Aging Changes In The Heart And Blood Vessels

The "aging process" causes specific cardiovascular changes. This leads to reduced physical and mental ability. Aging is also a risk factor for cardiovascular disease. Scientists a have learned great deal about the interaction of aging with cardiovascular disease related changes and have identified risk factors for both heart and vascular aging, and heart disease. This allows the development of strategies to prevent or to lessen the impact of both aging and disease. This series provides information which will enlighten you about how aging, disease, and their interaction impact on your heart and arteries. Initial articles will discuss how aging affects your heart and blood vessels. Subsequent articles will teach you about risk factors for cardiovascular disease, how aging interacts with risk factors and what you can try to do in an attempt to preserve your cardiovascular health.

Introduction

In article 10 of this Series, "How Badly Are Your Arteries Hardening With Aging?" we discussed large artery structure and function, and we explained why vascular aging is a risk factor for high blood pressure. We also told you how you could assess your individual vascular stiffness (hardening) by determining your pulse pressure from your blood pressure numbers (systolic minus diastolic). In this article we will show you that in addition to vascular hardening, other risky changes occur within blood vessels with aging. Presently these changes are NOT LABELED AS A MEDICAL CONDITION, but they play a role as a risk factor in a severe condition called atherosclerosis. And, they may be related to vascular stiffening as well.

The Vascular Intima and Function of The Endothelial Cells

In addition to the arteries themselves becoming stiffer with aging, the inner most of the arteries' three layers, the intima, becomes thickened. Refer to the following illustration as we discuss this process.

The three layers of the arterial wall are, from outside to inside, the adventia, the media and the intima. A flat layer of cells, called endothelial cells, forms a boundary between the blood in the lumen, or cavity, and the innermost layer of the arterial wall. Beneath the inner surface of the endothelial cell layer lies a sub endothelial space, which is separated from the vascular media by a basement membrane. Thus, the intima is composed of three components: endothelial cells, the sub endothelial space and the basement membrane. A vital function of the endothelial cells, because of their position and composition, is to form a barrier to prevent certain substances from the blood from entering the vessel wall. Another specialized function of these endothelial cells is to react to mechanical forces such as blood pressure, and blood flow generated by the heart's action. Endothelial cells react by releasing substances into the vessel wall that act on the vascular smooth muscle cells in the middle layer (media) of the arterial wall. You may recall that these smooth muscle cells contain contractile proteins that change their configuration in order to bring about a shortening, or contraction, of the cell. (Article 8 "Messages Transmitted From the Brain Fine Tune The Heart".) This action changes the tone, or firmness, of these vascular smooth muscle cells. When endothelial cells sense an injury signal they produced other substances that signal vascular muscle cells to change their "nature". In response to such signals the vascular muscle cells dismantle their contractile machinery, begin to produce their own substances, and march toward the site of vascular injury in the inner area of the intima where they reposition themselves just beneath the endothelial cell layer. In reaction to injury endothelial cells also produce substances that signal to circulating blood cells, making it easy for these cells to stick to the endothelial cells, instead of flowing through the vessel smoothly.

Functions of Endothelial Cells:

1. Form a barrier to prevent some substances from entering arterial wall

2. Sense mechanical forces (pressure and/or flow) and release substances which act to change the "contractile tone" of myocytes in medial layer.

3. Sense vascular injury:

a. produce substances to change the "nature" of vascular muscle cells causing them to migrate to the area of injury

b. signal blood cells to stick to endothelial cells

What Happens To The Inner Layer Of Your Arteries As You Become Older?

The lifetime of an endothelial cell is not infinite, and these cells, like those of your bowel, continuously multiply. However, with advancing age some of these specialized functions of the endothelial cell discussed above become blunted. The self-renewal process weakens. The endothelial barrier becomes leaky. Signals to vascular smooth muscle cells to regulate their function become altered. Vascular smooth cells as if perceiving endothelial injury migrate to the intima, multiply there and produce collagen, a matrix protein, and other molecules. The addition of these cells and matrix within the sub endothelial space results in intimal thickening. (See Illustration 1-Older Artery). The intima of older arteries becomes a battleground where multiple reactions occur that are similar to a process of chronic injury. This battleground that occurs with aging provides fertile soil in which the seeds of a disease process called atherosclerosis flourish.

