-91-7393-272-1
work_keys_str_mv AT milovanovicmicha plateletswithspecialreferencetoplateletdensitysubpopulationsstablecoronaryheartdiseaseandatrialfibrillation
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spelling ndltd-UPSALLA1-oai-DiVA.org-liu-626302013-01-08T13:06:53ZPlatelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillationengMilovanovic, MichaLinköpings universitet, Hälsa, Aktivitet, Vård (HAV)Linköpings universitet, HälsouniversitetetLinköping : Linköping University Electronic Press2010MEDICINEMEDICINThe current thesis was divided into two parts. Basic platelet research is the topic of the first section. The subsequent clinical part examines platelet reactivity in stable angina pectoris (AP) and in atrial fibrillation. Platelet heterogeneity was investigated in the first section (papers 1 and 2). The cells were separated according to density using linear Percoll™ (a density medium) gradients. The latter contained EDTA, prostaglandin E1 and theophylline to prevent platelet in vitro activity. The platelet population was then divided into density subpopulations (n = 16 - 20). Membrane attached fibrinogen was determined with a flow cytometer technique and used as a marker reflecting platelet in vivo activity. Platelet P-Selectin content was employed to estimate the quantity of platelet α-granules. Paper I examined healthy blood donors (n = 3). The second report (paper II) compared healthy volunteers (n = 2) and subjects with essential thrombocythemia (ET) (n = 2). The latter is a clonal disease being characterized by an excessive platelet production. Platelet counts were determined in all fractions. In manuscripts I and II determination of surface bound fibrinogen and intracellular P-Selectin was carried out in 12 and 16 platelet density fractions, respectively. High density platelets displayed more surface bound fibrinogen indicating in vivo activity. They also contained less P-Selectin. The latter finding implies platelet in vivo release reactions. Low density platelets circulated with more surface bound fibrinogen as well. Compared with peak density platelets, lighter cells contained more P-Selectin. ET was characterized by a similar platelet density pattern in that high and low density platelets displayed more surface bound fibrinogen. The similarity may explain why severe bleedings do not occur more frequently in ET. It is also obvious from the current thesis that the significance of platelet heterogeneity remains unclear and stimulates to further research. In particular, future work must involve more patients. The second part (papers III-VI) of the thesis was devoted to stable AP and atrial fibrillation. Determination of platelet reactivity i.e. platelet bound fibrinogen after stimulation was carried out in whole blood. A flow cytometer technique was employed (papers III-VI). Adenosine diphosphate (ADP) (1.7 and 8.5 μmol/L) and a thrombin-receptor activating peptide (TRAP-6) (57 and 74 μmol/L) were used as stimulating agents. Determination of peak platelet density (kg/L) was utilized as a further measure reflecting platelet reactivity (paper V). Surface bound and soluble P-Selectin were employed as platelet activity markers (paper VI). Gender differences with respect to platelet reactivity were investigated in paper III. Paper IV examined platelets in stable AP without significant coronary flow obstruction(s) as determined by coronary angiography. In a following study platelet reactivity was analysed in diabetes type II complicated by stable AP (paper V). Finally, long-term (more than 2 years) outcome of atrial fibrillation was related to platelet reactivity and activity (paper VI). In this study the subjects were investigated at the initial electrical cardioversion and the analysis were repeated after more than 2 years. Postmenopausal women with stable AP demonstrated more reactive platelets when stimulating with TRAP-6. They had higher platelet counts (paper III) as well. Stable AP without significant coronary flow obstruction(s) was associated with elevated platelet reactivity (paper IV). Diabetes type II was linked to higher peak platelet density and elevated platelet reactivity (paper V). Augmented platelet reactivity proved to be a feature of subjects remaining in atrial fibrillation more than 2 years after the electrical cardioversion (paper VI). In contrast, the irregular heart rhythm did not affect platelet activity. It is to assume that platelets at least partly are responsible for the sometimes atypical symptoms of females with stable AP. It is also conceivable to speculate that platelets contribute to chest pain in AP free from significant coronary flow obstruction(s). Theoretically, enhanced platelet reactivity could at least partly explain why diabetes type II affects the prognosis of coronary heart disease. The thesis further shows a possible theoretical link between atrial fibrillation, increased platelet reactivity and clot formation. Doctoral thesis, comprehensive summaryinfo:eu-repo/semantics/doctoralThesistexthttp://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-62630urn:isbn:978-91-7393-272-1Linköping University Medical Dissertations, 0345-0082 ; 1220application/pdfinfo:eu-repo/semantics/openAccess