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CORONARY ARTERY DISEASE 1

Coronary Artery Disease

A Public Health Perspective

MPH 510: Applied Epidemiology

Concordia University, Nebraska

Andrea Eden-Shingleton

4/22/2015


BackgroundDisease and Setting

Coronary artery disease (CAD) is a major cause of death and disability in the developed

world. (Wilson & Douglas, 2015). In the US, about 2,150 Americans die each day from heart

disease, one every 40 seconds. (American Heart Association, 2014). Figure 1 shows the number

(in thousands) of deaths attributable to diseases of the heart in the US from 1900-2010.

(American Heart Association, 2014) In this paper, I will focus on the screening test available for

asymptomatic adult residents of the State of Ohio. The age-adjusted heart disease mortality rates

in Ohio have continued to exceed the rates for the United States from 1999–2006. (Ohio

Department of Health, 2009) The prevalence of modifiable risk factors is higher for Ohio as

compared to the United States. (Ohio Department of Health, 2009)

Introduction

50% of patients with atherosclerotic disease (CAD) are asymptomatic; they present with

either ischemic heart disease or sudden death. Yearly, for 150,000 individuals suffer a fatal heart

attack as their the first symptom of heart disease. (American Heart Association, 2004) These

individuals die suddenly without knowing they are at risk for heart disease and are unable to

receive treatment. Making a strong case for prevention, the CDC (2008) declares that sudden

death and the high cost of disability to individuals and their families are the best reasons to have

widely accessible screening programs. The CDC (2008) reported that the annual cost of CAD to

the nation in 2002 exceeded $350 billion. Including direct health care costs (for hospital and

nursing home care, physicians and other professionals, drugs and other medical durables, and

home health care) and indirect costs (due to lost productivity from disability and death), this total


cost substantially exceeded comparable expenditures for all cancers ($202 billion) and for human

immunodeficiency virus (HIV) infections ($28.9 billion) reported in 2002. (CDC, 2008, p. 17)

Figure 2 is a visual representation from the American Heart Association (2014) of the projected

escalating cost (total dollars in billions) of heart disease until 2030.


Figure 1

Figure 2


Epidemiology of Coronary Artery Disease

When 610,000 Americans die yearly of any disease, an epidemiologic understanding is

needed. (Center for Disease Control, 2015) Coronary artery disease is a highly preventable, but

has a high death rate due to its insidious nature. According to the National Institute of Health

(2014), taking years to slowly develop layers of fatty deposits in the circulatory system,

atherosclerosis is defined as cholesterol plaques hardening and narrowing the arteries; see figure

3. As the vessels become narrower, the potential for blood clots increase and so does the risk of

sudden death. (National Institute of Health, 2014) Another silent killer, high blood pressure

compounds the constriction of the atherosclerotic arteries; the heart is deprived of oxygen-rich

blood. (Mayo Clinic Staff, 2014) The heart muscle dies quickly without adequate blood supply;

those who survive a heart attack can be faced with the debilitating chronic ailments of congestive

heart failure and arrhythmias. (National Institute of Health, 2014)

Figure 3: Atherosclerosis in Coronary Artery and Heart Attack: (medicinenet.com, 2014)


Specific target population for screening for CAD

With rising cost and a high death rate, CAD risk factors need to be identified and

screened for in appropriate populations. Due to the complex nature of chronic illnesses like heart

disease, the American College of Cardiology (ACC) and the American Heart Association (AHA)

have developed clinical practice guidelines for assessment of cardiovascular risk, lifestyle

modifications to reduce cardiovascular risk, management of blood cholesterol in adults, and

management of overweight and obesity in adults in collaboration with the National Heart, Lung,

and Blood Institute (NHLBI) and other professional organizations. (Goff Jr., Lloyd-Jones,

Bennett, Coady, D’Agostino Sr., & Gibbons, 2014) Decades of research studies were

systematically reviewed to develop a pertinent strategy for reduction of deaths from heart

disease. (Goff Jr., Lloyd-Jones, Bennett, Coady, D’Agostino Sr., & Gibbons, 2014)

Researchers have found that adults, men and women, all races over the age of 40 should

be screened at their yearly physical with a primary care doctor due to behavior modifiable risk

factors. (Goff Jr., Lloyd-Jones, Bennett, Coady, D’Agostino Sr., & Gibbons, 2014) The National

