Acute%20coronary%20syndromes%20w_out%20persistent%20st-segment%20elevation Diagnosis

Evaluation for Risk Stratification

Medical history, physical exam, electrocardiogram (ECG), biochemical cardiac markers and assessment of renal function can be used to estimate the risk of death and nonfatal cardiac ischemic events

• Assessment of risk is useful in selection of site of care (eg ICU, monitored unit, outpatient) and in selection of treatment
  • Risk assessment should be done repeatedly
• Patients with high likelihood of acute coronary syndrome (ACS) secondary to coronary artery disease (CAD) are at greater risk of untoward cardiac events than patients at less risk of CAD
  • High likelihood signs and symptoms: Chest or left arm pain or discomfort as chief symptom reproducing prior documented angina, known or prior history of CAD including MI, presence of transient mitral regurgitation, murmur, hypotension, diaphoresis, pulmonary edema or rales, elevated cardiac markers, and ECG result of new or presumably new, transient ST-segment deviation or T-wave inversion in multiple precordial leads
• Prognostic information to predict short- or mid-term risk of ischemic events, commonly use the Global Registry of Acute Coronary Events (GRACE), the Thrombolysis in Myocardial Infarction (TIMI) risk score, the Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) risk score, and the National Cardiovascular Data Registry-Acute Coronary Treatment and Intervention Outcomes Network (NCDR-ACTION) registry

Very High-Risk Criteria

• Acute heart failure
• Arrhythmias (life-threatening) or cardiac arrest
• Hemodynamic instability or cardiogenic shock
• Mechanical complications of MI
• Recurrent dynamic ST-T wave changes with or without intermittent ST-elevation
• Recurrent or ongoing chest pain refractory to medical treatment

High-Risk Criteria      

• Dynamic ST- or T-wave changes (symptomatic or silent)
• Rise or fall in cardiac troponin compatible with MI
• GRACE score >140
• TIMI risk score >4

Intermediate-Risk Criteria

• Diabetes mellitus
• Renal insufficiency (eGFR <60 mL/min/1.73 m²)
• Left ventricular ejection fraction (LVEF) <40% or congestive heart failure
• Early post-infarction angina
• Previous revascularization (PCI/CABG)
• GRACE score >109 and <140
• TIMI risk score 3 and 4

Low-Risk Criteria

• Any characteristics not mentioned in above criteria

• Major objectives:
  • Identify precipitating causes (eg uncontrolled hypertension, thyrotoxicosis or GI bleeding) and comorbid conditions (eg lung disease or cancer)
  • Assess the hemodynamic impact of the ischemic event
  • Exclude noncardiac causes of chest pain (eg pneumothorax, pulmonary embolism, pneumonia, pleural effusion, esophageal discomfort, gallstones, pancreatitis, or musculoskeletal origin)
  • Assess for nonischemic cardiac disorders (eg pericarditis, valvular disease, aortic dissection, acute pericarditis, cardiac tamponade)
• Measure vital signs (blood pressure [BP] in both arms, heart rate [HR], respiratory rate [RR] and temperature)
• Perform thorough cardiovascular (CV) and chest exam including auscultation of heart, neck veins, liver and peripheral pulses to check for murmurs, bruits or pulse deficits which signify severe underlying CAD
• LV dysfunction and shock should be suspected if patient has cold extremities, hypotension, pulmonary rales, S₃ gallop, displaced apex beat or S1<S2 at apex
• Aortic dissection may be present if there is pain in the back, unequal pulses, or a murmur of aortic regurgitation
• Acute pericarditis is suggested by a pericardial friction rub
• Cardiac tamponade may present as pulsus paradoxus
• If pneumothorax is present, patient may have acute dyspnea, pleuritic chest pain and differential breath sounds
• Chest pain caused by musculoskeletal chest wall syndromes may be found by performing palpation of the chest wall

Electrocardiogram (ECG)

In patients with ongoing chest pain, ECG should be obtained immediately (within 10 minutes of patient entering hospital) and as soon as possible in patients with resolved symptoms at the time of evaluation

• ECG is key in the assessment of patients presenting with suspected ACS and an ECG taken during an episode of chest pain is particularly valuable; ECG should be repeated (15- to 30-minute intervals at the 1st hour) as necessary or if there is high suspicion for ACS
  • Serial ECGs can identify ST-segment elevation indicative of STEMI which warrants immediate reperfusion and detect evolving ischemic changes in initial non-diagnostic ECGs
• Comparison with a previous ECG, if available, is important, especially in patients with coexisting cardiac pathology (eg LV hypertrophy or a previous MI)
• Continuous multilead ST-segment monitoring is an acceptable alternative to serial 12-lead ECG recordings in patients with high clinical suspicion for ACS but with initial ECG that is nondiagnostic

Unstable Angina/Non-ST-Segment Elevation Myocardial Infarction

• ST-segment depression (especially horizontal or downsloping) >0.1 mV in ≥2 contiguous leads
  • Highly suggestive of ACS
• Inverted T-waves >0.1 mV with predominant R-waves
  • Less specific for ACS
• T-wave inversion: Marked >0.2 mV symmetrical T-wave inversion in the precordial lead

