STANFORD — Seven recipients of artificial heart valves later developed a form of Legionnaires' disease, researchers at Stanford University Medical Center said Monday.
All seven recovered following treatment with antibiotics but four had to have their heart valves replaced, said Dr. Lucy Tompkins, director of the Stanford Medical Center clinical laboratory.
She said the origin of the legionella bacteria found in the heart valve patients is still under investigation. "We don't know how the patients got infected," she said.
Tompkins added that there had been no recurrence of the infection in any of the seven patients, all of whom had their heart surgery at Stanford.
The Stanford operating rooms were ruled out as a source of the bacteria, she said. Several types of heart valves made by different manufacturers were involved, making them an unlikely source, she added.
Other Sites Possible
Tompkins and co-researcher Dr. Blake Roessler said it is possible that the legionella infections, called legionella prosthetic valve endocarditis, are not occurring exclusively at Stanford.
But Tompkins cautioned, "These cases didn't develop in a short period of time, so we don't have an epidemic." The first Stanford case was reported in 1983.
She said there is some evidence that at least two other San Francisco Bay Area heart valve patients who didn't have their surgery at Stanford had contracted the legionella infection.
She described the legionella invasion of the heart patients as "a very smoldering kind of infection" and said doctors treating the seven patients did not immediately diagnose the problem, with symptoms occurring for months before an accurate diagnosis was made. Symptoms included persistent fevers, night sweats, fatigue, weight loss and congestive heart failure.
Sent Back to Stanford
"What finally happened was they were referred back to Stanford after their doctors thought they had endocarditis but couldn't show it using the usual tests. And then we did these extra tests and were able to make the diagnosis," she said.
Tompkins and Roessler recently wrote a brief report on the legionella cases for California Morbidity, a weekly report from the Infectious Disease Branch of the California Department of Health Services. Tompkins said they wanted to alert other laboratories in California about the legionella possibility in heart valve patients suffering similar symptoms.