Center for Biotechnology Information (NCBI, 2001) exerts that several behaviors have a strong

influence on health including diet, tobacco use, alcohol consumption, physical activity and

disease screening. Evidence has been available since the early 1980’s concerning the relationship

of certain behaviors to chronic diseases; more causal and conclusive sophisticated research like

dose-relationship studies has cemented the association. (NCBI, 2001) The slow developing

nature of heart disease in conjunction with the strong causal relationship of modifiable behaviors

demands early intervention for prevention of death due to CAD. Smoking is one of the most

preventable risk factors for stroke and heart disease and greatly elevates the risk of developing

disease. According to the Ohio Department of Health (2009) nearly one quarter (23.1 percent) of


Ohio adults currently smoke. In 2007, Ohio had the eighth-highest smoking prevalence in the

nation. (Ohio Department of Health, 2009) Because high blood pressure increases a person’s risk

of developing heart disease, stroke and other serious conditions, Ohio’s plan noted that in 2005,

nearly one-third of Ohio adults reported having high blood pressure. (Ohio Department of

Health, 2009) Additionally, one in ten Ohioans has been diagnosed with diabetes; another

modifiable risk factor. (Ohio Department of Health, 2009)

Common screening tests for CAD and Epidemiological data for the different tests

The common screening tests for CAD range from free to expensive, no risk to high risk

and no equipment to advanced equipment with highly trained personnel. The least expensive,

non invasive test is a cardiac risk questionnaire. Taking the questionnaire in a clinic or primary

care office, the clinician can contain basic demographic/ anthropometric information, behavioral

risk factors, genetic/ familiar links, co-morbidities and biochemical markers. This information

can be scrutinized to establish a 10 year risk assessment for future heart attack. (National Heart,

Lung and Blood Institute, 2014) Researchers have identified aging as a risk, specifically, men

over 40 years and women over 45 years. (Mayo Clinic Staff, 2014) The Mayo Clinic staff also

identify blood pressure and body mass index (BMI) are additional measurements that influence

the odds.(2014) A family history of heart disease, stroke and high blood pressure increases

possibility of CAD. (American Heart Association, 2014) Co-morbidities like diabetes and

hypercholesterolemia are also linked to heart disease. (Center for Disease Control, 2008)

Dietary habits, tobacco use and physical activity are strongly linked to CAD and are modifiable

factors. (American Heart Association, 2014) See Table below for common screening tests, their

costs and epidemiological data ( n/a- denoted that data was not available.)


Common Screening Test

Cost

Equipmentneeded

Sensitivity Specificity PV+ PV-

Questionnaire at home

$0 questions n/a n/a n/a n/a

Questionnaire at clinic

$0-150* Primary Care practice

n/a n/a n/a n/a

Blood test(Cholesterol, etc.)

$0-150* Access to lab n/a n/a n/a n/a

Blood pressure $0-30* Blood pressure monitor

n/a n/a n/a n/a

Electrocardiogram $500-3000*

ECG machine + cardiologist

89% 1

(with Chest Pain)

80%1

(with chest pain)

n/a n/a

Exercise Stress Test

$1000-5000*

Stress Lab + cardiologist

69%2

67%336%2

72%378%2 27%2

Myocardial Perfusion Imaging

$50-350* CT scanner +cardiologist

87%4

With chest pain

73%4

With chest pain

n/a n/a

EBCT Scanning(electron beam computerized tomography)

$50-350* CT scanner +cardiologist

62-78%5 78-100%5 83-100%5

n/a

Coronary CT angiography

$5000-10000

CT scanner+ cardiologist

98%2 74%2 90%2 94%2

*estimated cost from (Health Cost Helper, 2014)2 Information from (Ravipati, et al., 2008)

3Information from (American Heart Association, 1997)4 Information from (Fathala, 2011)5 Information from (Clouse, 2006)

Accuracy of Exercise Stress Test as a Screening Test for CAD

Chronic diseases like coronary heart disease are multi-factorial. Reducing morbidity and

mortality from CAD, two screening strategies recommended by NCBI (2001) need to be

implemented. The first involves screening for modifiable cardiac risk factors, such as

hypertension, elevated serum cholesterol, cigarette smoking, physical inactivity, and diet.


