How to retrive DNS Name associated with IP using boto?

import boto.route53
getRecord=connR.get_zone(domainname.com)
getRecord.get_records()

This List all the records associated with domainname.com. How Can I retrive application URL for specific IP address.

e.g Lets say I have 100 records set and one of records is having x.x.x.x IP . I want to retrive application Name associated with x.x.x.x. How can I get this?