Congenital chest wall deformities are common in children, causing self and parental concern mainly due to cosmesis. These defects rarely cause severe symptoms in patients.11-year-old girl with a complex chest wall deformity and severe scoliosis causing progressive neurological loss of function. When mobilized to prone position for orthopedic surgery, she suffered sudden hypotension immediately followed by a cardiac arrest, that reverted after moving the child back to supine position. The cardiac arrest was interpreted as a result of a decrease in venous blood return secondary to heart and great vessels compression. She was then proposed and submitted to a modified Ravitch procedure with retrosternal metal bar placement in order to allow ventral positioning. This was successfully achieved, and the patient underwent scoliosis correction 3 months later. After more than a year of follow up, she reduced the need for non-invasive ventilation and tolerates prone positioning.This case report alerts medical community that beyond cosmesis concerns, severe chest wall deformities can cause life-threatening events if not correctly managed.