An analog signal would suffer - noise, static, or other objectionable garbage is pretty much assured for both analog audio and analog video. Analog signals would include left/right audio, composite video, s-video, and component video. I'd also not run cable TV (the coax cable upstream of the cable box) in this manner. HDMI is purely a digital connection, so it is possible that the 1's and 0's would be OK, but it's also passing those 1's and 0's electrically. Short of first-hand experience saying that HDMI, DVI, and coaxial digital are OK run this way, the only cable I'd feel comfortable running in the same pipe as a power cord is optical, since the optical signal is going to be entirely unaffected by the power cord's EMI.