Diabetes. Diabetes increases the risk of coronary artery disease. have increased rates of obesity and diabetes which increases their risk factors. …
Coronary Artery Disease Background
Normal Coronary Artery Anatomy
There are two main epicardial, or surface coronary, arteries - right
coronary artery and left main coronary artery They both arise from the
root of the aorta near the left ventricle at the aortic sinuses The
coronary arteries supply blood, and thereby oxygen and other nutrients, to
the heart muscle surface as well as the muscular walls via endocardial
branches Blood flow through the coronary arterial system occurs almost
exclusively during diastole when the ventricles are filling and ventricular
muscle fibers are in a relaxed state Coronary blood flow depends upon the
driving pressure systemic diastolic pressure and resistance to flow
within the coronary vascular bed
The exact course of the major coronary vessels and their branches is
variable The most common patterns are presented in the following chart:
|Artery |Distribution |
|Right Coronary |Right atrium RA, most of right ventricle RV |
|Artery RCA |SA node 60, AV node 90, portion of both bundle |
| |branches
|
| |Origin of posterior descending artery 86 |
| |Origin of Marginal artery feeding RV |
|Left Main |Bifurcates quickly into left anterior descending |
|Coronary Artery |artery LAD and left circumflex artery LCA |
|LMCA | |
|Left Anterior |Anterior left ventricle LV |
|Descending |Anterior interventricular septum and adjacent RV |
|Artery LAD |Proximal and inferior portions of LV RV and apex |
| |Portions of both bundle branches, AV node 10 |
|Left Circumflex |Left atrium LA |
|Artery LCx |Lateral and inferior walls of LV |
| |SA node 40 |
| |Origin of posterior descending artery 12 |
|Posterior |Posterior LV |
|Descending |Posterior interventricular septum |
|Artery PDA |Half of the inferior LV |
As you can see from the chart, the
PDA can arise from the RCA 86 or the
LCA 12
and in rare cases 2, equally from both The three patterns of coronary
circulation are determined by which artery is primarily responsible for the
blood supply to the posterior wall of the LV; therefore, 86 of the
population is right dominant, 12 left dominant, and 2 balanced It should
also be apparent from reviewing the information in the above chart that the
majority of blood supply to the ventricles, apex, and bundle
branches/purkinjes distal electrical system is via the left coronary
arterial system and the majority of blood supply to the AV and SA nodes
proximal electrical system is via the right coronary arterial system
A right dominant system is viewed in the above graphic Our patient,
Damien, has this particular coronary arterial design
Before discussing coronary artery disease, a review of normal arterial
wall anatomy is in order Arteries consist of 3 layers: intima, media, and
adventitia The intima, or inner-most layer, is lined with endothelial
cells The media, or middle layer, consists mostly of smooth muscle cells
The outer most layer, or adventitia, consists mainly of collagenous elastic
fibers and blood vessels vasa
vasorum Arteries not only transport blood
and nutrients through their lumens, but they are also responsible for
transporting selected plasma proteins through the intima to the adventitia
and then into the lymphatic system It is the disturbance of this selective
transport process that acts as the prime mechanism for atherogenesis
Endothelial cell injury and concomitant lipid infiltration into the media
sets the stage for plaque formation that will be discussed later
Coronary Artery Disease
Etiology Epidemiology: Coronary artery disease is the most common type of
heart disease, affecting nearly 13 million Americans When the coronary
artery becomes blocked, the area of the heart supplied by that artery
becomes ischemic and infarction may result Angina pectoris, congestive
heart failure CHF and myocardial infarction MI are collectively called
coronary artery disease CAD CAD includes atherosclerosis hardening of
the arteries secondary to increased plaques, thrombus blood clots and
intermittent constriction spasm Each year, more than 500,000 Americans
die of complications of coronary artery disease CAD is slow in developing
and can be virtually
unnoticed until a person suffers a heart attack
Coronary artery disease is the leading cause of death for both men and
women in the United States
