Acute coronary syndromes

So far you have learned the essential elements of cardiac assessment, and rhythm and ECG analysis. In this section the focus is on
caring for the patient who is suffering acute coronary syndrome. This encompasses myocardial ischemia as well as acute myocardial
infarction (AMI). The nursing responsibilities in caring for a patient experiencing acute coronary syndrome includes community education
for early symptom recognition, prompt attention and prioritised management in the acute phase, discharge planning and cardiac
rehabilitation.
Learning outcomes for this section
Upon successful completion of this section, you should be able to:
identify assessment strategies for patients presenting with signs and symptoms of AMI
describe the differential diagnoses that may present with chest pain
relate the pathophysiology of heart disease to the anticipated plan of care for a patient experiencing an acute myocardial infarction
(AMI)
demonstrate an advanced physiological understanding of medication used in your practice setting
plan collaborative care that extends across the health care continuum for patients experiencing an uncomplicated AMI.
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Review
Acute coronary syndromes are most commonly associated with the rupture or erosion of an unstable atherosclerotic plaque and
subsequent formation of a platelet-fibrin thrombus. It is important to understand the pathophysiology of acute coronary syndromes
including the following:
Risk factors for the development of coronary artery disease.
Pathophysiology of the development of atherosclerosis.
The classifications of the different forms of angina.
The ECG characteristics of myocardial infarction from section 4.
Acute Coronary Syndrome (ACS) Patho…
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Readings (a choice)
Core text reading
Aitken, A, Marshall, A, & Chaboyer, W., chapter 9 ‘Cardiovascular alterations and management’, in ACCCN’s critical care nursing, Else
eReadings
Thompson, P 2011, Coronary care manual, 2nd edn, Elsevier, Australia.
Chapter 8 ‘Pathophysiology of atherosclerosis’, pp. 54-61.
Chapter 9 ‘Pathophysiology of coronary thrombosis’, pp. 62-71. – Click Here
Chapter 10 ‘Pathophysiology of myocardial infarction’, pp. 72-78.
Chapter 16 ‘Biochemical markers of myocardial necrosis’, pp.125-129 – Click Here
Chapter 60 ‘Prehospital coronary care’, pp. 454-458.
Chapter 61 ‘ACS: emergency department care’, pp. 459-466.
Chapter 62 ‘ACS: coronary care unit admission and care’, pp. 467-473. – Click Here
Chapter 63 ‘Management of ST elevation myocardial infarction’, pp. 474-484.
Chapter 64 ‘Management of non ST elevation ACS’, pp. 485-493.
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ACS in Women and ANZCOR Updates
eReading
Mehta, L.S., Beckie, T.M., DeVon, H.A., Grines, C.L., Krumholz, H.M., Johnson, M.N., Lindley, K.J., Vaccarino, V., Wang, T.Y., Watson,
Infarction in Women A Scientific Statement From the American Heart Association. Circulation, pp.CIR-0000000000000351. – Click He
Website
There have been some updates from the Australian and New Zealand Committee on Resuscitation (ANZCOR) (Australian Resuscitati
Australian and New Zealand Committee on Resuscitation: Guidelines Section 14: Acute Coronary Syndromes – Click Here
ANZCOR Guidelines Update on Acute Coronary Syndromes – Click here
4/9/2020 Study plan: Week 5 – Acute coronary syndromes
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Safety and Quality ACS Clincial Care Standard
Australian Commission on Safety and Quality in Health Care. Acute Coronary Syndromes Clinical Care Standard. Sydney: ACSQHC, 2
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Classification of acute coronary syndromes
In the previous module you learned the ECG characteristics of acute MI. It is important to distinguish between unstable angina, non ST
elevation myocardial infarct (NSTEMI) and ST elevation myocardial infarct (STEMI). Patients with symptoms of ischemic discomfort may
present with or without ST segment elevation on an ECG. Patients who present without ST segment elevation are experiencing either
unstable angina or NSTEMI. The distinction between these is made by assessment of the presence of elevated serum cardiac markers.
The majority of patients with NSTEMI do not develop Q waves (indicating irreparable necrosis) on their ECG and you may hear referred to
as having a Non Q wave MI (NQWMI) although this terminology is no longer commonly used. However some patients with NSTEMI do
develop Q waves on their ECG, (QWMI). Patients experiencing STEMI can also develop Q waves on their ECG with a smaller number
experiencing NQWMI. With a strong current focus on client early action and early clinical intervention in this cohort of patients the number
of people exhibiting Q waves is decreasing.
Figure 5.1: Classification of acute coronary syndromes (Adapted from Thompson, P 2008, Coronary care manual, 2nd edn, Churchill
Livingstone, Australia, and White, HD & Chew, DP 2008, ‘Acute myocardial infarction’, Lancet, vol. 372, pp. 570–584.)
