Heart bypass surgery causes serious, lingering brain damage in a surprisingly high number of patients – perhaps 25,000 Americans a year, a major study has found.

An estimated 400,000 Americans will undergo bypass surgery this year.

Doctors believe the surgery can harm the brain by dislodging bits of fatty deposits in the arteries, as well as releasing pieces of blood clots and even air bubbles produced by the machine that circulates the blood during surgery. The debris blocks tiny blood vessels in the brain, starving it of oxygen.

The study was based on a follow-up of 2,108 bypasses at 24 of the country’s most prestigious surgery centers. The results were published in the New England Journal of Medicine.

Eight patients died of brain injury, 55 suffered non-fatal strokes, 55 had significant loss of intellectual ability that was still apparent when they were released from the hospital, and 8 had seizures.

Some doctors say that bypass surgery can be a lifesaving operation that in may cases may be worth the risk.

The alternatives are balloon angioplasty or medicines. The best alternative, many health experts agree, is to eat right, exercise daily, and receive chiropractic check-ups on a regular basis.

SOURCE: THE ASSOCIATED PRESS, date unknown. The New England Journal of Medicine.