At the first of the "Sound of Silence" production, a person's heart monitor is shown and called 'a flatline.' They then proceed to resuscitate the person with cardioversion by shocking the heart. This sadly promotes the erroneous idea to someone viewing believing that resuscitation is possible and thus promotes a false hope in their life with a loved one or family member. However if cautiously watching and seeing even one heart response on a long flatline, then there is a likelihood that cardioversion could restore the heart to sinus activity. A more than one screen "flatline" however does denote a complete absence of the electrical conduction system with heart muscle. It only works when an abnormal rhythm such as "v-tach" or atrial fibrillation is present an can be converted to normal or 'sinus rhythm.' Without a conduction system working in the heart, shocking will always fail.
While treating Lou in the ER Meredith tells him that she grew up in Seattle. In earlier and later episodes she states that her mother took her to Boston when she was 4 or 5 years old to give birth to Maggie. After Maggie was born and put up for adoption she says the Ellis got a job at Mass-Gen and she then grew up in Boston before going to medical school.