Skip Navigation

Cardiovascular Research 1998 40(1):223-229; doi:10.1016/S0008-6363(98)00114-X
© 1998 by European Society of Cardiology
This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Eto, K.
Right arrow Articles by Isshiki, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Eto, K.
Right arrow Articles by Isshiki, T.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Copyright © 1998, European Society of Cardiology

Platelet aggregation in acute coronary syndromes: use of a new aggregometer with laser light scattering to assess platelet aggregability

Koji Etoa, Satoshi Takeshitaa,*, Masahiko Ochiaia, Yukio Ozakib, Tomohide Satoa and Takaaki Isshikia

aDepartment of Medicine (Cardiology), Teikyo University School of Medicine, Tokyo, Japan
bDepartment of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan

* Corresponding author. Tel.: 81 (3) 3964 1211 (ext. 1580); Fax: 81 (3) 5375 1308; E-mail: stake@blue.ocn.ne.jp

Received 16 December 1997; accepted 19 March 1998


   Abstract
Top
 Abstract
1 Introduction
 2 Methods
 3 Results
 4 Discussion
 References
 
Objective: Platelet aggregation has been implicated in the pathogenesis of acute coronary syndromes. Small aggregates consisting of ≤100 platelets cannot be quantified with a conventional aggregometer employing optical density. Using a recently developed aggregometer based on laser light scattering, we studied platelet aggregability in patients with acute coronary syndromes. Methods: Peripheral blood samples were obtained from 39 patients with acute myocardial infarction or unstable angina who had received no prior antiplatelet or anticoagulant therapy, to be assayed immediately using a PA-100 platelet aggregometer. Blood samples from 14 healthy volunteers were used as controls. Results: Spontaneous formation of platelet aggregates was observed only in patients with acute coronary syndromes. The size of these aggregates was small, consisting of ≤100 platelets (primary aggregation). Agonist-induced aggregation consisted of two phases. In the first few minutes, the number of small aggregates increased markedly (primary aggregation), followed by an increase in larger aggregates (secondary aggregation). The EC50 of epinephrine for primary aggregation was nearly 50 times lower in acute coronary patients than in controls (P<0.001), while the EC50 for secondary aggregation was only 2 times lower (P<0.001). Conclusions: Aggregometry using light scattering suggests that platelet hyperaggregability and hypersensitivity in acute coronary syndromes may occur in primary but not secondary aggregation.

KEYWORDS Atherosclerosis; Coronary disease; Ischemia; Platelets; Thrombosis


   1 Introduction
Top
 Abstract
 1 Introduction
2 Methods
 3 Results
 4 Discussion
 References
 
Platelets play an important but incompletely understood role in the pathogenesis of acute coronary syndromes [1, 2]. Several factors, including platelet hyperaggregability and platelet hypersensitivity to various agonists, have been implicated in the pathogenesis of coronary events [3–5].

Platelet aggregation in acute coronary syndromes has been studied by direct counting of formalin-fixed aggregates [6, 7], histopathologic examination of myocardial tissue sections [8], and aggregometry [3, 9–11]. Although these studies have provided important information, each method used has its specific limitations. Direct platelet counting, for example, does not evaluate reactivity of platelets to agonists. Histologic examination at necropsy is limited to one time point, and results can be affected by the time between the onset of ischemia and death. Conventional aggregometers, which measure the change in light transmission (LT) of a platelet suspension [9], have a limited ability to detect small aggregates of ≤100 platelets [12, 13]. Therefore, previous studies employing conventional aggregometers may have underestimated the initial aggregation process in the setting of acute coronary syndromes [14]. Recently, Ozaki et al. have developed a new aggregometer that employs a light-scattering (LS) method [15, 16]. This system is sensitive enough to detect aggregates as small as two or three platelets. Accordingly, in the current study, we employed this new instrument to investigate the precise aggregation process in patients with acute coronary syndromes.


