What is the significance and management of a Crochetage sign on an electrocardiogram (ECG)?

Crochetage Sign on ECG: Significance and Management

The crochetage sign on ECG is a specific electrocardiographic marker strongly associated with atrial septal defects (ASDs), particularly ostium secundum type, and requires further cardiac evaluation including echocardiography to confirm the underlying structural heart defect.

Definition and Appearance

• Crochetage sign (also called "notch sign") appears as a notch near the apex of the R wave in inferior limb leads (II, III, aVF)
• Most commonly associated with secundum atrial septal defects
• Often appears alongside incomplete right bundle branch block (RBBB)

Clinical Significance

Association with Cardiac Conditions

• Primary association: Atrial septal defects (ASDs)

  • Present in up to 73.1% of patients with secundum ASD 1
  • Highly specific (≥92%) when present in all three inferior limb leads 1
  • Correlates with the size of the anatomic defect and severity of left-to-right shunt 1

• Secondary associations:

  • Patent foramen ovale (PFO) - present in 45.3% of patients with PFO vs 21.2% without PFO 2
  • May also appear in other conditions with right heart volume overload

Diagnostic Value

• Independent of right bundle branch block pattern 1
• When combined with incomplete RBBB, specificity for ASD increases to ≥95.2% 1
• The combination of crochetage sign and RBBB has been shown to have a specificity of 75.8% for PFO detection 2

Recommended Management Approach

Step 1: Confirm ECG Finding

• Verify the presence of crochetage sign in inferior leads (II, III, aVF)
• Note if it appears in one, two, or all three inferior leads (presence in all three leads has highest specificity)
• Document associated ECG findings, particularly RBBB

Step 2: Cardiac Imaging

• Transthoracic echocardiography (TTE) should be performed as the first-line imaging study

  • Essential for evaluation of cardiac structure and function 3
  • Should include assessment for:
    • Atrial septal defect
    • Right ventricular size and function
    • Estimated pulmonary artery pressure
    • Presence and direction of shunting

• Transesophageal echocardiography (TEE) with agitated saline contrast

  • Indicated when TTE is inconclusive or to better characterize the defect
  • Gold standard for PFO detection 2

Step 3: Risk Stratification

• Assess for symptoms related to the underlying cardiac condition:

  • Dyspnea, fatigue, palpitations, chest discomfort
  • History of paradoxical embolism or stroke
  • Exercise intolerance

• Evaluate for complications:

  • Right heart failure
  • Pulmonary hypertension
  • Arrhythmias (particularly atrial fibrillation)
  • History of stroke or TIA

Step 4: Management Based on Underlying Condition

• For confirmed ASD:

  • Small defects (<5mm) without symptoms or chamber enlargement: clinical monitoring
  • Larger defects, symptoms, or right heart enlargement: referral to cardiology for consideration of closure
  • Surgical or percutaneous closure based on defect size, location, and patient factors

• For confirmed PFO:

  • Without history of stroke/TIA: generally no specific intervention needed
  • With history of cryptogenic stroke: consider PFO closure in appropriate candidates

Pitfalls to Avoid

• Do not rely solely on crochetage sign for diagnosis of ASD or PFO without confirmatory imaging
• Do not dismiss the finding as incidental, especially when present in all three inferior leads
• Do not overlook associated conditions that may require treatment (pulmonary hypertension, arrhythmias)
• Do not assume all notches on R waves represent true crochetage sign; proper ECG interpretation is essential

Special Considerations

• Crochetage sign may disappear after surgical correction of ASD in about 35.1% of patients, even when RBBB persists 1
• Selective His bundle pacing has been reported to eliminate crochetage sign in patients with ASD 4, suggesting a potential relationship with conduction system disorders
• The sign may be particularly valuable in settings where immediate echocardiography is not available 5

By following this structured approach to the evaluation and management of patients with crochetage sign on ECG, clinicians can appropriately identify and treat underlying structural heart defects that may impact morbidity and mortality.