Common cardiovascular diseases

5 Common cardiovascular diseases



5.1 Atheroma



5.1.1 Pathological anatomy


Atheromatous plaque (atheromas) can develop on the intima of large- and medium-caliber arteries. Plaque is an accumulation of cholesterol and other lipid compositions that forms on the inner walls of vessels. This deposit is covered by a cap of fibrosity.


These fatty deposits extend the length of the arterial wall and protrude on the vessel lumen. Sometimes the entire thickness and very long segments of the vessel wall can be affected. Plaque may break off, stimulating the production of blood clots created when the material beneath the intima comes in contact with the blood. This can cause a thrombus and a vasospasm, impeding blood flow. The most commonly affected arteries are those of the heart, brain, kidneys, small intestine, and lower extremities.



5.1.2 Etiology


Arterial obstruction is considered a disease of old age, as it is usually in this age group that clinical signs appear. However, plaques have been found in infancy in the developed world.


The origin of atheromatous plaque is uncertain, but it seems that predisposing factors exert their effects over a long period of time. These include:



• family history


• higher incidence in men than in women until menopause


• aging


• arterial hypertension


• diabetes


• smoking


• excessive stress


• food rich in refined carbohydrates, cholesterol, and saturated fatty acids


• obesity


• sedentary lifestyle


• excessive alcohol consumption.


Most of the time, a combination of factors underlies the formation of plaque.


Arterial obstruction by deposits in an arterial wall may be partial or total. These deposits can reduce or abolish blood supply. Their effects depend on the location and caliber of the associated artery, as much as on the available collateral circulation.


Incomplete arterial stenosis causes ischemia in the tissues downstream of the stenosis. The tissues can still receive adequate blood to meet their minimum requirements, but not enough to cope with increased metabolic activity. For example, when muscular activity increases, ischemic pain can occur, similar to a muscle cramp. The heart muscle and the skeletal muscles of the lower extremities are those most commonly affected by this phenomenon. Ischemic heart pain is called angina pectoris; ischemia of the lower extremity is called intermittent claudication.


In cases of complete occlusion of an artery, the tributary tissues degenerate rapidly and die. The extent of tissue lesions depends on the caliber of the occluded artery, the extent and type of tissue affected, and the degree of collateral circulation.


If the occlusion impacts:



• a coronary artery, myocardial infarction results


• a cerebral artery, the resulting cerebral ischemia leads to cerebral infarction.



5.1.3 Complications of atheroma



Thrombosis and infarction


If the fibrous coating of a plaque breaks off, blood platelets can become activated and a blood clot forms. These more or less plug the artery and can result in ischemia or infarction. Fragments of the clot may detach and be carried in the bloodstream where they cause an embolism in smaller arteries downstream of the clot.



Hemorrhage


If calcium salts deposit in plaque, the arterial wall becomes fragile, rigid, and responds poorly to high blood pressure. Plaque can break off and cause a hemorrhage.



Arterial aneurysm


A localized dilation of a blood vessel wall can be caused by atherosclerosis and hypertension.



5.1.4 Symptomatology


In atherosclerosis, the vessel lumen narrows as a result of atheromatous plaque lesions. Certain vessels are especially vulnerable to this arterial disorder and all may be involved by atheroma in the same patient. The most frequent locations are:



• the coronary arteries


• the carotid bifurcations


• the iliac and femoral arteries.


The pulse provides important information. An obliterated pulse in the lower extremity can be found in cases of extreme stenosis.


Atherosclerosis may be present in the aorta for some time before symptoms are noticed. Symptoms may not appear in the aorta itself owing to its large caliber. However, a blood clot may form in the aorta and migrate as an embolism to a distant area, or the disease may manifest as an abdominal aneurysm.


Usually there are no symptoms until one or several arteries have been obstructed by atheromatous plaque, and blood flow is severely reduced provoking ischemia.


Atherosclerosis progresses quietly and remains asymptomatic for a long time. For example, a coronary artery can gradually become 75% occluded and remain asymptomatic or produce episodes of angina sine dolore (painless episode of coronary insufficiency). The first symptom may be myocardial infarction, caused by obstruction of the residual lumen, from either atherosclerosis or a blood clot.


Typical symptoms of atherosclerosis are thoracic pain, when the coronary artery is involved, or leg pain, when an artery of the lower extremity is diseased.


Arterial hypertension often accompanies atherosclerosis.



5.2 Arteriosclerosis


Arteriosclerosis is a progressive degeneration of the arterial wall that develops with aging and hypertension.



5.2.1 Large- and medium-caliber arteries


The vessel wall is infiltrated by fibrous tissue and calcium. As a result, the vessels lose elasticity. The diameter of the arteries decreases, and they become stiffer and less compliant.


The loss of elasticity increases systolic arterial pressure, to the degree that it can no longer dilate during systole. Thus, in arteriosclerosis, the gap between systolic and diastolic pressures widens.



5.2.2 Small arteries and arterioles


The thickening of the arterial media narrows the lumen. Arteries, as we have explained, determine peripheral resistance. The narrowing of their lumen increases peripheral resistance and arterial pressure rises accordingly. Tissue ischemia may occur. The lower extremities are vulnerable to gangrene. The risk is especially severe in diabetics.


Senile arteriosclerosis is an affliction of the aged whereby progressive hardening of the arteries causes cerebral ischemia and a loss of mental function.



5.3 Arterial aneurysm



5.3.1 Pathological anatomy


Aneurysm refers to the localized dilation of the wall of a blood vessel. The thinning and weakening of a segment of arterial or venous wall creates a dilated pouch or ballooning. Aneurysms are variable in size.



5.3.2 Etiology


Although the pathogenesis of an aneurysm is unclear, there are several predisposing factors:



• atherosclerosis


• trauma


• atheroma


• arterial hypertension


• congenital anomalies in blood vessel formation


• defective collagen formation in the artery wall


• syphilis.



5.3.3 Forms


Types of aneurysm (Fig. 5.1) include:



• Fusiform distensions occur in the entire circumference of the vessel wall, affecting mainly the aorta and sometimes the iliac arteries. These aneurysms present with atheromatous lesions.


• Saccular aneurysm is a localized dilation of a vessel wall in which a small area, rather than the entire circumference, is distended, forming a sac-like swelling. These aneurysms can be due to defective collagen, atheromatous lesions, or congenital weakness.


• Dissecting aneurysm is a localized dilation, most commonly in the arch of the aorta. It is characterized by an infiltration of blood between the outer and middle layers of the vessel wall. It begins as an endothelial tear and extends little by little to become a longitudinal dissection along the artery.


• Microaneurysms occur in small arteries and arterioles of the brain. They are linked to hypertension. Transitory ischemic accidents are often the result of a thrombus or hemorrhage of these aneurysms.


image

Fig. 5.1 Arterial aneurysms.



5.3.4 Progression and treatment


Left untreated, aneurysms tend to enlarge. It is advisable periodically to monitor the thickness and size of the artery wall. Surgical treatment consists of resection and replacement of the excised section of aorta with a synthetic prosthesis.

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Nov 7, 2016 | Posted by in MANUAL THERAPIST | Comments Off on Common cardiovascular diseases

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