   2 Methods
Top
 Abstract
 1 Introduction
 2 Methods
3 Results
 4 Discussion
 References
 
The current investigation conforms with the principles outlined in the Declaration of Helsinki [17]. Written informed consent was obtained from all participants, and the study protocol was approved by the institutional ethics committee.

2.1 Patient population
The study group consisted of 39 patients with acute coronary syndromes (mean age 66±2 years), including 17 with primary unstable angina (UAP: 9 men, mean age 68±3 years, range 56 to 82) and 22 with acute myocardial infarction (AMI: 17 men, mean age 64±2 years, range 45 to 80). UAP in this study included Braunwald type B [18], and transient ST-segment depression or T-wave inversion was documented in all patients. Significant arterial narrowing (>50% luminal narrowing of one or more major coronary arteries) also was confirmed by coronary angiography in these patients. The diagnosis of AMI was based on the occurrence of ischemic chest pain exceeding 30 min accompanied by ST-segment elevation and a subsequent increase in serum creatine kinase. In AMI patients, coronary artery occlusion [TIMI grade 0 or 1 flow [19]] was confirmed by angiography performed within 90 min of admission. For the control group, blood samples were obtained from 14 healthy volunteers (10 men, mean age 56±4 years, range 30 to 82). No patients or normal volunteers had taken aspirin or other agents known to alter platelet function for at least 2 weeks prior to the study.

2.2 Blood sampling
In the case of UAP, blood samples were obtained within 90 min from the episode of ischemic chest pain accompanied by electrocardiographic changes described above. In the case of AMI, blood samples were obtained within 3 h from symptom onset. All samples were obtained via venipuncture before patients received antiplatelet or anticoagulant agents. Blood was collected in two tubes: one containing EDTA (ethylenediaminetetraacetic acid) was used for platelet counts; the other, containing 3.8% Na citrate, was used for the aggregability study (one volume of citrate to nine volumes of blood). Citrated samples were centrifuged to obtain platelet-rich plasma (PRP, 150 g for 10 min) and platelet-poor plasma (PPP, 300 g for 10 min).

2.3 Platelet aggregometer
Platelet aggregability was assessed using an aggregometer (PA-100, Kowa, Tokyo, Japan) recently developed by Ozaki et al. [15, 16]. This aggregometer can detect small aggregates consisting of only two or three platelets and simultaneously assess platelet aggregability using two different methods. The first method uses a conventional technique based on changes in the LT of a platelet suspension, which is used widely in laboratory and clinical studies [9]. In this study, the magnitude of platelet aggregation assessed by this method was expressed as%LT (% increase in the LT of PRP relative to the LT of PPP). The second method uses a particle-counting technique based upon LS [15, 16]. This method is based on the fact that the intensity of scattered light emitted from a particle increases in proportion to the square of its diameter. Briefly, 300 µl of PRP were maintained at 37°C in a cylindrical glass cuvette and stirred with a magnetic bar at 1000 rpm. A diode laser light beam (width, 40 µm; wavelength, 675 nm) was passed through a limited area of the sample, and the intensity of the light scattered by particles was recorded for 10 min by a four-channel photodiode array that minimized multiple LS signals. Each of the four photodiodes detects the light scattered from particles in its corresponding observation volume (one photodiode for each observation volume). The flow direction of stirred particles was diagonal to the line of the four-channel photodiode array, not allowing the same particle to pass two or more photodiodes successively. The light signals obtained were digitized with an A/D (analog/digital) converter and processed by a computer (PC-9821 Xa13, NEC, Tokyo, Japan). The data were recorded on a two-dimensional plot, one parameter being time (s) and the other (Xt) being total light intensity expressed as arbitrary units (AU). The parameter Xt is calculated as:


Formula

where K and Pk are the intensity of scattered light (volts, corresponding to particle size) and the frequency of each light signal (counts per 10 s, corresponding to the number of aggregates), respectively. Data obtained were summarized according to the size of the aggregates (small vs. large). In this study, we defined small aggregates as consisting of ≤100 platelets (K values from 0.2 to 2.0 volts) and large ones as consisting of ≤100 platelets (K values above 2.0 volts) [15, 16].

