rior veins in the legs and lower pelvis. Physical
inactivity is the primary cause of DVT. The veins,
which are not as muscular as the arteries, rely on
the skeletal MUSCLESto support them. The contrac-
tion and relaxation of skeletal muscles, such as
occurs during walking and other physical activi-
ties, helps move blood through the veins. This
support and massaging action is particularly
important for function of the large veins in the
legs, which transport significant volumes of blood
toward the HEARTagainst pressure that can reach
three times the force of gravity.
During periods of extended inactivity the skele-
tal muscles relax the tension they otherwise
would exert against the veins, allowing the flow of
blood to become sluggish. When other problems
with the veins exist, such as VENOUS INSUFFICIENCY
(inadequate function of the valves in the veins)
and VARICOSE VEINS, blood may pool. The pooling
provides opportunity for the blood to begin clot-
ting, which can cause the localized occlusion and
PAIN that characterizes DVT as well as HEART
ATTACK, STROKEor PULMONARY EMBOLISM(blood clot
in the LUNG) if a particle of the clot breaks away
and travels through the bloodstream.
Birth control pills, even low-DOSEfor-
mulations, increase the risk for deep
vein thrombosis, most significantly in
women who also smoke.The most effective approach for DVT is preven-
tion, which for many people can be as simple as
walking for a few minutes every couple hours
during the day, even if only around a desk or lift-
ing the legs as if marching in place. Additional risk
factors include OBESITY, DIABETES, VARICOSE VEINS,
PERIPHERAL VASCULAR DISEASE (PVD), and cigarette
smoking. Doctors may recommend ANTICOAGULA-
TION THERAPYas a further preventive measure to
reduce the blood’s clotting ability for people who
are at risk for developing DVT. Though extended
airline flights present a well-popularized risk for
DVT, less than one tenth of 1 percent of the 2 mil-
lion Americans who develop DVT do so as a result
of flying.
Once the thrombosis, or clot, develops it blocks
the flow of blood, which results in a backup of
fluid that seeps into the surrounding tissues
(edema). The clot also irritates the walls of the
VEIN, causing INFLAMMATION. Symptoms of DVT
include- redness and swelling (edema) at the site of the
clot - tenderness or PAINat the site of the clot
- FEVERand generalized discomfort
The diagnostic path may include ULTRASOUNDor
VENOGRAMof the suspected occlusion, which typi-
cally provides the visualization necessary to con-
firm the diagnosis. Treatment typically consists of- anticoagulation therapy to prevent the clot
from enlarging or other clots from forming - bed rest, with heat to the area to improve cir-
culation, until the clot dissolves - support stockings
People who have one experience with DVT face
increased risk for subsequent DVTs and usually
take prophylactic anticoagulation therapy to lower
the risk. Lifestyle measures such as daily walking
and other physical activity, SMOKING CESSATION, and
weight loss if necessary are also key to preventing
subsequent DVTs.
See also CARDIOVASCULAR DISEASE PREVENTION;
COAGULATION; LIFESTYLE AND CARDIOVASCULAR HEALTH;
WALKING FOR FITNESS; WEIGHT LOSS AND WEIGHT MAN-
AGEMENT.diabetes and cardiovascular disease A leading
consequence of DIABETES(type 1 or type 2) is CAR-
DIOVASCULAR DISEASE(CVD), and diabetes is a leading
cause of cardiovascular disease. The extent to
which diabetes and cardiovascular disease inter-
twine has caused some health experts to view dia-
betes as a form of cardiovascular disease. Among
people with diagnosed diabetes, more than 95 per-
cent have some form of cardiovascular disease, the
most common being HYPERLIPIDEMIA (elevated
BLOODlevels of cholesterol and triglycerides) and
HYPERTENSION(high BLOOD PRESSURE).
Diabetes causes numerous changes in the body
that influence or accelerate the development of
cardiovascular disease. Key among them are- dysfunctions of lipidMETABOLISMthat result in
elevated blood levels of low-density lipoprotein
48 The Cardiovascular System