Other ECG Presentations

• Persistent ST-segment elevation or new or presumed new left bundle-branch block (LBBB) has a high specificity for evolving STEMI
  • Patient should then be immediately evaluated for reperfusion therapy
  • Please see Myocardial Infarction w/ ST-Segment Elevation disease management chart for further information

• A completely normal ECG does not exclude the possibility of ACS
  • If normal ECG occurs during episode of chest pain, an alternative diagnosis should be suspected

Repeat Tests

• Perform serial ECGs or if patient experiences new episode of chest pain, obtain 12-lead ECG and compare with ECG taken without symptoms
• ECG recordings may be repeated at least 6-9 hours and 24 hours after presentation
  • >24-hour rhythm monitoring is recommended in NSTEMI patients at increased risk for cardiac arrhythmia; <24-hour monitoring is sufficient for those at low risk for cardiac arrhythmia
• For patients with highly suspicious ongoing ischemia, additional ECG leads (V3R, V4R, V7-V9) are recommended

Biochemical Indicators for Detecting Myocardial Necrosis

Cardiac Troponin T or I (Quantitative)

• High-sensitivity cardiac troponin I (hs-cTn I) assay is mandatory at presentation on patients with symptoms of possible or suspected ACS and have normal or non-diagnostic findings on ECG 
  • Rule in MI if there is a significant rise and/or fall of cTn with at least 1 value >99th percentile URL together with other clinical criteria 
  • For values <99th percentile, algorithms for ruling out ACS include the HEART (history, ECG, age, risk factor, troponin) pathway, European Society of Cardiology (ESC) 3-hour pathway and the ESC 1-hour pathway   
    • Cut-off levels for the different hs-cTn are assay specific; gender-specific cut-offs are also available
• cTn T and I are preferred markers for myocardial injury and necrosis because of high sensitivity and specificity 
  • Detected in blood at 6 hours using conventional assays (earlier with hs-cTn assays) and level may remain elevated for up to 14 days
  • Troponins accurately identify myocardial necrosis but should be used in conjunction with other criteria of MI which include ischemic symptoms and/or ECG and imaging findings

Myoglobin and/or Creatine Kinase - Myocardial Band (CK-MB)

• May be measured in patients with recent (<6 hours) symptoms as an early marker of MI and in patients with recurrent ischemia after recent (<2 weeks) infarction to detect further infarction

Other Biomarkers

• Myosin-binding protein C and copeptin are alternatives to cardiac troponin and CK-MB

Repeat Tests

• cTn test of <99th percentile should be repeated 3 hours later (2 hours later if hs-cTn) 
  • If >99th percentile or >50% change in levels within a 3-hour period*, patient is admitted 
  • If <99th percentile and <50% change in levels within a 3-hour period*, consider the following:
    • Admit patient if still with pain and/or HEART score >3** or TIMI score ≥2**; exclude other diagnosis 
    • Discharge patient for early outpatient cardiology consult if without pain and HEART score <3** or TIMI score is 0 or 1**

*If initial baseline cTn or hs-cTn is markedly >99th percentile, a change of >20% is significant; if baseline is less than or around the 99th percentile, a change of at least 50% is required to be significant. 
**Use HEART score for scoring if cTn is used. Use modified HEART score or Thrombolysis in Myocardial Infarction (TIMI) score if hs-cTn is used. 

Other Diagnostic Tests As Indicated

• Complete blood count (CBC), creatinine (Cr), blood urea nitrogen (BUN), estimated glomerular filtration rate, C-reactive protein, blood glucose, B-type natriuretic protein (BNP), N-terminal pro-BNP, lipid profile, thyroid function
  • Detect the presence of anemia, thyrotoxicosis, diabetes mellitus (DM), CAD
  • Identify infection: Several studies have shown an associated increased risk for ACS within 1-2 weeks after acute respiratory infection; absence of infection may be prognostic

Stress Test

• Stress test may be performed in patients with low and intermediate risk who have no ischemia at rest or with low level activity for a minimum of 12-24 hours; prior to discharge; or as an outpatient
• Confirms or establishes diagnosis of CAD and assesses risk for future CV events
• Patients with significant ischemia during exam should be considered for coronary angiography

• Chest X-ray to identify pulmonary congestion/edema and thoracic causes of symptoms
• Chest computed tomography (CT) to exclude pulmonary embolism and aortic dissection
  • D-dimer determination should be considered instead of imaging studies to rule out pulmonary embolism
• Coronary CT angiography may be considered instead of invasive angiography in order to exclude CAD in patients with normal or inconclusive troponin or ECG results 
• Echocardiography may be used to assess LV function and eliminate other CV causes of chest pain
• MRI may be used to determine myocardial viability and exclude differential diagnoses (eg pulmonary embolism or aortic dissection)
• Rest myocardial scintigraphy may be helpful in patients within chest pain without ECG changes or evidence of ongoing MI