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1. THROMBOSIS
The Primary influences that predisposes to
thrombosis (virchows triad).
Endothelial Injury
Stasis or turbulences of blood.
Blood hypercoagulability.
Endothelial injury.
This the most dominant influence.
By itself can lead to Thrombosis
Important in formation of Thrombus in heart
or arterial circulation.

2. In these two site high flow rate usually
hampers clotting by:
Preventing platelet adhesion
Dilution of coagulation factors.
Therefore endothelial injury contributes to;
Thrombus Formation in Heart Chambers.
Following Myocardial Infarction.
Arteries
Over Ulcerated plaque of atherosclerosis.
Or site of traumatic or Inflammatory Vascular
Injury.

3. Physical injury to endothelium Exposes
subendothelial ECM(allows adhesion of platelets,
and release of tissue factor- favouring coagulation.
Note that Endothelial injury may contribute to
thrombus even when endothelium is not
completely disrupted.
Thrombus results due to imbalance between
pro- and antithrombotic effects (dysfunction of
endothelium).
Significant disruption of endothelial Functions
may occur(In Absence of endothelial cell loss)in:

4. Stress of hypertension.
Turbulence of blood flow.
Scarred Valves.
Bacterial Toxin.
Alteration in normal blood flow.
Contributes to cardiac or arterial thrombosis
by: Causing endothelial injury or dysfunction.
: Causing countercurrents and pockets of
stasis
Normal Blood flow is Luminar

5. Formed Elements as platelets flow in central axis
Separated from endothelium by slow-flowing
plasma.
Stasis and turbulence
Bring platelets into contact with endothelium.
Prevents dilution of activated clotting factors by
flesh blood.
Retards inflow of clotting factor inhibitors.
Also permits build-up of thrombi.
Stasis is a major factor in development of
venous thrombi
 clinical setting that turbulence and stasis
contributes to thrombosis;

6.  Ulcerated atherosclerotic plaques
Exposes subendothelial ECM
Also creates a source of turbulence.
Aneurysms(abnormal aortic/arterial dilations)
Causes stasis and therefore favours thrombosis
MYOCARDIAL INFARCTION
Causes endothelial injury
Non-contractile myocardium brings an element of
stasis.

7. MITRAL Valve stenosis eg in Rheumatic heart
disease
Causes left atrial dilation
Profound stasis favors thrombosis.
HYPERCOAGULABILITY
Less frequent cause of thrombosis but
important
Defined as alteration in coagulation pathway
predisposing to thrombosis
Can be Primary (genetic) or Secondary
(acquired) disorder.

8.  Most common inherited causes are;
Mutation of factor V gene
Mutation of Prothrombin gene.
Acquired disorders leading to thrombosis
occurs in common clinical settings:
Examples
Cardiac failure or trauma;
Due to stasis
Vascular injury

9. Oral Contraceptives and Hyperestrogenic
state of Pregnancy
Disseminated cancer(Release of
Procoagulant factors)
Hypercoagulabily of advance age may be due
to;
 Susceptability to platelets aggregation
Smoking and obesity – promotes
hypercoagulability – reason unknown.
MORPHOLOGY

10.  Thrombi May develop anywhere in
cardiovascular system.
Are of Variable size and shape depending on
Size
Circumstances leading to their Development
Arterial or Cardiac Thrombi usually begins at
site of endothelial injury or;
At area of turbulence eg vessel bifurcation.
Venous thrombi characteristically occur at site
of stasis.

11. Arterial thrombi tends to grow in retrograde
direction.
Venous thrombi- Direction of Blood flow.
Propagating tail may not be well attached
(especially venous)
May detach causing embolus.
When arterial thrombi arise in Heart
Chambers or aortic Lumen are termed Mural
thrombi.

12. Common causes of Thrombi in Heart;
Abnormal myocardial contraction (arrythmias)
Dilated cardiomyopathy.
Myocardial infarction.
Aortic thrombus
Ulcerated atherosclerotic plaque
Aneurysms
Arterial thrombi are usually occlusive the
commonest site in descending order.

13. Coronary arteries
Cerebral arteries
Femoral arteries
Venous Thrombosis
Almost always occlusive
Creates a long cast along vein lumen.
Because they occurs in areas of stasis, there is
more emeshed erythrocytes therefore red.
Venous Thrombosis Commonly affects veins of
Lower extremities(90% of cases)

14. Less Common in upper limbs.
In special cases: Dura sinuses, portal vein or
hepatic veins.
Under special conditions thrombi may form in
heart valves.
FATE OF THROMBUS
If Patient survives initial effects of occlusion
thrombus may undergo the following;
PROPAGATION

15. Thrombus may accumulate more platelets
and fibrin( Propagate) – eventual Vessel
obstruction.
Embolization
Dislodge and travel to other sites of
Vasculature.
Dissolution
Thrombi removed by fibronolytic activity.

