The U.S. Food and Drug Administration (FDA) staff reviewers said on Friday they found no safety and effectiveness issues with devices made by Otsuka Holdings and rival Medtronic Plc for use in a blood pressure treatment surgery.

The FDA staff's assessment comes ahead of meetings of two independent expert panels next week, where they will make recommendations on whether or not to approve the devices for treatment.

The surgery, known as renal denervation, is allowed in Europe and other parts of the world, but is not yet approved in the U.S., after initial studies of older devices used in the procedure failed key trials.

The staff reviewers said the available safety data for the device made by ReCor, a unit of Otsuka Holdings, did not raise concerns, while pointing that there was limited long-term data. There was no specific comment on Medtronic's device.

ReCor's device, a balloon-like structure inside a catheter, is inserted through a small cut into the kidney's arteries and sends ultrasound energy to burn nerves that are believed to control blood pressure.

On the other hand, Medtronic's device is a spiral shaped catheter and generator combination that uses targeted radiofrequency energy to destroy select nerves.

The devices are meant for patients whose hypertension, or high blood pressure, cannot be controlled with drugs.

These devices have successfully met the main goal of reducing blood pressure as their makers re-designed their trials and reconstituted their patient groups after earlier tests failed. Details on the patient group were not available.

Needham analysts expect the devices might see limited sales for the first few years as the companies take time to build a market.

According to Medtronic, the market size could reach $500 million by 2026 and $2 billion to $3 billion by 2030.

The FDA advisers will meet on Tuesday to discuss ReCor's device and convene the day after to deliberate on rival Medtronic's equipment.

(Reporting by Sriparna Roy in Bengaluru; Editing by Vinay Dwivedi)