Natick medical device company Boston Scientific Corp. said it agreed to pay $275 million in cash to buy Bard EP, the electrophysiology business of C.R. Bard. The deal is expected to broaden the range of products Boston Scientific can offer to treat abnormal heartbeats and other cardiac problems. Electrophysiology is a $2.5 billion global market that is growing at nearly 10 percent annually. Bard EP is based in Lowell. The company generated sales of $111 million in 2012. The deal is expected to close later this year.