16. Organization and recanalization.
Thrombi may induce inflammation and fibrosis
( Organization) and;
Eventually because recanalized and establish
vascular flow.
 Clinic significance
Both Arterial and venous thrombus may
cause vessel occlusion.
Venous thrombus may cause Oedema and
Congestion in various bed distal to
obstruction.

17. Most dramatic (grave)Conquence is
embolization to lung – death.
Arterial thrombi may embolize.
But most important is obstruction at
critical sites.
-eg. Coronary artery leading to myocardial
infarction.
Venous thrombosis
Most occurs in superficial or deep veins of legs

18. Superficial veins thrombosis
Usually in salphenus vein(vericosity)
 Thrombi usually causes local congestion and
tenderness in affected vein.
Rarely embolizes
Impaired drainage predisposes to infection of
overlying skin from slight trauma – Varicose ulcer.
Deep vein thrombosis
Grave due to embolism
Deep vein obstruction may also cause local
pain, oedema and congestion

19. Because of collateral circulation 50% of affected
patients may be asymptomatic.
Deep vein thrombosis may occur with stasis or
hypercoagulability states
Cardiac failure a common cause of venous stasis.
Trauma, surgery, burns – reduced physical
activity, injury to vessels, release of procoagulants
by tissues.
Arterial thrombosis

20. Atherosclerosis is major contributor.
Cardiac Mural thrombus may occur in setting
to myocardial infarction.
Rheumatic heart diseases may results into
artrial mural thrombus( Mitral valve stenosis)
In addition to consequences of obstruction
may embolize Virtually to any tissue.
Principle targets, brain, kidney, spleen (Large
volume of flow).
EMBOLISM

21. Defn: Detached intravascular solid, fluid or
gaseous mass that is carried by blood to distant
site from origin.
Almost all emboli represent some dislodged
thrombus hence;
THROMBOEMBOLISM
Unless otherwise stated embolism refers to
thromboembolism.
Emboli lodges in a vessel to small to allow
further passage.
May lead to partial or complete vascular
occlusion.

22. Consequence of occlusion is ischaemic
necrosis of distal tissue ( infarction)
Depending on site of origin may lodge
anyway in vascular tree.
Clinical consequence depends whether
emboli lodges in pulmonary or systemic
circulation.
Pulmonary thrombo-embolism
Common in hospitalized patient.
In 95% of pulmonary embolism the origin is
thrombus in deep vein of lower extremity.

23. Carried through right side of heart to
pulmonary vasculature.
Depending on size;
May occlude Main Pulmonary artery.
 Impact across bifurcation(saddle embolus)
Pass into smaller branches.
Frequently there may be multiple smaller
emboli( shower from a single large mass)
In general a person with one pulmonary
embolus is at risk of having more.

24. Rarely embolus may pass through interatrial or
interventricular defect.
When if this happen it enters systemic circulation(
paradoxical embolism)
CLINICAL CONQUENCES.
Most pulmonary emboli(60-80%) are clinically
silent because they are small
Sudden death, right heart failure or cardiovascular
collapse may occur:
When more than 60% of pulmonary circulation is
obstructed.
Embolic obstruction of medium sized arteries may
result into
 pulmonary hemorrhage without infarction.

25. This due to dual blood flow from bronchial
circulation.
Obstruction of small end- artery infarction of
area distal to obstruction.
Multiple emboli. Over time may cause
pulmonary hypertension with right heart failure.
SYSTEMIC EMBOLISM
Emboli travelling in arterial circulation .
Most (80%) arise from intracardiac mural
thrombi
Two third of these associated with left
ventricular wall infarcts.

26. Another one quarter dilated fibrillating left
atiria.
Remainder from;
Aortic aneurysms
Thrombi on ulcerated atherosclerotic plaque
Valvular vegetations.
About 10-15% systemic embolism are
unknown origin.
Arterial emboli can travel wide to a variety of
sites

27. Major site of arterial embolism;
Lower extremities( 75%)
Brain 10%
Lesser extent, intestines, Spleen, upper extremities.
Consequences depends on;
Extent of collateral circulation in affected tissue.
Vulnerability of tissue to ischaemia.
The Caliber of Vessel.
In general arterial embolism causes infarction of tissue
downstream to obstruction.