Risk Factors: Several factors increase the risk of coronary artery disease
Some of the risk factors are controllable while others are not Three major
controllable risk factors are smoking, high blood pressure and high
cholesterol Exposure to cigarette smoke acts with other factors to greatly
increase the risk of coronary artery disease by damaging blood vessels,
while blood pressure greater than 115/75 can damage coronary arteries As
blood cholesterol levels rise, so does the risk of developing CAD Nearly
95 percent of people who developed a fatal cardiovascular disease had at
least one of these major risk factors A poor diet and being overweight
also contribute to cardiovascular disease Mayo clinic staff, 2004
Other risk factors include:
Physical inactivity Regular exercise is important in preventing heart
disease
Age 40 years old Most people who die of coronary artery disease are
older than 65
Male Men are generally at greater risk than are women for heart disease
The risk for women increases after menopause
Family
history Siblings, parents or grandparents who have heart disease
may increase a persons risk of developing CAD The patient may also be
predisposed and have a genetic condition that contributes to higher blood
cholesterol levels or high blood pressure Cultural habits and traits may
increase a persons risk factor by contributing to unhealthy habits such
as eating unhealthy, inactivity and smoking
Race African-Americans Caucasian African-Americans have a higher risk
of heart disease and high blood pressure than do whites Mexican-
Americans, American Indians and native Hawaiians also have an increased
risk of heart disease
Obesity especially upper bodyExcess weight increases the strain and
stress on the heart, raising blood pressure, increasing blood cholesterol
levels and increases the risk of developing diabetes With the rising
rates of obesity in younger Americans, more people may start developing
coronary artery disease at an earlier age
Diabetes Diabetes increases the risk of coronary artery disease The
risk increases if blood sugar glucose levels arent well controlled
Stress levels, type A personalities Stress and anger can increase
the
risk of coronary artery disease, especially as they may contribute to
participation in unhealthy habits, such as overeating, smoking and
inactivity
Low concentration of HDL in the blood, high concentration of fatty
compounds, and increased LDLs in the blood Goodman Snyder, 1995 A
high blood level of low-density lipoprotein LDL cholesterol bad
cholesterol can lead to atherosclerosis Higher levels of the good
HDL cholesterol, high-density lipoprotein HDL, may protect against
heart disease
A gene has been identified on chromosome 19, near the gene to LDL
receptor The gene has been called the atherosclerosis susceptibility
gene It ahs been reported that it may account for nearly 1/2 of all
cases of atherosclerosis Nishina, et al 1992 Ongoing research has
indicated that C-reactive proteins, homocysteine, fibrinogens and
lipoproteins may also play a role with regard to increased risk factors
Risk factors that are combined together may also increase the risk for
coronary artery disease Metabolic syndrome, also known as syndrome X,
includes obesity, abnormal cholesterol levels, high blood pressure and
insulin resistance
Further research indicates that a bacterium, such as Chlamydia
pneumoniae, may play a role in the narrowing of coronary arteries,
leading to CAD
Damien Cesar is a prime candidate for severe CAD based on the risk
factors He is African American, male, and 40 years old He has Type I DM,
HTN, high cholesterol, and a family history of CAD along with 2 previous
myocardial infarcts in his 30s These risk factors, along with his
relatively sedentary lifestyle exponentially magnify his heart disease and
increase his risk of future infarcts and/or sudden death If he can
maintain control of his HTN and DM, reduce his cholesterol, and safely
increase his physical activity level, he may be able to reduce that high
risk
Pathophysiology: According to Cohen Michel 1988, the pathogenesis of
CAD follows a set process: injury to the endothelial cell wall attributed
to various aforementioned risk factors which attracts platelet
aggregation, fibroblastic proliferation in the intima, and accumulation of
lipids at the junction of the arterial intima and media The initial
formation is termed a fatty streak because of the amount of lipid LDL-
laden monocytes and macrophages that flood the region
