ARTERIOSCLEROSIS

BY ERIN HARRINGTON

OVERVIEW• Arteriosclerosis is a condition which involves the thickening and hardening of

artery walls.

• This usually occurs in only the larger arteries, however, arteriolosclerosis is a form which affects the smaller arterioles.

• Arteriosclerosis is often confused with atherosclerosis, however, this a specific type of arteriosclerosis involving the build up of fatty acids and plaque on artery walls.

• Arteriosclerosis usually develops with age with eventual complications and infection.

• It is uncommon in young children and young adults but can happen in very rare occasions.

AETIOLOGY• Arteriosclerosis is a result of the healing of a damaged artery. A scar forms

over the site which was damaged and this causes the condition and its different forms.

• Damage can be done as a result of many things, physical as well as general lifestyle.

• Smoking is a serious risk factor as it can cause damage at more than one site and on a large scale. It can lead to the damage of whole arteries, however, it is not the only risk factor to be aware of.

• Age affects the possibility of arteriosclerosis also as, as one gets older, the arteries become weaker and less able to sustain themselves when faced with miscare.

• Industrial pollution is thought to be a major cause of arteriosclerosis presently and there is ongoing research regarding this.

• Diets including large amounts of carbohydrates, dairy products and food with additives and preservatives have been shown to increase a persons chance of contracting Arteriosclerosis.

• Certain lifestyles can also cause Arteriosclerosis also, for example lack of exercise, sleep, alcohol consumption etc.

• A family history of the condition may also increase a persons chances of getting Arteriosclerosis.

• Conditions associated with inflammation can also affect the arteries causing damage and resulting in the occurrence of Arteriosclerosis.

• Diabetes Mellitus: Endothelial injury may be the initial event in the genesis of atherosclerosis, followed by platelet adhesion at the site of injury as well as aggregation. In Diabetes it has been shown that endothelial dysfunction is present.

• Excessive emotional stress

• Hypertension i.e. high blood pressure can cause arteriosclerosis due to severe pressure on artery walls.

• A sedentary lifestyle has been known as a contributing factor to the contraction of an arteriosclerotic disorder. This is because exercise helps to maintain a healthy blood flow throw blood vessels.

CLASSIFICATION• Arteriosclerosis Obliterans:

Typically seen in larger arteries in the lower extremities

Characterised by the fibrosis of the tunica intima and the calcification of the tunica media

The lumen of the artery may be dangerously narrowed or completely destroyed

Age is a huge risk factor of this form of arteriosclerosis, typically affecting persons over 50 years old

Symptoms usually don’t become noticeable until the disease is very advanced

• Atherosclerosis:

A specific form of Arteriosclerosis where artery walls are thickened by the deposit and accumulation of calcium and fatty materials such as cholesterol and triglycerides

Most common of the Arteriosclerosis types due to Western diets containing large amounts of unsaturated fats and sugars

Results in a severe case of impeded blood flow to major organs and around the body as it affects the larger arteries

Affects males more than females, with 85% of deaths from Atherosclerosis being in persons aged 65 and up

Many complications can arise from this sometimes resulting in fatalities

• Medial Calcific Sclerosis:

Also known as Monckeberg’s Calcific Sclerosis

Seen mostly in the elderly

Affects the arteries associated with the body’s extremities

Characterised by the calcification of the tunica media, however, unlike Arteriosclerosis Obliterans the vessel lumen is not narrowed

An intramural calcification which presents the early signs of this arteriosclerosis is thought to be induced by a number of drugs that each have an antiproliferative mechanism of action

PATHOGENESIS• Arteriosclerosis in medium and large arteries is characterised by

patchy intramural thickening of the sub intima which encroaches on the arterial lumen.

• The earliest sign of Atherosclerosis is a fatty streak on the artery wall due to an accumulation of foam cells in the intimal layer

of the artery. These fatty streaks evolve into a fibrous plaque.

• If this streak becomes unstable, denudation of overlying endothelium or plaque rupture can occur. This may result in thrombotic occlusion of the overlying artery.

• Atherosclerotic lesions consist of three components:

1. Cellular component – smooth muscle cells and macrophages2. Connective tissue matrix and extracellular lipid3. Intracellular lipid – accumulates within macrophages converting them

to foam cells

• Atherosclerosis is likely initiated when endothelial cells over-express adhesion molecules. This is in response to turbulent flow in the setting of an unfavourable serum lipid profile.

• Knowledge of atherosclerosis at a molecular level has led to the development of specific molecular targets for anti-atherosclerotic therapy e.g. Peroxisome proliferator activated receptors (PPARs).

• Accumulation of foam cells enlarges the plaque which can lead to chronic stable angina.

• Monckeberg’s Arteriosclerosis has similar effects, however, it is the accumulation of calcium deposits rather than lipids like in Atherosclerosis.

• Calcified plaque can act in the same way as atherosclerotic plaque, blocking arteries an causing chronic stable angina.

• Arteriosclerosis Obliterans is characterised by occlusions of the arteries, mainly affecting the abdominal aorta and the small and medium sized arteries of the lower extremities.

SIGNS AND SYMPTOMSArteriosclerosis develops very gradually and often has no symptoms until it progresses to blocking arteries or forming blood clots. At this point, a heart attack or stroke can be triggered. In any case, the signs and symptoms, if they do appear, differ depending on where in the body and which arteries are affected.

Heart: symptoms such as chest pains or pressure (angina).

Brain: one may have signs and symptoms such as numbness and weakness in arms or legs, speech impairment or drooping muscles in the face. Theses are all signs of a TIA attack which can lead to a stroke if untreated.

