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ACUTE MYOCARDIAL INFARCTION
Acute Myocardial Infarction: A Bibliographical Essay
Ashley Yotkois
Ferris State University
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Acute Myocardial Infarction is better known as a heart attack. It is one of the leading
causes of death, in men and women, in the United States. It can affect the young and old alike.
Risk factors can be inherited or modifiable. Signs and symptoms are not always the same and
neither are treatments. These will be a few topics that we will be expanding on throughout this
essay.
Acute Myocardial Infarction (AMI) is a disease process that I am extremely interested in
for a few different reasons. I am a Registered Nurse working in a critical care unit, cardiology
and critical care are the specialty areas that I prefer, so this is something that I have a great deal
of interest in. Not only do we see many patients with an AMI diagnosis, but we also have a
cardiac program that treatment can range from medical management to cardiac catheterization to
having Coronary Artery Bypass Grafting (CABG) done. I am always interested in new
medicines and technology that is being used in the field of cardiology and I plan on keeping my
feet planted somewhere in these two fields while I am working in nursing.
Another reason that I am interested in AMI is because I lost my grandfather after an
emergent CABG. He had a positive stress test, went for a scheduled cardiac catheterization, and
ended up needing emergent open heart surgery. We never got to see him after his open heart
surgery. This is what drives me to learn and be the best open heart nurse I can possibly be. It
also drives me to educate patients, in the hospital and in the community, to know their risk
factors, signs and symptoms, and what steps they should take if they think they are having an
AMI.
I began gathering my information using the FLITE library smart search. This yielded
entirely too many options and was extremely frustrating to add things to my search and continue
to have a high volume of articles, some of which had nothing to do with my topic.
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I then chose the PubMed database and initially searched “Acute Myocardial Infarction”
and disease process which yielded 206 article. I then put a time frame of 5 years on the search,
accepting anything from as far back as 2008 to ensure I had up to date information. I also
included risk factors, diagnosis, and treatment in my searches. I got a total of 83 results. Of
these 83, I read abstracts of 25 articles and chose 8.
I also did a search on STAT!Ref of “AMI” and clinical presentation. I was able to get
information from two different sources through that database as it yielded 26 results. I chose the
three references because they went over my topic and subtopics in entirety and I felt it would be
a good base of information in addition to the articles and studies I collected.
PubMed and StatRef were great databases that gave a great deal of articles from
professional journals or reference books related to my topic. They were easy to use and also
aided me in finding a diversity of exemplary sources that address not only to AMI but also to the
subtopics that are key to this subject. The subtopics are as follows:
1.
Acute myocardial infarction: disease process
2. Risk factors
3. Signs and symptoms
4. Clinical presentation and Diagnosis
5. Core measures and Treatment
This essay provides an overview of commendable sources on AMI. My goal is to deliver
a guide for practitioners to find sources that are useful in aiding the education of our patients
regarding cardiovascular health.
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Acute Myocardial Infarction
Disease Process
AMI is divided into two different classifications. These classifications are Non ST
Elevation Myocardial Infarction (NSTEMI) or Unstable Angina (UA) and ST Elevation
Myocardial Infarction (STEMI) (Reed, 2013). ”Partial occlusion of a coronary artery may cause
UA/ NSTEMI, whereas STEMI occurs when blood supply is suddenly cut off due to a complete
occlusion of a coronary artery, most often by thrombus formation at a site of vascular injury”
(Reed, 2013). This information was retrieved from the STAT!Ref Database, Scientific American
Medicine journal. Scientific American Medicine focused on AMI, more specifically on STEMI,
which is the focus of the information provided in this essay. The article, ST Elevation
Myocardial Infarction, gave an overview of the following topics: epidemiology,
pathophysiology, clinical manifestations, diagnosis, and treatment (medical and reperfusion
therapy).
