OSAKA, Japan - A total of 140 people were subjected to unnecessary heart surgery at a Nara Prefecture hospital that was shut down in 2009 after revelations of fatal negligence and fraud, sources said Friday.

The patients at Yamamoto Hospital underwent coronary artery stenting, a catheterization procedure that expands an artery in the heart to prevent heart attacks. Using an X-ray device to observe the artery, doctors insert a stent - a tube made of wire net - in the coronary artery.

The operations were mainly conducted by former hospital director Fumio Yamamoto, 53.

Yamamoto is currently serving a prison term for falsely claiming to have performed catheterization surgeries on eight welfare recipients to obtain medical fees totaling about 8.3 million yen (S$128,650) between January 2005 and May 2007.

Yamamoto also was indicted in February last year for allegedly causing a male patient to bleed to death after damaging a vein in his liver during surgery for a vascular tumor in 2006.

Footage of the stenting procedures was recorded automatically by an X-ray photography device in the operating room of the hospital.

Discs containing the footage were among materials seized by Nara prefectural police in the fraud case and were later returned to the Osaka municipal government.

In the case of stenting operations, hospitals can only claim remuneration from the national health insurance system when 75 per cent or more of the diameter of a coronary artery is blocked.

The municipal government asked a university hospital to examine the discs, and a panel of seven doctors of cardiovascular internal medicine concluded that 98 of 116 patients did not need the stenting surgery.

The Sakai and Higashi-Osaka municipal governments in Osaka Prefecture and the Kyoto municipal government also conducted similar examinations of separate footage and concluded that 42 stenting operations were unnecessary.

"There was footage of operations on patients [whose coronary arteries] were not clogged at all. They are obviously fraudulent," an official of the Osaka municipal government said.

"There's a high risk of a ruptured artery or a blood clot with stenting. If the hospital deliberately performed [unnecessary] operations, a case can be made for injurious assault," a stent treatment specialist said.

Yamamoto Hospital accepted welfare recipients, including homeless people.

The Osaka and other municipal governments, which suspect the remuneration made from welfare payments to the hospital was improper and excessive, have filed a claim in court and are trying to gather evidence.

-- The Yomiuri Shimbun/Asia News Network