Platelet aggregation was assessed in the absence of agonists (i.e., spontaneous aggregation) as well as in the presence of epinephrine (Sigma Chemical, St. Louis, MO) and/or adenosine 5'-diphosphate (ADP, Sigma Chemical). The concentrations of each agonist used in this study ranged from 10–11 to 10–5 mol/l for epinephrine and 10–10 to 10–5 mol/l for ADP. Preliminary experiments performed in our laboratory showed that the dose–response curve of each agonist reached a plateau within these ranges of concentrations.

2.4 Statistical analyses
All measurements were performed in duplicate. Results are expressed as the mean±SEM. Statistical significance was evaluated using an ANOVA followed by Scheffe's procedure with Super ANOVA software (Abacus Concepts, Berkeley, CA) on a Macintosh computer. Concentration–response curves and the EC50 values (the concentrations required to produce 50% of the maximal aggregation) were estimated using Delta Graph software (DeltaPoint, Monterey, CA). A value of P<0.05 was considered statistically significant.


   3 Results
Top
 Abstract
 1 Introduction
 2 Methods
 3 Results
4 Discussion
 References
 
3.1 Platelet aggregation in the control group
Platelet aggregation in the control group was assessed simultaneously using LT and LS methods. In the absence of agonists, no detectable aggregation was observed by either method (Fig. 1A). Addition of relatively low concentrations of epinephrine (≤10–7 mol/l) also failed to produce aggregation detectable by LT, while as little as 10–8 mol/l of epinephrine demonstrated a significant increase in small aggregate formation (consisting of ≤100 platelets) by LS (Fig. 1B). Using the LT method, higher concentrations of epinephrine (>10–7 mol/l) caused significant increases in aggregate formation (Fig. 1C and 4A). This increase in aggregate formation occurred in two phases (Fig. 1C). The first phase consisted of a slight change (typically up to 15%) in LT that persisted for a few minutes. This was then followed by a second phase characterized by larger changes in LT. Simultaneous assessment using the LS method revealed that the first phase of aggregation represented formation of small aggregates, while the second phase represented formation of larger aggregates. Importantly, the number of small aggregates decreased concomitantly with an increase in the number of large aggregates, suggesting that small aggregates fused to form large aggregates.


Figure 1
View larger version (12K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Fig. 1 Representative aggregation patterns of platelets in healthy volunteers. Platelets in platelet-rich plasma (PRP) obtained from healthy volunteers were stimulated by various concentrations of epinephrine (Epi). Changes in light transmission (LT) were monitored using the conventional method. Light scattering (LS) was simultaneously measured in the same sample using a newly developed method based on particle counting. A: without epinephrine; B: 1x10–8 mol/l epinephrine; and C: 3x10–6 mol/l epinephrine. AU=arbitrary units. In all LS panels, small dots (thin lines) represent small aggregates and large dots (thick lines) represent large aggregates.

 
3.2 Platelet aggregation in patients with acute coronary syndromes
Platelet aggregation in patients with an acute coronary syndrome was also assessed using the LT and LS methods. As in the case of controls, no statistically significant spontaneous aggregation was detected by the LT method in either UAP or AMI patients. However, using the LS method, spontaneous aggregation of platelets was documented clearly (Fig. 2AFig. 3A). These aggregates typically consisted of ≤100 platelets, and no larger aggregates appeared during the 10-min measurement period. The total respective LS counts during the 10-min period were 13- and 20-times greater in the UAP (5.2±0.2x104 AU, P<0.0001) and the AMI (8.6±1.1x104 AU, P<0.0001) groups than in controls (0.4±0.1x104 AU). The total LS count in the AMI group was also greater than that in the UAP group (P<0.01). The platelet counts were similar in the three groups (for whole blood, control=22.6±0.5x104/µl, UAP=23.2±0.8x104/µl, AMI=21.8±0.7x104/µl, P=NS; for PRP, control=28.7±0.9x104/µl, UAP=29.5±1.2x104/µl, AMI=26.9±1.5x104/µl, P=NS), indicating that these differences in platelet aggregability were not due to the number of platelets.