According to Reed (2013), approximately 75% of AMI cases are caused by thrombus
formation typically due to repeated rupture of atherosclerotic plaque. This, as well as, platelet
aggregation and activation of the clotting cascade due to glycoprotein release and inflammatory
response will cause severe stenosis of coronary arteries which will impede blood flow to the
heart muscle (Reed, 2013). The amount of damage done to the cardiac muscle is determined by
the “severity of ischemia caused by coronary artery occlusion include whether the vessel was
partially or totally occluded, the duration of occlusion, the amount of myocardium supplied by
the culprit artery, whether collaterals are present, and the adequacy of perfusion when flow is
restored” (Reed, 2013). There are also other causes of AMI such as coronary artery spasm due
to cocaine use, embolus formation, and cardiac anomalies or defects (Reed, 2013).
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This article was very thorough however focused more toward the level of understanding
of a practioner versus a patient. Prior knowledge of inflammatory response, clotting, and
vascular physiology was necessary. Reed and Cannon’s article did give a complete overview of
all aspects of AMI and was a prime example of an article that did not focus in on one reperfusion
treatment but many.
Risk Factors
One area of information that was difficult to obtain was risk factors of heart disease. A
one-time search was conducted through the Health and Wellness Resource Center database of
heart attack. I was able to obtain an excerpt from the Gale Encyclopedia of Medicine (2011)
regarding risk factors that put someone at high risk for having a heart attack or developing
coronary artery disease. It was very general and did not explain very well as to why the
following were risk factors, however very easy for the lay person to understand. According to
Davidson (2011), there are many risk factors for heart disease, some of which are modifiable.
Modifiable risk factors include smoking, high cholesterol, hypertension, obesity, and use of
certain medications. Risk factors that are not modifiable are heredity, age, gender, race, diabetes
and long term stress (Davidson, 2011).
I also came across a pamphlet with information from the National Women’s Health
Resource Center (2005) that went into some detail as to how these risk factors affect the
cardiovascular system. According to the NWHRC (2005), smoking hardens the blood vessels
and speeds up atherosclerotic changes including narrowing of the vessels. Smoking can also
increase the formation of blood clots. This is one of the single most important modifiable risk
factors as it can compound the effects of other risk factors that one may have.
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Exercise and diet are also extremely important. Exercise can actually make the heart
muscle stronger, help control weight, and help manage diabetes (NWHCR, 2005). Diabetes is a
major risk factor that can double the chances of having a second heart attack in women as well as
triple the chance of having a heart attack versus those who do not have diabetes. Diet and
exercise is also very important in helping modifying cholesterol, controlling blood glucose
levels, and regulating HDL and LDL along with medications (NWHCR, 2005).
This pamphlet provided easy to understand, simplistic information regarding why certain
risk factors put people at higher risk for heart attack. It was geared toward women, however,
most information applied to both men and women. Information in this form is very easy to
understand and almost give step by step information to help people modify their risk factors and
decrease their chances of AMI. It would be a great piece of information for practitioners to
generate a fact sheet to hand out to their patients.
Signs and Symptoms
People need to be able to understand what is happening and what they should do. I chose
to look for information that the public would understand and retain. To find educational sources
regarding signs and symptoms of AMI I did another search in the Health and Wellness Resource
Center database. I like this database because they not only have articles and books, but they also
have a pamphlet section that gives great information that would be easily understood by medical
trained or lay persons.
According to Alexander in the Journal of Cardiovascular Medicine (September, 2008),
“A study of 3,522 patients who had recently suffered a heart attack or underwent
revascularization for severe coronary artery disease found that nearly half did not know the
symptoms of heart attack, or even perceive themselves to be at increased risk.” The classic
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symptoms of a heart attack include pressure or pain in the center of the chest, squeezing of the
chest, chest pain that radiates to the jaw and left arm, pain in the upper back or shoulder, nausea
or indigestion, dizziness or syncope, restlessness or feeling of impending doom, disorientation
and extreme fatigue (Alexander, 2008). Men typically experience the more well-known
symptoms such as the radiating pain and chest pressure while women will have the more unusual
symptoms such as fatigue and indigestion (Alexander, 2008).
