What cardiac labs should be ordered for a patient with a nondisplaced (without separation of bone fragments) sternum fracture, specifically electrocardiogram (ECG) and troponin levels?

Cardiac Labs for Nondisplaced Sternum Fracture

All patients with a sternal fracture—regardless of displacement—should have an immediate 12-lead ECG and cardiac troponin measured at presentation, with serial troponin repeated at 3-6 hours after injury. 1, 2

Initial Mandatory Testing

Obtain these labs immediately upon diagnosis:

• 12-lead ECG within 10 minutes of arrival to detect ST-segment changes, new arrhythmias, conduction abnormalities, or ischemic changes 1, 2
• Cardiac troponin I or T at presentation as the initial baseline measurement 1, 2
• Serial troponin at 3-6 hours post-injury to identify rising patterns that indicate myocardial damage 1, 2

The American College of Radiology explicitly states that myocardial contusion and malignant ventricular arrhythmias can occur with sternal fractures "only if there are ECG changes and cardiac troponin levels are rising," making both tests essential even in nondisplaced fractures. 1

Risk Stratification Based on Results

If both ECG and troponin are normal:

• The patient has low probability for significant blunt cardiac injury and can be safely discharged without prolonged observation or echocardiography 1, 2, 3
• The negative predictive value of combined normal ECG and troponin approaches 100% 3

If either ECG shows abnormalities OR troponin is elevated:

• Admit for 24-hour telemetry monitoring 1, 4
• Approximately 6% of sternal fracture patients develop arrhythmias or myocardial contusion 1, 4
• Consider additional troponin measurements beyond 6 hours if clinical suspicion remains high 1

What NOT to Order Routinely

Echocardiography is NOT recommended for isolated sternal fractures when ECG and troponins are normal. 1, 2 The American College of Radiology specifically states that "echocardiography is not recommended in isolated sternal fractures in the presence of a normal ECG and cardiac troponins to evaluate for myocardial contusion." 1

Reserve echocardiography only for patients with:

• Hemodynamic instability 5
• Abnormal ECG findings 5, 6
• Rising troponin levels 5
• Signs of heart failure or abnormal heart sounds 5

Critical Timing Considerations

The 3-6 hour repeat troponin is non-negotiable because cardiac biomarkers may not be elevated immediately after injury. 1, 3 If the time of injury is unclear, use the time of presentation as the starting point for serial measurements. 1

Common Pitfalls to Avoid

• Don't skip the serial troponin: A single normal troponin at presentation misses delayed myocardial injury 1, 3
• Don't order CK-MB or myoglobin: These are not useful with contemporary troponin assays and add no diagnostic value 1
• Don't assume nondisplaced means benign: Displacement status does not predict cardiac complications—only ECG and troponin results do 1, 4
• Don't routinely order echocardiography: This wastes resources and provides no additional benefit when ECG and troponins are normal 1, 2, 7