Saphenous Vein Graft (SVG)

A graft taken from the major vein within the foot and leg.

Saphenous Veins

The saphenous veins are large veins that run beneath the skin in the legs. Their function is to cool the body when it is overheated. There is a second deep system of veins in the legs. The saphenous veins, therefore, can be taken for use in the coronary bypass grafting.

Saturated Fat

Saturated fat is a type of fat that is usually solid or semi-solid at room temperature and can be found in animal as well as vegetable sources. A diet high in saturated fat frequently increases blood cholesterol and Low Density Lipoprotein (LDL). (See also Polyunsaturated Fat; Monounsaturated Fat; and Omega-3 Fatty Acids.)

Septal Defect

A septal defect is a congenital birth defect that results in a hole in the partition between the right and left sides of the heart (the septum). For both an atrial septal defect (between the left and right atrium) and a ventricular septal defect (the left and right ventricle) the blood flows through the hole from the high pressure left side of the heart to the lower pressure right side. The excess of blood in the right side of the heart can cause too much blood to flow through the lungs and may result in pulmonary hypertension or heart failure. Large holes, and some small holes, should be closed surgically.

Signs

Signs are objective findings discovered by a clinician/physician, e.g. heart murmur. See also: symptoms.

Sinoatrial Node (Sa Node)

The SA Node is the heart's natural pacemaker. Located in the right atrium near the entry of vena cava, the SA Node is composed of a group of specialized heart muscles that contract rhythmically at about 70 times per minute. Every time the SA node contracts it sends an impulse through the atrial muscle to contract. The atrial muscle in turn forwards the contraction message to the atrioventricular node (AV Node). The normal mode of the SA node can be sped up or slowed down by impulses sent to it from autonomic nervous system.

Stenosis

Stenosis is a segmental narrowing of an artery, leading to a decreased blood flow. Stenosis is usually caused by atheroma, fatty plaques and scar tissue that build-up on artery walls.

Stenotic Valve

A stenotic valve has been narrowed, thereby restricting the blood flow. Common causes of a stenotic valve include calcification as a result of the natural aging process, damage due to infection, and congenital narrowing.

Stent

An expandable metal tube that supports the vessel wall and maintains blood flow through the opened vessel.

Sternotomy

A sternotomy is the surgical division of the breastbone used in open heart surgery to give the surgeon access to the heart. The average length of a sternotomy is 30 cm long.

Stress Echocardiogram

A stress echocardiogram is similar to a graded exercise stress test, except that an echocardiogram is performed prior to the stress test and immediately following the stress test. A stress echocardiogram allows the physician to visualize changes in the pumping action of the heart between rest and exercise.

Stress Test

A test used to measure electrical activity in the patient's heart (ECG or EKG) while the patient is doing a controlled exercise. The results indicate whether there is damage to the heart or if blood flow has been restricted to areas of the heart.

Subclavian Artery

The subclavian arteries deliver blood to the neck and the arms. The left subclavian artery stems directly from the aortic arch. The right subclavian artery branches off the brachiocephalic (innominate) artery.

Sympathetic Nervous System

The sympathetic nervous system regulates those parts of the body, like the heart and the blood vessels, that the brain does not consciously control. Nerves for the sympathetic nervous system originate in the middle section of the spinal cord. As one of the two parts that compose the autonomic nervous system, the sympathetic nervous system is often responsible for giving the opposite message as its counterpart, the parasympathetic nervous system. The sympathetic nervous system usually functions to excite or speed up the systems it enervates.

Symptoms

Symptoms are subjective indications experienced by the patient, e.g. chest pain. See also signs.

Systemic Circulation

The systemic circulation refers to all of the blood vessels in the body except those that supply the lungs.

Systole

Systole is the period during a ventricular contraction. When a patient's blood pressure is taken the systolic pressure, or the measurement of this contraction period, is the first figure given. An average systole lasts roughly 0.3 seconds for a heart rate of 70 beats per minute.