3. INTRODUCTION
Thrombosis
The formation or presence of a blood clot in a blood
vessel is called Thrombosis .
It is normal for the body to produce clotting factors like
platelets and fibrin when a blood vessel is injured, to
prevent an excessive loss of blood from the body.
If this effect is over productive it can obstruct the flow of
blood and form an embolus that moves around the blood
stream.
Thrombus
A thrombus is a blood clot that forms in a vessel and
remains there.
4. THROMBUS
Development of
Thrombus
Thrombi may develop
anywhere in the
cardiovascular system
Within the cardiac
chambers
On valve cusps
Or in vessels i.e. arteries
veins or capillaries.
Arterial or cardiac
thrombi typically arise
at the sites of
endothelial injury(e.g.
atherosclerotic plaque)
or turbulence (e.g.
bifurcation of vessels)
Venous thrombi occurs
at the site of stasis.
5. THROMBUS
Size and Shape
They are of variable size
and shape
Characteristic
All thrombi are firmly
attached at the point of
origin.
Growth of Thrombi
Arterial thrombi
Grow in retrograde
direction
Venous thrombi
Extends in the direction of
blood flow
6. THROMBUS
Complication
Embolus
Thrombi are focally
attached to the
underlying vascular
surface and tend to
propagate toward the
heart.
The propagating portion
of thrombus tends to be
poorly attached and
therefore prone to
fragmentation and
migration through the
blood as embolus.
8. LINES OF ZAHN
Grossly and microscopically
apparent laminations of
thrombi called Lines Of
Zahn
These represent pale
platelet and fibrin layers
alternating with darker red
cell rich layers.
Signify that thrombus is
formed in flowing blood
Presence can distinguish
ante mortem thrombosis
from the bland
nonlaminated clots.
9. MURAL THROMBI
Occurs in heart chambers or in the aortic lumen
Precursors of Cardiac Mural Thrombi
Abnormal myocardial contraction
Arrhythmias
Dilated cardiomyopathy
Myocardial infarction
Endomyocardial injury
Myocarditis
Catheter trauma
Precursors of Aortic Thrombosis
Atherosclerotic plaque
Aneurismal dilation
11. ARTERIAL THROMBI
Also known as cardiac
thrombi
Frequently occlusive
Superimposed on an
atherosclerotic plaque or
other forms of vascular injury(
vasculitis, trauma).
Usually begins at sites of
turbulence or endothelial
injury
Composed of meshwork of
platelets, fibrin, red cells and
degenerating leukocytes.
Common sites of frequency:
Coronary>cerebral>femoral
arteries
12. VENOUS THROMBI
Also known as phlebothrombosis
Usually occurs at sites of stasis
Extends in direction of blood flow
almost invariably occlusive
These are formed in the sluggish
venous circulation ,they tend to
contain more enmeshed RBCs
leading to the moniker red or
stasis thrombi. Venous thrombi
may not be well attached and are
prone to detachment, creating
emboli.
The veins of lower extremities
are most commonly
affected.(90% of venous
thrombosis)
13. POSTMORTEM CLOTS
They have two portions
Dependent portion
gelatinous with dark red
dependent portion where
red cells are settled,
Upper portion
yellow chicken fat upper
portion
Usually not attached to
underlying wall
14. VEGETATION
Thrombi on heart valves are
called vegetation
Causes
Infective endocarditis
Can be either due to blood
borne bacteria or fungi
adhering to previously
damaged valves or can
directly cause valve damage.
Sterile vegetation also can
develop on non infected
valves in hyper coagulable
states –non bacterial
thrombotic endocarditis
Libman sacks endocarditis
sterile verrucuous
endocarditis occurring in
systemic lupus
erythematosus.
15. THROMBOSIS IN VESSELS
Features Arterial thrombosis Venous thrombosis
Sites Turbulence or
endothelial injury
Stasis
Occlusive Frequently Almost always
Appearance (+) lines of Zahn More enmeshed
RBC’s and platelets
Common sites of
involvement
Coronary>cerebral>fe
moral artery
Lower extremity veins
90%
16. PATHOGENESIS OF THROMBUS
The primary
abnormalities that lead
to intravascular
thrombosis are
Endothelial injury
Stasis or turbulent
blood flow
Hypercoagulability of
the blood
These three causes are
referred as Virchow's
triad.
17. ENDOTHELIAL INJURY
Most important factor in arterial thrombosis
Includes thrombus formation in heart and arterial
circulation , where the high rates of blood flow
impede clot formation.
Severe endothelial injury may triggers thrombosis
by exposing Von Willebrand factor and tissue factor.
Inflammation and other noxious stimuli also
promote thrombosis by shifting the pattern of gene
expression in endothelium to one that is
prothrombic
This change is sometimes refers to as endothelial
activation or dysfunction.
19. ENDOTHELIAL INJURY
Examples include
Myocardial infarction
Hemodynamic injury such as hypertension turbulent
flow over heart valves
Endotoxins, inflammation
Hyper cholestrolemia etc
20. ABNORMAL BLOOD FLOW
Turbulence or chaotic blood flow contributes to arterial
and cardiac thrombosis by causing endothelial injury or
dysfunction.
Stasis is the major factor in development of venous
thrombi.
Normal blood flow is laminar
Platelets are found mainly in the center of vessel lumen
Separated from the endothelium by a slower moving layer of
plasma.
By contrast, in stasis and turbulence;
Promote endothelial cells activation
Disrupt laminar flow
Slows washout of activated clotting factors
Impedes the inflow of clotting factors inhibitors.
21. ABNORMAL BLOOD FLOW
Clinical manifestations
include
aneurysm- aortic and
arterial dilation
Acute myocardial infarction
Rheumatic mitral valve
stenosis - results in left
arterial dilation
Hyper viscosity syndromes
such as polycythemia Vera
– increase resistance to
flow and cause small
vessels stasis
Sickle cell anemia – causes
vascular occlusions
22. HYPER COAGULABILITY
Hypercoagulability refers to an abnormally high
tendency of the blood to clot, and is typically
caused by alterations in coagulation factors.
Contributes infrequently to arterial or intracardiac
thrombosis but an important underlying risk factor
for venous thrombosis
alteration of the coagulation pathways are divided
into two categories
Primary genetic disorders
Secondary acquired disorders.
25. FATE OF THROMBUS
If a patient survives an initial thrombotic event, during
the ensuring days to weeks the thrombus evolves
through some combination of the following four
processes
Propagation
Accumulate more platelets and fibrin thus result to vessel
obstruction
Embolization
Dislodgement and travel to other location
Dissolution
Result of fibrinolysis
Organization and recanalization
By ingrowth of endothelial cells ,smooth muscles and fibroblasts ;
reestablishment of continuity of original lumen.
Older thrombi have extensive fibrin polymerization and tend to
become organized.
26. TREATMENT OF THROMBOSIS
Thrombosis is most commonly treated with
anticoagulants.
These drugs don’t breakup existing blood clots from
getting bigger and reduce your risk of developing more
clots
Blood thinners may be taken orally or given by IV or
injected subcutaneously.
Some examples of these drugs are;
Warfarine and vitamin K antagonists can be taken orally
Heparin by IV
Streptokinase can be administered IV in emergency condition
like heart attack.
Ultrasound-accelerated thrombolysis can also be used.