Chapter 20 Flashcards
What is responsible for the vast majority of vascular diseases?
Atherosclerosis
What are the four modifiable RFs of atherosclerosis?
Hyperlipidemia
HTN
DM
Smoking
What is the third leading cause of death in the US?
Stroke resulting from cerebrovascular dz
How is dx of carotid artery dz best accomplished?
With a combo of duplex ultrasonography and axial imaging (CTA or MRA)
When is carotid endarterectomy of proven benefit?
In pts with symptomatic stenosis
What is an alternative to carotid endarterectomy?
Endovascular therapy with angioplasty and stenting for high-risk pts
Where is arterial occlusive dz most commonly found?
Aortoiliac
Femoropopliteal
Tibioperoneal circulations
Initial tx for arterial occlusive dz
Conservation, though revascularization is indicated for pts with crippling claudication or critical limb ischemia
Traditional option for arterial occlusive dz
Bypass grafting, though endovascular angioplasty with or without stenting is rapidly emerging as a viable alternative
What remain a major cause of morbidity and mortality?
Aneurysms of the aorta, iliac arteries, visceral arteries and peripheral arteries
What is rapidly changing the practice of vascular surgery?
Endovascular aneurysm repair
What can cause neurologic, arterial, or venous sx by compression of the brachial plexus, subclavian artery, or subclavian vein?
Thoracic outlet syndrome (TOS)
Approach of neurologic TOS
Should be approached cautiously, as sx may not improve after surgery
Arterial and venous sx from TOS should prompt surgical resection of the compressing structure.
Surgical tx of mesenteric ischemia
Resection of nonviable bowel and revascularization of the remaining intestine
Tx of DVT
Anticoagulation and close monitoring for complications
What to do when anticoagulation fails or is contraindicated in DVT
Insertion of a vena cava filter dramatically decreases the incidence of pulmonary embolism
How are arteries and veins formed?
From endothelium, smooth muscle, and extravascular matrix synthesized by cells in the vessel wall
What are the three layers of arteries and veins?
Tunica intima
Tunica media
Tunica adventitia
Tunica intima
Lines the luminal surface of the vessel wall and is composed of a thin continuous layer of polygonal endothelial cells overlying subendothelial connective tissue
What do endothelial cells in the tunica intima do?
Modulate vascular tone, hemostasis, vessel permeability, and cell proliferation
How do endothelial cells in the tunica intima do what they do?
Through the release of vasoactive mediators, anti-inflammaotry cytokines, and antithrombic agents
What covers the endothelial cells of the tunica intima?
By a glycocalyx, which is responsible for the anti-thrombogenic properties of the surface
What has been theorized as one of the initiating factors in the development of atherosclerotic lesions?
In inflammatory conditions, portions of the glycocalyx coat are lost, leading to the trafficking of leukocytes
Basal lamina
Borders endothelial cells on their albuminal surface and forms a boundary separating the endothelium from the underlying intimal structures
How is the basal lamina formed?
Formed by: Glycoproteins Adhesion molecules such as fibronectin and laminin Various proteoglycans Microfibirils of types IV and V collagen
Function of the basal lamina
Strengthen the vascular wall through polymer networks of type IV collagen and laminin chains
Regulates numerous functions such as endothelial cell regeneration and vessel permeability
Internal elastic lamina
A layer of elastic fibers dividing the subendothelial intima from the tunica media
What do the elastic laminae do?
Function as barriers to macromolecule accumulation in the vessel wall
What is the tunica media layer comprised of?
Vascular smooth muscle cells, elastic, and collagen separating the internal elastic lamina from the adventitia
How are the components of the tunica media layer organized?
Arranged with closely packed layers of smooth muscle cells, elastin and collagen fibers surrounded by a basement membrane of laminin, type IV collagen and firbonectins.
Tunica adventitia
A collection of adipose and other supportive connective tissue that extends from the media to the perivascular connective tissue
What is only present in the tunica adventitia?
What does it do?
Vasa vasorum
Functions as the blood supply of the vessel wall
What is also present in the tunica adventitia?
Vasomotor nerve fibers that mediate vasoconstriction and vasodilation via adrenergic alpha and beta receptors, respectively
How are arteries classified?
Elastic
Distributing
Small
What are the largest arteries?
What are examples?
Elastic
Aorta and its largest branches, such as the brachiocephalic, common carotid, and common iliac arteries
What are the second largest arteries?
Examples?
Distributing
Coronary, renal, and hepatic arteries
Where are the small arteries contained?
Example?
Contained within the substance of organs and tissues
Arterioles
Primary function of arterioles
Control tissue blood flow and systemic arterial pressure
What are the smallest vessels?
Function?