Figure 2
View larger version (12K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Fig. 2 Representative aggregation patterns of platelets in patients with unstable angina pectoris. Platelets in platelet-rich plasma (PRP) obtained from patients with unstable angina pectoris were stimulated by various concentrations of epinephrine (Epi). Changes in light transmission (LT) were monitored using the conventional method. Light scattering (LS) was measured simultaneously in the same sample using a newly developed method based on particle counting. A: without epinephrine; B: 1x10–8 mol/l epinephrine; and C: 3x10–6 mol/l epinephrine. AU=arbitrary units. In all LS panels, small dots (thin lines) represent small aggregates and large dots (thick lines) represent large aggregates.

 

Figure 3
View larger version (12K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Fig. 3 Representative aggregation patterns of platelets in patients with acute myocardial infarction (AMI). Platelets in platelet-rich plasma (PRP) obtained from patients with acute myocardial infarction were stimulated by various concentrations of epinephrine (Epi). Changes in light transmission (LT) were monitored using the conventional method. Light scattering (LS) was measured simultaneously in the same sample using a newly developed method based on particle counting. A: without epinephrine; B: 1x10–8 mol/l epinephrine; and C: 3x10–6 mol/l epinephrine). AU=arbitrary units. In all LS panels, small dots (thin lines) represent small aggregates and large dots (thick lines) represent large aggregates.

 
Platelet aggregation in acute coronary syndromes was also assessed during stimulation with epinephrine. With low doses of epinephrine (<10–7 mol/l), the conventional LT method detected a slight increase in LT in both the UAP and the AMI group (Fig. 2BFig. 3BFig. 4A). However, the change in the LT was not statistically significant. Simultaneous evaluation using the LS method revealed that this slight increase in aggregate formation observed by the LT method represented a significant increase in the number of small aggregates (Fig. 2BFig. 3B). Notably, the concentration of epinephrine required to induce a significant increase in platelet aggregation was up to 10 000 times lower using LS (10–11 mol/l for small aggregates; 10–8 mol/l for large aggregates) than by the LT method (10–7 mol/l).


Figure 4
View larger version (22K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Fig. 4 Concentration–response curves for platelet aggregation. Platelets in platelet-rich plasma (PRP) were stimulated by various concentrations of epinephrine (panels A, B, and C) or adenosine 5'-diphosphate (ADP) (panels D, E, and F). Changes in light transmission (LT) were monitored by the conventional platelet aggregometry method (panels A and D). Light scattering (LS) intensities were measured simultaneously to detect small aggregates (panels B and E) as well as large aggregates (panels C and F). Open circles: controls; squares: patients with unstable angina pectoris; and closed circles: patients with acute myocardial infarction.

 
With higher concentrations of epinephrine (>10–7 mol/l), the LT method documented a statistically significant increase in platelet aggregation in acute coronary syndromes (P<0.0001, Fig. 2CFig. 3CFig. 4A). Simultaneous evaluation using the LS method revealed that these doses of agonist produced greater numbers of small and large aggregates at a faster rate than did lower doses of agonist (<10–7 mol/l) in both the UAP and the AMI group. Interestingly, the increase in small as well as large aggregate formation was more prolonged in the AMI group than the UAP group (Fig. 2CFig. 3C, lower panels).

When assessed by LT, the EC50 of epinephrine was 2- and 3-fold lower in the UAP (2.8±0.1x10–7 mol/l, P<0.01) and AMI (1.8±0.3x10–7 mol/l, P<0.01) groups compared with the control group (6.2±0.1x10–7 mol/l). Such differences in EC50 were more apparent when assessed by the LS method. The EC50 of epinephrine for small aggregates was nearly 50 times lower in the UAP group (8.6±0.3x10–10 mol/l, P<0.0001) and the AMI group (7.8±0.2x10–10 mol/l, P<0.0001) than the control group (38.0±1.7x10–9 mol/l). In contrast, the difference in EC50 for large aggregate formation was not as evident as in the case of small aggregate formation. The EC50 for large aggregates in the AMI group (1.5±0.2x10–7 mol/l) was relatively higher, half that for controls (3.1±0.3x10–7 mol/l, P<0.01). No statistically significant difference in EC50 was seen between the UAP group (2.1±0.2x10–7 mol/l) and controls (Fig. 4A, B and C).

