Diagnostic Imaging Pathways - Suspected Acute Coronary Syndrome
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This pathway provides guidance on the imaging investigation of adult patients with suspected acute coronary syndrome (ACS). This pathway does not provide guidance on the management of suspected ACS.
Date reviewed: May 2018
Date of next review: May 2021
Published: April 2019
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SYMBOL | RRL | EFFECTIVE DOSE RANGE |
![]() | None | 0 |
![]() | Minimal | < 1 millisieverts |
![]() | Low | 1-5 mSv |
![]() | Medium | 5-10 mSv |
![]() | High | >10 mSv |
Images
Teaching Points
Teaching Points
- Acute coronary syndromes include ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI) and unstable angina
- The initial diagnosis of myocardial infarction (MI) is based on clinical assessment, repeat troponin assays and ECG changes. There are a number of different validated HS-troponin protocols to rule out MI
- A small proportion of patients with troponin negative chest pain may have ischaemic heart disease, which can be evaluated with imaging. This may be done in the outpatient setting shortly after discharge for chest pain presentations to the emergency department, such as through a rapid access chest pain clinic. The timing of investigation should be based on clinical judgement
- Investigations can be divided into tests that assess coronary anatomy (CTCA and invasive coronary angiogram) or functional tests that demonstrate ischaemia (stress ECG, stress echo, MPS)
- Non-invasive imaging techniques avoid the risks of a catheter angiogram in patients who would otherwise not require invasive treatment
- CTCA is recommended as the first line non-invasive test to evaluate suspected ACS
- Patients with prior confirmed coronary artery disease should have functional imaging instead of CTCA. This includes patients with a history of ischaemic heart disease, or evidence of coronary artery disease on any previous CT, including non-gated studies
- The overall choice of non-invasive imaging technique depends on various factors, particularly local expertise & availability of services
acs
Acute Coronary Syndrome (ACS)
- In Australia, ischaemic heart disease and acute coronary syndrome (ACS) account for over 19 000 deaths and 156 000 hospitalisations per year 1
- In the emergency setting, acute chest pain represents around 5-10% of all presentations, yet only 15-25% of patients have a final diagnosis of ACS 2
- The current gold standard of excluding acute myocardial infarction (AMI) is serial ECGs and repeat troponins
- High-sensitivity troponin assays are now widely available and can rule out an AMI earlier than standard troponins
- Algorithms for repeat high-sensitivity troponins at 1, 2 and 3 hours from presentation have been validated with negative predictive values over 99% to rule out AMI 3
- As current assays quickly and accurately rule out AMI in the Emergency Department setting, imaging may not initially be required for diagnosis
cxr
Chest Radiography
- Plain chest films (CXR) should be considered where a non-cardiac cause of chest pain is suspected 4,5
- They can be useful in diagnosing non-cardiac causes of chest pain
- CXR may demonstrate complications of myocardial infarction, such as pulmonary oedema, or secondary diagnoses, such as pneumonia
- 12-19% of patients presenting with chest pain have abnormal findings on CXR 6,7 however findings are not always clinically significant. A retrospective study found that CXR potentially changed the management of only 3.8% of patients 8
- Although CXR has a low yield in patients presenting with chest pain, it is easily accessible in the acute setting
- A chest radiograph should not delay urgent reperfusion therapy where indicated
ctca
CT Coronary Angiography
- CT coronary angiography (CTCA) is an established technique that uses contrast to enhance the coronary arteries
- CTCA is comparable to invasive cardiac angiogram for assessing coronary artery anatomy, but avoids the risks of an invasive procedure 9
- A normal CTCA has a high negative predictive value for coronary artery disease, between 97 and 99% 10,11
- Multiple studies have validated the accuracy of CTCA to detect coronary artery stenosis. Meta-analysis found CTCA to have a sensitivity of 96% and specificity of 79% for detecting 50% stenosis 5
- Currently no statistical difference in mortality or major cardiac events has been demonstrated between patients randomised to CTCA compared with standard treatment, 12 functional testing 13 or stress ECG 14 over an approximately 2 year follow-up period
- Limitations:
- Some protocols require the patient to have an optimal target heart rate around 65bpm, and IV beta-blockers may be administered to achieve this. The patient may also need to hold their breath for around 10 seconds
- Contraindications for CTCA include renal failure, contrast allergy, severe arrhythmia and haemodynamic insufficiency. Coronary arteries cannot be fully evaluated in some patients due to calcifications. With modern techniques and scanners, the radiation dose of a CTCA is around 2-5mSv 5
- If anatomical disease is demonstrated, further stress testing to confirm functional ischaemia is still recommended. 9 Severe stenosis may warrant proceeding to catheter angiography with a view to treatment
functional
Functional Imaging
- Functional imaging is performed when subjecting the heart to either exercise or pharmacological stress to assess the presence of stress-related ischaemia
- Stress echo, MPS and cardiac MR have comparable accuracy so choice of functional test should be based on local and patient factors, taking into consideration availability and radiation exposure 9
- Read about:
stressecho
Stress Echocardiogram
- Stress echocardiogram (stress echo) is a functional test that can demonstrate cardiac ischaemia
- The testing method normally occurs as follows. A baseline resting reading is taken. The patient's heart is stressed through exercise (e.g. treadmill, supine bike) or pharmacologically for patients who are unable to exercise (e.g. dobutamine, dipyridamole or adenosine). A second reading is taken while the patient is at peak stress. The two readings are then interpreted together
- Stress echocardiography (stress echo) is considered positive if there is abnormal ventricular wall motion or thickness in response to stress
- Contrast echocardiography using microbubbles to show myocardial capillaries can also assess perfusion which improves the diagnostic accuracy of stress echo 15-17
- In meta-analysis, the sensitivity of stress echo was 76-84% to detect 50% stenosis, with a specificity of 79-86%. 5 The specificity is higher (88-90%) for detecting stenosis over 70% 5
- A normal stress echo has a good prognosis: normal results are associated with an annual risk of 0.4-0.9% for cardiac mortality or acute myocardial infarction 18
- Unlike MPS, there is no radiation dose from stress echo
- Limitations:
- As with other forms of ultrasound imaging, the quality and hence overall diagnostic accuracy of echocardiography is limited by the experience of the sonographer and the interpreting physician
- There is risk associated with inducing stress, with death in 1 in 10 000 and ventricular arrhythmia or MI in 1 in 5 000 5
- Dipyridamole and adenosine are relatively contraindicated in severe asthma or profound obstructive pulmonary disease 5,19
- Stress echo, MPS and cardiac MR have comparable accuracy so choice of functional test should be based on local and patient factors, taking into consideration availability and radiation exposure 9
- If the study is suboptimal and unable to answer the clinical question, for example the acoustic window is restricted due to body habitus, cardiac MR could be considered 4
mps
Myocardial Perfusion Scintigraphy
- Myocardial perfusion scintigraphy (MPS) using single photon emission computed tomography (SPECT) is a widely available and well validated method of functional cardiac imaging 20
- A radioactive tracer (such as technetium-99m or thallium-201) is injected, followed by imaging of the myocardial uptake via SPECT. This is usually done twice; once with the patient at rest and later with the patient under stress, either during exercise or after administration of a vasodilator (such as dipyridamole or adenosine). The images at rest and under stress are assessed together. Areas of myocardium that show reversible defects (i.e. tracer uptake at rest, but not under stress) represent myocardial ischaemia. Areas that show irreversible defects (no tracer uptake at rest or under stress) represent infarcted myocardium
- Meta-analysis found MPS to have a sensitivity of 78% and specificity of 81% to detect 50% stenosis. MPS combined with CTCA has a sensitivity of 94% and specificity of 95% 5
- A normal MPS has a good prognosis: a meta-analysis of 31 studies showed that the rate of death or myocardial infarction was 0.85% per year, which is comparable to event rates in populations without coronary artery disease 21
- Limitations:
- The main disadvantage of MPS is the high radiation dose. Generally, the radiation dose from MPS using technetium-99 is around 7mSv 22 but can be >20mSv with thallium-201 23 – dose also depends on the protocol used