This article also goes on to say that people who are having a heart attack wait to go to the
hospital. This could be a fatal mistake because, “a delay of 30 minutes can decrease your life
expectancy by 1 year” (Alexander, 2008). She also goes on to say that reperfusion of coronary
blood flow will increase your survival rate by half (Alexander, 2008). It is also important for
people to know that they should take 325mg of Aspirin or 4 Baby Aspirin. It is very important to
chew the Aspirin versus swallow it as this will help to increase blood flow as much as possible
by decreasing the “stickiness” of the platelets and causing further blockage in an already partially
blocked vessel. It is also very important to call 9-1-1 instead of transporting yourself to the
Emergency Room. There could be complications of the heart attack, such as cardiac arrest or a
lethal arrhythmia, which medical personnel can manage as well as get you to the hospital more
quickly.
This resource was simplistic and to the point. It gave the important information as well
as statistics that gave the information urgency. Although the article was slightly outdated, the
information is up to date.
According to Lippincott’s Manual of Nursing Practice (Nettina, 2014) additional signs
and symptoms that a practioner will be looking for is pallor, diaphoresis and jugular vein
distention (Nettina, 2014). You may also see tachypnea due to hypoxia, pulmonary congestion
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due to heart failure, and heart murmurs or S3 or S4 heart sounds may also be present (Nettina,
2014). Some patients, typically women and diabetics, have no symptoms at all (Nettina, 2014).
The Lippincott’s Manual is a highly used reference book for nursing students and nurses alike. It
covers all body systems as well as a large array of diseases and their treatments. It is easily
understood regarding pathophysiology and interventions.
Clinical Presentation and Diagnosis
The article “Diagnostic accuracy of the TIMI risk score in patients with chest pain in the
emergency department: a meta-analysis” is an example of an article focused on one area of AMI
and more specifically on one area that determines the probability that a patient coming into the
emergency department is experiencing a cardiac event based on a risk score of 0-7. This article
is a statistical approach to whether or not the TIMI risk score is an accurate determinant of
cardiac events. The TIMI risk score predictors are as follow: 65 years old or greater, three or
more risk factors for atherosclerosis, history of coronary artery disease (CAD), two or more
episodes of chest pain within a 24 hour period, Aspirin use within seven days of hospitalization,
ST segment elevation of .05mV or greater, and elevated cardiac enzymes (Hess et al., 2010). The
conclusion of this study was a high correlation between patients with high TIMI risk scores and
possible cardiac events.
There are multiple diagnostic tests that will help diagnose if a patient is having an
STEMI. One of these diagnostics is an Electrocardiogram or ECG. “ The American College of
Cardiology/American Heart Association has published guidelines that state a 12-lead
Electrocardiogram or ECG should be performed on a patient presenting to the ED with chest
pain within 10 minutes of arrival”(Nables, 2009). This article goes on to explain the different
characteristics of a heart rhythm that a person experiencing an STEMI may experience. Nables
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gives examples of bundle branch blocks, ST segment elevation, ventricular fibrillation, and Q
wave changes. This article also goes on to explain the pathophysiology that is causing the
changes in the ECG. This is extremely important for practitioners to know so that they can begin
planning care for this patient immediately. Early detection of STEMI could mean more heart
muscle saved.
There are also a few blood draws that will be done if a patient is suspected of having a
STEMI. These blood tests are complete Blood Count (CBC) which will show anemia. This is
important for someone having an MI who is having decreased blood flow and could be at risk for
decreased oxygenation. Hemoglobin A1C and lipid profile to test for diabetes and cholesterol.
These are modifiable risk factors but unimportant acutely.
Troponin and CPK are biochemical markers. “Injury to myocardial cells results in a
release of intracellular enzymes (cardiac biomarkers) into circulating blood, permitting their
detection” (Reed, 2013). Troponins are extremely important because it is specific to cardiac
muscle damage and is sensitive to cardiac tissue insult within 2-3 hours of onset of AMI (Reed,
2013). A troponin level will also elevate after a patient has been defibrillated or received chest
compressions due to needing cardiopulmonary resuscitation (CPR). CPK is also detects muscle
damage but is not specific to cardiac muscle ischemia and is much less valuable of a study
(Reed, 2013).