Platelet hypersensitivity in patients with acute coronary syndromes was also assessed using ADP. The platelet response curve to ADP was similar to that observed for epinephrine, except that the formation of large aggregates occurred earlier for ADP (Fig. 4D, E and F). Using the LT method, the EC50 of ADP was 2.5- and 1.5-fold lower in the AMI group (1.1±0.1x10–6 mol/l, P<0.001) and the UAP group (1.8±0.2x10–6 mol/l, P<0.05) compared with controls (2.8±0.4x10–6 mol/l). Using the LS method, the EC50 of ADP for small aggregate formation was 30- and 10-fold lower in the AMI group (7.2±0.3x10–9 mol/l, P<0.0001) and the UAP group (2.1±0.4x10–8, P<0.0001) compared with controls (2.2±0.7x10–7 mol/l). For large aggregate formation, however, the EC50 for ADP was only five or two times lower in the AMI (5.8±0.3x10–7 mol/l, P<0.001) and the UAP group (1.2±0.2x10–6 mol/l, P<0.001) compared with controls (2.8±0.3x10–6 mol/l). EC50 values for small and large aggregate formation in AMI patients were significantly lower than those in UAP patients (P<0.05). This difference was not detected by the LT method.


   4 Discussion
Top
 Abstract
 1 Introduction
 2 Methods
 3 Results
 4 Discussion
References
 
Conventional aggregometers measuring the change in the LT of a platelet suspension have limited ability to detect platelet aggregates, especially those consisting of ≤100 platelets [12, 13]. In the present study, physiologic concentrations of agonists (10–11 to 10–8 mol/l for epinephrine; 10–10 to 10–7 mol/l for ADP) [20, 21]failed to induce statistically significant increases in LT in either controls or patients with acute coronary syndromes. In contrast to the LT method, the LS method is sensitive enough to identify aggregates consisting of only two or three platelets, which allowed us to precisely assess aggregation processes in the setting of acute coronary syndromes. For example, after stimulation with physiologic concentrations of epinephrine, a significant increase in the number of small as well as large aggregates was observed in AMI patients. Although the LT method also documented a significant increase in platelet aggregation, the concentrations required were up to 1000 times in excess of the physiologic ranges [10, 21, 22]. In this regard, the current investigation using the LS method appears to be the first to document platelet hypersensitivity to physiologic levels of agonists in the setting of acute coronary syndromes.

Agonist-induced platelet aggregation consisted of two phases. In patients with acute coronary syndromes, stimulation with physiologic levels of epinephrine induced a marked increase in the number of small aggregates. The same dose of epinephrine, however, could induce only a modest increase in the number of large aggregates. When stimulated with higher, supraphysiologic concentrations of epinephrine, more rapid and greater increases in the number of small aggregates were observed in both controls and acute coronary patients. After a few minutes, the number of large aggregates increased, with a concomitant decrease in the number of small aggregates (Fig. 1CFig. 2CFig. 3C). These two phases of aggregate formation represented the ‘primary’ and the ‘secondary’ aggregation processes [15, 23]. It is important to note that the concentration of agonist required to stimulate each aggregation process was different. Physiologic concentrations of agonists enhanced mainly primary but not secondary aggregation. This suggests that platelet hypersensitivity during acute coronary syndromes may be confined to the level of primary aggregation.

