As well, there are correlations, though
researchers do not fully understand them, among
BIRTH DEFECTSinvolving the heart that occur in con-
junction with specific birth defects affecting other
body structures. About a third of infants born with
ESOPHAGEAL ATRESIA(incomplete formation of the
ESOPHAGUS) also have the heart malformation
patent ductus arteriosus (PDA). Heart malforma-
tions are also common in children who have NEURAL
TUBE DEFECTSsuch as SPINA BIFIDA. These correlations
strongly suggest GENEmutations.
Gender and race are other hereditary factors
that influence the development of cardiovascular
conditions. Men, until about age 60, have three to
five times the risk for CORONARY ARTERY DISEASE
(CAD) and HYPERTENSION (high BLOOD PRESSURE).
Men under age 60 are also more likely to have
HEART ATTACKor STROKE. The risk for cardiovascular
disease is exponentially higher among African
Americans. Hypertension is the leading cause of
stroke and kidney failure among African Ameri-
can men between the ages of 35 and 50.
Other forms of cardiovascular disease that tend
to “run in the family” may have genetic underpin-
nings that manifest with interplay from certain
lifestyle factors such as cigarette smoking, lack of
physical exercise, and eating habits. Such cardio-
vascular conditions include hypertension (high
blood pressure), ATHEROSCLEROSIS, CAD, and PERIPH-
ERAL VASCULAR DISEASE (PVD). Evidence is very
strong that appropriate lifestyle interventions can
delay or even prevent the onset of such conditions
despite any genetic predisposition.
See also CARDIOVASCULAR DISEASE PREVENTION;
LIFESTYLE AND CARDIOVASCULAR HEALTH; RISK FACTORS
FOR CARDIOVASCULAR DISEASE.
homocysteine An amino acid in the BLOODthat
the body’s METABOLISMof the essential amino acid
methionine produces. (An essential amino acid is
one the body cannot synthesize itself but must
obtain from dietary sources.) B vitamins and folic
acid are necessary to break down homocysteine.
Accumulation of homocysteine in the blood
circulation appears to accelerate development of
ATHEROSCLEROSIS. In the mid-1990s researchers dis-
covered a connection between elevated blood
homocysteine levels and early atherosclerosis.
Doctors had known since the 1960s of a rare
genetic condition, homocystinuria, that caused
extensive atherosclerotic disease in teens and
young adults. But new research led them to corre-
late atherosclerosis with elevated homocysteine
levels in adults who had no known genetic foun-
dation for them.
Some researchers believe that elevated homo-
cysteine irritates the inside walls of the arteries.
The irritation causes INFLAMMATION, which opens
the way for ATHEROSCLEROTIC PLAQUEto infiltrate
the intima, the innermost layer of the arterial
walls. People between the ages of 45 and 60 who
have significant atherosclerosis or CORONARY ARTERY
DISEASE (CAD) often have elevated homocysteine
levels. In people who have elevated homocysteine
levels, atherosclerosis may develop more rapidly
and at earlier ages. However, research studies as
yet have not established a cause and effect rela-
tionship between elevated homocysteine and early
atherosclerosis.
A blood test can measure the homocysteine
level in the blood. Most doctors view homocys-
teine as a risk factor for CARDIOVASCULAR DISEASE
(CVD), though not one that is alone significant
enough to cause cardiovascular disease. They rec-
ommend people receive the minimum daily
amounts of vitamins B 6 , B 12 , and folic acid
through dietary sources when possible and with
supplements if necessary, as a matter of general
health as well as to aid in breaking down homo-
cysteine. People who have elevated homocysteine
levels along with other RISK FACTORS FOR CARDIOVAS-
CULAR DISEASEshould do what they can to reduce
their overall risks, though health experts do not
advise folic acid supplementation beyond the rec-
ommended intake (400 micrograms daily for an
adult) as a preventive measure for cardiovascular
health. Adequate folic acid intake appears essen-
tial for numerous health reasons, and may help
reduce the risks for other health conditions.
See also COENZYME Q 10 ; DIET AND CARDIOVASCULAR
HEALTH; NEURAL TUBE DEFECTS.hyperlipidemia A disorder of lipidMETABOLISM,
also called hyperlipoproteinemia, that results in
abnormally high levels of cholesterol, triglycerides,
and lipoproteins in the BLOODcirculation. Hyper-
lipidemia is a key contributor to ATHEROSCLEROSIS,
CORONARY ARTERY DISEASE(CAD), and PERIPHERAL VAS-64 The Cardiovascular System