Threads of heart tissue that surgeons routinely cut while replacing valves may be more important than previously thought.
The threads, which help keep the valve closed as the heart pumps, also may provide cross support, reinforcing the heart, Stanford University researchers told a recent American Heart Association meeting.
In experiments on 22 dogs, when those chordae tendineae threads were cut, heart efficiency decreased, Dr. David Hansen said. "People are undergoing surgery that could possibly have detrimental side effects," he said.
Hansen advocated the use of pig valves, instead of artificial ones, to replace a failing human mitral valve, which regulates blood flow between the heart's upper and lower left chambers. While the threads would become tangled in an artificial valve and must be removed, they are usually left in when a pig valve is used.
About 12,000 mitral valves were replaced in the United States in 1984.
No effect on the human heart from removal of the threads has been proved. If it does cause decreased heart efficiency, as occurs in dogs, most people's hearts probably can compensate by growing thicker and heavier, Hansen and his colleagues said.
But in an already damaged heart, removal of the threads may weaken the heart just enough to cause it to fail, they said.