FDA approval this week of the Emblem S-ICD made by Boston Scientific (NYSE:BSX) puts the company in place to take market share in the cardiac rhythm management space from rivals St. Jude Medical (NYSE:STJ) and Medtronic (NYSE:MDT), Wells Fargo analysts said.

Revenues from St. Jude’s CardioMEMS device, which that company is counting on, won’t be enough to offset the share losses from Boston’s Emblem device, the analysts wrote in a note to investors.

Wells Fargo downgraded its rating on St. Jude, from "outperform" to "market perform," and cut the price target from $73-$74 to $69-$70.

"We currently model St. Jude losing 100 basis points of CRM share in 2015 versus the company’s guidance of flat share. While we continue to believe that CardioMEMS has elements that could make it successful over time, the feedback from the heart failure physicians with whom we spoke at the American College of Cardiology this past weekend was lukewarm. Given St. Jude’s lower top- and bottom-line growth versus its peers in 2015, we believe St. Jude should trade at a discount," the analysts wrote.

"Emblem approvals came at least 2 quarters earlier than we expected, although Boston Scientific does not plan to launch Emblem until May in Europe and the 3rd quarter in the U.S. Given Emblem’s advantages over the current version of S-ICD (smaller size, better battery life, remote patient monitoring), Emblem should help Boston Scientific take additional share from St. Jude (and Medtronic) in the single-chamber ICD market," they wrote.

STJ shares were trading at $67.01 apiece in mid-day activity today, up half a percent. BSX shares were trading at $17.93 each, up ⅔ of a percent.