The presence of Q waves is often associated with transmural infarction, or one which extends through the full thickness of the
myocardium. However, Q waves are not a consistent indicator of transmural infarction. Similarly the presence of ST segment depression
without elevation elsewhere on the ECG is usually but not always associated with subendocardial injury. The lack of consistency of ST and
Q wave changes as indicators of subendocardial or transmural zones of injury has lead to the classification of acute coronary syndrome by
their ECG characteristics alone.
4/9/2020 Study plan: Week 5 – Acute coronary syndromes
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Clinical assessment: the patient with chest pain
Activity
Some disorders mimic the chest pain of AMI. Construct a table that describes the pain location, pain
characteristics and common assessment findings such as any ECG changes for each disorder listed below.
Disorders that may mimic the chest pain of AMI
pulmonary embolism pneumonia
aortic dissection pneumothorax
angina gastric reflux
Pericarditis
Approach to Chest pain
An Approach to Chest Pain
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Diagnosis of acute myocardial infarction
Acute cardiac care is a dynamic discipline. Research in regard to management strategies including diagnostic tools, drug therapy, invasive
and non-invasive treatments are under constant review by clinicians and researchers. Evidence based practice at this stage supports early
clinical presentation, cardiac enzymes and ECG changes as the standard for diagnosis of AMI. However, there are circumstances when
further intervention such as catheter lab or CT is required to confirm suspected diagnosis.
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Clinical presentation
The diagnosis and determination of the severity of an AMI is on a clinical diagnosis which requires a thorough history and physical
examination.
Pain, shortness of breath, diaphoresis are usually the most significant symptoms for most patients experiencing a STEMI or NSTEMI and
normally follow a characteristic pattern. However, some patients with acute coronary syndromes may not experience pain, and the
intensity of pain varies with the pain threshold of different patients. The intensity of the pain experienced is neither indicative nor diagnostic
of the severity of the ACS the patient may be experiencing.
Chest pain may be caused by many different conditions; however, it is important to remember that the patient with chest pain should be
considered cardiac in origin until proven otherwise. The patient who presents with acute chest pain requires prompt efficient nursing care
to help alleviate their suffering and the potential damage to the myocardium.
Myocardial Infarction in the ICU setting –
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Diagnostic tools and procedures
Activity

1. Research the clinical signs which are common on presentation with an acute MI. Are there any signs or
   symptoms which are common with particular types or zones of infarction?
2. Using your text find the sections that discuss the variety of diagnostic procedures and tools available for the
   diagnosis and treatment of Acute Coronary Syndromes. The list of investigations below can be performed to
   assist with the diagnosis and ongoing management of myocardial infarction and heart failure.
   Chest x-ray
   ECG
   Arterial blood gases
   Echocardiograph (two types and why use different methods?)
   Stress exercise electrocardiography
   Cardiac catheterisation: angiography and angioplasty
   Complete blood count
   Serum electrolytes/liver function tests/complete cholesterol screen
   Radionuclide studies
   Magnetic Resonance Imaging
3. Provide information on why each test/procedure may be performed. (That is, what do you think the team is
   looking for or treating?) There could be more than one reason.
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   Biomarkers
   Knowledge of the purpose and significance of laboratory values assisting in the diagnosis and prognosis of AMI can enhance the quality of
   nursing care available to patients. Laboratory studies include routine blood analysis and special studies such as cardiac enzymes.
   Enzymes are found in all living cells and act as catalysts in biochemical reactions. They are present in low amounts in the serum of
   healthy people. The loss of membrane integrity in myocardial cells undergoing necrosis allows intracellular molecules to diffuse out into
   the cardiac interstitium and subsequently the blood stream. Detection of the abnormal presence of biomarkers is the ultimate diagnostic
   criteria for distinguishing between unstable angina and NSTEMI. Some cardiac enzymes are present in other organs, so elevation of these
   enzymes is not always an indicator of cardiac damage.
   A biomarker, known as Troponin or, in correct terminology, ‘cardiac Troponin’ was discovered in the 1990’s and is used successfully today
   for assisting in the diagnosis of cardiac muscle damage. There are three different types of Troponin; Troponin I (TnI), Troponin C (TnC)
   and Troponin T (TnT), with Trop I and T used for detection of damage specifically to the cardiac muscle. Troponin is a protein consisting of
   three sub-units and plays a key role in muscle contraction alongside actin and myosin. These are known collectively as contractile
   proteins.
   Activity
   Consult the section on biomarkers in your prescribed text to find the answers to the following questions.
4. Describe how Troponin (T/I) differs from existing cardiac enzymes, namely creatine kinase (CK), and the
   isoform of creatine kinase (CK-MB).
5. Compose a table that lists all of the current biomarkers associated with AMI, the time they take to peak, and
   the duration of elevation.
6. Consider how these and other investigations might be of some benefit in the diagnosis of myocardial
   infarction. Your list should include procedures such as laboratory assessments.
   It is important to note that the initial diagnosis of STEMI can be made by clinical and ECG criteria alone.
   It is not necessary to wait for results of biochemical markers to arrive before initiating therapy in patients
   at risk.