What is the recommended approach for scoring and classification of Acute Coronary Syndrome (ACS) patients, including risk assessment and initial management?

Scoring and Classification of ACS Patients

Use the GRACE risk score as your primary risk stratification tool for all ACS patients, as it demonstrates superior discriminative ability (C-statistic 0.83) compared to TIMI and outperforms clinical judgment alone. 1, 2

Initial Diagnostic Classification

Immediate Assessment (Within 10 Minutes)

• Obtain a 12-lead ECG within 10 minutes of arrival at an emergency facility 1
• Measure cardiac troponin (cTnI or cTnT) at presentation and repeat at 3-6 hours after symptom onset 1
• Perform serial ECGs at 15-30 minute intervals during the first hour if initial ECG is nondiagnostic 1

Classification Based on ECG and Biomarkers

ACS patients are classified into three categories: 1

• STEMI: ST-segment elevation on ECG with elevated troponin (most develop Q-wave MI)
• NSTEMI: No ST-elevation but elevated cardiac biomarkers (troponin I or T above 99th percentile)
• Unstable Angina (UA): Ischemic symptoms with ECG changes but normal troponin levels

Risk Stratification Tools

GRACE Risk Score (Primary Recommendation)

The GRACE score should be calculated at hospital admission for all confirmed ACS patients to predict in-hospital, 6-month, 1-year, and 3-year mortality or death/MI. 1, 2

GRACE uses 8 variables: 1, 2

• Age
• Killip class (heart failure severity)
• Systolic blood pressure
• Heart rate
• ST-segment deviation on ECG
• Cardiac arrest at presentation
• Serum creatinine
• Positive cardiac biomarkers

Risk Categories: 1, 2

• High risk (GRACE >140): Requires aggressive therapy including early invasive strategy, intensive antiplatelet therapy, and close monitoring
• Intermediate risk: Further evaluation and observation needed
• Low risk: May be suitable for conservative management

TIMI Risk Score (Alternative Tool)

The TIMI score uses 7 equally-weighted variables (1 point each): 1, 2

• Age ≥65 years
• ≥3 CAD risk factors
• Known coronary stenosis ≥50%
• ST-segment deviation ≥0.5 mm
• ≥2 anginal events in prior 24 hours
• Aspirin use in prior 7 days
• Elevated cardiac biomarkers

TIMI Risk Stratification for NSTE-ACS: 1

• Score 0-1: 4.7% event rate at 14 days
• Score 2: 8.3% event rate
• Score 3: 13.2% event rate
• Score 4: 19.9% event rate
• Score 5: 25.2% event rate
• Score 6-7: 40.9% event rate

HEART Score (Emergency Department Specific)

For undifferentiated chest pain in the ED before ACS confirmation, use the HEART score (0-10 points total): 2

Components (0-2 points each): 2

• History (highly suspicious = 2, moderately suspicious = 1, slightly suspicious = 0)
• ECG (significant ST depression = 2, nonspecific repolarization = 1, normal = 0)
• Age (≥65 years = 2,45-64 years = 1, <45 years = 0)
• Risk factors (≥3 factors or history of atherosclerotic disease = 2,1-2 factors = 1, none = 0)
• Troponin (≥3× normal limit = 2,1-3× normal = 1, normal = 0)

HEART Score Risk Categories: 2

• Low risk (0-3): <1% 30-day MACE rate; safe for discharge with negative troponins
• Intermediate risk (4-6): 8-20% 30-day MACE rate; requires further evaluation
• High risk (7-10): >26% 30-day MACE rate; requires aggressive therapy and invasive evaluation

Clinical Features That Increase ACS Likelihood

High-Risk Demographics and History 1

• Older age (especially ≥65 years)
• Male sex
• Prior myocardial infarction
• Diabetes mellitus
• Peripheral arterial disease
• Hypertension
• Family history of premature CAD
• Renal insufficiency

High-Risk Symptoms 1

• Retrosternal pressure-type chest pain lasting ≥10 minutes
• Pain radiating to arms, neck, or jaw
• Pain at rest or with minimal exertion
• Diaphoresis
• Severe dyspnea
• Syncope or presyncope
• Palpitations

Atypical Presentations (More Common in Elderly, Women, Diabetics) 1

• Unexplained new-onset or increased exertional dyspnea
• Epigastric pain or indigestion
• Unexplained fatigue
• Nausea and vomiting without chest pain

Critical Pitfalls to Avoid

Do not rely on nitroglycerin response to diagnose or exclude ACS - sublingual nitroglycerin relieves symptoms in 35% of ACS patients and 41% of non-ACS patients 1

Do not use CK-MB or myoglobin for ACS diagnosis - with contemporary troponin assays, these biomarkers provide no diagnostic benefit 1

Do not discharge patients with HEART scores ≥7 without definitive evaluation - their 30-day MACE risk exceeds 26% 2

Remember that 10-17% of ACS patients present with normal ECGs - normal ECG does not exclude ACS when other risk factors are present 2

Obtain supplemental leads V7-V9 in patients with initial nondiagnostic ECG who are at intermediate/high risk - this can identify posterior wall ischemia 1

Comparative Performance of Risk Scores

GRACE demonstrates superior discriminative ability across all ACS presentations with pooled C-statistics of 0.82-0.84 for short and long-term outcomes 1, 2, 3

TIMI performs adequately but is inferior to GRACE with pooled C-statistics of 0.54-0.77 depending on ACS type and timeframe 3, 4

In the ED setting with undifferentiated chest pain, TIMI outperforms GRACE and PURSUIT with an AUC of 0.757 versus 0.728 and 0.691 respectively 4