Facts on File Encyclopedia of Health and Medicine

For further discussion of the SA node within
the context of cardiovascular structure and func-
tion please see the overview section “The Cardio-
vascular System.”
See also BUNDLE BRANCH; BUNDLE BRANCH BLOCK;
CARDIAC CYCLE; SICK SINUS SYNDROME.

smoking and cardiovascular disease CARDIOVAS-
CULAR DISEASE(CVD) is the most frequent and sig-
nificant consequence of cigarette smoking, with
smoking accounting for one in six deaths due to
CVD. Smoking significantly increases the risk for
HYPERTENSION(high BLOOD PRESSURE), ATHEROSCLERO-
SIS, and CORONARY ARTERY DISEASE(CAD). The combi-
nation of cigarette smoking and using oral
contraceptives (birth control pills) presents a par-
ticular risk of BLOODclot formation in women,
especially women over age 35. This raises the risk
forSTROKEand HEART ATTACKsuch that many doc-
tors will not prescribe oral contraceptives for
women who smoke. Smoking is also a key factor
in numerous pulmonary diseases, affecting the
cardiovascular system’s ability to circulate oxygen-
rich blood.
The US Surgeon General offered the first con-
clusive evidence of the correlations between
smoking and cardiovascular disease in the land-
mark 1964 report, Smoking and Health: Report of the
Advisory Committee to the Surgeon General of the Public
Health Service. Researchers have since continued to
accumulate knowledge and understanding of the
mechanisms through which smoking affects car-
diovascular health. Cigarette smoke contains more
than 2,000 identifiable chemicals, dozens of which
are carcinogenic (CANCER-causing) or have other
deleterious actions on health. Two in particular,
NICOTINEand carbon monoxide, are highly toxic to
the cardiovascular system.

Nicotine and Cardiovascular Function

NICOTINEis a CENTRAL NERVOUS SYSTEMstimulant that
acts on nerves throughout the body. In the cardio-
vascular system, nicotine stimulates the nerves
that regulate smooth MUSCLE tissue, causing
smooth muscle cells to contract. This constricts
blood vessels, notably arteries, reducing the chan-
nel for blood flow. Nicotine further stimulates the
baroreflex sensors (clusters of NERVEcells in the
major arteries and the heart that sense the flow

and pressure of blood). These actions result in

increased blood pressure, HEART RATE, and cardiac

workload. Nicotine further acts as an irritant

within the arteries, causing INFLAMMATIONof the

inner layer of the arterial wall. Researchers believe

such inflammation may be the foundation for ath-

erosclerosis.

Carbon Monoxide and Cardiovascular Function

Carbon monoxide is a poison. It has a greater

affinity than oxygen for HEMOGLOBIN and binds

with hemoglobin, blocking hemoglobin from car-

rying oxygen. This reduces the amount of oxygen

that enters the bloodstream from the LUNGS. By

the end of a cigarette, a smoker can have concen-

trations of carbon monoxide as high as 7 percent;

10 percent is the level at which symptoms of car-

bon monoxide poisoning begin to become appar-

ent. Carbon monoxide in the bloodstream

deprives cells in the BRAINand heart, which rely

on oxygen for fuel.

Environmental Smoke Exposure

Cigarette smoke also raises the risk for health

problems, including cardiovascular disease, among

people who are themselves nonsmokers though

live or work in a smoking environment. Children

are at particular risk. Numerous studies show the

children of smokers have more EAR infections,

sinus infections, and upper respiratory infections

than children who live in smoke-free environ-

ments. Long-term exposure to ENVIRONMENTAL CIG-

ARETTE SMOKE, called passive smoking, has the

same health consequences as active smoking.

Smoking Cessation

The health risks of cigarette smoking diminish

within 30 to 40 minutes of the last puff. With sus-

tained SMOKING CESSATION, the risk for cardiovascu-

lar disease gradually diminishes over 5 to 10 years,

finally reaching a level consistent with the risks

for a nonsmoker. Any damage that has already

occurred to the cardiovascular system is perma-

nent, however.

See alsoANTISMOKING EFFORTS; CARDIOVASCULAR

DISEASE PREVENTION; CONTRACEPTION; HEALTH RISK

FACTORS; INHALED TOXINS; LIFESTYLE AND CARDIOVASCU-

LAR HEALTH; SMOKING AND CANCER; SMOKING AND

HEALTH.

smoking and cardiovascular disease 105