The cardiovascular system—with its complex pathways of arteries, veins and capillaries—keeps life pumping through the body. In this review, the first of two parts, we cover the normal structure and function of the cardiovascular system, and describe common disease processes.

The Major Players
The cardiovascular system consists of the heart, blood vessels and blood. It has three main functions:

1. Transport of nutrients, oxygen and hormones to cells throughout the body, and removal of metabolic wastes (carbon dioxide, nitrogenous wastes and heat).

2. Protection of the body by white blood cells, antibodies and complement proteins against foreign microbes and toxins. Clotting mechanisms also protect the body from blood loss after injury.

3. Regulation of body temperature, fluid pH and water content of cells.¹

A central retinal arterial occlusion (CRAO) may result from an embolus or atherosclerotic changes.

The cardiovascular system, along with the lymphatic system, is the major component of the body’s circulatory system. The circulatory system is the route by which cells get the oxygen and nutrients that they need. The cardiovascular system distributes blood, while the lymphatic system distributes lymph—a clear, colorless fluid containing water and blood cells.¹

In the cardiovascular system, the arteries deliver oxygen and nutrients to the body’s organs, tissues and cells. Veins remove tissue waste matter. Blood is carried from the heart to the rest of the body through a network of arteries, arterioles and capillaries. Blood is returned to the heart through the venules and veins.

The lymphatic system helps to protect and maintain the body’s environment by filtering and draining lymph away from each region.¹

Cells + Plasma = Blood
Blood is the carrier of oxygen and nutrients. It is made up of about 45% solids (cells) and 55% fluids (plasma).3 Plasma is 90% water. In addition to water, plasma contains salts and glucose. Plasma also contains proteins that carry important nutrients to the body’s cells and strengthen the immune system.

There are three types of blood cells that circulate with the plasma: red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes). Blood helps keep the body at optimum temperature, carries hormones to cells, and sends antibodies to fight infection. Blood also contains clotting factors to help tissues heal after injury.²

Cardiovascular Review of Systems: Case History • Leg pain in calf or thigh            • Chest pain (sharp, crushing or heaviness) • Heart racing (palpitations)            • Fainting spells • Sudden shortness of breath at night or lying down • Swelling of legs (edema) • Depression • Stress • Smoking or drinking alcohol • Diet high in salt, saturated fats • Lack of exercise • Family history of heart problems • Visual changes

Common Disease Processes
Every patient visit begins with a thorough case history and review of systems. When you suspect cardiovascular disease, question the patient further. (See “Cardiovascular Review of Systems: Case History.") Most often, vascular disease affects blood flow through arteries and/or veins by blocking or weakening the vessel, or by damaging the valves that are found in veins. As a result of decreased or blocked blood flow, organs and other body structures may be damaged by vascular disease.¹

Atherosclerosis is the most frequent cause of morbidity from vascular disease. The highest incidence occurs in Finland, Great Britain, Canada and the United States.^1,3 Atherosclerosis is defined as a fibrous plaque (atheroma) within the intima of an artery. Atheromas are frequently found in the coronary arteries (heart), the larger branches of the carotid arteries, the circle of Willis (brain), the large arteries of the lower extremities, and the renal and mesenteric arteries.^1,3

The incidence of atherosclerosis increases with age. Other risk factors for the formation of atheromas are gender (more common in men in all age groups, but the incidence increases in postmenopausal women), hypercholesterolemia (especially high LDL levels), hypertension, diabetes mellitus, cigarette smoking, obesity, “type A” personality, physical inactivity and the use of oral contraceptive drugs.^1,3

Atheromatous plaques have a central core consisting of cholesterol and cholesterol esters, lipid-laden macrophages, calcium and necrotic cellular debris.^1,3

Ulceration, hemorrhage into the plaque or calcification of the plaque may occur. Systemic obstructive disease ensues if a thrombus develops at the site of the plaque or embolization occurs.⁴

A thrombus is a solid mass of platelets and/or fibrin (and other components of blood) that forms locally in a vessel.1,3,4 An embolus moves through the bloodstream until it lodges in a narrowed vessel and blocks circulation. Cardiogenic emboli are a recognized etiology of ischemic stroke and retinal vascular occlusive disease. The mitral and aortic valves are the most common sources of cardiac emboli. Amaurosis fugax (transient monocular vision loss) and cerebral transient ischemic attacks may also occur from cardiogenic emboli.1,3,4

Atherosclerosis may lead to ischemic heart disease and myocardial infarction (the most common cause of death in the United States). Other complications include stroke, ischemic bowel disease, peripheral vascular occlusive disease and renal arterial ischemia with secondary hypertension. Weakening of the blood vessel wall may also lead to aneurysm formation.1,3,5

Inflammation may also cause vascular disease. In general, inflammation of blood vessels is referred to as vasculitis. Inflammation may cause narrowing and/or blockage of vessels. Trauma or injury that involves a blood vessel may lead to inflammation or infection. This, in turn, may damage the vessel and lead to its narrowing and/or blockage.1,6

Phlebitis means inflammation of a vein. Thrombophlebitis is the term used when a blood clot in the vein causes the inflammation. Venous blood clots may be caused by longtime bed rest and/or immobility, damage to veins from injury or infection, damage to the valves in the vein causing pooling near the valve flaps, pregnancy and hormones (such as estrogen or birth control pills), genetic disorders, conditions causing slowed blood flow/thicker blood, congestive heart failure (CHF), and certain tumors.7

Deep vein thrombosis (DVT) is a blood clot that occurs in a deep vein such as in a leg. If a blood clot breaks loose from a vein and travels to the lungs, the result is known as a pulmonary embolism.7 Chronic venous insufficiency (CVI) can also occur if a damaged valve of a vein or a DVT causes long-term pooling of blood and swelling in the legs. If uncontrolled, fluid will leak into the surrounding tissues in the ankles and feet. Skin breakdown and ulceration may eventually occur.7

Next column: When blood to the eye is in short supply.

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4. Dul M, Haskes C. Cardiogenic Emboli and Valvular Heart Disease. In: Marks E, Adamczyk D, Thomann K. Primary Eyecare in Systemic Disease. Norwalk, Conn.: Appleton & Lange; 1995:Ch. 4.
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7. Ginsberg J. Peripheral Venous Disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia: Saunders Elsevier; 2007:Ch. 81.