Vascular Thrombosis and Embolism

 Thrombus

An aggregate of coagulated blood containing

platelets, fibrin, and cellular elements

Thrombosis

The process of blood clot formation (Thrombus) in the vessels, obstructing the blood flow

Pathogenesis of Thrombosis- virchow’s triad

Endothelial Injury

Injury in the Endothelial Cells of blood vessel leads to the release of tissue factors

Fibrin and platelets will be recruited to stop the bleeding of the Endothelial Cells leading to aggregation hence formation of thrombus.

Circulatory Stasis

laminar flow vs turbulent flow

laminar flow

Platelets and other cells flow centrally in the lumen, separated from the endothelium by a clear zone of plasma.

turbulent flow

Platelets flow into contact with the ECs. Promote endothelial cell activation and thrombus formation.

Hypercoagulability

Alteration of the coagulation pathways that predispose to thrombosis

can be primary (Genetic)

can be secondary (acquired)

primary (Genetic) Hypercoagulability

Factor V Mutation

Prothrombin Mutation

Antithrombin III Deficiency

Protein C or S Deficiency

acquired (acquired) Hypercoagulability

Prolonged bed rest/immobilization

Myocardial infarction

Tissue damage (Surgery, Fracture, Burns)

Cancer

Prosthetic Cardiac Valve

Disseminated Intravascular Coagulation

Atrial Fibrillation

Contraceptive pills

Sickle Cell Anemia

Types of Thrombus

Pale Thrombus

Red Thrombus

Mixed Thrombus (Lines of Zahn)

Pale Thrombus formed from

• Mainly platelets

Pale Thrombus characteristics

(Chicken Fat)

Firm, pale, gray, tan

pale thrombus location

seen in Cardiac chambers or arteries

red thrombus contains

• Fibrin, RBCs, WBCs and platelets

red thrombus characteristics

currant jelly

Soft dark red and gelatinous

red thrombus location

as a result of Stagnant blood in veins

Mixed Thrombus (Lines of Zahn) contains and looks like

• Alternating layers of platelets, fibrin, RBCs

-appears as  Alternating red and pale layers

Mixed Thrombus (Lines of Zahn) location

in heart or aorta

aorta at level of kidney

-mixed thrombus (lines of zahn)

red thrombus

-in vein

red thrombus

-vein

-mixed

-in aorta

mixed

-LV

mixed

right atrium

thrombosis

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system.

Arterial and Cardiac thrombosis

• Occur in site of endothelial Injury or turbulance e.g. atherosclerosis

• Pale or mixed thrombus

Venous thrombosis

• Occur in sites of stasis

• Tail of thrombus is prone to fragment creating an embolus (can move to the lung)

• Red or dark thrombus

arterial thrombosis leads to in different locations

Renal Infarction

Stroke

Intestinal Infarction

Myocardial Infarction

Gangrene

-due to blockage of oxygen delivery to those regions

gangrenous necrosis

Intestinal Infarction

stroke

renal infarction

-coagulative necrosis

myocardial infarction

-coagulative necrosis

Cardiac Thrombosis common causes

• Myocardial infarction: Mostly the left ventricle, part of muscle wall not working so not all blood pumped out so remenant blood can lead to thrombus formation

• Endocarditis: Vegetation(fibrin, platelets, bacteria) may develop on cardiac valve

usually mitral or aortic that are damaged by bacterial

infection. Vegetation can detach leading to embolism

• Atrial fibrillation: Disorganized electrical signals leads to slower blood flow.

how does atrial fibrillation lead to a stroke

Atrial Fibrillation

Atrium do not empty completely

Blood in the atrium may stagnate

Blood clot formation

Clot may detach (Emboli)

Emboli may pass into Brain vessels

Block the vessels

Stroke

If a blood clot forms in the left atrium, it can dislodge and enter the systemic circulation through the left ventricle. From there, it can travel up the carotid arteries to the brain. If the clot lodges in a cerebral artery, it can block blood flow, leading to an ischemic stroke.

most common venous thrombosis

-swelling of leg due to blockage

-congested with blood and engorged

-redness at that area

-warm on touch due to accumulation of the blood

DVT findings

 -Leg engorged, red, swollen and warm

-usually in one leg

what is Peripheral Artery Disease (PAD)

arterial thrombosis in the leg

PAD clinical findings

• Arterial block leads to ischemia

• Leg looks pale-bluish-gangrene

• Leg is cold because there is no blood

Varicose Veins

 Venous valves are weak

• Affect superficial small veins

• dilated veins are blue

-doesnt block the veins

fate of the thrombus

-resolution: body removes the clot

-embolization to the lung

-organization and recanalization

-propagation: blood clot grows

A cross section of coronary artery at autopsy showing one of the fate of a thrombus which is the organization and recanalization.

Embolus

A detached intravascular solid or gaseous mass that is carried by the blood from its point of origin to a distant

site, where it often causes tissue dysfunction or

infarction

Pulmonary Embolism (PE)

part of the DVT detaches and goes to left side of the heart into the pulmonary artery into the lungs causing lung infarction

lung infarction symptoms

shortness of breath, cough, dyspnea, orthopnea

DVT and ASD/VSD

In ASD/VSD, emboli can enter the arterial circulation (Paradoxical Embolism) and lead to stroke

Emboli in ARTERIAL circulation mostly from

– 60% left ventricular wall infarcts

– 25% left atrial dilation or fibrillation

– 15% aortic aneurysms and valvular vegetations

Consequences of arterial embolism depend on what

Consequences depend on caliber of occluded vessel and wether a collateral blood supply exist.

total blockage --> infarction

-collateral blood supply: other blood supply going to the same area

Types of Embolism

-Fat and marrow embolism

-Air Embolism

-Amniotic Embolism

Fat and marrow embolism

-when fracture happens part of marrow or fat pass through the small veins and do same as DVT and can lead to pulmonary embolism.

-mostly tibial or femoral fracture

A cross section of pulmonary vessels at autopsy showing the presence of fat embolism blocking the the vessels.

Air Embolism occurs in what sickness

decompression sickness

-dive in deep sea levels, sudden drop in atmospheric pressure leads to rupture of alveoli, the air moves from ruptured alveoli to the capillaries and go to the brain, block those vessels and lead to stroke.

-also why u remove air bubbles from injections

Amniotic Embolism

when placenta is detached, the uterine veins rupture and some amniotic fluid or fetal tissue can pass into the mothers circulation leading to an embolism

A cross section of pulmonary vessel at autopsy showing the presence of squamous cells shed from fetal skin.