What is the next diagnostic step for a patient with tachycardia and a negative Focused Assessment with Sonography for Trauma (FAST) exam after a motor vehicle accident (MVA)?

Next Diagnostic Step for Post-MVA Patient with Tachycardia and Negative FAST

In a 45-year-old female with tachycardia (HR 114) and negative FAST exam after motor vehicle accident, proceed immediately to CT chest/abdomen/pelvis with IV contrast to evaluate for occult injuries, as tachycardia in isolated chest trauma suggests either ongoing hemorrhage or blunt cardiac injury that FAST examination cannot reliably exclude. 1, 2

Immediate Diagnostic Pathway

Why CT is the Next Step

• CT with IV contrast is the imaging modality of choice for hemodynamically stable trauma patients, providing comprehensive evaluation of visceral organs, vascular injuries, cardiac chambers, pericardium, and thoracic injuries that FAST examination cannot detect 1, 2

• FAST has significant limitations in trauma evaluation—it has high false-negative rates for pelvic fractures, lacks sensitivity for solid organ injuries, cannot detect retroperitoneal hemorrhage, and has lower specificity compared to CT for excluding thoracic and abdominal injuries 1

• Persistent tachycardia after negative FAST is a red flag that warrants advanced imaging, as it may indicate occult bleeding, blunt cardiac injury, or other injuries requiring intervention 1, 2

Specific CT Protocol

• Obtain whole-body CT (chest/abdomen/pelvis) with IV contrast if the mechanism suggests high-energy trauma (>35 mph collision, rollover, ejection, or significant deceleration injury) 1

• Contrast-enhanced CT has greater sensitivity for detecting visceral organ and vascular injury compared to noncontrast CT and should be used unless absolutely contraindicated 1

• Arterial phase imaging of the chest is particularly important if there is concern for aortic or major vessel injury based on mechanism 1

Critical Clinical Context

Hemodynamic Status Determines Everything

• This patient appears hemodynamically stable (HR 114 is tachycardic but not severely so, and she's not described as hypotensive), which makes CT the appropriate next step rather than immediate operative intervention 1, 2

• If the patient were truly unstable (persistent hypotension despite resuscitation), she would bypass CT and go directly to the operating room, as a positive FAST with hemodynamic instability mandates immediate surgical intervention 1

Why Tachycardia Matters Here

• Tachycardia in isolated chest trauma should not be dismissed—it may represent pericardial tamponade, tension pneumothorax, ongoing hemorrhage, or blunt cardiac injury even when FAST is negative 1, 2

• The American College of Radiology notes that patients with abnormal vital signs (including persistent tachycardia) after trauma have clinically significant rates of major injury on CT chest 1

• Blunt cardiac injury ranges from silent arrhythmias to cardiac rupture, and tachycardia may be the only initial sign—ECG and troponin should also be obtained during the workup 2, 3, 4

Additional Concurrent Workups

Cardiac Evaluation

• Obtain 12-lead ECG and cardiac troponin in this patient with tachycardia and chest trauma, as normal ECG and troponin indicate low probability of significant blunt cardiac injury 2

• If ECG shows abnormalities or arrhythmias, or if troponin is elevated, proceed with echocardiography after CT to evaluate for myocardial contusion, valvular injury, septal rupture, or pericardial injury 1, 2

• Transthoracic echocardiography (TTE) is indicated if the patient develops signs of heart failure, abnormal heart sounds, or persistent hemodynamic instability after excluding other causes 1, 2

Portable Radiographs

• Portable chest and pelvis radiographs should be obtained if not already done, as they can rapidly identify tension pneumothorax, significant mediastinal injury, and unstable pelvic fractures 1

• However, chest radiographs have lower sensitivity for thoracic injuries compared to CT and should not delay definitive imaging 1

Common Pitfalls to Avoid

• Do not assume negative FAST excludes significant injury—FAST is primarily a triage tool with limited sensitivity for many injuries, and its role is to identify patients needing immediate surgery, not to rule out all injuries 1

• Do not attribute tachycardia solely to pain or anxiety in trauma patients—assume it represents physiologic compensation for injury until proven otherwise 1

• Do not delay CT to repeat FAST—the case report of right atrial rupture demonstrates that even a second FAST may be equivocal while CT definitively identifies the injury 5

• Do not forget that cardiac rupture can occur without external signs of trauma, as demonstrated in survivors of blunt cardiac injury who appeared initially stable 5

Clinical Decision Algorithm

1. Confirm hemodynamic stability (adequate blood pressure with or without minimal resuscitation) 1, 2
2. If stable with tachycardia and negative FAST: Proceed to CT chest/abdomen/pelvis with IV contrast 1, 2
3. Obtain concurrent ECG and troponin during CT preparation 2
4. If CT shows cardiac injury or ECG/troponin abnormal: Add echocardiography 1, 2
5. If patient becomes unstable at any point: Abort imaging and proceed to operating room 1