ACUTE CORONARY
SYNDROMES

Edited by Mariano E. Brizzio

Acute Coronary Syndromes
Edited by Mariano E. Brizzio Published by InTech
Janeza Trdine 9, 51000 Rijeka, Croatia

Copyright © 2012 InTech
All chapters are Open Access distributed under the Creative Commons Attribution 3.0
license, which allows users to download, copy and build upon published articles even for
commercial purposes, as long as the author and publisher are properly credited, which
ensures maximum dissemination and a wider impact of our publications. After this work
has been published by InTech, authors have the right to republish it, in whole or part, in
any publication of which they are the author, and to make other personal use of the
work. Any republication, referencing or personal use of the work must explicitly identify
the original source. Contents

Preface IX
Chapter 1 Antiplatelet Therapy in
Cardiovascular Disease –
Past, Present and Future 1
Mariano E. Brizzio
Chapter 2 Thrombotic Inception at Nano-Scale 7
Suryyani Deb and Anjan Kumar Dasgupta
Chapter 3 Physiopathology of the
Acute Coronary Syndromes 27
Iwao Emura
Chapter 4 Evolution of Biochemical
Diagnosis of Acute Coronary Syndrome – Impact
Factor of High Sensitivity Cardiac Troponin Assays 45
Amparo Galán, Josep Lupón and Antoni Bayés-Genis
Chapter 5 Pathogenesis of Acute Coronary Syndrome,
from Plaque Formation to Plaque Rupture 65
Hamdan Righab, Caussin Christophe,
Kadri Zena and Badaoui Georges
Chapter 6 Plaque, Platelets, and Plug –
The Pathogenesis of Acute Coronary Syndrome 77
Anggoro B. Hartopo, Budi Y. Setianto,
Hariadi Hariawan, Lucia K. Dinarti, Nahar Taufiq,
Erika Maharani, Irsad A. Arso, Hasanah Mumpuni,
Putrika P.R. Gharini, Dyah W. Anggrahini and
Bambang Irawan

Preface

This book has been written with the intention of providing an up-to-the minute review
of acute coronary syndromes. Atherosclerotic coronary disease is still a leading cause
of death within developed countries and not surprisingly, is significantly rising in
others. Over the past decade the treatment of these syndromes has changed
dramatically. The introduction of novel therapies has impacted the outcomes and
surviving rates in such a way that the medical community need to be up to date
almost on a “daily bases”.
It is hoped that this book will provide a timely update on acute coronary syndromes
and prove to be an invaluable resource for practitioners seeking new and innovative
ways to deliver the best possible care to their patients.

Mariano E. Brizzio, MD
Editor in Chief
The Valley Heart and Vascular Institute, Ridgewood, New Jersey
USA


1
Antiplatelet Therapy in Cardiovascular

sometimes increase the risk of “undesirable” bleeding complications (6).
2. The traditional anti-platelet agents
Many anti-platelet agents have been tested and used as an effective treatment in arterial
thrombosis. Acetyl salicylic acid, commonly known as aspirin was the first anti-platelet

Acute Coronary Syndromes

2
agent used and proven to be effective to reduce the incidence of myocardial infarction and
stroke in many high risk vascular patients (2).The recurrence of vascular events in
patients treated with aspirin alone ranges between 10 – 20% within five years of the initial
event (2-7).
Aspirin is effective by blocking the synthesis of TXa2, a powerful platelet activator.
In the last decade, the thienopyridines such as clopidogrel have been used to improve
outcomes in the treatment of ACS. This anti-platelet agent irreversibly blocks the P2Y12
receptor, precluding the platelet activation by ADP (2). Its anti-platelet mechanism of action
clearly differs from aspirin. In the majority of cardiovascular patients the combination of
clopidogrel and aspirin has additive beneficial effects when compared with clopidogrel or
aspirin alone (8). Clopidogrel also has some limitations, which have prompted the
development of newer anti-platelet agents which interact at different sites of the coagulation
cascade.
The following figure reflects the site of action of the common antiplatelet agents (figure 1)
3. The thromboxane A2 antagonist
Dipyridamole (Persantine) acts as a thromboxane synthase inhibitor, therefore lowering the
levels of TXA2 and thus stops the effects of TXA2 as a platelet activator (9).
Also can causes systemic vasodilation when given at high doses over a short period of time.
The latter, due to the inhibition of the cellular reuptake of adenosine into platelets, red blood
cells and endothelial cells leading to increased extracellular concentrations of adenosine (9).
It also inhibits the enzyme adenosine deaminase, which normally breaks down adenosine
into inosine. This inhibition leads to further increased levels of extracellular adenosine,