Circulating platelets are not believed to aggregate spontaneously in vivo [24]. Indeed, in the current study, no spontaneous formation of platelet aggregates was observed in normal subjects by either LT or LS. In patients with acute coronary syndromes, however, spontaneous platelet aggregation clearly was observed using the LS method. These spontaneous aggregates consisted of ≤100 platelets, and no larger aggregates were observed. This suggests that platelet hyperaggregability during acute coronary syndromes may also exist for only the primary aggregation process.

Finally, the current study showed a difference in platelet aggregability between UAP and AMI. First, spontaneous aggregate formation was increased significantly in the AMI group over that seen in the UAP group. Second, platelet aggregate formation in response to agonist stimulation was more prolonged in the AMI than the UAP group (Fig. 2CFig. 3C). Third, platelet response to ADP (assessed by EC50) was greater in the AMI group than the UAP group. These findings suggested that platelet hyperaggregability as well as platelet hypersensitivity was greater in AMI patients than in UAP patients. The mechanisms underlying the difference in aggregability between these two pathologic conditions require further clarification.

In summary, light-scattering (LS) aggregometry allowed us to distinguish primary from secondary aggregation processes in patients with acute coronary syndromes. The results described here suggest that platelet hyperaggregability and hypersensitivity during these acute coronary events may exist at the primary but not the secondary aggregation process. This new technique may provide important information concerning the pathophysiology of acute coronary disease, as well as a rationale for planning antiplatelet therapies to prevent and treat this syndrome.

Time for primary review 28 days


   Acknowledgements
 
We are grateful to Haruaki Nakaya, M.D. for his comments.


   References
Top
 Abstract
 1 Introduction
 2 Methods
 3 Results
 4 Discussion
 References
 

