What does a Crochetage sign on an electrocardiogram indicate and what is the appropriate next step in management?

Crochetage Sign: Diagnostic Significance and Management

What the Crochetage Sign Indicates

The crochetage sign—a notch near the apex of the R wave in inferior limb leads (II, III, aVF)—is highly specific for atrial septal defect (ASD), particularly secundum ASD, and should prompt immediate echocardiographic evaluation to confirm the diagnosis and assess shunt severity. 1

The crochetage pattern represents a distinctive ECG finding that correlates directly with:

• Shunt severity: The presence of crochetage increases with larger anatomic defects (p<0.0001) and greater left-to-right shunt volume (p<0.0001), even when pulmonary hypertension is present 1
• Defect size and location: Multiple regression analysis demonstrates that only shunt size (p<0.0006) and defect location (p<0.0001) determine the presence of this sign 1

Diagnostic Specificity

The diagnostic accuracy of the crochetage sign varies based on its distribution:

• When present in all three inferior limb leads (II, III, aVF): Specificity exceeds 92% for ASD diagnosis across all patient populations 1, 2
• When present in at least one inferior limb lead: Sensitivity is 31.7% with specificity of 86.1% in pediatric populations 2
• In adults with ASD: The sign appears in 73.1% of cases, compared to only 7.4% in normal subjects 1

Key Distinguishing Feature

The crochetage pattern is independent of incomplete right bundle branch block (RBBB). 1, 2 When both findings coexist, the specificity for ASD diagnosis increases to ≥95.2%, but the crochetage sign alone carries diagnostic weight separate from the RSR' pattern seen in RBBB 1. This is critical because incomplete RBBB is common in athletes and considered a normal training-related finding requiring no evaluation 3, 4, whereas crochetage demands investigation.

Appropriate Next Steps in Management

Immediate Evaluation

1. Obtain transthoracic echocardiography to confirm ASD presence, measure defect size, quantify shunt ratio (Qp:Qs), and assess for pulmonary hypertension 1, 5, 6

2. If transthoracic echo is inadequate (poor acoustic window), proceed directly to transesophageal echocardiography, which provides superior visualization of atrial septal anatomy 5, 7

3. Assess for associated complications:

   • Right ventricular enlargement and dysfunction 1, 6
   • Pulmonary artery pressure elevation 1
   • Paradoxical embolism risk, particularly pulmonary thrombosis in patients with Eisenmenger physiology 6
   • Conduction abnormalities including high-grade AV block (rare but reported) 7

Clinical Context Considerations

In athletes presenting with crochetage: Do not dismiss this as a training-related finding. While incomplete RBBB with RSR' pattern and QRS <120 ms is normal in athletes 3, 4, the crochetage notch is pathological and warrants the same evaluation as in non-athletes 1.

In pediatric patients: The sign maintains high specificity (>92% when present in all three inferior leads) and should trigger echocardiographic screening even in asymptomatic children 2.

Post-operative monitoring: The crochetage pattern disappears in 35.1% of patients following successful ASD closure, even when RBBB persists, making it a useful marker for assessing hemodynamic correction 1.

Common Pitfalls to Avoid

• Do not confuse crochetage with the terminal R' wave of incomplete RBBB: The crochetage notch occurs near the apex of the R wave in inferior leads, while the RSR' pattern appears in V1-V2 1, 6
• Do not assume the finding is benign in athletes: Unlike many ECG variants in trained individuals, crochetage indicates structural heart disease 1
• Do not delay echocardiography: When clinical suspicion is high and echo is initially unavailable, the ECG finding of crochetage should elevate urgency for definitive imaging 5