Bivalirudi
n

Modified release dipyridamole is used in conjunction with aspirin (under the trade names
Aggrenox in the USA or Asasantin Retard in the UK) in the secondary prevention of stroke
and transient ischemic attack. This practice has been confirmed by the ESPRIT trial (9). A
triple therapy of aspirin, clopidogrel and dipyridamole has been investigated, but this
combination led to an increase in adverse bleeding events (10).
Via the mechanisms mentioned above, when given as 3 to 5 min infusion it rapidly increases
the local concentration of adenosine in the coronary circulation which causes vasodilation.
Vasodilation occurs in healthy arteries, whereas stenosed arteries remain narrowed. This
creates a "steal" phenomenon where the coronary blood supply will increase to the dilated
healthy vessels compared to the stenosed arteries which can then be detected by clinical
symptoms of chest pain, electrocardiogram and echocardiography when it causes ischemia.
Flow heterogeneity (a necessary precursor to ischemia) can be detected with gamma cameras
and SPECT using nuclear imaging agents such as Thallium-201 and Tc99m-Sestamibi (9).
Terutroban is a selective antagonist of the thromboxane receptor. It blocks thromboxane
induced platelet aggregation and vasoconstriction (11). As of 2010, it is being tested for the
secondary prevention of acute thrombotic complications in the Phase III clinical trial.
However, the recent publication of the finalized trial PERFORMS shown no clinical
advantage in comparison with patients with aspirin monotherapy in preventing strokes (12).
At the time of this publication its use in clinical practice is not approved in the USA.
4. Other P2Y 12 antagonist
Ticlopidine an anti-platelet drug in the thienopyridine family inhibits platelet aggregation
by altering the function of platelet membranes by irreversibly blocking ADP receptors. This

Acute Coronary Syndromes

4
prevents the conformational change of glycoprotein IIb/IIIa which allows platelet binding

IIb/IIIa receptor blockade are present for up to 15 days after the infusion is terminated (18).
Tirobiban (Aggrastat) is a synthetic, non-peptide inhibitor acting at glycoprotein (GP) IIb/IIIa
receptors. It has a rapid onset and short duration of action after proper intravenous
administration. Platelet activity returns to normal 4 to 8 hours after the drug is withdrawn (19).
Eptifibatide (Integrilin) is the newer anti-platelet drug which inhibits the glycoprotein IIb/IIIa
inhibitor. It belongs to the class of the so-called arginin-glycin-aspartat-mimetics and
reversibly binds to platelets. Eptifibatide has a short half-life, 3 to 5 hours after the
discontinuation platelet activity recovers to normal levels (20).The drug is the third inhibitor of
GPIIb/IIIa that has found broad acceptance within interventional cardiologists nowadays.
6. Proteasa-activated receptors antagonist
Vorapaxar (formerly SCH 530348) is a thrombin receptor (PAR-1) antagonist based on the
natural product himbacine. It is an experimental pharmaceutical treatment for acute coronary
syndrome as a very powerful platelet inhibitor (21).In January 2011, the clinical trial was