- MPS is time consuming, taking three to four hours. 5 Some protocols comparing rest and stress images require the tracers to leave the heart which may take up to a week, requiring two visits and delaying results 24
- A false negative result may occur when there is widespread ischaemia throughout the whole myocardium, such as in triple vessel disease. 25 This is because the interpretation of the study relies on comparison of ischaemic areas to normal areas
- There is a 1 in 10 000 risk of death associated with stress induction 5
- Stress echo, MPS and cardiac MR have comparable accuracy so choice of functional test should be based on local and patient factors, taking into consideration availability and radiation exposure 9
cardiacmri
Cardiac Magnetic Resonance Imaging
- Cardiac magnetic resonance imaging (cardiac MR) is becoming increasingly used to assess stable coronary artery disease
- It has the benefit of assessing both coronary artery anatomy and functional ischaemia. Vasodilator techniques use adenosine or regadenoson with gadolinium contrast to assess perfusion defects. 24 Stress cardiac MR can be performed with dobutamine to demonstrate wall motion abnormalities indicating ischaemia 26
- Cardiac MR is also accepted as the non-invasive gold standard for assessing cardiac structure and function. 24 Other cardiac conditions that may cause chest pain can be demonstrated on cardiac MR, including Takotsubo cardiomyopathy and myocarditis 4
- Cardiac MR has a sensitivity and specificity of 86% for detecting 50% stenosis compared to invasive coronary angiogram 5
- There is no associated radiation dose and the safety is comparable to stress echo 4
- Limitations 5,19
- Availability is one of the main limitations. Access to cardiac MR and reporting expertise is limited
- Long procedure (approximately 1hr) during which patients must be able to lie still. Scan may not be tolerated due to claustrophobia
- Incompatible metal implants and foreign bodies are contraindicated in MRI
- Renal failure is a relative contraindication to gadolinium contrast
- There is risk of death and cardiac events associated with inducing stress
- Stress echo, MPS and cardiac MR have comparable accuracy so choice of functional test should be based on local and patient factors, taking into consideration availability and radiation exposure 9
stressecg
Stress ECG
- Stress electrocardiography (stress ECG) is a widely available and affordable test that can demonstrate reproducible symptoms of cardiac ischaemia
- Exercise can be performed on a treadmill or exercise bicycle, with exercise increased incrementally until the patient reaches a target heart rate (normally 85% of maximum heart rate) or the patient can no longer continue. A stress ECG test is considered positive if the stress elicits ST segment elevation or depression of ≥0.10 mV
- Treadmill score correlate well with prognosis. 27 A low risk score has a good prognosis with an associated mortality rate of 0.25% per year compared to 5% per year for a high risk score. 28 The negative predictive value has been found to be over 99% 29
- The reported sensitivity is 66-94% with specificity 75-95% with higher sensitivity in specificity in low risk populations (prevalence of NSTEMI or unstable angina ≤10%) 30-34
- The sensitivity and specificity of stress ECG is lower than functional studies, however there are no randomised trials to suggest that this has an adverse effect on patient outcomes 4,35
- Limitations:
- The main limitation with stress ECG is patients with pre-existing ECG changes. These changes (such as left bundle branch block, baseline ST depression, digoxin therapy or pacemakers) make interpretation difficult
- Patients who are unable to exercise for other reasons, such as musculoskeletal problems, are also not suitable for stress ECG
- Testing may be inconclusive if the patient is unable to achieve the target heart rate in the absence of symptoms of ischaemia
- The presence of anatomical disease cannot be confirmed, so stress ECG is only recommended for patients who have had coronary artery disease previously confirmed with invasive or non-invasive studies 5
ica
Invasive Coronary Angiography
- Invasive coronary angiography (ICA) is considered to be the gold standard for diagnosing coronary artery disease
- Intervention such as balloon angioplasty or stenting may be simultaneously undertaken if disease is found
- Limitations:
- ICA is expensive and depends on operator expertise
- There are risks associated with performing an invasive procedure. Serious risks include stroke, myocardial infarction and death. The rate of non-fatal complications is 74 per 10 000. 9 The side-effects make ICA less acceptable to patients
