Crochetage sign

Crochetage sign

The Crochetage sign is an electrocardiographic (ECG) finding classically associated with an ostium secundum atrial septal defect (ASD).

🔹 Definition

  • The Crochetage sign is a notch near the apex of the R wave in the inferior leads (II, III, aVF) on ECG.
  • It resembles a crochet hook (hence the name).

🔹 Mechanism

  • Caused by interatrial conduction delay due to the presence of an ostium secundum ASD.
  • The abnormal right atrial depolarization produces a distinct R-wave notch in inferior leads.

🔹 Clinical Importance

  • Diagnostic value:
    • Highly suggestive of ostium secundum ASD.
    • Reported in ~73% of patients with secundum ASD.
  • Specificity:
    • When present in all 3 inferior leads (II, III, aVF), it has ~92% specificity for ASD.
  • Post-surgical relevance:
    • If the crochetage sign persists after ASD closure, it may indicate residual shunting.

🔹 Differentiation

  • Must be distinguished from notched R waves seen in:
    • Left ventricular hypertrophy
    • Right bundle branch block
    • Normal variant R-wave notching

✅ Key Point:
The Crochetage sign = notched R wave in inferior leads, highly specific for ostium secundum ASD and may persist if residual shunt remains after surgery.

Crochetage Sign & ECG Findings of Secundum ASD – 20 MCQs
Click an option → Correct = Green-Yellow, Wrong = Red. Explanations are collapsible.
Q1
Definition
The Crochetage sign on ECG is best described as:
A) A notch at the apex of the R wave in inferior leads
B) A deep S wave in V1 with ST depression
C) A delta wave in pre-excitation
D) Fragmented QRS in lateral leads
Crochetage is a notch resembling a crochet hook at the apex of the R wave in II, III, aVF.
Q2
Leads
In which leads is the Crochetage sign most typically seen?
A) I and aVL
B) II, III, and aVF
C) V3–V5
D) aVR and V1
Inferior limb leads best demonstrate the Crochetage sign.
Q3
Mechanism
The Crochetage sign most likely reflects:
A) Pre-excitation via accessory pathway
B) Left ventricular conduction delay
C) Interatrial conduction delay in ostium secundum ASD
D) Ventricular scar after MI
Abnormal conduction due to septal defect produces the notch in inferior leads.
Q4
Specificity
The Crochetage sign is most strongly associated with which condition?
A) Ventricular septal defect
B) Hypertrophic cardiomyopathy
C) Ebstein’s anomaly
D) Secundum atrial septal defect
Crochetage sign is a specific ECG marker for ostium secundum ASD.
Q5
Prevalence
Crochetage sign is present in approximately what percentage of secundum ASD cases?
A) 70–80%
B) 20–30%
C) 40–50%
D) >95%
Studies show Crochetage appears in about 70–80% of secundum ASD patients.
Q6
Other ECG
Which additional ECG feature is commonly seen in secundum ASD along with Crochetage?
A) Delta waves
B) Tall T waves in V5–V6
C) Incomplete right bundle branch block
D) Left axis deviation
Incomplete RBBB is a classical finding in ASD due to RV volume overload.
Q7
Sensitivity
The sensitivity of the Crochetage sign for secundum ASD is around:
A) ~20%
B) ~40%
C) ~70%
D) ~95%
Crochetage is moderately sensitive (~70%) but highly specific for secundum ASD.
Q8
Specificity
The specificity of Crochetage sign for secundum ASD is approximately:
A) 40%
B) 55%
C) 65%
D) >90%
It has a high specificity (>90%), especially in adults.
Q9
Differential
Crochetage must be differentiated from notching due to:
A) Atrial flutter waves
B) Bundle branch blocks
C) U waves
D) Hyperkalemia
Notches in QRS may occur in BBB; clinical context differentiates them.
Q10
Post-surgery
What happens to Crochetage sign after surgical closure of ASD?
A) It often disappears
B) It becomes more prominent
C) It changes to delta waves
D) It persists permanently
The sign usually resolves after correction of ASD.
Q11
P waves
Which P-wave finding most supports right atrial enlargement in secundum ASD?
A) Tall peaked P in lead II (>2.5 mm) with prominent initial positivity in V1
B) Broad, notched P in lead II (>120 ms)
C) Inverted P in lead II suggesting ectopic low atrial rhythm
D) Completely isoelectric P in limb leads
Chronic right-sided volume overload can produce classic RA enlargement: tall P in II and a positive initial P deflection in V1.
Q12
Axis patterns
Which frontal QRS axis pattern favors primum ASD rather than secundum ASD?
A) Normal axis (−30° to +90°)
B) Marked left axis deviation (< −45°)
C) Mild rightward axis
D) Extreme axis deviation (northwest)
Primum (AV canal) defects commonly show left axis deviation. Secundum ASD more often has normal to rightward axis.
Q13
V1 morphology
A typical right ventricular volume-overload pattern in secundum ASD is:
A) QS pattern in V1 with deep ST depression
B) Predominantly negative QRS in V1 with wide S
C) rSr′/rsR′ pattern in V1 (incomplete RBBB)
D) Dominant R in V5–V6 with deep Q in III
Right-sided volume overload frequently produces an rSr′/rsR′ pattern in V1–V2, often termed incomplete RBBB.
Q14
Subtypes
Crochetage is least expected in which ASD subtype?
A) Small ostium secundum
B) Moderate ostium secundum
C) Large ostium secundum
D) Sinus venosus ASD
Crochetage is classically linked with secundum ASD; sinus venosus defects have different anatomic/electrical associations.
Q15
Confirmatory test
In an adult with inferior lead Crochetage and rsR′ in V1, the best initial test to confirm an ASD with shunt is:
A) Chest X-ray
B) Transthoracic echocardiography with color Doppler
C) Cardiac MRI stress perfusion
D) Holter monitoring
TTE with color Doppler directly visualizes the defect, estimates Qp:Qs, and assesses right-sided size/pressures.
Q16
Differentials
Which finding most strongly argues for pre-excitation (WPW) rather than Crochetage?
A) rSr′ in V1 with narrow QRS
B) Inferior R-wave notching without PR change
C) Normal PR interval with inferior notches
D) Short PR interval with delta wave at QRS onset
WPW features a short PR and delta wave; Crochetage is a notch near the R apex, not a slurred QRS onset.
Q17
Associated lesions
In suspected sinus venosus ASD where Crochetage is absent, which associated anomaly should be actively sought?
A) Partial anomalous pulmonary venous return (PAPVR)
B) Coarctation of the aorta
C) Bicuspid aortic valve
D) Coronary fistula
Sinus venosus ASDs frequently coexist with PAPVR, explaining RV volume overload in the absence of Crochetage.
Q18
Hemodynamics
Which hemodynamic statement best fits patients with Crochetage due to secundum ASD?
A) Qp:Qs ≈ 1:1 with no volume overload
B) Exclusive right-to-left shunt at rest
C) Left-to-right shunt causing increased pulmonary flow (often Qp:Qs ≥ 1.5:1)
D) Pure LV pressure overload with concentric LVH
Secundum ASD typically causes an L→R shunt with pulmonary overcirculation and right-sided dilation.
Q19
Pattern recognition
Which combination is LEAST consistent with classic secundum ASD/Crochetage physiology?
A) Inferior lead R-wave notching + rsR′ in V1
B) Wide and fixed splitting of S2 on exam
C) Right atrial and right ventricular enlargement on imaging
D) Marked left axis deviation with AV canal features
Marked left axis deviation suggests primum/AV canal defects, not classic secundum ASD with Crochetage.
Q20
Clinical utility
How should Crochetage most appropriately influence management?
A) It replaces echocardiography for definitive diagnosis
B) It raises strong suspicion for secundum ASD and should prompt confirmatory imaging
C) It quantifies shunt size precisely without imaging
D) It mandates urgent surgery irrespective of symptoms/shunt
Crochetage is a valuable ECG clue; decisions rely on echo (and sometimes MRI/TEE) to confirm and size the shunt.

