Medtronic reports upbeat early results from blood pressure trial

Six years after paying $800 million to acquire a startup company that made a medical device to lower high blood pressure, Medtronic this week presented study data that suggest the therapy might actually work as intended.

Minnesota-run Medtronic is aiming to sell devices for a medical therapy called "renal denervation," in which a doctor uses a thin, spiral-shaped electrode to permanently burn away nerves in the renal artery that can trigger high blood pressure. The device system was originally designed by the California startup Ardian, which Medtronic acquired in 2011, but the therapy failed a key clinical trial three years later.

Now fresh data from a new "proof of concept" trial presented at an industry conference this week in Barcelona show that renal denervation using Medtronic's redesigned Symplicity Spyral system could successfully lower blood pressure in a small, carefully selected group of patients three months after treatment.

"The magnitude of the observed [blood pressure] reductions in the renal denervation group ... represents clinically meaningful reductions in blood pressure," study investigators wrote in a paper published Monday in the medical journal the Lancet. "Blood pressure reductions of similar magnitudes have been associated with reduced rates of cardiovascular death, coronary death, and stroke."

The positive early findings mean that Medtronic will continue a larger "pivotal" study of its renal denervation therapy in patients who are not taking anti-hypertension drugs. Competitors Boston Scientific and St. Jude Medical (now owned by Abbott Laboratories) also have ongoing trials of renal denervation devices.

None of the devices are approved for commercial sale in the U.S., but the sustained interest in renal denervation as a therapy is driven partly by the magnitude of the market.

About 75 million Americans have high blood pressure, and only half of them have their condition "under control," the Centers for Disease Control and Prevention in Atlanta says. The agency cited economic studies that estimate high blood pressure costs $46 billion a year, including the cost of treatments and medications and missed days of work. High blood pressure increases risks for heart attack, stroke and heart failure.

Reducing salt intake and body weight and increasing exercise are common ways to reduce high blood pressure, and doctors may also prescribe drugs for it.

Renal denervation is a minimally invasive experimental medical procedure in which a doctor inserts a thin wire studded with electrodes into the artery that pumps blood into the kidney. Signals traveling to and from the nerves embedded in the artery wall help regulate the body's "fight or flight" response, and severing those nerves with radio-frequency energy is supposed to disrupt the biological chain reaction that leads to chronically elevated blood pressure.

At least, that's how it works in theory. Medtronic acquired Ardian in 2011 following clinical studies documenting early positive results, but three years later, no clear benefit was evident in the data from Medtronic's larger, placebo-controlled trial of the same technology. After the "Symplicity HTN 3" trial flopped, health care trade publication MedPage Today ran a headline asking, "Is This the End for Renal Denervation?"

Not quite. In 2016, after analyzing early results, Medtronic announced it would continue pursuing the therapy, but with stricter controls over whether patients were taking medications in the trial or not. Medtronic also revamped the design of its radio-frequency catheter and its training on how to use the device.

The new study compared the results of 37 patients who got renal denervation with 41 patients who underwent a "sham" placebo procedure. After three months, patients in the experimental arm saw an average 10-point reduction in their systolic blood pressure, compared to a 2-point reduction in the control group.

An opinion article that accompanied Monday's Lancet article noted that "interim" studies may overestimate treatment effects and underestimate the risk of adverse events (none were reported in either group). Also, the study populations in this proof-of-concept trial were not large enough to draw statistically significant conclusions for larger groups of people.

Still, Medtronic officials cheered the results in the trial and vowed to press on. "We intend to continue consulting with our physician advisers and global regulatory authorities about these results so that we can appropriately move forward with a pivotal trial design to ultimately support regulatory approval in the U.S., Japan and other countries where the technology is not currently available," Salmon said.