- Procedures may take approximately 1.5 hours
- There is also a significant associated radiation exposure of 4-6mSv 5
- There are risks associated with contrast administration and renal failure is a relative contraindication
- ICA is rarely indicated for diagnosis only; non-invasive imaging techniques are recommended to identify patients who can be managed conservatively and can avoid the risks of an invasive procedure
References
References
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- Cardiovascular health compendium. AIHW; 2017. View the reference
- Cullen L, Than M, Brown AF, Richards M, Parsonage W, Flaws D, et al. Comprehensive standardized data definitions for acute coronary syndrome research in emergency departments in Australasia. Emerg Med Australas. 2010;22(1):35-55. (Review article). View the reference
- Andruchow JE, Kavsak PA, McRae AD. Contemporary emergency department management of patients with chest pain: a concise review and guide for the high-sensitivity troponin era. Can J Cardiol. 2018. 34(2):98-108.(Review article) View the reference
- Montalescot G, Sechtem U, Achenbach S, Andreotti F, Arden C, Budaj A, et al. 2013 ESC guidelines on the management of stable coronary artery disease: the task force on the management of stable coronary artery disease of the European society of cardiology. Eur Heart J. 2013;34(38):2949-3003. (Guideline). View the reference
- National Institute for Health and Care Excellence. Chest pain of recent onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin (update). NICE Guidelines; 2016. (Review article). View the reference
- Al Zadjali N, Al-Senawi R, Al Reesi A, Al-Zakwani I, Nemeth J, Perry JJ. Predictors of positive chest radiography in non-traumatic chest pain in the emergency department. Oman medical journal. 2009. 24(1):22-6. (Level II evidence) View the reference
- Goldschlager R, Roth H, Solomon J, Robson S, Green J, Green S, et al. Validation of a clinical decision rule: chest x-ray in patients with chest pain and possible acute coronary syndrome. Emergency radiology. 2014. 21(4):367-72. (Level II-III evidence) View the reference
- Ng JJ, Taylor DM. Routine chest radiography in uncomplicated suspected acute coronary syndrome rarely yields significant pathology. Emerg Med J. 2008. 25(12):807-10. (Level II evidence) View the reference
- Moss AJ, Williams MC, Newby DE, Nicol ED. The updated NICE guidelines: cardiac CT as the first-line test for coronary artery disease. Current cardiovascular imaging reports. 2017;10(5):15. View the reference
- Budoff MJ, Dowe D, Jollis JG, Gitter M, Sutherland J, Halamert E, et al. Diagnostic performance of 64-multidetector row coronary computed tomographic angiography for evaluation of coronary artery stenosis in individuals without known coronary artery disease: results from the prospective multicenter ACCURACY (assessment by coronary computed tomographic angiography of individuals undergoing invasive coronary angiography) trial. J Am Coll Cardiol. 2008. (Level III evidence);52(21):1724-32. View the reference
- Meijboom WB, Meijs MF, Schuijf JD, Cramer MJ, Mollet NR, van Mieghem CA, et al. Diagnostic accuracy of 64-slice computed tomography coronary angiography: a prospective, multicenter, multivendor study. J Am Coll Cardiol. 2008. 52(25):2135-44. (Level II evidence) View the reference
- CT coronary angiography in patients with suspected angina due to coronary heart disease (SCOT-HEART): an open-label, parallel-group, multicentre trial. Lancet. 2015. 385(9985):2383-91. (Level II evidence) View the reference
- Douglas PS, Hoffmann U, Patel MR, Mark DB, Al-Khalidi HR, Cavanaugh B, et al. Outcomes of anatomical versus functional testing for coronary artery disease. N Engl J Med. 2015. 372(14):1291-300. (Level II evidence) View the reference
- McKavanagh P, Lusk L, Ball PA, Verghis RM, Agus AM, Trinick TR, et al. A comparison of cardiac computerized tomography and exercise stress electrocardiogram test for the investigation of stable chest pain: the clinical results of the CAPP randomized prospective trial. European heart journal cardiovascular Imaging. 2015. 16(4):441-8. (Level II evidence) View the reference
- Gurunathan S, Senior R. Stress echocardiography in stable coronary artery disease. Curr Cardiol Rep. 2017. 19(12):121. (Review article) View the reference
- Tsutsui JM, Elhendy A, Anderson JR, Xie F, McGrain AC, Porter TR. Prognostic value of dobutamine stress myocardial contrast perfusion echocardiography. Circulation. 2005. 112(10):1444-50. (Level III evidence) View the reference
