Chapter 3Chapter 3

Disorders of Vascular FlowDisorders of Vascular Flow

Yiran Ni M.DYiran Ni M.D401761415@qq.com

This chapter will describe major disturbances involving hemodynamics and the maintenance of blood flow, including:

1. edema

2. hyperemia and congestion

3. hemorrhage

4. thrombosis

5. embolism

6. infarction

7. shock.

Key points of the last lecture

• 1. Virchow triad

• 2. Morphology of thrombus

• 3. The fate of thrombus

EmbolismEmbolism

Definition

• Embolism is the occlusion or obstruction of a vessel by an abnormal mass transported from a different site by the circulation

• An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin.

• Virtually 99% of all emboli represent some part of a dislodged thrombus, hence the term thromboembolism.

Definition

• Rare forms of emboli include:

• fat droplets

• bubbles of air or nitrogen

• atherosclerotic debris (cholesterol emboli),

• tumor fragments

• bits of bone marrow

• foreign bodies such as bullets.

Definition

• However, unless otherwise specified, an embolism should be considered to be thrombotic in origin.

• Inevitably, emboli lodge in vessels too small to permit further passage, resulting in partial or complete vascular occlusion.

Definition

• The consequences of thromboembolism include ischemic necrosis (infarction) of downstream tissue.

• Depending on the site of origin, emboli may lodge anywhere in the vascular tree; the clinical outcomes are best understood from the standpoint of whether emboli lodge in the pulmonary or systemic circulations.

Possible moving pathways of an embolus Possible moving pathways of an embolus

depends on the sites of its origindepends on the sites of its origin

A. The emboli from systemic vein or right heartA. The emboli from systemic vein or right heart

B. The emboli from left heart or main arteryB. The emboli from left heart or main artery

C. The emboli from mesenteric vein or portal veinC. The emboli from mesenteric vein or portal vein

D. Crossed embolismD. Crossed embolism

E. Retrograde embolismE. Retrograde embolism

Crossed Crossed embolismembolism

Types of EmbolismTypes of Embolism

• Thrombembolism Thrombembolism

• FAT EMBOLISM

• AIR EMBOLISM

• AMNIOTIC FLUID EMBOLISM

ThrombembolismThrombembolism

• 1) Pulmonary embolism1) Pulmonary embolism The origin of emboli: The origin of emboli: ＞＞ 90%90% from from deep leg veindeep leg vein

The sequel:The sequel:

SSmall embolimall emboli may lodge in the branching may lodge in the branching

arterioles of pulmonary artery,and usually arterioles of pulmonary artery,and usually

be clinical silent be clinical silent

LargeLarge emboliemboli often occlude the main often occlude the main

pulmonary artery and cause sudden death pulmonary artery and cause sudden death

2) Systemic embolism2) Systemic embolism

The origin of emboli:The origin of emboli:

Most arise from intracardiac mural thrombiMost arise from intracardiac mural thrombi

the remainder may originate from ulcerated the remainder may originate from ulcerated

atherosclerotic plaques atherosclerotic plaques

The sequel: Arteriolar embolization (e.g. The sequel: Arteriolar embolization (e.g.

the brain, kidneys , spleen and intesrines)the brain, kidneys , spleen and intesrines)

Arteriolar embolization of brainArteriolar embolization of brain

Arteriolar embolization of kidneyArteriolar embolization of kidney

Arteriolar embolization of spleenArteriolar embolization of spleen

Arteriolar embolization of intesrineArteriolar embolization of intesrine

（（ 22 ）） Fat embolismFat embolism

The origin of emboli: The origin of emboli:

Fat globules in the circulation after fractures Fat globules in the circulation after fractures

of long bone, trauma of sofe tissue and a liver with of long bone, trauma of sofe tissue and a liver with

fatty changefatty change

The sequel:The sequel:

depends on the size and the number of fat globulesdepends on the size and the number of fat globules

>20μm>20μm in diameter: occlusion of the branching in diameter: occlusion of the branching

arterioles of pulmonary arteryarterioles of pulmonary artery

< 20μm< 20μm in diameter: pass through the pulmonary in diameter: pass through the pulmonary

circulation and enter left heart, and consequently cause circulation and enter left heart, and consequently cause

embolism of cerebral microvasculatureembolism of cerebral microvasculature

（（ 33 ） ） Air embolismAir embolism

Gas bubbles with the circulation can obsruct Gas bubbles with the circulation can obsruct

cardio-vascular flow. Generally, in excess of 100ml cardio-vascular flow. Generally, in excess of 100ml

of air is required to produce a clinical effect.of air is required to produce a clinical effect.

The origin of gas:The origin of gas: Air may enter the circulation Air may enter the circulation

during obstetric procedures or as a result of chest during obstetric procedures or as a result of chest

wall injury wall injury

The sequel: The sequel: The gas bubbles may form frothy The gas bubbles may form frothy

masses with blood in right heart, and then act like masses with blood in right heart, and then act like

physical obstructions to occlude major vesselsphysical obstructions to occlude major vessels

Decompression sickness:Decompression sickness:

Occurs when individuals are exposed to sudden Occurs when individuals are exposed to sudden

change in atmospheric pressure. When air is breathed change in atmospheric pressure. When air is breathed

at high pressure, increase amount of gas (particularly at high pressure, increase amount of gas (particularly

nitrogen) become dissolved in the blood and tissues.If nitrogen) become dissolved in the blood and tissues.If

the diver then ascends (depressurized) too rapidly, the the diver then ascends (depressurized) too rapidly, the

nitrogen expands in the tissues and bubbles out of nitrogen expands in the tissues and bubbles out of

solution in the blood to form gas emboli.solution in the blood to form gas emboli.

（（ 33 ） ） Amniotic fluid embolismAmniotic fluid embolism

The amniotic fluid and its component are The amniotic fluid and its component are

infusedinfused into the maternal circulation via a tear in into the maternal circulation via a tear in

the placental membranes and rupture of the the placental membranes and rupture of the

uterine veins. The onset is characterized by sudden uterine veins. The onset is characterized by sudden

severe dyspnea,cyanosis,DIC and shock, followed severe dyspnea,cyanosis,DIC and shock, followed

by seizures and coma.by seizures and coma.