Encyclopedia of Health and Medicine

16 The Cardiovascular System
Many people who are on anticoagulation therapy
have underlying cardiovascular conditions
that would benefit from lifestyle modifications as
well, such as increased physical activity and SMOK-
ING CESSATION. Regularly stretching the muscles
throughout the day, especially leg muscles, and
walking for 5 to 10 minutes every few hours help
keep blood from pooling and clotting.
See also ARRHYTHMIA; GASTROINTESTINAL BLEEDING;
LIFESTYLE AND CARDIOVASCULAR HEALTH; THROMBOCY-
TOPENIA; THROMBOLYTIC THERAPY.
aorta The ARTERY that carries BLOOD from the
HEART to the body. The largest blood vessel in the
body, the aorta arises from the left ventricle. At its
widest point the aorta is about one and a half
inches in diameter. As the aorta leaves the heart it
ascends to curve behind the right atrium. The first
arteries to branch from the base of the ascending
aorta are the right and left CORONARY ARTERIES that
supply the heart MUSCLE (MYOCARDIUM) with blood.
Branching from the arch as the aorta crests over
the heart are the three arteries that carry blood to
the upper body:
• the brachiocephalic artery (also called the
innominate artery), which transports blood to
the right arm and right side of the BRAIN, head,
and face
• the left common carotid artery, which transports
blood to the left side of the brain, head,
and face
• the left subclavian artery, which transports blood
to the left arm
The aorta then crosses over the PULMONARY
ARTERIES and drops behind the heart to descend
through the chest and into the abdomen, aligned
along the front of the spine, branching into the
iliac arteries at the top of the pelvis. Numerous
arteries branch from the descending aorta along its
passage from the chest to the abdomen, supplying
vital organs such as the LIVER, kidneys, STOMACH,
and intestines. Acquired cardiovascular conditions
that can affect the aorta include ATHEROSCLEROSIS,
ANEURYSM, and AORTIC STENOSIS. A number of congenital
malformations also can affect the aorta,
including aortic coarctation, tetralogy of Fallot,
and transposition of the great arteries (TPA). Most
aortic conditions require surgical repair.
For further discussion of the aorta within the
context of cardiovascular structure and function,
please see the overview section “The Cardiovascular
System.”
See also CONGENITAL HEART DISEASE; PULMONARY
VEINS; VENA CAVA.
aortic stenosis Narrowing of the aortic valve
that restricts the flow of BLOOD from the heart’s left
ventricle to the AORTA. Aortic stenosis may be congenital
or acquired; in either, it tends to show
symptoms later in life. Acquired aortic stenosis
develops as a consequence of calcium and arterial
plaque deposits that infiltrate the aortic valve.
Untreated aortic stenosis results in left ventricular
hypertrophy (enlargement of the left ventricle),
diminished CARDIAC OUTPUT, and ultimately congestive
HEART FAILURE.
Symptoms of aortic stenosis may include PALPI-
TATIONS, ANGINA PECTORIS, fatigue, SYNCOPE (fainting),
and unexplained inability to participate in
aerobic activities. The diagnostic path typically
includes ECHOCARDIOGRAM and CARDIAC CATHETERIZA-
TION. Treatment is surgery to replace the damaged
aortic valve. After valve replacement most people
experience dramatic relief from symptoms and are
able to return to regular activities. Sometimes
medications are necessary to treat companion
conditions such as HEART failure. As with other
valve operations, aortic valvuloplasty or prosthesis
increases the risk for blood clots to form. Most
people will need to take ANTICOAGULATION THERAPY
to mitigate this risk.
See also ANTIBIOTIC PROPHYLAXIS; CONGENITAL
HEART DISEASE; RHEUMATIC HEART DISEASE; VALVULAR
HEART DISEASE.
apolipoprotein B100 (apoB100) A protein on
the surface of lipid molecules that directs the
lipid’s route of METABOLISM. ApoB100 occurs primarily
on low-density lipoprotein (LDL) molecules,
the form of cholesterol with the highest risk
for CORONARY ARTERY DISEASE (CAD). The normal
level of apoB100 in the blood is 40 to 125 milligrams
per deciliter (mg/dL). Elevated levels suggest
familial HYPERLIPIDEMIA. ApoB100 levels also
rise after MYOCARDIAL INFARCTION, when there is