atherosclerosis

                        ATHEROSCLEROSIS

  

what is atherosclerosis?

- a pattern of vascular disease which is characterized by intimal lesions called atheromas /atheromatous / atherosclerotic plaques that protrude into and obstruct the vascular lumen and weaken the underlying tunica media.

what are the common sites of formation of atheromas?

- proximal portion of coronary arteries

-  internal carotid arteries

-  the circle of willis

- large vessels of the lower extremities

- renal arteries

- mesenteric arteries

   

morphology of atheromatous plaques

A) MACROSCOPIC :

• color : white yellow ,if superimposed thrombus over ulcerated plaque then it is red - brown 
• size   : vary in size

• shape : patchy and eccentric
• cut section : a) central necrotic core  b)subendothelial superficial fibromuscular cap
• periphery of the lesions : NEOVASCULARIZATION

  

B)MICROSCOPIC : three principal component 

• cells : smooth muscle cell,macrophage and  t cell
• extracellular matrix : collagen,elastic fibers and proteoglycans 
• intracellular and extracellular lipid : mostly cholesterol and cholesterol esters 
  
  
  
  
  

what are the risk factors for atherosclerosis

?

major risk factors :

modifiable :

1. Age

        2. gender 

3. genetics

          4. family history 

non modifiable :

         1.hypertension

         2.hypercholesterolemia

         3.cigarette smoking

         4.alcohol

         5.diabetes

addictional risk factors : 

  1. inflammation and CRP ( C - reactive protein)

    2. hyperuricemia

    3. hyperhomocystinemia

    4. metabolic syndrome 

    5. lpoprotein A

    6. factor affecting hemostasis ( e.g - thrombin and platelet derived factors)

    7. other factors

             - obesity

             - lack of excercise and physical inactivity

             - high carbohydrate intake

             - 'type A personality'  with stress factors in lifestyle

how atheromas are formed? 

atherosclerosis progress in the following sequence - 

 1. endothelial injury and dysfunction

 2. accumulation of lipo protein

 3. monocyte adhesion  to the endothelium

 4. platelet adhesion

 5. factor release from activated platelets, macrophage and vascular wall cell

 6. smooth muscle cell proliferation,extracellular matrix production and recruitment of T - cell

 7. lipid accumulation both extracellularly and within cells  ( macrophage and smooth muscle Cell)

what are the complications of atherosclerosis?

 

1. rupture ,ulceration or erosion of the surface of atheromatous plaques

2.  ishchemia

3.  hemorrhage

4.  atheroembolism

5.  aneurysm formation

6.  calcification

7.  infarction :

     - heart : myocardial infraction

     - brain : cerebral infraction

     - aorta : aortic aneurysms

     - peripheral vessels : peripheral vascular disease (gangrene of the legs)

8. complications due to atherosclerotic stenosis

     - mesenteric occlusion and bowel ischemia

     - sudden cardiac death

     - chronic ischemic heart disease

     - ischemic encephalopathy

     - intermittent claudication (diminished perfusion of the extremities)

 

how to prevent atherosclerosis?

  1.primary prevention :

        - cessation of cigarette smoking

        - control of hypertension

        - weight reduction

        - increase exercise

        - moderation of alcohol consumption

        - lowering total and LDL blood cholesterol levels while increasing HDL

  2.secondary prevention : prevent recurrence of events such as MI  in patient with symptomatic disease