Diagnosing Acute Coronary Syndrome

Diagnosing acute coronary syndrome

The classic symptom of acute coronary syndrome (ACS) is acute chest pain, usually localised behind the sternum or experienced over a more diffuse area, such as across the anterior chest. Pain from ACS often radiates to the left arm or to both arms, as well as to the shoulders, back, and jaw. Patients typically describe the pain as crushing, squeezing, pressing, or burning.^{51, 52} Women are more likely than men to present with symptoms other than chest pain. Such symptoms may include dyspnoea, nausea, vomiting, fatigue, indigestion, sweating, and pain localised in the arm or shoulder.⁵³

Diagnosing ACS — assessing the need for emergent intervention

An initial diagnosis of ACS is based on a detailed medical history, clinical risk scores and, in some cases, coronary artery imaging or other cardiac imaging tests. These studies help differentiate patients with the more severe ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) who need emergent revascularisation procedures from other patients with ACS for whom less aggressive intervention is indicated.^{51, 52}

Electrocardiogram

The electrocardiogram (ECG or EKG) remains the single most important diagnostic tool for identifying and diagnosing ACS. Current clinical standards of care dictate that an ECG be obtained in any patient complaining of acute chest pain promptly upon their arrival in the emergency department.²⁶² An ECG uses sensors on the skin to detect electrical activity within the heart, and is used to measure the heart’s rate and rhythm. The ECG can also detect changes in blood flow to the heart muscle. Acute blockage of blood flow can manifest as changes in the appearance of the portion of the ECG trace known as the “ST-segment”. On the basis of these and other ECG findings, along with a detailed clinical history and blood tests of biomarkers, clinicians determine whether a patient is having a STEMI or an NSTEMI.²⁶²

ECG showing NSTEMI

Biomarkers

Specific proteins are released by heart muscle cells in response to ischaemia (ie, inadequate blood flow). Two of these proteins are a cardiac-specific form of the enzyme creatinine kinase (CK-MB) and troponin, a component of the heart muscle’s contractile tissue. These proteins are described as “biomarkers”, as measurement of their blood levels can help identify patients who have sustained an injury to the heart. This information helps determine the need for emergent revascularisation of the coronary arteries.^{51, 52}

Blood tests for these biomarkers of cardiac injury are obtained when the clinical situation indicates that a patient may be suffering from ACS.

Imaging studies

In addition to history, physician exam and blood tests, studies used to assess possible ACS, for risk stratification and treatment planning, may include:^{23, 51}

Echocardiogram (cardiac echo)
Coronary angiogram (cardiac catheterisation)
CT angiogram
Magnetic resonance angiography

Cardiac echo

An echocardiogram (echo) is a safe, non-invasive ultrasound-based image of the heart. This test allows the clinician to visualise the size, motion, and status of the 4 cardiac chambers. These images provide more information than routine X-rays, and, unlike X-rays, cardiac echo requires no radiation. Clinicians often use echos to assess heart function in patients with chest pain symptoms that are atypical for ACS, along with normal or nondiagnostic results for ECG and/or cardiac biomarkers. Echo data also can help confirm the diagnosis and extent of complications of myocardial infarction (MI) such as thrombus formation within the heart’s chambers or dysfunction of the cardiac valves.¹⁷⁷

Coronary angiogram

Coronary angiogram (cardiac catheterisation) is an invasive imaging procedure involving the injection of dyes that render the coronary arteries and cardiac chambers visible on an X-ray. Direct visualisation of the coronary arteries with angiography can detect the location and contours of atherosclerotic thickening of the artery wall, as well as the location and obstruction caused by a thrombus within the arteries. This imaging modality is therefore helpful in determining which procedure, such as angioplasty, stent placement or coronary artery bypass surgery, would be the most appropriate intervention.^{262, 286}
Cardiac catheterisation often is performed emergently — during the first hours after the onset of symptoms — to provide access for urgent intervention (eg, angioplasty and stent insertion) to restore normal arterial blood flow. In addition, coronary angiograms also are performed as a non-emergent diagnostic test in patients with known or suspected coronary artery disease.²⁵⁶

CT angiogram

A computed tomography (CT) angiogram uses multiple X-rays to produce 3-dimensional images of the heart. Unlike the older, catheter-based coronary angiogram, CT angiogram is non-invasive and therefore does not pose a risk of bleeding or infection.²⁶² An emerging imaging technique, CT angiograms are becoming more widely used to evaluate coronary artery disease in patients with a low to intermediate probability of ACS. For example, a test result showing no calcification of the coronary arteries is currently used to rule out the diagnosis of ACS. This particular application of CT angiography can help expedite appropriate diagnosis and treatment in the emergency care setting.²⁰⁴

