Myocardial Infarction w/ ST-Segment Elevation Initial Assessment

Last updated: 08 July 2025

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Clinical Presentation

Content on this page:

Clinical Presentation

Clinical Presentation

Characteristics of Ischemic-type Chest Discomfort

Chest discomfort is characterized as retrosternal/substernal chest pain lasting 10 to 20 minutes or longer. The pain is usually described as heaviness, pressure, dull, sharp, stabbing, squeezing, tearing, tightness, or burning in nature and may not be severe. The pain may occur at rest or during activity and does not respond fully to Glyceryl trinitrate (GTN).  The pain, which is usually central or in the left chest may radiate to the jaw, neck, left arm, back or shoulder. The discomfort is diffuse, not localized or positional nor is it affected by movement of the region. Occasionally, symptoms are mistaken for indigestion or heartburn if pain occurs in the epigastric region. 



Myocardial Infarction w ST-Segment Elevation_Initial Assesment 1Myocardial Infarction w ST-Segment Elevation_Initial Assesment 1




Accompanying symptoms may include nausea, vomiting, dyspnea, diaphoresis, palpitations, lightheadedness, dizziness, confusion, syncope, fatigue and weakness. Atypical patterns may occur, especially in females, diabetics and elderly patients, where the pain develops in the arm, shoulder, wrist, jaw or back without occurring in the chest. MI should be suspected, especially if the symptoms are severe and occur suddenly. MI may present with autonomic nervous system activation (eg pallor, sweating), hypotension or narrow pulse pressure, bradycardia or tachycardia, a third heart sound (S3), basal rales or occasionally syncope in the elderly.

History

The ischemic-type chest discomfort as described previously may be caused by a cardiac, possible cardiac or non-cardiac etiology. Inquire about the patient’s medical, social and family history and assess cardiovascular (CV) risk factors.

Physical Examination

The patient may exhibit pallor and diaphoresis or may be completely normal. Basilar rales may indicate heart failure (HF). Apical systolic murmur, S3 or S4 may be present. 



Myocardial Infarction w ST-Segment Elevation_Initial Assesment 2Myocardial Infarction w ST-Segment Elevation_Initial Assesment 2

Diagnosis or Diagnostic Criteria

Initial Diagnosis of ST-Elevation Myocardial Infarction  

The patient presents with a history of prolonged chest pain/discomfort, ie symptoms of acute myocardial ischemia. Electrocardiogram (ECG) reveals new ischemic changes, persistent ST-segment elevations, (presumed) new left bundle-branch block (LBBB), or pathological Q waves. A decision to start treatment using percutaneous coronary intervention (PCI) may be based on the patient’s clinical history and ECG results. Rapid diagnosis and risk stratification of patients with chest pain are important to identify AMI patients who will benefit from reperfusion therapy (ie reopening of the occluded artery).  

Acute Coronary Syndrome (ACS)  

Acute Coronary Syndrome with Persistent ST-Segment Elevation  

ST-segment elevation myocardial infarction (STEMI) presents with elevated levels of cardiac biomarkers. This usually has a completely occluded vessel, resulting in transmural myocardial ischemia and infarction.  

Acute Coronary Syndrome without Persistent ST-Segment Elevation (Non-ST Elevation ACS [NSTE-ACS])  

Unstable angina (UA) is ischemic discomfort that presents with normal cardiac biomarkers in the blood with or without ischemia-related ECG changes. Non-ST-segment elevation myocardial infarction (NSTEMI) presents with elevated levels of cardiac biomarkers. This may have a partially occluded coronary artery resulting in subendocardial ischemia.

Screening

Risk Stratification  

Identifying patients who are at increased risk of further reinfarction or death is essential in order that it can be prevented or intervention can be done accordingly. A referral of high-risk patients to specialty centers should be made for early coronary angiography and revascularization. Risk stratification of post-STEMI patients can be done clinically or by using the Thrombolysis in Myocardial Infarction (TIMI) risk score for a 30-day outcome risk assessment and the Global Registry of Acute Coronary Events (GRACE) risk score for a 6-month outcome risk assessment. This is relevant for patients who did not receive PCI, including those with >48 hours of presentation. Risk assessment should be done repeatedly during hospitalization and at discharge.  

High-Risk Patients  

High-risk patients are those with left ventricular ejection fraction (LVEF) <35%, ischemia that affects >50% of viable myocardium and are post-revascularization (PCI or CABG).  

The clinical indicators for high-risk patients include:

  • Advanced age
  • Hypotension and cardiogenic shock
  • Anterior infarction
  • Elevated initial serum creatinine
  • Malignant arrhythmias
  • Early angina on minimal exertion/post-infarct angina
  • Tachycardia
  • Killip class >1
  • Previous infarction
  • History of heart failure (HF)
  • Persistent chest pain
  • Peripheral arterial disease


Medium-Risk Patients  

Medium-risk patients are patients not considered low risk or high risk based on imaging criteria and should be treated based on symptomatic status.  

Low-Risk Patients  

Low-risk patients are those who have LVEF >50% or mild inducible ischemia that affects <20% of viable myocardium.