ENDOCARDITIS; HIV/AIDS; MYOCARDITIS; TAMPONADE,
CARDIAC.
pericardium A tough, two-layer membranous
sac that encloses the HEART. The pericardium’s
fibrous outer layer, called the fibrous pericardium,
protects the heart from contact with the chest wall
and other structures in the chest, including the
LUNGS and the sternum. The pericardium wraps
completely around the heart, extending around
the bases of the great vessels (AORTA, superior and
inferior VENA CAVA, pulmonary ARTERY, pulmonary
VEIN) as they arise from the heart. Two ligaments
attach the top of the pericardium to the back of
the sternum. Other ligaments loosely connect the
bottom of the pericardium to the DIAPHRAGM.
These structures anchor the heart in its place in
the chest.
The inner layer of the pericardium is a filmy
envelope. Its two surfaces are the parietal peri-
cardium, which contacts the fibrous pericardium,
and the epicardium, which covers the MYOCARDIUM
somewhat like a wet tissue. Inside the envelope is
a watery fluid that lubricates the heart. The inner
pericardium forms a nearly frictionless contain-
ment field for the beating heart. The pericardium
is vulnerable to INFLAMMATIONand INFECTION(PERI-
CARDITIS).
For further discussion of the pericardium
within the context of cardiovascular structure and
function, please see the overview section “The
Cardiovascular System.”
See also ENDOCARDIUM; LIGAMENT.
peripheral vascular disease (PVD) ATHEROSCLE-
ROSISthat affects the peripheral arteries, notably
those in the legs. ATHEROSCLEROTIC PLAQUEinfil-
trates the inner wall of the arteries, the intima.
This causes the intima to thicken and stiffen,
restricting the FLEXIBILITYof the ARTERYas well as
narrowing the passage for BLOOD(arterial lumen).
PVD can affect the largest to the smallest of the
peripheral arteries and is the cause of INTERMITTENT
CLAUDICATIONas well as often an underlying factor
in ERECTILE DYSFUNCTION. NEUROPATHYof DIABETEScan
severely exacerbate PVD, resulting in restricted
circulation and limb ischemia (oxygen depriva-
tion) that can cause tissue death (GANGRENE). PVD
due to diabetes is a leading cause of limb amputa-
tion. PVD also may contribute to HYPERTENSION
(high BLOOD PRESSURE).Symptoms and Diagnostic Path
PVD often has firmly established itself by the time
symptoms manifest. Intermittent claudication—
PAINwith walking—is the primary symptom of
PVD affecting the lower extremities. Leg or foot
pain at rest, with coolness and pallor or CYANOSIS
of the limb, suggests embolism (clot or atheroscle-
rotic fragment blocking the flow of blood). Other
symptoms may include lack of sensation (PARES-
THESIA) or inability to move the limb (PARALYSIS),
and wounds that do not heal. In severe PVD there
is sometimes a mottled appearance to the SKIN.
The doctor may be unable to feel a PULSEin the leg
or foot, depending on the level of the occlusion or
embolism. The diagnostic path often includes
Doppler ULTRASOUNDexamination, and sometimes
MAGNETIC RESONANCE IMAGING(MRI), of the legs.Treatment Options and Outlook
The primary thrust of treatment when symptoms
are present is ANTICOAGULATION THERAPY, which may
include intravenous heparin when the doctor sus-
pects an embolism. For symptoms such as inter-
mittent claudication or rest ischemia, the
treatment is typically the oral anticoagulant war-
farin or antiplatelet agents such as cilostazol to
reduce the risk for clot formation. A program of
progressive walking improves blood flow in the
legs as well as strengthens the leg muscles so they
can provide additional support for the blood ves-
sels. Weight loss reduces pressure on the arteries.
The treatment regimen often includes lipid-lower-
ing medications in conjunction with lifestyle mod-
ifications to lower blood lipid levels, which are
usually elevated in PVD. Lifestyle changes include
daily physical exercise such as walking, nutritious
EATING HABITS, and SMOKING CESSATION. When symp-
toms fail to improve with these therapeutic meas-
ures, the doctor may consider ATHERECTOMY, an
OPERATIONto remove segments of atherosclerotic
plaque from the arterial walls. Many people who
have intermittent claudication benefit from wear-
ing support stockings, which are tight against the
legs to help support the blood vessels.
PVD is a progressive condition closely linked
with CORONARY ARTERY DISEASE(CAD). Therapeutic96 The Cardiovascular System