Magnetic resonance angiography

Magnetic resonance angiography (MRA) is a promising non-invasive imaging technique that, like CT angiography, provides an accurate, 3-dimensional visualisation of the coronary arteries. This technology enables the clinician to study the patient’s heart anatomy in any image plane. It can be used to detect vascular deformities such as the ballooning of blood vessels (aneurysms) as small as 4 millimetres in diameter. In addition, MRA does not require invasive catheter insertion or radiation exposure. For these reasons MRA may be used more widely for cardiac diagnosis in the future.²³²

Print page

Email page

Article references

51 - Anderson JL. ST segment elevation myocardial infarction and complications of myocardial infarction. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007. www.mdconsult.com. Accessed February 12, 2008.
52 - Waters DH. Acute coronary syndrome: unstable angina and non-ST segment elevation myocardial infarction. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007. www.mdconsult.com. Accessed February 12, 2008.
53 - Milner KA, Funk M, Richards S, Wilmes RM, Vaccarino V, Krumholz HM. Gender differences in symptom presentation associated with coronary heart disease. Am J Cardiol. 1999;84(4):396-399.
262 - Scirica BM. Acute coronary syndrome: emerging tools for diagnosis and risk assessment. J Am Coll Cardiol. 2010;55(14):1403-1415.
23 - Bassand JP, Hamm CW, Ardissino D, et al; Task Force for Diagnosis and Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes of European Society of Cardiology. Guidelines for the diagnosis and treatment of non-ST-segment elevation acute coronary syndromes. Eur Heart J. 2007;28(13):1598-1660.
177 - Coulter SA. Echocardiographic evaluation of coronary artery disease. In: Willerson JT, Cohn NJ, Wellens HJ, Holmes DR Jr, eds. Cardiovascular Medicine. 3rd ed. London, England: Springer-Verlag London Limited; 2007:811-839.
286 - Wilson RF, White CW. Coronary angiography. In: Willerson JT, Cohn JN, Wellens HJJ, Holmes DR Jr, eds. Cardiovascular Medicine. 3rd ed. London, England: Springer-Verlag London Limited; 2007:745-810.
256 - Ricciardi MJ, Boehar N, Davidson CJ. Cardiac catheterization and coronary angiography. In: Rosendoff C, ed. Essential Cardiology: Principles and Practices. 2nd ed. Totowa, NJ: Humana Press; 2005:197-219.
204 - Hoffmann U, Bamberg F, Chae CU, et al. Coronary computed tomography angiography for early triage of patients with acute chest pain: the ROMICAT (Rule Out Myocardial Infarction using Computer Assisted Tomography) trial. J Am Coll Cardiol. 2009;53(18):1642–1650.
232 - Lockie T, Nagel E, Redwood S, Plein S. Use of cardiovascular magnetic resonance imaging in acute coronary syndromes. Circulation. 2009;119(12):1671-1681.

Acute coronary syndrome: This is an umbrella term used to cover any group of clinical symptoms compatible with acute myocardial ischaemia (chest pain due to insufficient blood supply to the heart muscle that results from coronary artery disease). Acute coronary syndrome covers the spectrum of clinical conditions ranging from unstable angina to STEMI and NSTEMI.
Myocardial infarction: Destruction of heart tissue due to reduced blood flow to the heart. Also known as a heart attack. It usually results from coronary artery disease and is more severe than angina.
Non-ST-segment elevation myocardial infarction: Acute ischaemia of heart tissue sufficient to cause tissue damage where there is no ST-segment elevation on electrocardiogram (ECG) recordings.
ST-segment elevation myocardial infarction: Acute ischaemia of heart tissue sufficient to cause tissue damage where there is ST-segment elevation on electrocardiographic (ECG) recordings.
Angiography: Angiography is imaging of the blood vessels using X-rays or magnetic resonance tomography. The vessels are visualised by injecting contrast medium into a vein. Angiography is used to diagnose disorders of the blood vessels.
Coronary artery disease: Coronary artery disease (CAD) is the end result of the accumulation of plaques within the walls of the arteries that supply the muscle of the heart with oxygen and nutrients. The process by which the coronary arteries become narrowed or completely occluded is known as atherosclerosis.
Computed tomography: Also know as CAT scan. A radiographic technique that uses a computer to assimilate multiple X-ray images into a two-dimensional cross-sectional image.