Sunshine Heart Inc. is creating plenty of buzz with a new heart assist device that could reverse heart damage in some patients.

How much buzz? The Eden Prairie start-up recently completed a $46 million stock sale based on the promise of its C-Pulse device, designed to help those with serious heart failure.

Though U.S. clinical trials are just starting, doctors and analysts are already intrigued. The C-Pulse rhythmically squeezes the aorta to take strain off the heart and helps it pump more efficiently. Piper Jaffray & Co. senior analyst Thomas Gunderson said the product has a potential worldwide market of up $1 billion.

“All of that makes it intriguing and interesting to the investment clientele,” ­Gunderson said. “Not only is it a bigger market, but the technology seems to have grabbed the attention of big-name ­physicians.”

The C-Pulse is designed to help people with Class III heart failure, or those with Class IV who can still move around. Class III patients’ physical activity is limited because they often are short of breath or can feel chest pain after walking just a short distance. Class IV patients are even worse and many will eventually need a new heart. Dave Rosa, CEO of the medical device firm, said there is an untapped market.

“There are 1.5 million patients with Class III heart disease in the U.S., and another 3.7 million in Europe,” Rosa said in a recent interview. “The patients are out there.”

Many of those patients are treated with medicine only. Rosa said the C-Pulse can be inserted through an incision between the second and third rib in a minimally invasive way. A driver worn on the outside of the body sends air through a tube that inflates and deflates the cuff wrapped around the outside of the ascending aorta. That squeezing helps the heart push blood through the body.

Left ventricular assist devices, or LVADs, also help the heart pump blood. But an LVAD is surgically implanted just below the heart and is surgically attached to the heart. It becomes part of the circulatory system. So that device is intended for patients whose hearts are in worse shape.

A patient can safely disconnect from the C-Pulse for a short time, say to take a shower, unlike an LVAD. And the device can safely be removed if it is no longer needed. In fact, a few patients in the device’s pilot study had their hearts improve to the point that they no longer needed the device, Rosa said.

“Can this help the heart recover? Is that a realistic expectation for heart failure patients? The answer is, we don’t know yet,” said Dr. Benjamin Sun of the Minneapolis Heart Institute, medical ­adviser to Sunshine Heart. “Heart failure patients bounce up and down.”

What C-Pulse may do is provide treatment for people who don’t have many options.

Sunshine’s management team, led by Rosa, hosted a breakfast last week for analysts at the Transcatheter Cardiovascular Therapeutics (TCT) gathering in San Francisco. Three physicians made presentations on the C-Pulse: One gave the early results of the device’s European clinical trial, one discussed three patients who were weaned off the device as their hearts became healthier and one reported the progress of the company’s next generation fully-implantable device now in development.

News of patients being weaned off the device has analysts like Joshua Jennings of Cowen looking with favor on the device’s prospects. “We view these weaning events as a future driver of positive physician sentiment and stronger adoption/utilization trends,” he wrote in a note to investors.

Sun of the Minneapolis Heart Institute said there are good things about the technology. But he also wonders if patients might be put off by the hardware they have to carry. That’s why Sunshine Heart has begun developing a fully implantable ­system.

What still has to be determined is “does it really keep people stable, or does the progression of the disease overdrive the power of this pump,” Sun said.

Dr. William T. Abraham, professor of medicine and director of the Division of Cardiovascular Medicine at the Ohio State University and the principal investigator for the C-Pulse clinical trial, likes the device’s potential.

“The C-Pulse device is one I am really quite enthusiastic about,” said Abraham, who receives consulting fees from the company but owns no stock. “The niche that I see for C-Pulse is for patients who cannot climb a flight of stairs, who get tired walking half a block or so, patients for whom an LVAD is not warranted. With this device, there is the potential to reverse the disease or halt the progression.”

Rosa said the clinical trial will be conducted at up to 30 sites around the country and enroll 388 patients. Half, chosen at random, will be treated medically. Half will get the device. The goal will be to see if C-Pulse can reduce the rate of negative events — such as hospitalization or death — for patients with the device. The trial will track total negative events; once 265 events have been recorded, the trial will be over and officials will see how well their device worked. Rosa said he expects the trial to take about 2½ years to complete, so it could be a few years before the device actually makes it to market. The trial needs to show a 30 percent reduction in negative events.

At a time when the value of medical technology is being tied more and more to whether it can reduce overall costs, Gunderson said the impact of reducing hospitalizations or even healing the heart could be significant on the firm’s fortunes.