(National Center for Biotechnology Center, 2001, p. 1) The second strategy is early detection of

asymptomatic CAD; screening tests for this silent killer include resting electrocardiograms and

exercise stress testing. (National Center for Biotechnology Center, 2001) Myocardial Perfusion

scanning and EBCT are less commonly used for screening purposes due to cost and will not be

discussed in detail in this paper.

Resting electrocardiogram (ECG) findings include ST depression, T-wave inversion, Q

waves, and left axis deviation; all of which increase the likelihood of coronary atherosclerosis

and of future coronary events. (National Institute of Health, 2014) However, these findings are

uncommon in asymptomatic persons, occurring in only 1-4% of middle-aged men without

clinical evidence of CAD (Sox, Garber, & Littenberg, 1989) and they are not specific for

CAD. Routine ECG screening testing in asymptomatic persons with low 10 year risk of heart

attack is relatively low, is not an efficient process for detecting CAD or for predicting future

coronary events. (National Center for Biotechnology Center, 2001) In patients with active

CAD symptoms like chest pain, the sensitivity is 89% and the specificity 80%. (National

Institute for Health and Clinical Excellence, 2010)

According to research, the exercise ECG is more accurate than the resting ECG for

detecting clinically important CAD and in predicting future coronary events. (National Center

for Biotechnology Center, 2001) ECG changes often do not become apparent until an

atherosclerotic plaque has progressed to the point that it significantly impedes coronary blood

flow. (Epstein, Quyymi, & Bonow, 1989) Historically, a 1989 meta-analysis found considerable

variability in the accuracy of exercise-induced ST depression for predicting CAD (sensitivity 23-

100%, specificity 17-100%) (Gianross, Detrano, Mulvihill, & al, 1989) Currently, a literature


review determined the diagnostic accuracy of exercise stress testing for CAD. Banerjee,

Newman, Van den Bruel, & Heneghan (2012) examined prospective studies comparing exercise

stress testing with a reference standard of coronary angiography in patients without known CAD.

After analyzing 34 studies with 3,352 participants, the prevalence of CAD ranged from 12% to

83% and the positive and negative likelihood ratios of stress testing increased in low prevalence

settings. (Banerjee, Newman, Van den Bruel, & Heneghan, 2012) Treadmill echo testing (LR+ =

7.94) performed better than treadmill ECG testing (LR+ = 3.57) for ruling in CAD and ruling out

CAD (echo LR− = 0.19 vs. ECG LR− = 0.38). Bicycle echo testing (LR+ = 11.34) performed

better than treadmill echo testing (LR+ = 7.94), which outperformed both treadmill ECG and

bicycle ECG. This meta-analysis concluded that a positive exercise test is more helpful in

younger patients (LR+ = 4.74) than in older patients (LR+ = 2.8). (Banerjee, Newman, Van den

Bruel, & Heneghan, 2012, p. 487)

Ethical considerations in public health professional for CAD screening

There are many ethical considerations in public health. Specifically, for screening test for

CAD, the principle of justice and beneficence are paramount. Justice is equity or fairness,

especially regarding the fair distribution of benefits in the targeted population of a screening test

for CAD. (Weed & McKeown, 2001) It is evident from the higher mortality and morbidity rates

in impoverished neighborhoods that there is a lack of fair distribution of services. (Weed &

McKeown, 2001) Beneficence involves an obligation to promote benefits of things judged to be

good, weighing produced good against risks. (Weed & McKeown, 2001) In public health,

beneficence implies acting in the best interest of the population in need of prevention strategies

for the number one killer of Americans and Ohioans; heart disease. Epidemiologists must partner


with governmental systems to create programs that not only create awareness of heart disease

risks, but also provide affordable screening test and treatments.

Recommendations

What screening test would you recommend for adults in Ohio. Why?

When examining the various screening test available, there are a few that can be

immediately ruled out. The American College of Cardiology and the American Heart

Association do not recommended invasive testing like Coronary Artery Angiogram as first line

diagnostic test for patients presenting to emergency rooms with chest pain, due to the cost and

risk to patients; making it simple to rule this out as a screening test. Non invasive testing is safer

for patients, but some of them are expensive, making them implausible for a large scale

screening program. Tests like Myocardial Perfusion Imaging and EBCT requiring fluoroscopy,

which according to Wexler, et al (1996) is widely available, but it has several disadvantages.

