Diagnostic Evaluation in STEMI

• Diagnostic tools for ACS include: ECG, cardiac enzymes, and imaging studies such as cardiac CT or nuclear myocardial perfusion imaging

Risk stratification and use of appropriate diagnostic tests is essential for accurate diagnosis and timely treatment of ACS

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History and Physical Exam

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Electrocardiography

• Provides information about the heart’s electrical activity and rhythm
• Helps identify changes associated with ischemia, injury, and infarction
• Can reveal ST segment elevation, T wave inversions, and Q waves
• Should be performed as soon as possible in patients with suspected ACS
• Repeat ECGs should be obtained for dynamic ECG changes
• Serial ECGs can also be useful for monitoring response to treatment
• Can help determine the appropriate reperfusion strategy for STEMI patients

	STEMI	NSTEMI
Indicates	Transmural ischemia and infarction	Subendocardial ischemia and/or nontransmural infarct
ST segment elevation	Present	Absent
T wave inversions	May be present	May be present
Q waves	Present, indicating transmural infarction	May be present, indicating prior MI or ischemia
Dynamic changes	ECG changes may evolve over time	ECG changes tend to be more stable
Serial ECGs	Useful for monitoring response to treatment	Useful for monitoring response to treatment
Appropriate reperfusion strategy for STEMI patients	ECG findings help determine the appropriate reperfusion strategy for STEMI patients	ECG findings do not directly determine reperfusion strategy but can help with risk stratification and treatment planning

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Cardiac biomarkers

• Biomarkers are substances released into the bloodstream in response to myocardial cell injury or death
• Troponin is the most sensitive and specific biomarker for myocardial infarction
• Elevated troponin levels confirm the diagnosis of MI and help with risk stratification
• CK-MB is a less specific biomarker but can still be useful in some clinical scenarios
• Biomarker levels should be obtained at presentation and at 3-6 hours after symptom onset
• Serial biomarker testing can help monitor response to treatment and risk for complications
• High-sensitivity troponin assays are increasingly used for early detection and risk stratification of ACS

Biomarker	Description	Timing	Sensitivity	Specificity	Clinical Utility
Troponin	Regulatory protein released during myocardial injury	Measured at presentation and repeated	High	High	Diagnosis, risk stratification, monitoring response to treatment
CK-MB	Enzyme released during myocardial injury	Measured at presentation and repeated	Low	Moderate	Diagnosis
Myoglobin	Heme protein released during myocardial injury	Measured at presentation only	Low	Low	Rule-out ACS in low-risk patients
BNP	Hormone secreted by the heart in response to stress or volume overload	Measured at presentation only	Low	High	Diagnosis, risk stratification, monitoring response to treatment

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Other diagnostic tests and imaging

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Stratification in ACS

• Multiple risk assessment tools are available for evaluating patients with ACS
• TIMI (Thrombolysis in Myocardial Infarction) score, HEART (History, Electrocardiogram, Age, Risk factors, Troponin) score, and GRACE (Global Registry of Acute Coronary Events) score are commonly used
• These tools can aid in risk stratification, guiding management decisions, and identifying patients who may benefit from more aggressive treatment

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Calculating Risk Scores