Electrocardiogram Showing Right Axis Deviation With Crochetage Pattern in Leads II, III, and aVF

Point Important Fact
1Crochetage sign is a notching of the R wave in inferior leads (II, III, aVF).
2Highly associated with ostium secundum atrial septal defect (ASD).
3Appears like a crochet hook—hence the term “Crochetage.”
4Represents interatrial conduction delay due to ASD.
5Present in ~73% of patients with ostium secundum ASD.
6When seen in all inferior leads, specificity reaches ~92% for ASD.
7May persist after surgical or device closure if residual shunt exists.
8Best observed in lead II but often present in III and aVF too.
9It is not pathognomonic but strongly suggestive of ASD.
10Other ECG signs of ASD include incomplete RBBB and right axis deviation.
11Crochetage sign reflects atrial depolarization abnormalities.
12Helps differentiate ostium secundum ASD from other ASD types.
13If absent, ASD cannot be excluded; sensitivity is limited.
14More reliable when combined with echocardiography findings.
15May mimic notching seen in LVH or conduction abnormalities.
16First described by Shah et al. in 1974 as a specific marker for ASD.
17Useful in screening ECGs when ASD is suspected clinically.
18Can guide further imaging studies like TEE or cardiac MRI.
19Persistence post-closure warrants evaluation for residual defect.
20Simple, inexpensive, and quick ECG marker—valuable in resource-limited settings.

Short Questions & Answers – Crochetage Sign

Q1. What is the Crochetage sign on ECG?
Ans: Notching of the R wave in inferior leads (II, III, aVF).
Q2. Crochetage sign is most strongly associated with which condition?
Ans: Ostium secundum atrial septal defect (ASD).
Q3. In which ECG leads is Crochetage sign best observed?
Ans: Inferior leads – II, III, and aVF.
Q4. What does the “crochet hook” pattern represent?
Ans: Interatrial conduction delay due to left-to-right shunting across ASD.
Q5. What is the approximate prevalence of Crochetage sign in secundum ASD?
Ans: Around 70–75% of cases.
Q6. If present in all inferior leads, what is the specificity of Crochetage sign for ASD?
Ans: Up to 92% specificity.
Q7. Does Crochetage sign disappear after surgical or device closure of ASD?
Ans: It may persist if a residual shunt remains; sometimes resolves with complete closure.
Q8. Which other ECG abnormalities are common in ASD apart from Crochetage sign?
Ans: Incomplete right bundle branch block (RBBB) and right axis deviation.
Q9. Who first described the Crochetage sign?
Ans: Shah et al. in 1974.
Q10. Why is Crochetage sign clinically important?
Ans: It serves as a simple, inexpensive ECG marker for suspecting ASD, especially in resource-limited settings.

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