Antiplatelet Therapy in Cardiovascular Disease – Past, Present and Future

5
halted for patients with stroke and mild heart conditions due to safety reasons. It is unknown
if it will continue.
7. Direct thrombin inhibitors
Bivalirudin (Angiomax) is a specific and reversible intravenous direct thrombin inhibitor.
Clinical studies demonstrated consistent positive outcomes in patients with stable angina,
unstable angina (UA), non-ST segment elevation myocardial infarction (NSTEMI), and ST-
segment elevation myocardial infarction (STEMI) undergoing PCI in 7 major randomized
trials (22). Coagulation times and platelet activity return to baseline approximately 1-6 hour
following cessation of bivalirudin administration (23).
8. Conclusions
Antiplatelet therapy plays a crucial role in the treatment of coronary patients. The continuous
introduction of new agents is geared to improve results in patient ongoing percutaneous
coronary interventions. However, the side effects of theses should be monitored closely. In

Acute Coronary Syndromes

6
dipyridamole) in the secondary prevention of stroke: safety, tolerability and
feasibility". PLoS One. 2008 Aug 6;3(8):e2852
[11] Sorbera LA, Serradel N, Bolos J, Bayes M. Terutroban sodium.Drugs of the Future
2006;31 (10):867-873.
[12] Hennerici, M. G.; Bots, M. L.; Ford, I.; Laurent, S.; Touboul, P. J. "Rationale, design and
population baseline characteristics of the PERFORM Vascular Project: an ancillary
study of the Prevention of cerebrovascular and cardiovascular Events of ischemic origin
with teRutroban in patients with a history oF ischemic strOke or tRansient ischeMic
attack (PERFORM) trial". Cardiovascular Drugs and Therapy 2010; 24 (2): 175.
[13] Berger PB. Results of the Ticlid or Plavix Post-Stents (TOPPS) trial: do they justify the
switch from ticlopidine to clopidogrel after coronary stent placement? Curr Control
Trials Cardiovasc Med. 2000; 1(2): 83–87.
[14] Bennet CL, Davidson CJ, Raisch DW, et al. Thrombotic Thombocytopenic purpura with
ticlopidine in the setting of coronary artery stents and stroke prevention. Arch
Intern Med. 1999;159:2524-2528.
[15] Wiviott S et al. Prasugrel versus clopidogrel in patient with acute coronary syndromes.
N Engl J Med 2008;357:2001-2015
[16] Raju NC, Eikelboom, Hirsh J. Platelet ADP-receptor antagonist for cardiovascular
disease:past, present and future. Nature Cini Pract 2008;5(12):766-779
[17] Wallentin, Lars; Becker, RC; Budaj, A; Cannon, CP; Emanuelsson, H; Held, C; Horrow,
J; Husted, S et al. Ticagrelor versus Clopidogrel in Patients with Acute Coronary
Syndromes". N Engl J Med 2009;361 (11): 1045–57.
[18] Tcheng, JE; Kandzari, DE; Grines, CL; Cox, DA; Effron, MB; Garcia, E; Griffin, JJ; Guagliumi,
G et al. "Benefits and risks of abciximab use in primary angioplasty for acute
myocardial infarction: the Controlled Abciximab and Device Investigation to Lower
Late Angioplasty Complications (CADILLAC) trial." Circulation 2003;108 (11): 1316–23
[19] Shanmugam G. Tirofiban and emergency coronary surgery. Eur J Cardiothorac Surg

do interfere with the thrombo-static equilibrium. While this shift on one hand is a matter
of concern, it may provide us a tool to handle or diagnose diseases in which such
equilibrium is shifted. One of the finest models to test this dual aspect of the nano-scale
objects is Acute Coronary Syndrome (ACS), a leading cause of death in the global
scenario. What is known today regarding the effect of nanoscale objects may really be a
tip of iceberg and with the advent of smarter nanoparticles one may think of more
versatile use of nanotechnology in the management of ACS.
2. Role of platelets in Acute Coronary Syndrome (ACS)
ACS is a complex and multi-factorial disease (Badran et al., 2009). ACS is an umbrella like
term which includes mainly three diseases i). ST elevated myocardial infarction (STEMI),
ii). Non ST elevated myocardial infarction (NON STEMI), and iii) unstable angina. The
patho-physiological event of ACS can be divided into four phases:
a. Atherosclerotic plaque formation.
b. Rupture of an unstable plaque.
c. The acute ischemic event.
d. Long term risk of recurrent coronary event.
2.1 Platelet basic physiology
Platelets play a pivotal in manifestation of ACS. Platelets are discoid in shape, with
approximate number density 150,000-300,000/µl, and dimension of the order of 2000-4000
nm. Derived from megakaryocyte (figure 1) (Thompson, 1986) they contain mitochondria,
peroxisomes, endoplasmic reticulum. They also contain granules and glycogen bodies.