Another of the diagnostic testing that can be done is also a treatment. Cardiac
catheterization is the introduction of a sheath into the groin followed by insertion of a guidewire.
This guidewire is threaded up to the coronary arteries and contrast can be injected in order to see
if there are blockages present. Coronary Angiography will also show where and the severity of
the lesion (Nettina, 2014).
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Treatment
There are also guidelines to help manage all AMI the same way and to have the best
possible outcomes for the patients. These are called Core Measures. Treatments for AMI can
range from medication to manage symptoms to Coronary Artery Bypass Grafting (CABG).
Core Measures.
The Centers for Medicare and Medicaid (CMS) as well as the Joint Commission
(JCAHO) have assembled a set of guidelines called the Core measures for AMI. “ Use of
medications such as aspirin, betablockers, statins, and angiotensin-converting enzyme
inhibitors/angiotensin receptor antagonists in patients with acute myocardial infarction improves
long-term outcomes” (Kumbhani, 2013). These medications in addition to an ejection fraction
must be dictated on the patients chart and patient must be discharged home on Aspirin, a betablocker, and ACE/ARB if the patient has left ventricular dysfunction causing a decreased
ejection fraction (Kumbhani, 2013). These as well as smoking cessation materials are the six
Core measures.
The article “Predictors of adherence to performance measures in patients with acute
myocardial infarction” by Kumbhani et. al (2013) is a study that shows if all six Core Measures
are met during hospital stay and then continued after discharge by patient, the patient outcomes
are significantly better over time. This article is difficult to understand as it is a statistical
analysis looking at characteristics of patients, hospitals and many other factors. This importance
of this article in this paper is the proof that there is improvement in patient outcomes with
adherence to the core measures. It is also very important to mention the core measure while
talking about AMI as it is not only the gold standard of how patients need to be treated but also
how hospitals are reimbursed by the CMS.
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Medications.
The Washington Manual of Therapuetics is another source I used from STAT!Ref. It is
another great source of information that explains the components of treatments very well and
easy to understand. It is very similar to Scientific American Medicine in the sense that it
explains all aspects of the disease process very well. I did use both of these in this section due to
how well these sources explain the information. This is a great generalized source for medical
personnel to use when teaching patients about medications. Not only does it explain what the
medication is but why it needs to be taken. It is very important as health care providers to
explain to our patients why they need to take something. If the importance of the medication is
not explained well to the patient, they may have the tendency to not take it due to lack of
information and education.
Aspirin is a very effective drug for someone who is having a STEMI. An Aspirin will
make platelets slippery in order to allow them to slide through a narrowed blood vessel and
promoting as much blood flow and oxygenation to that area of the heart as possible. This is
extremely important in order help to avoid extensive ischemia to the cardiac muscle. According
to Kizilbash (2014), the dosage of Aspirin should be anywhere from 81mg to 325mg.
In addition to Aspirin, Plavix should also be included as a second antiplatelet therapy
(Kizilbash, 2014). A loading dose of 300mg to 600mg should be given prior to angioplasty and
a maintenance dose of 75mg daily after that (Kizilbash, 2014). There are other possibilities of
antiplatelet medications as well known as Prasugrel or Ticagrelor. These medications may be
used in the case of failed Plavix therapy.
Glycoprotien IIb/IIIa inhibitors work on platelet inhibition in another way than Plavix or
the other P2Y inhibitors. GPIIb/IIIa inhibitors work on the surface of the platelets therefore
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decreasing the chances of a thrombus forming in an already stenosed area of the coronary
arteries. These are usually used for a specified number of hours post intervention. The use of IV
heparin is also a possible treatment option while deciding what kind of intervention the patient
will be receiving.
Beta blockers are a medication that decreases heart rate and work load of the heart
(Kizilbash, 2014). This is considered a first line medication in people with AMI as well as a
CORE measure. The type of beta blocker and dosage can be adjusted in order to achieve a goal
heart rate of 50-60 beats per minute (Kizilbash, 2014). Beta blockers are contraindicated in
patients with bronchospasm, certain atrioventicular blocks, bradycardia, and heart failure
(Kizilbash, 2014).
