Shares of medical device maker St. Jude Medical fell 3.5 percent on Tuesday after the company said it would have to recall some of its implantable heart devices because of “premature battery depletion.”

The device’s malfunction led to two patient deaths, according to a letter the St. Paul, Minn., company sent to doctors.

Short-seller Muddy Waters Research, which had attacked the company in August saying its devices could be hacked, tweeted the company letter on Tuesday.

The company denied the allegation and has sued the firm.

The shares closed at $78.41.