CHICAGO (Reuters) - People on Medicare who get elective surgery to open blocked heart arteries often do not get the recommended stress tests to confirm the surgery is warranted, US researchers said on Tuesday.

The surgery, known as PCI or percutaneous coronary intervention, involves threading a balloon-tipped catheter through the arteries and opening up a clog. A tiny wire-mesh coil called a stent is often inserted to prop open the artery.

PCI costs Medicare, the US government's health insurance programme for people age 65 and older, $10,000 to $15,000 per procedure and has contributed significantly to increases in Medicare spending since the mid-1990s.

"It's important to document that patients are receiving PCI for appropriate indications to ensure the optimal use of Medicare resources," said Dr. Grace Lin of the University of California, San Francisco, whose study appears in the Journal of the American Medical Association.

More than 800,000 PCI procedures are performed each year and they represent big business for medical device makers including Boston Scientific Corp, Medtronic Inc, Abbott Laboratories Inc and Johnson & Johnson.

A number of prior studies have suggested that many stable patients with chest pain can get about the same level of relief with standard drug therapy, but at far lower cost.

Lin and colleagues wanted to see if doctors who are performing PCI surgeries were following widely accepted practice guidelines that call for people to undergo a stress test to determine whether the procedure is needed.

Stress tests, which are typically done on a treadmill, can show whether a person has ischemia, or inadequate supply of blood to the heart caused by a blocked artery.

"What really matters is whether or not that blockage is affecting blood flow to the heart. That is why the stress test is important," Lin said in a telephone interview.