Acute Coronary Syndromes

8
Granules occur as i) dense granules (δ), ii) alpha granules (α). Dense granules mainly
contains ATP, ADP, serotonin etc., whereas alpha granules contain fibronectin, fibrinogen,
platelet activation factor (PAF) etc. (Marcus et al, 1966; Flaumenhaft et al, 2005). Ca
++
, one of

exposed to sub-endothelial collagen and vWf (1) adhered on it (2). This is followed by
activation and shape changes (3). The next phase is granules release and secondary phase
aggregation (4) and lastly the stable platelet plaque forms(5).
The detailed mechanism of platelet function depends on the complex intracellular signalling
pathways. This leads to platelet activation by simulating a series of physiological events.
Briefly, after binding of agonists, the corresponding receptors trigger downstream signalling
cascades and initiates Ca
++
mobilisation from endoplasmic reticulum. Platelet granules
release (α and δ), platelet shape change and the thromboxane A2 (TXA2) production then
follows. The cumulative effects of these events initiate activation of fibrinogen receptor
(GPIIbIIIa) and triggering of primary phase aggregation. The released granules-content
(ADP, ATP etc.) along with TXA2 activate other resting platelets resulting the secondary
phase aggregation (Kroll & Schafer, 1989; Ashby, 1990) (figure 3). The important signalling
molecules that help the above process through a complex interplay among different G-
protein coupled receptors, integrin receptors, second messengers, kinases, phosphatise and
Ca
++
mobilisation etc (Dorsam & Kunapuli, 2004; Wu e al., 2006,2010; Roberts et al.,2004;
Karniguian et al., 1990; Farndale, 2006; Spalding et al., 1998; Patscheke , 1980; Clifford et al.,
1998; Hoffman et. al. 2009).

Acute Coronary Syndromes

10

Fig. 3. Schematic diagram of agonists induced platelet activation. Binding of agonists with
corresponding receptors, triggers downstream signalling cascade, and causes mobilisation
of intracellular Ca
++

where the former one is G
q
and the later one is Gi coupled. Gz coupled alpha 2a are adrenergic
receptors for epinephrine, where G
s
coupled PGI2R are the receptors of prostaglandin I
2
(PGI2)
or prostaglandin E1 (PGE1), these being inhibitory receptors. Protease-activated receptor 1
(PAR1), protease-activated receptor 4 (PAR4), are coupled with Gq and G
13
these being the
receptors of thrombin. Thromboxane A
2
(TxA
2
)

receptor TP is also coupled with G
q
and G
13.
Released TxA2 (b in figure 5) and ADP (a in figure5 ) further act on their corresponding
receptors. The second messengers and other signalling mediators include, (DAG)
diacylglycerol; (PLCβ) phospholipase C β; (PKC) protein kinase C; (PIP
2
)

R) inositol triphosphate receptor; (PP) protein
phosphorylation; (PLA
2
)

