Crochetage sign in atrial septal defect was described by Heller J et al in 1996 in study published in the Journal of American College of Cardiology . It is a notch near the apex of the R wave in inferior leads. They noted a sensitivity of about 73% and specificity of 92% if the sign was present in all the three inferior leads. Early disappearance of the crochetage sign after surgical correction of atrial septal defect was found in 35% of cases even when the incomplete right bundle branch block (RBBB) pattern was persisting. The ECG illustrated above shows the notch at the apex of the R wave in leads II and aVF and a notch in the ascending limb of lead III.
This ECG also shows right atrial overload as evidenced by P wave amplitude of 0.3 mV in lead II. Incomplete RBBB pattern is seen as slurred S waves in lead I and rSrS pattern in V1.
Heller J, Hagège AA, Besse B, Desnos M, Marie FN, Guerot C. “Crochetage” (notch) on R wave in inferior limb leads: a new independent electrocardiographic sign of atrial septal defect. J Am Coll Cardiol. 1996 Mar 15;27(4):877-82.