The detection of calcium-depositing plaque is dependent on the skill and experience of the

operator, the number of views studied and motion of breathing artifacts. (Wexler, et al., 1996)

All factors limiting its be taken into the community.

Exercise stress testing is a well-established procedure that has been in widespread clinical

use for many decades. (Ravipati, et al., 2008) Although exercise testing is generally a safe

procedure, both myocardial infarction and death have been reported and can be expected to occur

at a rate of up to 1 per 2500 tests. (Banerjee, Newman, Van den Bruel, & Heneghan, 2012) It is

apparent that the true diagnostic value of the exercise ECG lies in its relatively high specificity,

accurately identifying patients without CAD and alerting clinicians of individuals in need of

further testing. (Ravipati, et al., 2008)


When examining the Likelihood Ratios (LR) for different testing modalities (see figure

4), Banerjee, Newman, Van den Bruel & Heneghan (2012) concluded that the diagnostic

accuracy of exercise testing varies, depending upon the age, gender and clinical characteristics of

the patient, the prevalence of CAD, and the modality of test used. The study found that exercise

stress testing seems most useful in low and intermediate prevalence. In high prevalence, the

change in probability will not lead to the exclusion or definite inclusion of CAD. (Banerjee,

Newman, Van den Bruel, & Heneghan, 2012) In young patients and in men, a positive exercise

test is better at discriminating CAD than in older patients and women. (Banerjee, Newman, Van

den Bruel, & Heneghan, 2012)

Figure 4 meta-analysis of included studies by patient subgroup, exercise test modality and risk of CAD


The accuracy of the exercise ECG for diagnosis of coronary disease in women can be

problematic. Exercise-induced ST depression is less sensitive in women than men, reflecting a

lower prevalence of severe coronary disease and the inability of many women to exercise to

maximum aerobic capacity. (Banerjee, Newman, Van den Bruel, & Heneghan, 2012) Studies

that demonstrated lower specificity in women have cited lower disease prevalence, non-Bayesian

factors, and possible hormonal differences. (Gianross, Detrano, Mulvihill, & al, 1989)

Banerjee, Newman, Van den Bruel & Heneghan (2012) report that interpretation of

exercise tests in the elderly differs somewhat from younger patients due to resting ECG

abnormalities. Nonetheless, the application of standard ST-segment response criteria to elderly

subjects is not associated with a significantly different accuracy from younger patients.

(Banerjee, Newman, Van den Bruel, & Heneghan, 2012) Due to the greater prevalence of both

CAD and severe CAD, it is not surprising that exercise testing in this group is reported to have a

slightly higher sensitivity than in younger patients. (Banerjee, Newman, Van den Bruel, &

Heneghan, 2012) A slightly lower specificity has also been reported, which may reflect the

coexistence of LVH due to valvular disease and hypertension. (American Heart Association,

1997) Regardless of the variability of the patient characteristics, the exercise stress test provides

a high accuracy for predicting future myocardial events. (Clouse, 2006)

How you would you go about increasing the participation levels in the screening?

Making exercise stress testing more readily available and lowering the cost is the way to

increase awareness and participation. Free public health screenings events are a great arena to

introduce the community to exercise stress testing. Additionally, mobile testing centers could

travel to neighborhoods where little to no primary care services currently exist. Employers can


increase employee awareness and promote incentive-bases healthy living programs where

occupational nurses could make referrals or invite mobile testing centers to screen employees

yearly on-site. All of these ideas will increase participation. Not only would the test be available

for little to no cost to communities, the educational awareness in the workplace would increase,

with the positive consequence of decreasing sudden cardiac death.

It is imperative for public health to play an increasing role in implementing and

sustaining evidence-based screening programs. When an epidemiologist travels to a field

assignment for an outbreak investigation, they use proven scientific methods to resolve the

deadly incident. Chronic diseases require more tenacity than outbreaks due to their multi-

factorial and insidious nature. Even if a job is difficult, the public health professional has an

ethical obligation to the public to not give up. It is our duty to influence governmental and non-

governmental agencies; shining the light on the importance of prevention of chronic disease.

Public Health organizations can provide evidence-based research to justify allocation of funds to

screening tests and policy changes.


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