* H1 operating income 344 mln Sfr vs Rtrs poll avg 366 mln Sfr

* Tracleer sales below estimates, Opsumit slightly above (RAdds earnings, drug sales)

By Ludwig Burger

ZURICH, July 21 (Reuters) - Actelion, Europe's biggest biotech company, raised its full-year outlook despite posting lower than expected earnings on Tuesday, with the sales decline in an older lung drug overshadowing growth in a replacement treatment.

The Swiss drugmaker has a dominant position in treatments for pulmonary arterial hypertension, which weakens the heart, and is banking on its new drug for the condition, Opsumit, to help to cut the company's reliance on its original blockbuster Tracleer, which loses patent protection this year.

First-half operating income edged 1 percent lower to 344 million Swiss francs ($357.11 million), missing the 366 million franc average forecast in a Reuters poll of analysts.

Tracleer's second-quarter sales fell by 19 percent year on year to 301 million francs, falling short of the analysts' average estimate of 324 million francs. Opsumit sales almost tripled to 113 million francs, slightly ahead of a forecast of 111 million francs.

Actelion is facing competition from a new drug called Adempas, sold by German rival Bayer and marketing partner Merck & Co..

The Swiss company, however, lifted its earnings forecast for the year, predicting 2015 core earnings growth, adjusted for currency swings, to be in the mid-to-high-teen percentage range, excluding the impact of 2014 U.S. rebate reversals.

It had previously forecast core earnings growth in a low double-digit range. ($1 = 0.9633 Swiss francs) (Editing by David Goodman)