<prompt> In coarctation of aoa, the side of rib notching isSuperior to ribInferior to ribAt sternumAt veebra  <response>: Rib notching is unusual in infancy but becomes more frequent with increased age; it is present in 75 of adults with coarctation. Rib notching occurs along the inferior margin of the third to the eighth ribs; it is caused by pulsation of dilated intercostal aeries. Ref Davidson 23rd edition pg 443 