What does the retro‑aortic anomalous coronary (RAC) sign on echocardiography indicate and what are the recommended next steps for evaluation and management?

RAC Sign on Echocardiography

The RAC (retro-aortic anomalous coronary) sign on echocardiography is a tubular echogenic density visualized in the atrioventricular groove that indicates an anomalous coronary artery taking a retroaortic course, most commonly an anomalous left circumflex artery arising from the right coronary sinus. 1

What the RAC Sign Indicates

The RAC sign represents visualization of an anomalous coronary artery coursing posterior to the aorta. This finding has high specificity for detecting a retroaortic coronary anomaly and can be reliably documented in echocardiography reports as highly suggestive of an anomalous aortic origin of a coronary artery (AAOCA). 1

The retroaortic course is generally considered benign according to AATS guidelines, as these subtypes (posterior/retroaortic) are not believed to be clinically significant, unlike interarterial courses which carry risk of sudden cardiac death. 2

Recommended Next Steps

Immediate Evaluation

Obtain coronary CT angiography (CCTA) for definitive anatomical characterization. 3 CCTA is the preferred imaging modality because it:

• Delineates the origin, course, and termination of the anomalous vessel
• Identifies the location and number of ostia
• Defines the relationship to adjacent cardiovascular structures
• Assesses for high-risk anatomical features
• Evaluates for concomitant atherosclerotic disease

CCTA has higher sensitivity for detecting coronary anomalies than invasive angiography (7.9% vs 2.1% prevalence). 3

Risk Stratification Based on Anatomy

Once CCTA confirms the anomaly, determine the specific course:

Retroaortic course (what RAC sign typically indicates):

• Generally benign and not clinically significant 2
• No activity restriction typically needed
• Rare instances may cause ischemia 1

Interarterial course (high-risk):

• Courses between aorta and pulmonary artery
• Associated with sudden cardiac death risk
• Requires different management approach 2

Functional Assessment

For retroaortic courses: Functional testing is generally not required unless symptoms suggest ischemia. 1

If interarterial course is identified instead:

• Perform exercise stress testing with imaging (stress echo or nuclear perfusion) to evaluate for inducible ischemia 2
• Consider Holter monitoring if syncope or arrhythmia suspected

Management Algorithm

For confirmed retroaortic anomalous coronary (typical RAC sign finding):

1. Asymptomatic patients: Conservative management with periodic follow-up

   • Annual cardiology follow-up
   • No activity restrictions needed
   • Document as incidental, likely benign finding 1

2. Symptomatic patients with documented ischemia:

   • Activity restriction
   • Surgical consultation (unroofing, ostioplasty, or reimplantation) 2
   • Consider percutaneous intervention if high surgical risk 4

If CCTA reveals interarterial course instead (misidentified on echo):

• Anomalous left main from right sinus with interarterial course:

  • Restrict from all competitive sports 2
  • Offer surgery even if asymptomatic 2

• Anomalous right coronary from left sinus with interarterial course:

  • Evaluate for inducible ischemia
  • If negative stress test and asymptomatic: may permit athletics after thorough counseling 2
  • If positive: surgery recommended 2

Common Pitfalls

• Don't assume all coronary anomalies are high-risk: Retroaortic courses are generally benign, unlike interarterial courses 2, 5
• Don't rely on echocardiography alone: Agreement between echo reports and surgical findings is poor (kappa = 0.11-0.74 for various features) 6
• Don't miss concomitant atherosclerotic disease: In adults, this often represents the predominant cause of symptoms rather than the anomaly itself 7
• Ensure CCTA is performed with proper gating: Non-gated chest CTA is inadequate for coronary anomaly evaluation 3

Post-Diagnosis Follow-up (if intervention performed)

• Annual cardiology visits
• Annual ECG and echocardiogram
• Exercise stress testing every 1-3 years based on activity level
• Annual stress testing if participating in competitive sports 2