Encyclopedia of Health and Medicine

premature ventricular contraction (PVC) 97
approaches, which must include lifestyle modifications
to be successful, often can slow its progress.
Risk Factors and Preventive Measures
The risk factors for PVD include smoking, other
atherosclerotic disease processes such as CAD, diabetes,
and HYPERLIPIDEMIA. Controlling or eliminating
these factors reduces the risk for PVD. Once
PVD shows symptoms, then the most effective
approach is aggressive management to prevent the
condition from worsening.
See also ATRIAL FIBRILLATION; CARDIOVASCULAR DIS-
EASE PREVENTION; DEEP VEIN THROMBOSIS (DVT); WALK-
ING FOR FITNESS.
physical exercise and cardiovascular health
The influence of regular physical activity on the
structures and functions of the cardiovascular system.
Regular AEROBIC EXERCISE has numerous
effects on the cardiovascular system, improving
the heart’s pumping efficiency as well as the circulation’s
oxygen transport to the tissues of the
body. It also improves the efficiency with which
cells throughout the body, and notably those of
skeletal MUSCLE, use oxygen. This decreases
demand on the HEART, generally slowing the HEART
RATE and decreasing BLOOD PRESSURE. As well, physical
activity increases INSULIN sensitivity, which
helps the body maintain a healthy BLOOD lipid balance
to reduce the risk for HYPERLIPIDEMIA.
PHYSICAL EXERCISE RECOMMENDATIONS
• 30 to 45 minutes of moderate physical activity
five to seven days a week
• 20 to 45 minutes of vigorous physical exercise
three to four days a week
Health experts consider physical inactivity to be
the prime lifestyle factor contributing to most
acquired CARDIOVASCULAR DISEASE (CVD). Though recommendations
call for 30 minutes of moderate
physical exercise daily and 30 to 45 minutes of vigorous
aerobic exercise three to four times a week,
fewer than 20 percent of American adults are physically
active at these levels and about 20 percent get
no physical exercise at all. Health experts attribute
at least 250,000 of deaths from cardiovascular disease
to physical inactivity. Yet the level of physical
activity that could prevent these deaths is minimal,
only 30 minutes a day of moderately brisk walking
(a pace of 3 to 4 miles per hour).
Small amounts of moderately intense physical
activity that accumulate to the recommended
exercise times are equally effective as contiguous
blocks of exercise time, an important finding to
emerge from recent research into the relationship
between physical activity and cardiovascular
health. Meeting the recommended minimum
activity levels could prevent as much as 40 percent
of cardiovascular disease. Ideal activities for
cardiovascular health include walking, bicycling,
running, and swimming.
See also AEROBIC FITNESS; CARDIOVASCULAR DISEASE
PREVENTION; DIET AND CARDIOVASCULAR HEALTH; DIET
AND HEALTH; EXERCISE AND HEALTH; LIFESTYLE AND CAR-
DIOVASCULAR HEALTH; WALKING FOR FITNESS.
premature ventricular contraction (PVC) An
early heartbeat that causes the sensation of a
skipped beat. Most often PVCs are harmless. They
may occur spontaneously, without apparent
cause, and are most noticeable at rest or following
strenuous exercise. CAFFEINE, pseudoephedrine (a
vasoconstrictor and stimulant common in cold
and allergy products), NICOTINE (tobacco), and anxiety
(stress) may also cause PVCs. PVCs require a
doctor’s evaluation when they occur
• frequently
• repeatedly over a period of time rather than in
isolation
• with CHEST PAIN or discomfort
• with lightheadedness, dizziness, or SYNCOPE
(fainting)
A doctor also should evaluate PVCs in anyone
who has diagnosed CARDIOVASCULAR DISEASE (CVD),
particularly an ARRHYTHMIA disorder. Occasionally
PVCs can trigger a more serious arrhythmia such
as ventricular tachycardia. An ELECTROCARDIOGRAM
(ECG) can identify PVCs. Because PVCs tend to be
intermittent, the doctor may use a Holter monitor
ECG, which records the heart’s electrical activity
over a period of 24 hours.
Unless PVCs indicate a serious underlying
arrhythmia, cardiologists usually do not treat them.
Often, eliminating potential causes such as caffeine
can put an end to the PVCs. The cardiologist may