RIO DE JANEIRO, Feb 28 (Reuters) - Brazilian insurer and hospital operator Hapvida Participacoes e Investimentos SA and competitor Notre Dame Intermedica Participacoes SA disclosed the share conversion terms of a previously announced tie-up that would create the country's largest hospital chain.

The companies said that Intermedica shares will be incorporated into Hapvida, with one Intermedica share being swapped for 5.249 Hapvida shares and an additional 6.45 reais, according to a pair of Saturday night securities filings.

Hapvida shareholders will own 53.6% of the combined company after the deal.

The chief executives of both companies will be active of the board of directors of the combined company, the securities filings said.

The transaction costs will likely come to 116 million reais ($20.7 million), the companies said.

In January, Hapvida offered 49 billion reais ($8.75 billion) to purchase Intermedica. The combined company will have 8.4 million healthcare clients and 70 hospital spread throughout the country.

The final deal is still subject to the approval of the companies' shareholders, as well as health and antitrust authorities in Brazil.

($1 = 5.60 reais)

(Reporting by Gram Slattery; Editing by Lisa Shumaker)