Peripheral arterial disease pathophysiology: Difference between revisions

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==Pathophysiology==
==Pathophysiology==
* PAD is a manifestation of systemic [[atherosclerosis]] that has developed over many years.
*[[Peripheral arterial disease]] is characterized by a narrowing of the peripheral blood vessels leading to decreased blood flow to the limbs. The most common underlying cause of PAD is atherosclerosis.
* Atherosclerosis is a complex process that involves endothelial dysfunction, lipid disturbances, platelet activation, [[thrombosis]], oxidative stress, vascular smooth muscle activation, altered matrix metabolism, remodeling and genetic factors
===Atherosclerosis==
* Atherosclerosis frequently develops at arterial bifurcations and branches where endogenous atheroprotective mechanisms are impaired as a result of the effects of disturbed flow on endothelial cells
*[[Atherosclerosis]] is a systemic disease that progresses over time and might involve the aorta, coronary , carotid and the medium-sized peripheral arteries.
* The stages of atherosclerosis are divided into the following:
*When the [[atherosclerosis]] involves the peripheral limb blood vessels, the blood flow to the limbs is compromised. Such atherosclerotic plaques tend to occur at [[vessel]] bifurcations due to both impaired atheroprotective mechanisms and turbulant blood flow. At the beginning the vessels try to adapt by metabolic and myogenic autoregulation. At this stage, the patient might be asymptomatic. As the atherosclerosis progresses with time beyond the ability of the vessels to compensate for it, mainly upon increased blood demand in exercise, symptoms of [[claudication]] start.
*:* Lesion initiation
*When the atherosclerotic plaques become unstable, thrombi form on top of a ruptured plaque located at a disease arterial segment. '''Atherothrombosis''' is the term currently used to describe this process.
*:*:* Results from endothelial dysfunction
; Below is an image illustrating the narrowing of the blood vessel due to the presence of the atherosclerotic plaque.
*:* Formation of the fatty streak
*:*:* Results from an inflammatory lesion that develops first
*:*:* Affects the intima of the artery and leads to formation of the foam cell
*:*:* Fatty streak consists primarily of smooth muscle cells, [[monocytes]], [[macrophages]], and T and B cells
*:* Fibroproliferative atheroma development
*:*:* Originates from the fatty streak
*:*:* Contains larger numbers of smooth muscle cells frlled with lipids
*:* Advanced lesion development
*:*:* Results from continued accumulation of cells that make up the fatty streak and fibroproliferative atheroma
*:*:* Highly cellular
*:*:* Contains intrinsic vascular cell walls (both endothelial and smooth muscle), and inflammatory cells (monocytes, macrophages, and T lymphocytes)
*:*:* Also contains a lipid core covered by a fibrous cap
* Arteries initially compensate for atherosclerosis by remodeling, which causes the blood vessels to increase in size
* Advanced lesions eventually intrude into the lumen, resultsing in flow-limiting stenoses and chronic ischemic syndromes
* Acute arterial events occur if the fibrous cap is disrupted, the resulting exposure of the "prothrombotic" necrotic lipid core and subendothelial tissue leads to thrombus formation and flow occlusion
* In addition to coronary artery disease and cerebrovascular disease, PAD is one of the three major syndromes of atherothrombosis
* '''Atherothrombosis''' is the term currently used to describe the process of thrombus formation on top of a ruptured plaque located at a disease arterial segment
* Such atherosclerotic plaques tend to occur at vessel bifurcations, presumed to be due to both impaired atheroprotective mechanisms and disturbed blood flow leading to local intimal injury
* '''Panvascular disease''' refers to clinically significant atherosclerosis is present in multiple vascular beds
 
[[Image:arterylumen.jpg|thumb|center|300px|Diagram of arterial lumen (Image courtesy of Amjad Almahameed)]]
[[Image:arterylumen.jpg|thumb|center|300px|Diagram of arterial lumen (Image courtesy of Amjad Almahameed)]]


===Associated Disorders===
===Other Pathophysiologies===
Many PVD patients also have [[angina pectoris]] or have had [[myocardial infarction]]. There is also an increased risk for [[stroke]].


==References==
==References==

Revision as of 16:19, 31 October 2012

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Pathophysiology

  • Peripheral arterial disease is characterized by a narrowing of the peripheral blood vessels leading to decreased blood flow to the limbs. The most common underlying cause of PAD is atherosclerosis.

=Atherosclerosis

  • Atherosclerosis is a systemic disease that progresses over time and might involve the aorta, coronary , carotid and the medium-sized peripheral arteries.
  • When the atherosclerosis involves the peripheral limb blood vessels, the blood flow to the limbs is compromised. Such atherosclerotic plaques tend to occur at vessel bifurcations due to both impaired atheroprotective mechanisms and turbulant blood flow. At the beginning the vessels try to adapt by metabolic and myogenic autoregulation. At this stage, the patient might be asymptomatic. As the atherosclerosis progresses with time beyond the ability of the vessels to compensate for it, mainly upon increased blood demand in exercise, symptoms of claudication start.
  • When the atherosclerotic plaques become unstable, thrombi form on top of a ruptured plaque located at a disease arterial segment. Atherothrombosis is the term currently used to describe this process.
Below is an image illustrating the narrowing of the blood vessel due to the presence of the atherosclerotic plaque.
Diagram of arterial lumen (Image courtesy of Amjad Almahameed)

Other Pathophysiologies

References


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