  1. Frink R.J., Rooney P.A.J., Trowbridge J.O., Rose J.P. Coronary thrombosis and platelet/fibrin microemboli in death associated with acute myocardial infarction. Br Heart J (1988) 59:196–200.[Abstract/Free Full Text]
  2. Weinberger I., Fuchs J., Davidson E., Rotenberg Z. Circulating aggregated platelets, number of platelets per aggregate, and platelet size during acute myocardial infarction. Am J Cardiol (1992) 70:981–983.[CrossRef][Web of Science][Medline]
  3. O'Brien J.R., Heywood J.B., Heady J.A. The quantitation of platelet aggregation induced by four compounds: A study in relation to myocardial infarction. Thromb Diath Haemorrh (1966) 16:752–767.[Web of Science][Medline]
  4. Willerson J.T., Campbell W.B., Winniford M.D., et al. Conversion from chronic to acute coronary artery disease: Speculation regarding mechanisms. Am J Cardiol (1984) 54:1349–1354.[CrossRef][Web of Science][Medline]
  5. Hirsh J. Hyperreactive platelets and complication of coronary artery disease. N Engl J Med (1987) 316:1543–1544.[Web of Science][Medline]
  6. Wu K.K., Hoak J.C. A new method for the quantitative detection of platelet aggregates in patients with arterial insufficiency. Lancet (1974) 2:924–926.[Web of Science][Medline]
  7. Fuchs J., Weinberger I., Rotenberg Z., Joshua H., Almozlino A., Agmon J. Circulating aggregated platelets in coronary artery disease. Am J Cardiol (1987) 60:534–537.[CrossRef][Web of Science][Medline]
  8. Falk E. Unstable angina with fatal outcome: dynamic coronary thrombosis leading to infarction and/or sudden death: Autopsy evidence of recurrent mural thrombosis with peripheral embolization culminating in total vascular occlusion. Circulation (1985) 71:699–708.[Abstract/Free Full Text]
  9. Born G.V.R. Aggregation of blood platelets by adenosine diphosphate and its reversal. Nature (1962) 194:927–929.[Medline]
  10. Mueller H.S., Rao P.S., Greenberg M.A., et al. Systemic and transcardiac platelet activity in acute myocardial infarction in man: Resistance to prostacyclin. Circulation (1985) 72:1336–1345.[Abstract/Free Full Text]
  11. Trip M.D., Cats V.M., van Capelle F.J.L., Vreeken J. Platelet hyperreactivity and prognosis in survivors of myocardial infarction. N Engl J Med (1990) 322:1549–1554.[Abstract]
  12. Kitek A., Breddin K. Optical density variations and microscopic observations in the evaluation of platelet shape change and microaggregate formation. Thromb Haemost (1980) 44:154–158.[Web of Science][Medline]
  13. Gear A.R., Lambrecht J.K. Reduction in single platelets during primary and secondary aggregation. Thromb Haemost (1981) 45:298.[Web of Science][Medline]
  14. Thompson N.T., Scrutton M.C., Wallis R.B. Particle volume changes associated with light transmittance changes in the platelet aggregometer: dependence upon aggregating agent and effectiveness of stimulus. Thromb Res (1986) 41:615–626.[CrossRef][Web of Science][Medline]
  15. Ozaki Y., Satoh K., Yatomi Y., et al. Detection of platelet aggregates with a particle counting method using light scattering. Anal Biochem (1994) 218:284–294.[CrossRef][Web of Science][Medline]
  16. Yamamoto T., Egawa Y., Shirasawa Y., et al. A laser light-scattering in situ system for counting aggregates in blood platelet aggregation. Meas Sci Technol (1995) 6:174–180.[CrossRef][Web of Science]
  17. World Medical Association, Inc. World Medical Association Declaration of Helsinki: recommendations guiding physicians in biomedical research involving human subjects. Cardiovasc Res 1997;35:2–3.
  18. Braunwald E. Unstable angina: A classification. Circulation (1989) 80:410–414.[Free Full Text]
  19. TIMI Study Group. The thrombolysis in myocardial infarction (TIMI) trial: phase 1 findings. N Engl J Med 1985;312:932-936.
  20. Siess W., Lorenz R., Roth P., Weber P.C. Plasma catecholamines, platelet aggregation and associated thromboxane formation after physical exercise, smoking or norepinephrine infusion. Circulation (1982) 66:44–48.[Abstract/Free Full Text]
  21. Siess W. Molecular mechanisms of platelet activation. Physiol Rev (1989) 69:58–178.[Free Full Text]
  22. Elwood P.C., Renaud S., Sharp D.S., Beswick A.D., O'Brien J.R., Yarnell J.W.G. Ischemic heart disease and platelet aggregation: the Caerphilly collaborative heart disease study. Circulation (1991) 83:38–44.[Abstract/Free Full Text]
  23. Satoh K., Ozaki Y., Qi R., et al. Factors that affect the size of platelet aggregates in epinephrine-induced activation: a study using the particle counting method based upon light scattering. Thromb Res (1996) 81:515–523.[CrossRef][Web of Science][Medline]
  24. Kumpuris A.G., Luchi R.J., Waddell C.C., Miller P.R. Production of circulating platelet aggregates by exercise in coronary artery patients. Circulation (1980) 61:62–65.[Free Full Text]

Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 Cardiovasc ResHome page
A. R Prieto, H. Ma, R. Huang, G. Khan, K. A Schwartz, E. E Hage-Korban, A. H Schmaier, J. M Davis, A. A.K Hasan, and G. S Abela
Thrombostatin, a bradykinin metabolite, reduces platelet activation in a model of arterial wall injury
Cardiovasc Res, March 1, 2002; 53(4): 984 - 992.
[Abstract] [Full Text] [PDF]

Home page
 Arterioscler. Thromb. Vasc. Bio.Home page
K. Eto, T. Isshiki, H. Yamamoto, S. Takeshita, M. Ochiai, N. Yokoyama, R. Yoshimoto, Y. Ikeda, and T. Sato
AJvW-2, an Anti-vWF Monoclonal Antibody, Inhibits Enhanced Platelet Aggregation Induced by High Shear Stress in Platelet-Rich Plasma From Patients With Acute Coronary Syndromes
Arterioscler Thromb Vasc Biol, April 1, 1999; 19(4): 877 - 882.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Eto, K.
Right arrow Articles by Isshiki, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Eto, K.
Right arrow Articles by Isshiki, T.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?