What is the approach to a patient presenting with chest pain, considering potential cardiac involvement and possible acute coronary syndrome?

Approach to Chest Pain

All patients presenting with chest pain require an ECG within 10 minutes of arrival and immediate cardiac troponin measurement to rapidly identify or exclude acute coronary syndrome, which is the most critical life-threatening diagnosis to address. 1

Immediate Initial Actions

Time-Critical Diagnostics

• Obtain a 12-lead ECG within 10 minutes of first medical contact, regardless of setting (office, ED, or EMS), specifically to identify STEMI 1, 2
• Measure cardiac troponin (preferably high-sensitivity) as soon as possible upon ED presentation to detect myocardial injury 1, 2
• Perform chest radiography to evaluate for alternative cardiac, pulmonary, or thoracic causes of symptoms 1

Critical Transport Decisions

• Patients with suspected ACS or life-threatening causes must be transported urgently to the ED via EMS without delaying transfer for office-based troponin testing 1, 2, 3
• Pain relief, hemodynamic stabilization, and correction of abnormalities should occur without delay 1

Systematic Clinical Assessment

History Taking - Focus on High-Risk Features

• Characterize chest pain using specific descriptors: nature (pressure, tightness, squeezing), onset and duration, location and radiation (especially both arms), severity, precipitating factors, relieving factors, and associated symptoms 2, 4
• Recognize that "chest pain" encompasses more than chest discomfort: pain, pressure, or discomfort in shoulders, arms, neck, back, upper abdomen, or jaw, plus shortness of breath and fatigue are all anginal equivalents 4
• In women, expect chest pain as the dominant symptom but with more frequent accompanying symptoms like nausea and shortness of breath 4
• In elderly patients (≥75 years), consider ACS when shortness of breath, syncope, acute delirium, or unexplained falls occur even without classic chest pain 4
• Screen for cocaine and methamphetamine use as potential causes of acute chest pain 1

Physical Examination - Identify Complications and Alternatives

• Assess vital signs for hypotension, tachycardia, tachypnea, or hemodynamic instability 1, 5
• Look for ACS-specific findings: diaphoresis, crackles, S3 gallop, new mitral regurgitation murmur 2
• Evaluate for alternative life-threatening diagnoses: 4
  • Aortic dissection: pulse differentials, new aortic regurgitation murmur
  • Pulmonary embolism: unilateral leg swelling, tachypnea
  • Pneumothorax: unilateral absent breath sounds, dyspnea on inspiration
  • Pericarditis: fever, pericardial friction rub, pain worse when supine

ECG Interpretation Algorithm

Immediate ECG-Based Management 1

• If STEMI pattern present: Treat according to STEMI guidelines with urgent reperfusion therapy (primary PCI within 60-120 minutes if available, or fibrinolysis if PCI unavailable) 1, 5
• If ST-depression or new T-wave inversions: Treat according to NSTE-ACS guidelines 1
• If diffuse ST-elevation: Consider pericarditis 1
• If new arrhythmia: Follow arrhythmia-specific guidelines 1
• If nondiagnostic or normal ECG with persistent symptoms or high clinical suspicion: Perform serial ECGs every 15-30 minutes during the first hour, as 30-40% of acute MI patients present with initially normal ECGs 1, 3
• Consider supplemental leads V7-V9 in patients with intermediate-to-high ACS suspicion and nondiagnostic initial ECG to rule out posterior MI 1

Biomarker Strategy

Troponin Testing Protocol

• High-sensitivity cardiac troponin is the preferred biomarker because it enables more rapid detection or exclusion of myocardial injury with increased diagnostic accuracy 1
• Serial troponin measurements are essential: Obtain on arrival and repeat at 6-12 hours from symptom onset, as a single measurement drawn less than 6 hours from onset may miss myocardial injury 1, 3
• Monitor for rising or falling pattern indicative of acute myocardial injury 1
• Do not use CK-MB or myoglobin when troponin is available, as they are not useful for diagnosis of acute myocardial injury 1

Risk Stratification and Disposition

Using Clinical Decision Pathways

• Apply validated risk scores incorporating history, ECG, age, risk factors, and troponin: 6
  • HEART score (0-10): High-risk range (7-10) has LR 13 for ACS; low-risk range (0-3) has LR 0.20 against ACS
  • TIMI score (0-7): High-risk range (5-7) has LR 6.8 for ACS; low-risk range (0-1) has LR 0.31 against ACS

Disposition Based on Risk 1, 2, 4

• Low-risk patients (by validated clinical decision pathway): Can be discharged or evaluated in outpatient setting; urgent diagnostic testing not needed
• Intermediate-risk patients: Use shared decision-making regarding admission, observation, discharge, or outpatient evaluation; patient decision aids improve understanding and reduce low-value testing 1
• High-risk patients (severe continuing pain, ischemic ECG changes, positive troponin, left ventricular failure, hemodynamic abnormalities): Admit to coronary care unit or chest pain unit for continuous monitoring 1

Advanced Imaging for Alternative Diagnoses

When Obstructive CAD is Excluded but Troponin Positive 1

• CMR or echocardiography can establish alternative diagnoses in high-risk patients

Specific Life-Threatening Conditions 1

• Suspected aortic dissection: CTA of chest, abdomen, and pelvis is recommended; if contraindicated, use TEE or CMR
• Suspected pulmonary embolism: CTA using PE protocol in stable patients with high clinical suspicion; guide further testing by pretest probability
• Suspected myopericarditis with nonobstructive coronaries: CMR with gadolinium contrast distinguishes myopericarditis from MINOCA
• Suspected nonischemic cardiac conditions (pericardial effusion, endocarditis): TTE is recommended

Initial Medical Management

When ACS is Suspected 1, 3

• Aspirin 250-500 mg immediately if no contraindications 1, 3
• Low-molecular-weight heparin can be started in the ED 1
• Continuous cardiac monitoring with defibrillator readily available 3
• Oxygen only if hypoxemic 1

Nitroglycerin Considerations 7

• Sublingual nitroglycerin (not swallowed): 1 tablet dissolved under tongue at first sign of angina, may repeat every 5 minutes up to 3 tablets over 15 minutes
• Critical pitfall: Response to nitroglycerin is NOT diagnostic of myocardial ischemia and should not guide decision-making 2
• Contraindicated with PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) due to severe hypotension risk 7

Special Populations

Prior CABG Surgery 1

• If acute chest pain without ACS: Perform stress imaging to evaluate for ischemia or CCTA for graft stenosis/occlusion
• If indeterminate/nondiagnostic stress test: ICA is useful

Dialysis Patients 1

• Patients experiencing acute unremitting chest pain during dialysis require transfer by EMS to acute care setting

Critical Pitfalls to Avoid

• Never rely on a single normal ECG to exclude ACS when clinical suspicion remains high 3
• Never discharge based on a single troponin drawn less than 6 hours from symptom onset 3
• Never delay ED transfer from office settings to obtain troponin testing 1, 2, 3
• Never interpret nitroglycerin response as diagnostic of cardiac ischemia 2
• Never miss serial ECGs when initial ECG is nondiagnostic but symptoms persist 1, 3
• Avoid discharging patients without proper observation in chest pain units, as the risk of missed ACS remains significant 1