The Atherosclerotic Process

With advancing age, as the above changes are occurring within the blood vessel wall, other "intruders" enter into the battle. These "intruders" are constituents of the atherosclerotic process, which has some aspects in common with the aging process. However, unlike the aging process within blood vessels per se, atherosclerosis includes cholesterol accumulation and recruitment of other blood cells to join the battle; these are called inflammatory cells.

Atherosclerosis is so common in older persons (at least one out of two persons over sixty five years of age has atherosclerosis) that some experts had previously thought it was part of the "normal aging process". An alternate view is that atherosclerosis is a disease process that takes advantage of the previously discussed changes that occur within the artery with aging. The vascular aging process and the atherosclerotic process become intertwined as we age, and they influence each other. The more severe your vascular aging process, the easier it is for atherosclerosis to take hold; the more severe your atherosclerosis, the bigger its impact on vascular aging. Thus, it appears that the atherosclerosis process and the aging process combine forces to enable the disease called atherosclerosis to be more visible and more severe in older persons. Please refer to Illustration 2 as we continue our discussion.

Atherosclerosis begins with changes in endothelial cell function that cause white blood cells moving through the blood to stick to the endothelial cells instead of flowing by normally. The barrier normally formed between endothelial cells and the blood becomes weakened and both blood cells and substances circulating in the blood pass through the endothelial cell barrier to join the battleground in the vessel's sub-endothelial space of the intimal compartment. Lipid or fat cell-like substances such as cholesterol in the blood then accumulate there. The lipids become "oxidized" and this enables them to signal the endothelial cells, which then alert others that the battle has begun. Smooth muscle cells that react to endothelial cells and to the fatty infiltration then join in. The smooth muscle cells march from their normal residence in the vascular media and invade the basement membrane by secreting enzymes, which attack the protein in the membrane. Depending on an individual's risk factors (life style variables such as a poor diet, lack of exercise, smoking, high blood pressure and the aging process itself) fat accumulation continues and the atherosclerotic process accelerates. White blood cells called macrophages then enlist in the battle and invade the area to digest the fat. Vascular smooth muscle cells that are resident in the intima and that have already changed their nature also scavenge the fat. These fat-laden white blood cells and vascular smooth muscle cells become known as "foam cells". Vascular smooth muscle cells also try to curtail the injury by producing collagen, which forms a cap over the injury site. This fibrous cap is a weapon against disaster, just like scar formation in a wound. Then calcium accumulates and forms a material resembling bone. This complex array of foam cells, calcification, and lipid accumulation it is called an "atherosclerotic plaque". This plaque grows and becomes similar to an armed bomb. As the war progresses the fibrous cap weakens and ruptures due to the action of enzymes called proteases. The plaque cap can explode or rupture, thus exposing the plaque contents to the blood. The "detonation" gives the signal for the "special forces". These are blood cells called platelets. The platelets accumulate, resulting in a blockade, or blood clot on the inner surface of your blood vessel wall. This clot called a "thrombus" can become surprisingly large and occlude the vessel. By this mechanism of rupturing, even small plaques can interfere with blood flow.

Alternatively, atherosclerotic plaques can enlarge to such a degree as to completely block blood flow. When blood flow within an artery is severely compromised by either a larger plaque or a thrombus or both, the cells of your body organs that depend upon blood flow from that artery becomes damaged or die. This is similar to an enemy cutting off your food supply. Coronary atherosclerosis cuts off the heart's blood supply by occluding the heart's arteries and thus stopping the oxygen supply to the heart, causing a heart "attack" or myocardial infarction. A stroke results when the atherosclerosis processes cut off the oxygen supply to the brain.

The Battle is Not Over Yet

You can join in the battle occurring within you arteries by (1) becoming aware of the risk factors that increase the likelihood for atherosclerosis to occur and that determine its severity and (2) by taking steps required to reduce these risk factors. The most widely recognized risk factors are controllable risk factors. These are high blood pressure,

high blood cholesterol, cigarette smoking, diabetes, obesity and lack of exercise.

Newer risk factors continue to be identified.

