On August 5, 2012, at 0331 central daylight time, a Bell 407 helicopter, N429PH, sustained minor damage when it contacted a tower guy wire while it was on approach to the helipad at the San Antonio Military Medical Center (SAMMC), San Antonio, Texas. The pilot, flight nurse, flight paramedic, and patient were not injured. The emergency medical services EMS helicopter was registered to and operated by PHI, Inc., under the provisions of the 14 Code of Federal Regulations Part 135. Night visual meteorological conditions prevailed for the flight, which was on a company visual flight rules (VFR) flight plan. The flight departed from the College Station Medical Center, College Station, Texas, at 0302. The operator reported that the helicopter was on a visual descent to the SAMMC helipad when the helicopter's left skid contacted a tower guy wire, located northeast of the helipad, which resulted in a portion of the left skid separating from the helicopter. The pilot declared an emergency and diverted to the San Antonio International Airport (SAT), San Antonio, Texas. The operator reported that there was no malfunction or system failure of the helicopter before the incident.