Encyclopedia of Health and Medicine

undle branch block 25
• diabetes, which damages the blood vessels, particularly
the smaller arteries and the arterioles
• OBESITY, which increases body mass and creates
additional pressure against the blood vessels
Health experts recommend reduced salt consumption,
WEIGHT LOSS AND WEIGHT MANAGEMENT,
daily physical exercise, and no smoking to maintain
optimal blood pressure. Many people who
have hypertension also are on ASPIRIN THERAPY or
ANTICOAGULATION THERAPY to reduce their risk for
heart attack and stroke.
See also ARTERY; EXERCISE AND HEALTH; LIFESTYLE
AND CARDIOVASCULAR HEALTH.
body shape and cardiovascular health Although
OBESITY in general raises the risk for numerous
health conditions, the distribution pattern of excess
body fat correlates to the level of risk for CARDIOVAS-
CULAR DISEASE (CVD) as well as other health conditions
such as DIABETES. Numerous research studies
affirm that people who carry excess body fat primarily
around the waist, the “apple” or “fat tire” body
shape, are three times more likely to develop cardiovascular
conditions such as HYPERTENSION (high
BLOOD PRESSURE), ATHEROSCLEROSIS, CORONARY ARTERY
DISEASE (CAD), ISCHEMIC HEART DISEASE (IHD), and
PERIPHERAL VASCULAR DISEASE (PVD).
WAIST AND HIP MEASUREMENTS
To measure the waist:
1. Breathe out.
2. Place a measuring tape (or piece of string)
snugly but not cinched around the waist,
between the crest of the hip bones and the
navel (belly button).
3. Note the measurement (or use a ruler to measure
the string).
To measure the hips:
1. Place a measuring tape (or piece of string)
snugly but not cinched around the hips at
their widest point.
2. Note the measurement (or use a ruler to measure
the string).
Researchers believe the “apple” pattern of body
fat distribution reflects a higher level of INSULIN
RESISTANCE than the “pear” body shape in which
the body stores excess fat in the hips, thighs, and
more equitably throughout the body. This is significant
because INSULIN plays a key role in LIPID
METABOLISM and regulating blood levels of cholesterol
and triglycerides. Excesses of these lipids
(HYPERLIPIDEMIA) lead to atherosclerosis, the accumulation
of deposits in the inner layer of the walls
of the arteries. Atherosclerosis is the foundation of
occlusive cardiovascular conditions such as CAD
and PVD, and the cause of some types of hypertension
(namely renal vascular hypertension).
The WAIST-TO-HIP RATIO (WHR), which is the WAIST
CIRCUMFERENCE divided by the hip circumference,
determines a person’s body shape classification. A
WHR greater than 0.9 in men or 0.8 in women
defines a body shape as “apple.” Maintaining a
healthy weight and daily physical exercise are
especially important for people who have “apple”
body shapes. Exercise improves INSULIN sensitivity
and helps keep blood lipid levels and blood pressure
within healthy ranges. In turn, this reduces
the risk for diabetes as well as cardiovascular disease.
See also ABDOMINAL ADIPOSITY; EXERCISE AND
HEALTH; LIFESTYLE AND CARDIOVASCULAR HEALTH;
WEIGHT LOSS AND WEIGHT MANAGEMENT.
bundle branch An organization of NERVE fibers
along the heart’s ventricular septum that conveys
electrical impulses to the ventricles to cause them
to contract, also called the BUNDLE OF HIS. The right
bundle branch extends to the right ventricle and
the left bundle branch to the left ventricle. The
electrical impulses, which originate with the
SINOATRIAL (SA) NODE, intensify as they travel along
the bundle branches. The bundle branches, as the
name implies, branch out into smaller and smaller
fibers culminating in the Purkinje fibers, which
disperse the electrical impulses to the myocardial
cells throughout the ventricles.
For further discussion of the bundle branches
within the context of cardiovascular structure and
function, please see the overview section “The
Cardiovascular System.”
See also ATRIOVENTRICULAR (AV) NODE; BUNDLE
BRANCH BLOCK; ELECTROCARDIOGRAM (ECG); HEART.
bundle branch block An impediment, partial or
complete, that prevents electrical impulses from