due to increased
endothelial permeability This leads to smooth muscle cell proliferation
and migration into the intima Faxon et al, 2004 Inflammatory processes
marked by C-reactive proteins, cytokines, and macrophages serve to further
atherosclerotic formation As fatty streaks progress to advanced lesions,
fibrous plaques develop around the lesions to wall them off from the
arterial lumen In the early phases of atherosclerosis, the lumen diameter
is minimally affected by plaque growth due to the adventitias elastic
fibers expansion ability This is termed positive remodeling At a certain
point, the arterial wall can expand no further and the luminal diameter
begins to shrink This is termed negative remodeling or obstructive disease
Varnava, 2002 Negative remodeling is also associated with calcification
of the atherosclerotic plaque Severe arterial stenosis creating cardiac
muscle hypoxia or rupture of the plaque creating a thrombosis leads to an
acute coronary event It is interesting to note that most plaques occur at
bends, branches, and bifurcations of coronary arteries implicating altered
laminar blood flow sites in the development of atherosclerosis
Damiens CAD is of the
negative remodeling type His cardiac
catheterization showed high levels of stenosis in 3 vessels In fact, the
LAD artery was totally occluded and the RCA was 80-90 occluded
Race/Cultural Issues and CAD
African-Americans have a higher risk of CAD as compared to whites;
however, more white men die from CAD African-Americans have increased
blood pressure overall A study by Clark et al 2001 found that African
Americans have the highest overall mortality rate from CAD of any ethnic
group in the United States They were also found to have a higher risk of
sudden cardiac death and present more often with unstable angina and MI
than whites Damiens cardiac picture aligns with these facts and places
him at a high risk for sudden death if he does not change his lifestyle and
modify the appropriate risk factors
Clark et al also reported less obstructive CAD on angiography but
greater amounts of atherosclerosis with positive remodeling in African
Americans They identified the disproportionately high prevalence and
severity of hypertension and diabetes in African Americans as the likely
culprit Native Americans have increased rates of obesity and
diabetes
which increases their risk factors Heart disease risk is also higher
among Mexican-Americans, American-Indians, native Hawaiians, and some Asian-
Americans National Heart, Lung, and Blood Institute The major
difference is that these populations have decreased cholesterol levels
overall and this helps decrease their overall risk Although factors such
as high blood cholesterol can be an inherited factor, it is also a result
of poor health habits, such as eating a high-fat, high-cholesterol diet,
which is now a common American diet In fact, according to a study by
Mooteri et al 2004, duration of residence in the United States is
emerging as an independent risk factor of CAD in the immigrant population
Unfortunately, we have no information, at this time, on Damiens dietary
habits
References
Blessey, RL 1990 Atherosclerosis: an overview of the basic mechanism
of
atherogenesis, pathophysiology, and natural history In S Irwin J
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al 2001
Coronary heart disease in African
Americans Heart Disease, 32, 97-
108
Dean, E and Hobson, L 1996 Cardiopulmonary anatomy In D Frownfelter
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Dean Eds, Principles and practice of cardiopulmonary physical
therapy
pp 23-51 St Louis: Mosby - Year Book, Inc
Faxon, DP, Fuster, V, Libby, P, et al 2004 Atherosclerotic vascular
disease
conference:writing group III: pathophysiology Circulation, 109,
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Mayo clinic staff 2004 Novel risk factors: identifying new culprits in
heart disease
Retrieved February 15, 2005 from http://wwwmayocliniccom
Mooteri, SN, Petersen, F, Dagubati, R, and Pai, RG 2004 Duration
of residence in
the United States as a new risk factor for coronary artery disease
American
Journal of Cardiology, 933, 359-361
Varnava, AM, Mills, PG, and Davies, MJ 2002 Relationship between
coronary
artery remodeling and plaque vulnerability Circulation, 105, 939-
943
Watchie, J 1995 Cardiology In Cardiopulmonary physical therapy: a
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Source:acicpt.com
