CMS has now posted clarification to Transmittal 1417/CR 5912 dated January 18, 2008. If you provide and bill for only one session of cardiac rehabilitation for a patient in a given day, that session does not have to be a minimum of 60 minutes. For one session of cardiac rehab, "session" and "hour" are not synonymous. You can read the complete Q & A here for further clarification on billing more than one session in a day.