What was the difference between the account management and the key account management ?

Thanks for invitation,

Account management:

Is the responsibility for the day-to-day management of a particular customer's account with the business, including contacts, and provides customer support, up selling, technical assistance and general relationship management. 

Whereas, Key Account Management (KAM ), as defined by Harvard Business Review:

Is a radically different organizational process used by business-to-business suppliers to manage their relationships with strategically-important customers, and it produces measurable business benefits.