Question 1#

Regarding chest pain, which ONE of the following statements is TRUE?

A. Pain radiating to the right arm or shoulder is more predictive of myocardial infarction than pain radiating to the left arm or shoulder

Answer: A: A detailed history obtained from the patient regarding the nature of chest pain is important for the diagnosis and risk stratification. The positive likelihood ratios (LRs) have been determined for various descriptions of chest pain. The positive LR for pain radiating to the right arm or shoulder as an indicator of myocardial infarction is 4.7 compared with LR of 2.3 for pain radiating to left arm. The positive LR for pain radiating to both arms and shoulders is 4.1. Burning or indigestion pain can be associated with ACS (LR 2.8), while pain reproducible by palpation and described as pleuritic, sharp or positional does not exclude ACS or AMI.

References:

1. Goodcare S. Chest pain. In: Cameron P, Jelinek G, Kelly A, et al, editors. Textbook of adult emergency medicine. 3rd ed. Edinburgh: Churchill Livingston Elsevier; 2009. p. 202–7.
2. Green G, Hill P. Chest pain: cardiac or not. In: Tintinalli J, Stapczynski J, Ma O, et al, editors. Tintinalli’s emergency medicine: a comprehensive study guide. 7th ed. NewYork: McGraw Hill Medical; 2011:361–7.

Question 2#

Regarding investigations for chest pain, which ONE of the following statements is TRUE?

A. A new ST segment elevation ≥1 mm in two contiguous leads on electrocardiogram (ECG) has a 50% positive predictive value for diagnosis of acute myocardial infarction (AMI)

Answer: C:  Approximately half of the patients with AMI will have an initial ECG showing a new ST segment elevation ≥1 mm in two contiguous leads. Its positive predictive value for diagnosis of AMI has been described as >90%.

Patients with an elevated troponin have a worse 2- and 28-day prognosis compared with patients without an elevated troponin.

Compared with conventional troponin assays, with the use of new high-sensitive troponin assays (both TnT and TnI), troponin can be detected at much lower levels. Consequently, these superior performing high-sensitivity assays have increased sensitivity in early detection of AMI. However, these increased sensitivities have been achieved at the expense of reduced specificities (table below).

SENSITIVITY AND SPECIFICITY IN THE DIAGNOSIS OF AMI USING HIGH-SENSITIVITY TROPONIN ASSAYS (WHEN A CUT-OFF VALUE OF 0.07 MCG/L OR 99TH PERCENTILE IS USED)

In the absence of ischaemic heart disease, troponin can be elevated in a range of non-ischaemic pathologies. This should be considered when interpreting troponin results. Troponin can be elevated in the following non-ischaemic conditions including:

• Sepsis and critically unwell patients
• PE
• Renal failure
• Myocarditis, myopericarditis and myocardial extension of endocarditis
• Stroke and subarachnoid haemorrhage
• Aortic dissection 
• Congestive cardiac failure – both acute and chronic
• Cardiac contusion
• Pacing, ablation, cardiac surgery
• Tachyarrhythmias, bradiarrhythmias and heart block
• Respiratory failure

Exercise stress testing is a functional test that is prognostically useful in predicting adverse events for coronary artery disease (CAD) despite its limited sensitivity and specificity in diagnosing CAD. It is useful for risk stratifying low to intermediate risk patients.

References:

1. Goodcare S. Chest pain. In: Cameron P, Jelinek G, Kelly A, et al, editors. Textbook of adult emergency medicine. 3rd ed. Edinburgh: Churchill Livingston Elsevier; 2009. p. 202–7.
2. Green G, Hill P. Chest pain: cardiac or not. In: Tintinalli J, Stapczynski J, Ma O, et al, editors. Tintinalli’s emergency medicine: a comprehensive study guide. 7th ed. NewYork: McGraw Hill Medical; 2011:361–7.
3. Loten C, Isbister G, Jamcotchian M, et al. Adverse outcomes following emergency department discharge of patients with possible acute coronary syndrome. Emerg Med Austral 2009;21:455–64.
4. Chew D, Aroney C, Aylward P, et al. Addendum to the National Heart Foundation of Australia/Cardiac Society of Australia and New Zealand guidelines for the management of acute coronary syndromes (ACS) 2006. Heart Lung Circ 2011;8:487–502.

Question 3#

Regarding risk stratification for patients with suspected non-ST segment elevated ACS (NSTEAC), which ONE of the following statements is TRUE?

A. The thrombolysis in myocardial infarction (TIMI) score is a useful tool to identify which NSTEAC patients will benefit from early invasive therapy

Answer: A: TIMI score has been validated as a predictor of adverse outcomes (subsequent myocardial infarction, mortality, arrhythmia) and the need for early invasive management for NSTEAC syndrome. TIMI refers to the name of the research organisation that conducted the trials.