Capillaries
In tissues, they are the primary site for exchange of oxygen, nutrients, and waste
Lymphatics- what are they?
Function?
Small, thin-walled structures with an endothelial lining
Function as conduits, which carry extracellular fluids centrally away from tissues for processing in the lymph nodes and eventual return to the vascular system
Atherosclerosis
A dz whose hallmark is the deposition and accumulation of smooth muscle cells and lipids within the arterial intimaThe source of thromboembolic phenomenon
What are the two types of lesions characteristic of late atherosclerosis?
Fibrous and complicated plaques
Fibrous plaques
Consists of a necrotic core, containing foam cells (lipid filled smooth muscle cells or macrophages) and extracellular lipids, covered by a fibrous cap of smooth muscle cells, lymphocytes, and connective tissue
Complicated plaques
Calcification, ulceration, plaque rupture with subsequent hemorrhage, and thrombosis
What can accelerate the process by which a fibrous plaque evolves into a complicated one?
HTN
Cigarette smoking
What are risk factors for atherosclerosis?
Hyperlipidemia HTN DM Tobacco Age Gender FHx
Role of LDLs in atherosclerosis
Undergo oxidative modification in the bloodstream. The oxidized end products then function as inflammatory mediators, inducing adhesion molecule expression by endothelial cells
Role of HDLs in atherosclerosis
Exert a protective effect against atherosclerosis because they are involved in transporting cholesterol away from the periphery to the liver for processing and excretion
Role of HTN in atherosclerosis
The chronic elevation of blood pressure causes endothelial damage, which incites atherogenic inflammatory pathways
Induces increased arterial wall stiffness through the renin-angiotensin-aldosterone system
DM is associated with a _____ increase in myocardial infarction and a ______ increase in gangrene of the lower extremities
2-fold
8- to 15-fold
How DM contributes to atherosclerosis
Diabetics have impaired vasodilation due to dysfunction of endothelial nitric oxide synthase and increased production of endothelin I, a potent vasoconstrictor.
Platelet hyperactivity also contributes to decreased microvascular blood flow
Hyperglycemia results in the formation of reactive oxygen species and advanced glycation end products, which promote inflammatory pathways
How cigarette smoking contributes to atherosclerosis
alters endothelium-mediated vasoreactivity in both the peripheral and coronary circulations by decreasing the availability of nitric oxide
Increases circulating proinflammatory markers
Age trends in atherosclerosis
The risk for PAD increases 1.5- to 2-fold for every 10-yr increase in age
Gender trends in atherosclerosis
Women appear to develop CVD 10 yrs later than do men and typically after menopause
FHx and atherosclerosis
Multifactorial
What is the third leading cause of death in the United States?
Stoke
What percentage of strokes are ischemic and what percentage of strokes are hemorrhagic?
87%
13%
What is the most common source of emboli in a CVA?
Internal carotid artery, followed by cardiac emboli
Risk factors of CVA
All risk factors for atherosclerosis Hx of A fib TIA Sedentary lifestyle Excessive alcohol consumption Obesity
Sx of CVA
Contralateral weakness or sensory deficit of the face, arm, or leg, or transient ipsilateral blindness (amaurosis fugax)
Aphasia, alexia, anomia
Neglect, visual or sensory extinction, anosognosia, or asomatognosia
PE of CVA
Carotid bruit may be found
Initial carotid studies for CVA
Carotid artery duplex ultrasonography (DUS)
Noninvasive and reliable
Estimates the degree of stenosis on the basis of flow velocity
Cannot reliably distinguish very high-grade stenoses from occlusion
Cannot evaluate intracranial portions of the carotid artery system
Highly dependent on technique
What is seeing increasing use in the dx of carotid stenosis?
Magnetic resonance angiography (MRA)
Tends to overestimate degree of stenosis
What is less susceptible to overestimating the degree of carotid stenosis and is more rapid than MRA?
CTA
What is the criterion standard test for carotid stenosis?
Catheter-based DSA
Medical management of carotid dz
Lowering BP to a target of <140/90 with antihypertensive meds
Quit smoking
Lipid-lowering therapies
Daily aspirin
In terms of carotid pathology, what should prompt a CEA?
Stenosis >50%
When should CEA be considered in asymptomatic pts?
When pts have >60% stenosis
Where is a carotid endarterectomy incision made?
Along the medial border of the sternocleidomastoid muscle or an oblique transverse incision in the neck.
Complications of carotid endarterectomy
Stroke
MI
Postoperative HTN and/or hemorrhage
Vagus nerve most commonly traumatized
When is carotid stenting preferred over CEA?
In pts with previous ipsilateral neck surgery or external beam radiotherapy
Medically infirm pts with extremely high perioperative risk, such as those with severe and uncorrectable CAD, CHF, or COPD
