Definition: 

Interrupt-Driven Organisation are like a hospital emergency room where changes are constantly popping up and the real focus becomes successfully triaging opportunities to ensure teams are always working on the most important items. Few organisations are in industries that change so rapidly that they cannot set priorities at the start of the sprint and leave them alone. Many organisations think they exist in that environment, which they are not. 

It is usually a matter of becoming accustomed to thinking ahead. There are multiple factors which triggers an interrupt such as change in market situations, regulations, policies which needs to be absorbed for competitive advantage.  If organisation is one from whom sudden, near constant change is a fact, it is better to consider using shorter sprint. 

Further Reading:
Book: SUCCEEDING WITH AGILE Software Development Using Scrum by Mike Cohn