Age, diabetes and previous aspirin use are all variables that need to be considered in risk stratification of NSTEACS. Patients with a low TIMI score still have considerable risk for adverse events, with a score of 0–1 having a risk of up to 4.7%.

TIMI score calculations (1 point for each factor present):

• Age 65 years or over
• At least 3 risk factors for CAD (hypertension ≥140/90 or on antihypertensives, cigarette smoking, HDL < 40, diabetes, family history of CAD (CAD in male first-degree relative, or in father when <55 years of age, female first-degree relative or mother <65 years of age)
• Aspirin use in the past 7 days
• At least 2 angina episodes within last 24 hours
• Known coronary artery disease (coronary stenosis 50% or more)
• ST changes of at least 0.5 mm on ECG
• Elevated serum cardiac biomarkers 

Table below shows the percentage of risk at 14 days of mortality due to all causes, new or recurrent MI or severe recurrent ischaemia requiring urgent revascularization.

References:

1. Goodcare S, Kelly A. Acute coronary syndromes. In: Cameron P, Jelinek G, Kelly A, et al, editors. Textbook of adult emergency medicine. 3rd ed. Edinburgh: Churchill Livingston Elsevier; 2009. p. 208–14.
2. Brady W, Harrigan R, Chan T. Acute coronary syndrome. In: Marx J, Hockberger R, Walls R, et al, editors. Rosen’s emergency medicine: concepts and clinical practice. 7th ed. Mosby Elsevier; 2009. p. 947–83.
3. Antman E, Cohen M, Bernink P. The TIMI risk score for unstable angina/non-ST elevation MI. JAMA 2000;284(7):835–42.

Question 4#

Regarding ST elevation myocardial infarction, all of the following are true EXCEPT:

A. ST elevation in leads II, III and aVF may be associated with occlusion of the right coronary artery or circumflex artery

Answer: B: ST elevation in leads II, III and aVF suggests an inferior infarction that may involve the right coronary or circumflex arteries, as can posterior infarctions. Posterior infarction may also be caused by occlusion of the circumflex artery in patients with dominant left-sided circulation. Inferior and posterior AMI may be associated with RV infarction. Posterior AMI are associated with ST segment depression in V1 and V2 and ST segment elevation in posteriorly placed leads. One of the earliest markers of an inferior AMI may be ST depression in lead aVL.

References:

1. Goodcare S. Chest pain. In: Cameron P, Jelinek G, Kelly A, et al, editors. Textbook of adult emergency medicine. 3rd ed. Edinburgh: Churchill Livingston Elsevier; 2009. p. 202–7.
2. Hollander J, Diercks D. Acute coronary syndromes, acute myocardial infarctionand unstable angina. In: Tintinalli J, Stapczynski J, Ma O, et al, editors. Tintinalli’s emergency medicine: a comprehensive study guide. 7th ed. NewYork: McGraw Hill Medical; 2011. p. 367–85.
3. Janz T, Hamilton G. Acute coronary syndromes: regional issues. In: Chan C, Brady W, Harrigan R, et al, editors. ECG in emergency medicine and acute care. Philadelphia: Elsevier Mosby 2005. p. 173–81.

Question 5#

Regarding the ECG in ST segment elevation myocardial infarction, which ONE of the following statements is TRUE?

A. ST segment elevation in lead aVR in a patient with ischaemic pain is a marker of left main coronary artery stenosis

Answer: A:  ST segment elevation in aVR in a patient with ischaemic-sounding chest pain is a marker for proximal left system disease, which has a mortality of up to 70%, and should not be treated as a non-STEMI.

Posterior STEMI is often difficult to diagnose. It is characterized by: 

• ST depression in the anterior chest leads
• Tall/wide R waves in V1–V2
• R/S ratio >1 in V1–V2 without right axis deviation
• Upright T waves in V1–V2
• ST segment elevation when leads V7–9 are performed

Wellen’s syndrome is characterised by abnormal T wave inversion or biphasic T waves, especially in leads V2–4. These changes may be a marker of proximal left main disease, particularly in patients with ischaemic-sounding chest pain. 

ECG criteria for reperfusion are:

• ST segment elevation of ≥1 mm in two or more contiguous limb leads, or
• ST segment elevation of ≥2 mm in two or more contiguous chest leads, or
• New LBBB

References:

1. Goodcare S, Kelly A. Acute coronary syndromes. In: Cameron P, Jelinek G, Kelly A, et al, editors. Textbook of adult emergency medicine. 3rd ed. Edinburgh: Churchill Livingston Elsevier; 2009. p. 208–14.
2. Brady W. T wave. In: Chan C, Brady W, Harrigan R, et al, editors. ECG in emergency medicine and acute care. Philadelphia: Elsevier Mosby; 2005. p. 66–9.
3. Dunn R, Dilley S. Acute coronary syndromes (ACS) In: Dunn R, Dilley S, Brookes J, et al, editors. Manual of emergency medicine. Adelaide: Venom Publishing; 2010. p. 407–38.