Calcium channel blockers can be used with beta blockers or alone if a beta blocker is
contraindicated (Kizilbash, 2014). The heart rate lower inotropic effects are thought to be
beneficial (Reed, 2013). Recent studies have shown that calcium channel blockers can actually
cause reflex tachycardia and the only reason that they should be used in lieu of beta blockers is if
someone is beta blocker intolerant (Reed & Cannon, 2013).
ACE (angiotensin converting enzyme) inhibitors should be used with patients who have
an ejection fraction of less than 40% and if their medical history include diabetes, renal failure,
or high blood pressure (Kizilbash, 2014). “Angiotensin-converting enzyme (ACE) inhibitors
reduce blood pressure and cardiac afterload, reduce myocardial oxygen demand, and improve
ventriculoarterial coupling” (Reed, 2013). ARB’s (angiotensin receptor blockers) work to also
decrease afterload in the heart which will also work to decrease the heart myocardial oxygen
consumption by decreasing workload (Reed, 2013).
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Lipid lowering agents such as Lipitor or Zocor are also part of the CORE measures of
AMI treatment. Elevated cholesterol levels, LDL, and a low HDL put a patient at high risk of
AMI due to the buildup of plaque in the blood vessels and atherosclerotic changes (Reed, 2013).
Multiple studies show that the uses of statins drastically decrease the risk of death (Reed, 2013).
Nitrates are another group of medication that can dilate vessels, decrease coronary
vasospasm, and increase coronary blood flow (Reed, 2013). Nitrates can be used with acute
symptoms of chest pain either sublingually, topically, or in IV form. Nitrates can also be
prescribed to patients as long term everyday use in a pill form. This can aid in chronic angina.
Intervention.
In this portion of the essay we will be discussing different areas of treatments beyond
medication. “PCI has proven highly effective in the immediate treatment of acute myocardial
infarction by opening up the occluded artery and preserving viable myocardium” (Rosenfeldt,
2012). With both of these interventions, the goal is to reperfuse the cardiac muscle. Bare metal
stents or drug eluting stents can be used. Plavix or P2Y inhibitors are necessary to prevent reocclusion of the stent. The “golden standard” for this therapy is door to PCI in 90 minutes
(Rosenfeldt, 2012). Rosenfeldt (2012) also goes on to say that the deployment of stents as well
as the techniques and medications used has been improved upon so much that this procedure is
now safe for stable angina patients as well as for those who come in with AMI.
The article “Process factors affecting door to percutaneous coronary intervention for
acute myocardial infarction patients” discusses factors that affect or prohibit meeting the set
standards. I thought it was very interesting that the study showed depending on the day of the
week or time of the day, the door to PCI time fell outside of the standards (Horst, 2012). I found
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it extremely disturbing that on weekends there are ten more deaths per 1000 admissions in a year
due to prolonged PCI time (Horst, 2012).
This article was very good at looking at the areas that need to be improved upon while
observing cases that fall through the cracks due to certain factors. I believe this article can be
looked at by any hospital as a constructive way to improve their cardiac catheterization protocol
to meet standards when treating a STEMI patient.
Many hospitals have protocols or different
codes that alert cath lab staff and physicians to clear a suite and that there is someone who needs
to be seen immediately because they are experiencing a STEMI. There is also on-call staff on
weekends that have to be able to get to the hospital in a certain amount of time in order to meet
these standards of care.
While supporting the use of PCI as an effective treatment for a STEMI, the Rosenfeldt
article also supports coronary artery bypass grafting (CABG) as a very safe and effective
procedure for patients with multivessel disease. Rosenfeldt (2012) also states that more patients
that have received any type of PCI are being referred on for CABG more frequently. In this
article a side by side comparison of CABG and PCI is made. CABG is also the preferred method
of revascularization for those who have re-occluded stents, 100% blockages and for those who
need additional heart surgeries such as valve replacements or repairs (Rosenfeldt, 2012). PCI is
the preferred procedure for those patients who are not surgical candidates or are high risk
(Rosenfeldt, 2012).
