Boston Scientific lowered its outlook, as it expects to end a difficult year with a fourth-quarter sales decline.

Shares were down 6% to $42.38 in premarket trading.

The medical company said it now expects annual sales to increase about 4.25%, down from its previous guidance range of 5.5%-to-6.5% growth. It also cut its adjusted earnings-per-share projection to $3.16 to $3.18, from the prior $3.28 to $3.32.

Boston Scientific said it expects sales to decline in the current fourth quarter by 1% to 3%, with adjusted earnings per share seen at 77 cents to 79 cents.

"This has been a challenging year for Boston Scientific and I'm proud of how our global teams have responded," Chief Executive Mike Mahoney said, adding that he was still confident in the company's long-term strategy.

In August, the company suffered a cyberattack that disrupted its manufacturing and shipping operations within its medical-device division. In September, the company said it likely wouldn't be able to meet its third-quarter and full-year financial expectations because of the attack.

For the third quarter, Boston Scientific posted a profit attributable to shareholders of $582 million, or 40 cents a share, compared with $755 million, or 51 cents a share, a year earlier.

Stripping out certain one-time items, adjusted per-share earnings were 73 cents, ahead of the 72 cents anticipated by analysts, according to FactSet.

Revenue rose 1.5% to $5.14 billion. Analysts surveyed by FactSet forecast revenue of $5.06 billion.

Boston Scientific's MedSurg business, which develops medical and surgical devices, reported 0.6% sales growth, while sales in its cardiovascular segment rose 1.9%.

A 13.1% increase in neuromodulation sales helped offset the less-than-1% decline in endoscopy revenue and 3.2% slide in urology revenue.

Along with the cyberattack, Boston Scientific said in July it was facing unexpected challenges with two of its core heart-disease products, which weighed on sales earlier this year.