Final answer:
iRhythm Technologies provides professional diagnostics and heart rhythm analysis for the Zio XT service under their Direct Bill program.
Step-by-step explanation:
Under Zio XT's Direct Bill program, iRhythm Technologies, Inc. is the provider for the professional diagnostics portion of the Zio service. This specifically includes the detailed heart rhythm analysis that is performed after a patient wears the Zio patch. iRhythm's team of certified cardiac technicians, along with proprietary algorithms, interpret the collected data to provide a comprehensive report that helps in the diagnosis of cardiac arrhythmias.