Unfortunately age itself has been identified as the major risk factor for atherosclerosis. It is becoming clear that the risk conferred by age is attributable in large measure to the vascular aging process described above. Some doctors are now beginning to realize this and research is underway to design drugs that will combat the vascular aging process, which as noted above, is not identical with atherosclerosis, but intertwined with atherosclerosis as time goes by. Fortunately, like atherosclerosis, the vascular aging process can be impacted by exercise and perhaps diet. We will discuss how healthy aging, via exercise and a proper diet, can reduce your risk for atherosclerosis in an upcoming article.

Source: healthandage.com

Source: Wikipedia, the free encyclopedia

The arterial system the blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.

Anatomy

All blood vessels have the same basic structure. The inner lining is the endothelium and is surrounded by subendothelial connective tissue. Around this there is a layer of vascular smooth muscle, which is highly developed in arteries. Finally, there is a further layer of connective tissue known as the adventitia, which contains nerves that supply the muscular layer, as well as nutrient capillaries in the larger blood vessels. Capillaries consist of little more than a layer of endothelium and occasional connective tissue. When blood vessels connect to form a region of diffuse vascular supply it is called an anastamosis (pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages. Laid end to end, the blood vessels in an average human body will stretch approximately 62,000 miles--2.5 times around the earth.

Types

There are various kinds of blood vessels:· Arteries o Aorta (the largest artery, carries blood out of the heart) o Branches of the aorta, such as the carotid artery, the subclavian artery, the celiac trunk, the mesenteric arteries, the renal artery and the iliac artery. · Arterioles · Capillaries (the smallest blood vessels) · Venules · Veins o Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein. o Venae cavae (the 2 largest veins, carry blood into the heart) They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart. The term "arterial blood" is nevertheless used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen.

Physiology

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis), but arteries - and veins to a degree - can regulate their inner diameter by contraction of the muscular layer. This changes the blood flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation. Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100%) with oxygen. In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 70%. (The values are reversed in the pulmonary circulation.)The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg. Vasoconstriction is the constriction of blood vessels (narrowing, becoming smaller in cross-sectional area) by contracting the vascular smooth muscle in the vessel walls. It is regulated by vasoconstrictors (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandins), a number of hormones (e.g. vasopressin and angiotensin) and neurotransmitters (e.g. epinephrine) from the nervous system. Vasodilation is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide (termed endothelium-derived relaxing factor for this reason).Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins, which leads to most of the symptoms of inflammation (swelling, redness and warmth).

Role in disease

Blood vessels play a role in virtually every medical condition. Cancer, for example, cannot progress unless the tumor causes angiogenesis (formation of new blood vessels) to supply the malignant cells' metabolic demand. Atherosclerosis, the formation of lipid lumps (atheromas) in the blood vessel wall, is the prime cause of cardiovascular disease, the main cause of death in the Western world. Blood vessel permeability is increased in inflammation. Damage, due to trauma or spontaneously, may lead to haemorrhage. In contrast, occlusion of the blood vessel (e.g. by a ruptured atherosclerotic plaque, by an embolised blood clot or a foreign body) leads to downstream ischemia (insufficient blood supply) and necrosis (tissue breakdown).Vasculitis is inflammation of the vessel wall, due to autoimmune disease or infection.

Source: Medline Plus

Heart disease - aging; Atherosclerosis - aging

Information

Some changes in the heart and blood vessels normally occur with age, but many others are modifiable factors that, if not treated, can lead to heart disease.

BACKGROUND

The heart has two sides. The right side pumps blood to the lungs to receive oxygen and get rid of carbon dioxide. The left side pumps oxygen-rich blood to the body.

Blood flows out of the heart through arteries, which branch out and get smaller and smaller as they go into the tissues. In the tissues, they become tiny capillaries.

Capillaries are where the blood gives up oxygen and nutrients to the tissues, and receives carbon dioxide and wastes back from the tissues. Then, the vessels begin to collect together into larger and larger veins, which return blood to the heart.

Aging causes changes in the heart and in the blood vessels. Heart and blood vessel diseases are some of the most common disorders in the elderly.