Phospholipase A
2
; (AA) arachidonic acid; AkT and Rap1B (which
are serine /threonine kinase), (PI3K) phosphatidylinositol 3-kinase; (AC) adenylyl cyclase;
(PKA) phosphokinase A; (cAMP) cyclic adenosine mono phosphate; (VASP) vasodialator
stimulated phosphor protein; (P160 ROCK) a Rho activated kinase, (MLCK) myosine light
chain kinase, (LIM-K) LIM kinase; (PGG2) prostaglandin G2; (PGH2) prostaglandin H2; (PL)
membrane phospholipids; (COX1) cyclooxygenase 1; (TS) thromboxane synthetase and
(PDEIII) phosphor di-esterase III. As platelets are the key player in ACS, any extra-
physiological environmental materials that can alter platelet signalling circuit is of great
challenge in combating the disease. This is the context where nanotechnology can come in
picture.
3. Nano-interface
Nanotechnology has the potential to interfere with basic biological mechanisms because of
their tunable electrical, magnetic and optical properties, and small size ( Chen et al., 2005;
Gobin et al., 2007; Fu et al., 2007). This tunability makes them potential tool in diagnostics
(e.g. bio-imaging) therapy and a smart combination of both of these properties (Smith et al.,
2008; Peng et al., 2000; Li et al., 2003; Murry et al., 2000).
Some of advancement of nanotechnology inspired application include improved imaging
contrast agents by SPIONS (super-paramagnetic iron oxide nanoparticles), targeted
delivery of drugs, molecular chaperons and agents to kill specific cancer cells (Yu et al.,
2011; Petkar et al., 2011; Patra et al., 2007). Another exclusive application involve magnetic
induction (radio frequency) heating or laser induced heating of designer particles, with
desirable material and shape attributes (Peterman et al., 2003; Plech et al., 2004). The
hyperthermic killing of tumor cells, is one of the most important examples (Rao et al.,

with blood cells. Conversely exposure to unwanted nanoparticles (e.g. gas phase
exhaust from car or industry ) inhaled by human, that can penetrate the alveolar space
and interfere with circulation may lead to cardiovascular diseases ( Yamawaki & Iwai,
2006; Mohmmad et al., 2011; Chen et al., 2008). In both cases such interaction deserves a
special attention.
In case of ACS patients, if nanoparticles activate platelets then they may induce life
threatening alarm. Till now there are a number of papers (Geys et al., 2008; Oberdörster et
al., 2007; Deb et al., 2007,2011; Wiwanitkit et al., 2009; Radomski et al., 2005; Shrivastava et
al., 2009; Koziara et al., 2005; Mayer et al., 2009; Li et al., 2009; Ramtoola et al., 2010;
McGuinnes et al., 2010; Nemmar et al., 2003; Gulati et al., 2010; Cejas et al., 2007; Wilson et
al., 2010; Rückerl et al., 2007) about the effect of nanoparticles on platelets (Table. 2.)
where most of the citations show that nanoparticles can induce platelet aggregation. What
makes a nanoparticle pro-aggregarory (Geys et al., 2008; Oberdörster et al., 2007; Deb et
al., 2007,2011; Wiwanitkit et al., 2009; Radomski et al., 2005; Mayer et al., 2009; McGuinnes
et al., 2010; Nemmar et al., 2003; Cejas et al., 2007; Wilson et al., 2010; Rückerl et al., 2007;
Miller et al., 2009), inert (Li et al., 2009; Ramtoola et al., 2010; Gulati et al., 2010) or even
anti-platelet in nature (Shrivastava et al., 2009; Koziara et al., 2005; Miller et al., 2009) is of
great importance in development of ACS based nano-drugs, risk assessment in ACS , and
also in evaluating resistance to ACS related drugs (Guha et al., 2009; Jogns et al., 2006;
Michelson et al., 2006).

Thrombotic Inception at Nano-Scale

15
TYPE OF NANOMATERIALS
EFFECT ON
PLATELETS
Carbon NP
Carbon nanoparticle (C
60

Amidine White Polystyrine Latex NP(+ve)
Aminated Polystyrine Latex NP (+ve)
Carboxylated Polystyrine Latex NP (-ve )
Unmodified Polystyrine Latex NP
PNIPAAM
PEG coated PNIPAAM
poly(D,L-lactide-co-glycolide) (PLGA)
Chitosan nanoparticles
Human and Bovine derived NP
Hydroxyapatite
E78 NPs
PEG coated E78 NPs
Activation
Activation
Activation
Activation
Inert
Inert
Inert
Inert
Inert
Anti-platelet effect
Anti-platelet effect
Anti-platelet effect
Anti-platelet effect
Aerosol
Ultra fine particles
Ambient Particulate Matter
Activation
Activation