Shareholders overwhelmingly approved Boston Scientific Corp.'s (BSX) $27 billion acquisition of medical device maker Guidant Corp. (GDT), the companies said Friday.

Boston Scientific trumped Johnson & Johnson (JNJ) two months ago in a bidding war for Indianapolis-based Guidant.

The deal is still subject to getting approval by U.S. and European antitrust authorities and customary closing conditions. But Boston Scientific said it expects to close the deal around the middle of April.

Boston Scientific will pay Guidant shareholders about $4.5 million a day in interest for each day after Friday that the acquisition fails to win regulatory clearances required before the deal can be closed.

Analysts said that's small change compared to the earnings potential the companies can expect from combining their medical devices portfolios — a move Boston Scientific expects will nearly double its annual sales from $6.3 billion last year to about $12 billion by 2008.

Ninety-seven percent of Natick-based Boston Scientific's shareholders approved the deal, company spokesman Paul Donovan said.

Among Guidant shareholders, 99 percent of voters approved the merger.

"In Indiana-speak, that's pretty close to unanimous," Guidant CEO James Cornelius said.

Nearly all of the voting was done by proxy. A handful of shareholders voted in person at meetings in Boston and Indianapolis, respectively.