For thousands of pacemaker patients, an MRI scan has been out of the question.

That changed Tuesday, when an MRI-compatible pacemaker developed by Medtronic Inc. received Food and Drug Administration approval for use in the United States. With earlier models, an MRI scanner's powerful magnetic fields could interfere with the pacemaker as it delivered therapy.

Fridley-based Medtronic said it will begin shipping its Revo MRI SureScan pacing system immediately.

Both Medtronic and FDA officials said a lingering warning letter issued by the agency to the company's Mounds View cardiac rhythm division in 2009 won't hamper the device's commercial release. The letter outlined problems with the company's procedures for preventing and identifying potential issues with devices, and the way it communicates them to the FDA.

"We determined that there is a significant public health need for this device and that approval should not be delayed due to the warning letter," said FDA spokeswoman Karen Riley, noting that many pacemaker patients "also have a clear and established need for future MRIs. This is the only device that addresses that need."

Tim Nelson, an analyst with Nuveen Asset Management, said the go-ahead from the FDA "is a good sign that the warning letter will probably be lifted soon" and bodes well for future approvals coming out of the Mounds View operation. Among them: An implantable cardioverter defibrillator called Protecta, which minimizes unnecessary shocks to the heart.

Medtronic estimates that 200,000 pacemaker patients in the United States forgo MRI scans, which are increasingly common for diagnosing a wide variety of ailments, particularly in aging baby boomers. Patients over age 65 are twice as likely as younger people to need an MRI.

Medtronic's device, which costs between $5,000 and $10,000, can't be used for all MRI scans, however.