WASHINGTON (AP) -- The Food and Drug Administration has approved a new implantable device to help doctors monitor patients with severe heart failure as they go about their day.

The agency cleared the CardioMEMS HF system Wednesday for patients who have been hospitalized in the previous year due to heart failure.

The device uses an implanted sensor in the peripheral artery to measure blood pressure and heart rate. The information is then wirelessly beamed to an electronic database that can be accessed by the patients' physician.

About 5.8 million people in the U.S. have heart failure, in which the heart cannot pump enough blood to meet the body's oxygen needs. The new device was specifically approved for a subgroup of patients with heart failure that limits their physical activity, even the ability to walk short distances.

The FDA cleared the device based on a study of 550 patients in which patients implanted with CardioMEMS HF had significantly fewer heart failure-related hospitalizations than patients without the device.

Manufacturer CardioMEMS Inc. is based in Atlanta. Medical device giant St. Jude Medical of St. Paul, Minnesota holds a 19 percent stake in the smaller company and was granted in 2010 the option to acquire the rest of the company for $375 million. St. Jude said Wednesday it will now exercise that option and expects to complete the acquisition in the second quarter of this year.

Wells Fargo analyst Larry Biegelsen said in a research note that the new device could reach annual sales of $259 million by 2018.

Shares of St. Jude Medical climbed $2.25, or 3.51 percent, to $66.40 in midday trading.