The health venture led by Dr. Atul Gawande is working with a global consulting powerhouse to hone its strategy for improving care of chronically ill patients who account for the vast majority of medical costs, according to a person familiar with the arrangement. The partnership with Boston-based Monitor Group, the business consulting arm of Deloitte, signals a desire to deliver stepped-up services — enabled by data and modern technology — to frequent users of health care within Amazon, Berkshire Hathaway, and JPMorgan Chase, the companies that hired Gawande to rein in their 1.2 million employees’ health spending. (Casey Ross, STAT)