Arms and Legs: symptoms of peripheral artery disease, such as leg pain when walking (intermittent claudication) or muscle pain in the arms.

Kidneys: can cause high blood pressure and can lead to development of kidney failure.

Genitals: can cause erectile dysfunction in males and high blood pressure in women.

General symptoms can include the following:

• Angina• Paralysis in face, arms, legs or on one side of the body• Confusion• Trouble seeing in one or both eyes• Dizziness, loss of balance or coordination• Fainting• Sudden, severe headache

COMPLICATIONSThe complications of Arteriosclerosis are similar for each form of the disease.

Thrombosis and Infarction

• A thrombus (blood clot) can form if the fibrous cap which overlaps a plaque breaks down. Platelets are activated forming the blood clot which can block the artery.

• This increases the chances of ischemia which is a restriction in blood supply to tissue causing a shortage of glucose and oxygen, needed for cell metabolism.

• Emboli (small benign growths) can also break off from the site and lodge in small arteries causing infarcts in other parts of the body such as in Arteriosclerosis Obliterans i.e. in the lower extremities.

Coronary Artery Disease

• Coronary artery disease can result when it occurs in arteries near the heart. This can lead to angina pains, heart attack or heart failure.

Aneurysms

• When an arterial wall is weakened by the spread of plaque between tissue layers, a local dilation and weakening in the blood vessel may develop i.e. an aneurysm.

• Aneurysms can rupture the vessels causing haemorrhage which can be very serious and in many cases fatal.

Carotid Artery Disease

• When arteries near the brain are narrowed, carotid artery disease may develop which can lead to a transient ischemic attack (TIA) or stroke.

CLINICAL MANIFESTATIONS• Clinically, Arteriosclerosis and it’s complications are related mainly to

the lesion of occlusion of small or medium-sized arteries in the body.

• Acute and chronic arterial occlusion can be compared in terms of the nature of the diseases, however, their symptoms differ. This is due to the variation in oxygen requirements of the tissue involved. The vulnerability of a site to the disease depends on this and the ability to endure oxygen deprivation.

• Studies show that Nervous tissue has large requirements of oxygen and low tolerance for lack of it. On the other hand, Renal and Myocardial tissue have less need for oxygen and a much higher endurance for oxygen deprivation.

• The usual symptoms of occlusive vascular episodes, relating to arteriosclerosis of cranial arteries, are often grouped in the all-inclusive category of strokes. Common manifestations include Hemiplegia, Hemianopia and Aphasia.

Other arteriosclerotic lesions include:

• Aneurysms • Pressure effects of the arteriosclerotic vessels themselves on blood

flow• Arterial embolisms• Isolated calcific aortic stenosis occurs in the aged which is a

causative factor of heart failure and sudden death

• Arteriosclerosis can sometimes be difficult to name an exact cause for.

“It is a strange but well-known fact that at times, necropsy will reveal extensive atherosclerosis of cerebral vessels, when a review of the clinical history fails to reveal any neurological disturbance. Similar findings are often made in other parts of the body also, for example, in the heart or extremities”

- Howard B. Burchell, M.D.; Edgar V. Allen, M.D.; Frederick P. Moersch, M.D.

STAGES

This diagram shows how Atherosclerosis develops. Monckeberg’s Arteriosclerosis develops in a similar way.

CLINICAL & LABORATORY INVESTIGATIONS AND FINDINGS

EPIDEMIOLOGY• Arteriosclerosis increases with age. It’s more frequent in Diabetes

Mellitus, chronic kidney disease, Systemic Lupus Erythematosus, chronic inflammatory conditions, hypervitaminosis D and rare genetic disorders, such as Keutel syndrome.

• Monckeberg’s Arteriosclerosis in the general population is estimated at about <1%, and on the basis of an ankle brachial index about >1.5.

• It is difficult to collect a whole lot of viable information regarding the epidemiology of arteriosclerosis as there are many contributing factors as well as factors that may have previously been thought to have an effect on the disease that in fact do not.

TREATMENT AND MANAGEMENTAtherosclerosis

• Statins are drugs which lower bad cholesterol levels and are widely used for cholesterol related diseases.

• Fibrates reduce triglyceride levels, which if high contribute to the progression of atherosclerosis.

• Niacin (Nicotinic Acid) is a vitamin which in small amounts improves overall cholesterol. Some people have an intolerance to this however, and it also increases blood sugar levels which is a problem for diabetics.

• Lowering high blood pressure is essential in the prevention, management and treatment of atherosclerosis. This can be done by exercise and diet in most cases.

Arteriosclerosis Obliterans

• Studies of arteriosclerosis obliterans indicate that approx. 75% show little progression of the disease over a five-year period.

• Angiography (arteriography) is a technique used which views inside the arterial lumen. It demonstrates the segmental type of occlusion seen in this disease.

• Angiography can determine whether or not a patient is suitable for arterial grafting, which is the preferred treatment of arteriosclerosis. Morbidity in patients undergoing angiography has been 0.1%, with no resulting deaths.

• Sympathectomy, a procedure in which one or more sympathetic ganglion is removed, is sometimes performed on patients with arteriosclerosis obliterans. It is an irreversible procedure and its effect on the progression of the disease is difficult to determine.

Monckeberg’s Arteriosclerosis

• Similar to other forms of arteriosclerosis, simple things like exercise and diet can help in the treatment of the disease. It all depends on how serious the case is.

• In severe cases, stents may have to be implanted and also surgical re-routing of the blood supply or a vascular resection.

REFERENCES