AGING CHANGES

HEART

• Normal changes in the heart include deposits of the "aging pigment," lipofuscin. The heart muscle cells degenerate slightly. The valves inside the heart, which control the direction of blood flow, thicken and become stiffer. A heart murmur caused by valve stiffness is fairly common in the elderly.
• The heart has a natural pacemaker system that controls heartbeat. Some of the pathways of this system may develop fibrous tissue and fat deposits. The natural pacemaker (the SA node) loses some of its cells. These changes may result in a slightly slower heart rate.
• Heart changes cause the ECG of a normal, healthy aged person to be slightly different than the ECG of a healthy younger adult. Abnormal rhythms (arrhythmias) such as atrial fibrillation are common in older people, which may be caused by heart disease.
• A slight increase in the size of the heart, especially the left ventricle, is not uncommon. The heart wall thickens, so the amount of blood that the chamber can hold may actually decrease despite the increased overall heart size. The heart may fill more slowly.

BLOOD VESSELS

• The main artery from the heart (aorta) becomes thicker, stiffer, and less flexible. This is probably related to changes in the connective tissue of the blood vessel wall. This makes the blood pressure higher and makes the heart work harder, which may lead to hypertrophy (thickening of the heart muscle). The other arteries also thicken and stiffen. In general, most elderly people experience a moderate increase in blood pressure.
• Receptors, called baroreceptors, monitor the blood pressure and make changes to help maintain a fairly constant blood pressure when a person changes positions or activities. The baroreceptors become less sensitive with aging. This may explain the relatively common finding of orthostatic hypotension, a condition in which the blood pressure falls when a person goes from lying or sitting to standing, resulting in dizziness.
• The wall of the capillaries thickens slightly. This may cause a slightly slower rate of exchange of nutrients and wastes.

BLOOD

• The blood itself changes slightly with age. Aging causes a normal reduction in total body water. As part of this, there is less fluid in the bloodstream, so blood volume decreases.

• The number of red blood cells (and correspondingly, the hemoglobin and hematocrit levels) are reduced. This contributes to fatigue. Most of the white blood cells stay at the same levels, although certain white blood cells important to immunity (lymphocytes) decrease in number and ability to fight off bacteria. This reduces the ability to resist infection.

EFFECT OF CHANGES

Under normal circumstances, the heart continues to adequately supply all parts of the body. However, an aging heart may be slightly less able to tolerate increased workloads, because changes reduce this extra pumping ability (reserve heart function).

Some of the things that can increase heart workload include illness, infections, emotional stress, injuries, extreme physical exertion, and certain medications.

COMMON PROBLEMS

• Heart and blood vessel diseases are fairly common in older people. Common disorders include high blood pressure and orthostatic hypotension.
• Arteriosclerosis (hardening of the arteries) is very common. Fatty plaque deposits inside the blood vessels cause it to narrow and can totally block blood vessels.
• Coronary artery disease is fairly common.
• Angina (chest pain caused by temporarily reduced blood flow to the heart muscle), shortness of breath with exertion and heart attack can result from coronary artery disease.
• Abnormal heart rhythms (arrhythmias) of various types can occur.
• Heart failure is also very common in the elderly. In people older than 75, heart failure occurs 10 times more often than in younger adults.
• Valve diseases are fairly common. Aortic stenosis, or narrowing of the aortic valve, is the most common valve disease in the elderly.
• Anemia may occur, possibly related to malnutrition, chronic infections, blood loss from the gastrointestinal tract, or as a complication of other diseases or medications.
• Transient ischemic attacks (TIA) or strokes can occur if blood flow to the brain is disrupted.

Other problems with the heart and blood vessels include the following:

• Peripheral vascular disease , resulting in claudication (intermittent pain in the legs with walking)
• Varicose veins
• Blood clots
  • Thrombophlebitis
  • Deep vein thrombosis

PREVENTION

You can help your circulatory system (heart and blood vessels). Heart disease risk factors that you have some control over include high blood pressure, cholesterol levels, diabetes, obesity, and smoking.

• Eat a heart-healthy diet with reduced amounts of saturated fat and cholesterol, and control your weight. Follow your health care provider's recommendations for treatment of high blood pressure, high cholesterol or diabetes. Minimize or stop smoking.
• Moderate exercise is one of the best things you can do to keep your heart, and the rest of your body, healthy. Consult with your health care provider before beginning a new exercise program. Exercise moderately and within your capabilities, but do it regularly.
• People who exercise usually have less body fat and smoke less than people who do not exercise. They also tend to have fewer blood pressure problems and less heart disease.
• Exercise may help prevent obesity and helps people with diabetes control their blood sugar.
• Exercise may help you maintain your maximum abilities as much as possible and reduces stress.