Notch near the apex of the R wave of inferior leads seen in a large proportion of patients with an ostium secundum atrial septal defect (ASD), the most common form of ASD

Inferior leads demonstrating Crochetage sign. Source: BMJ
  • First described in 1958 by Toscano et al, the electrophysiological mechanism behind this ECG change remains unknown
  • A 1996 retrospective case study observed this pattern in at least one inferior lead of 73% of patients with a secundum ASD, and 36% of patients with ventricular septal defect (VSD), compared with 7% of the general population
  • Specificity for the diagnosis of ASD increased to 92-100% when associated with an incomplete RBBB pattern, or when present in all three inferior leads
  • In ASD, the incidence of Crochetage sign increases with larger anatomic defect or greater left-to-right shunt
  • A 2018 case control study found 28% of patients with ASD had this characteristic R wave notching in all three inferior leads compared to just 2% of age matched controls

ECG features of secundum ASD

ECG Examples of Crochetage sign

Example 1
Sarma A. Crochetage sign. IJCCM
  • Right axis deviation
  • Incomplete RBBB pattern
  • Crochetage sign in leads II, III and aVF

This patient was found to have a 20mm ostium secundum ASD. There was resolution of crochetage sign following operative repair

Example 2
  • Right axis deviation
  • Crochetage sign in leads II, III and aVF


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MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

Emergency physician MA (Oxon) MBChB (Edin) FACEM FFSEM with a passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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