Coronary artery bypass grafting (CABG) is a way of restoring oxygen rich blood to the
myocardium by bypassing the occluded vessels by using a grafted vessel from another area of
the body, typically the saphenous vein in the lower leg. CABG has shown increased survival
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rates in patients with greater than 50% left main disease, three-vessel disease, LV ejection
fraction less than 35%, and multiple other cases (Kizilbash, 2014).
All patients experiencing AMI have a long road ahead no matter what treatment options
they choose. Not only do they need to recover from a hospitalization and begin their cardiac
rehab, they also need to begin a new lifestyle. Decreasing risk factors is a large part of further
cardiac events. Weight loss, exercise, healthy diet, and smoking cessation in conjunction with
the prescribed medications are a huge part of this change. Recognizing an AMI and being aware
of the risk factors is a great way to be proactive when considering your cardiac health. The
articles and texts that I have highlighted did a great job explaining these in addition to the
medications and procedures that could be used as treatments for someone experiencing an AMI.
It is of increasing importance for all people to be aware of their risk factors for heart disease and
what to do if they are experiencing one. These sources are valuable for all healthcare providers
when educating their patients and their families or support system.
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References
Alexander, K. P. (September, 2008). Heart attack symptoms: recognition is key to survival.
Cardiovascular Medicine, pp. 3.
Davidson, T. (2011). Heart attack. L. J. Fundukian (Ed). The Gale Encyclopedia of Medicine.
(4th ed., pp.1988-1994) Detroit MI: Gale.
Hess, E. P., Agarwal, D., Chandra, S., Murad, M. H., Erwin, P. J., Hollander, J. E., . . . & Stiell,
I. G. (July, 2010). Diagnostic accuracy of the TIMI risk score in patients with chest pain
in the emergency department: a meta-analysis. Canadian Medical Association Journal,
182(10), pp. 1039-1044.
Horst, M. A, Stuart, J. J., McKinsey, N., & Gambler, A. S. (2012). Process factors affecting
door to percutaneous coronary intervention for acute myocardial infarction patients.
American Journal of Medical Quality, 27(1), pp. 16–20. DOI:
10.1177/1062860611409199. Retrieved from http://ajmq.sagepub.com.
Kizilbash, M., Parker, J. R., Sarwar, M. A., & Meyers, J. D. (2014). Ischemic heart disease: STsegment elevation myocardial infarction general principles. The Washington Manual of
Medical Therapuetics (34th Ed.) In H. Godara, A. Hirbe, M. Nassif, H. Otepka, &
Rosenstock, A. (eds.). Department of Medicine, Washington University School of
Medicine. St. Louis, MO.
Kumbhani, D. J., Fonarow, G. C., Cannon, C. P., Hernandez, A. F., Peterson, E. D., Peacock,
W., . . . & Bhatt, D. L. (January, 2013). Predictors of adherence to performance measures
in patients with acute myocardial infarction. The American Journal of Medicine, 126(1),
pp.74e1-74e9. http://dx.doi.org/10.1016/j.amjmed.2012.02.025
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Nable, J. V., & Brady, W. (2009). The evolution of electrocardiographic changes in ST-segment
elevation myocardial infarction. Journal of Emergency Medicine, pp. 734–746.
Retrieved from: www.elsevier.com/locate/ajem
Nettina, S. M. (2014) Cardiovascular function and therapy. In L. Patchkofsky (Ed). Lippincott
Manual of Nursing Practice (10th Ed). Wolters Kluwer Health | Lippincott Williams &
Wilkins.
Reed, G. M. & Cannon, C. P. (2014). ST-segment elevation myocardial infarction. Elizabeth
Nabel (Ed). Scientific American Medicine. DOI 10.2310/7900.1079
Rosenfeldt, F. L., Wilson, M.D., Buxton, B.F., & Marasco, S. F. (2012). Coronary artery Bypass
surgery provides long-term results superior to percutaneous coronary intervention. Heart,
Lung and Circulation, pp. 1-11. doi 10.1016/j.hlc.2011.08.008.