What is the management for a patient with chest pain and elevated creatine kinase (CK) levels?

Management of Chest Pain with Total CK 202

A total CK of 202 U/L with chest pain requires immediate measurement of high-sensitivity cardiac troponin (hs-cTn) and CK-MB, as total CK alone is neither sensitive nor specific enough to diagnose or exclude acute myocardial infarction. 1

Why Total CK Alone is Inadequate

• Total CK should NOT be used as the sole marker for detecting myocardial injury in patients with chest pain suggestive of acute coronary syndrome (ACS). 1
• Total CK has poor diagnostic performance with only 38% sensitivity and 80% specificity for acute myocardial infarction (AMI) when measured as a single sample in the emergency department. 2
• Total CK lacks cardiac specificity and can be elevated from skeletal muscle injury, intramuscular injections, strenuous exercise, hypothyroidism, or other non-cardiac causes. 3

Immediate Diagnostic Actions Required

Obtain a 12-lead ECG within 10 minutes of presentation to identify:

• ST-segment elevation ≥1 mm indicating STEMI requiring immediate reperfusion therapy 1, 4
• ST-segment depression or T-wave inversions suggesting NSTE-ACS 1
• New left bundle branch block (LBBB) or other conduction abnormalities 1

Measure cardiac-specific biomarkers immediately:

• High-sensitivity cardiac troponin (hs-cTnT or hs-cTnI) is mandatory as it is more sensitive and specific than CK or CK-MB for detecting myocardial injury 1
• CK-MB mass (not CK-MB activity) should be measured if troponin is not immediately available 1, 3
• Serial measurements at 3-6 hour intervals are required, as a single troponin measurement has insufficient sensitivity (10-15% of AMI patients have negative initial troponin) 5, 6

Risk Stratification Based on Clinical Features

High-risk features requiring immediate coronary care unit admission: 1

• Prolonged ongoing rest pain (>20 minutes)
• Hemodynamic instability (hypotension, pulmonary edema, new mitral regurgitation murmur)
• Dynamic ST-segment changes on serial ECGs
• Elevated troponin above the 99th percentile (even if CK is only mildly elevated)

Intermediate-risk features: 1

• Prior history of myocardial infarction or coronary artery disease
• Age >70 years
• Diabetes mellitus
• Rest angina >20 minutes that has resolved

Immediate Medical Management

Administer aspirin 160-325 mg immediately (chewed, not swallowed) unless contraindicated by active gastrointestinal bleeding or known aspirin allergy. 1, 4

Provide pain relief with intravenous morphine (4-8 mg initially, with additional 2 mg doses at 5-minute intervals as needed), as pain relief reduces sympathetic activation and myocardial oxygen demand. 1

Give sublingual nitroglycerin unless systolic blood pressure <90 mmHg or heart rate <50 or >100 bpm, to decrease ischemia and reduce cardiac filling pressures. 1, 4

Administer oxygen 2-4 L/min if the patient is breathless, hypoxemic, or has features of heart failure. 1

Critical Pitfalls to Avoid

• Do NOT rely on total CK elevation alone to diagnose AMI - it misses 62% of cases when used as a single measurement in the emergency department. 2
• Do NOT assume a mildly elevated CK (202 U/L) excludes significant cardiac injury - troponin can be elevated indicating myocardial infarction even when CK is normal or minimally elevated. 1, 7
• Do NOT wait for biomarker results before initiating reperfusion therapy if the ECG shows ST-segment elevation - door-to-needle time for thrombolysis must be <30 minutes. 1
• Do NOT discharge the patient based on a single negative troponin - serial measurements over 9-12 hours are required to exclude AMI with adequate sensitivity. 1, 6

Disposition Algorithm

If ST-elevation is present on ECG:

• Immediate reperfusion with primary PCI (preferred, door-to-balloon <90 minutes) or fibrinolytic therapy (door-to-needle <30 minutes) 1

If troponin is elevated (>99th percentile) without ST-elevation:

• Admit to coronary care unit with continuous cardiac monitoring 1
• Initiate dual antiplatelet therapy (aspirin plus clopidogrel, ticagrelor, or prasugrel) 1, 4
• Start anticoagulation with heparin, enoxaparin, or fondaparinux 1
• Consider early invasive strategy with coronary angiography within 24-48 hours for high-risk patients 1

If initial troponin is negative:

• Repeat troponin at 3-6 hours and again at 9-12 hours after symptom onset 1, 5
• Continue cardiac monitoring and serial ECGs 1
• If all serial troponins remain negative and ECGs show no ischemic changes, consider stress testing before discharge to evaluate for inducible ischemia 1

Additional Diagnostic Considerations

Obtain chest X-ray to evaluate for alternative diagnoses such as pneumothorax, pneumonia, pleural effusion, or aortic dissection if clinical suspicion exists. 1

Consider echocardiography if hemodynamic disturbances, new murmurs, or diagnostic uncertainty exists - regional wall motion abnormalities occur within seconds of coronary occlusion. 1, 7

The combination of CK-MB mass and cardiac troponin I provides 100% sensitivity and 100% negative predictive value when measured 12 hours after admission, making this the most reliable approach for excluding AMI. 6