- Gaibazzi N, Reverberi C, Lorenzoni V, Molinaro S, Porter TR. Prognostic value of high-dose dipyridamole stress myocardial contrast perfusion echocardiography. Circulation. 2012. 126(10):1217-24. (Level III evidence) View the reference
- Metz LD, Beattie M, Hom R, Redberg RF, Grady D, Fleischmann KE. The prognostic value of normal exercise myocardial perfusion imaging and exercise echocardiography: a meta-analysis. J Am Coll Cardiol. 2007. 49(2):227-37. (Level I evidence) View the reference
- Mangla A, Oliveros E, Williams KA, Sr., Kalra DK. Cardiac imaging in the diagnosis of coronary artery disease. Curr Probl Cardiol. 2017. 42(10):316-66. (Review article) View the reference
- Mastouri R, Sawada SG, Mahenthiran J. Current noninvasive imaging techniques for detection of coronary artery disease. Expert Rev Cardiovasc Ther. 2010;8(1):77-91. (Review article). View the reference
- Shaw LJ, Iskandrian AE. Prognostic value of gated myocardial perfusion SPECT. J Nucl Cardiol. 2004. 11(2):171-85. (Level I evidence) View the reference
- Rausch I, Fuchsel FG, Kuderer C, Hentschel M, Beyer T. Radiation exposure levels of routine SPECT/CT imaging protocols. Eur J Radiol. 2016. 85(9):1627-36. (Level II evidence) View the reference
- Einstein AJ, Moser KW, Thompson RC, Cerqueira MD, Henzlova MJ. Radiation dose to patients from cardiac diagnostic imaging. Circulation. 2007;116(11):1290. (Review article). View the reference
- Mordi IR, Badar AA, Irving RJ, Weir-McCall JR, Houston JG, Lang CC. Efficacy of noninvasive cardiac imaging tests in diagnosis and management of stable coronary artery disease. Vascular health and risk management. 2017. 13:427-37. (Review article) View the reference
- Aarnoudse WH, Botman KJ, Pijls NH. False-negative myocardial scintigraphy in balanced three-vessel disease, revealed by coronary pressure measurement. Int J Cardiovasc Intervent. 2003. 5(2):67-71. (Level V evidence) View the reference
- Kramer CM, Barkhausen J, Flamm SD, Kim RJ, Nagel E. Standardized cardiovascular magnetic resonance (CMR) protocols 2013 update. J Cardiovasc Magn Reson. 2013. 15:91. (Guideline) View the reference
- Roger VL, Jacobsen SJ, Pellikka PA, Miller TD, Bailey KR, Gersh BJ. Prognostic value of treadmill exercise testing: a population-based study in Olmsted County, Minnesota. Circulation. 1998. 98(25):2836-41.(Level II evidence) View the reference
- Mark DB, Shaw L, Harrell FE, Jr., Hlatky MA, Lee KL, Bengtson JR, et al. Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease. N Engl J Med. 1991. 325(12):849-53. (Level II evidence) View the reference
- Newman RJ, Darrow M, Cummings DM, King V, Whetstone L, Kelly S, et al. Predictive value of exercise stress testing in a family medicine population. J Am Board Fam Med. 2008. 21(6):531-8. (Level III evidence) View the reference
- Hamilton-Craig C, Fifoot A, Hansen M, Pincus M, Chan J, Walters DL, et al. Diagnostic performance and cost of CT angiography versus stress ECG--a randomized prospective study of suspected acute coronary syndrome chest pain in the emergency department (CT-COMPARE).. Int J Cardiol. 2014. 177(3):867-73. (Level II evidence) View the reference
- Amsterdam EA, Kirk JD, Diercks DB, Lewis WR, Turnipseed SD. Immediate exercise testing to evaluate low-risk patients presenting to the emergency department with chest pain. J Am Coll Cardiol. 2002. 40(2):251-6. (Level III evidence) View the reference
- Bennett P, Dyer P. Exercise stress test utility in patients with chest pain presumed to be of cardiac origin. Acute medicine. 2013. 12(3):146-50. (Level III evidence) View the reference
- Conti A, Gallini C, Costanzo E, Ferri P, Matteini M, Paladini B, et al. Early detection of myocardial ischaemia in the emergency department by rest or exercise (99m)Tc tracer myocardial SPET in patients with chest pain and non-diagnostic ECG. Eur J Nucl Med. 2001. 28(12):1806-10. (Level III evidence) View the reference
- Gaibazzi N, Reverberi C, Badano L. Usefulness of contrast stress-echocardiography or exercise-electrocardiography to predict long-term acute coronary syndromes in patients presenting with chest pain without electrocardiographic abnormalities or 12-hour troponin elevation. Am J Cardiol. 2011. 107(2):161-7. (Level III evidence) View the reference
- Shaw LJ, Mieres JH, Hendel RH, Boden WE, Gulati M, Veledar E, et al. Comparative effectiveness of exercise electrocardiography with or without myocardial perfusion single photon emission computed tomography in women with suspected coronary artery disease: results from the what is the optimal method for ischemia evaluation in women (WOMEN) trial. Circulation. 2011. 124(11):1239-49. (Level II evidence) View the reference
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