Infections linked to high death rate for women after heart surgery

Updated 11:00 AM March 6, 2006

Infections linked to high death rate for women after heart surgery

By Kara Gavin
UMHS Public Relations

For years, experts have puzzled over the fact that women who have heart bypass surgery are far more likely than their male counterparts to die within days or weeks of their operation. This gender gap means many extra female deaths among the 270,000 Americans who have bypass surgery each year.

Now, a U-M study suggests the answer to the mystery may lie with infections, regardless of their location in the body.

In a paper in the Archives of Internal Medicine, U-M Health System researchers report that 96 percent of the gender difference in death risk within 100 days of coronary artery bypass surgery may be explained by differences in infection. They used hospital and post-hospital data from 9,218 Michigan residents who had bypass surgery in a 15-month period. All were Medicare beneficiaries 65 years or older.

"We found that 16 percent of women patients had an infection, compared with 10 percent of men," says lead author Mary A. M. Rogers, research director of the Patient Safety Enhancement Program (PSEP) and the VA Ann Arbor Healthcare Center.

This difference persisted after taking into account age, race, urgency of the operation, length of hospital stay, most co-existing medical conditions, and the number of bypass operations performed at each hospital or by each surgeon, she says.

"We suspect that there may be a systemic, or body-wide, response to infection, making infection at any site a concern in elderly patients," Rogers continues. She notes that women in the study were more likely than men to have infections of the urinary, respiratory and digestive tracts. Women also were more likely than men to have skin and post-operative infections.

Although women who had heart surgery were much more likely to have an infection than their male counterparts, women with an infection were less likely to die than men who had an infection.

"Women tend to live with their disease; men die of it," she says. In this case, the overall mortality was higher in women because infections were much more prevalent among them.

Rogers, a faculty member in the General Medicine Division of the Department of Internal Medicine, works with a range of U-M physicians and researchers who study various aspects of patient safety and health care quality.

She had been working with Dr. Sanjay Saint, PSEP director and associate professor of general medicine at U-M and VA, on projects related to urinary tract infections among hospitalized patients with catheters.

At the same time, she was working with heart-care quality researchers Dr. Brahmajee Nallamothu and Dr. Catherine Kim to examine differences among women and men in heart disease and care.

Curious to see if research had been done on the role of infection in heart-related gender differences, Rogers explored the literature and found little information. So, she embarked on the study with her colleagues, using data from a project led by Dr. Ken Langa, assistant professor of general medicine and member of the Institute for Social Research.

In all, about 12 percent of patients in the study who had infections during their hospital stay died before leaving the hospital, compared with 4 percent of those without infections. When the researchers looked at who had died in the first 30 and 100 days after their operation, those who had had an infection in the hospital were far more likely to die.

Until the new results can be confirmed and the precise role of infection determined, Rogers and her co-authors say there is much that heart patients of both sexes can do to prevent pre- and post-operation infections. Elderly Americans should keep up-to-date with their yearly influenza vaccination and, every five years, be vaccinated against bacterial pneumonia. Both vaccinations could be life-saving.

While in the hospital, bypass patients should heed their doctors' advice to get up and start walking the hospital floor after their operation, because staying in bed for long periods of time may encourage respiratory infections.

Additional authors include Dr. Laurence McMahon Jr., professor and chief of the Division of General Medicine and professor of public health; Dr. Preeti Malani, a clinical assistant professor of internal medicine and VA research scientist; Brant Fries, professor of public health and gerontology at U-M and chief of health systems research at the VA Ann Arbor Healthcare System Geriatric Research, Education and Clinical Center; and Samuel Kaufman of PSEP.

Infections linked to high death rate for women after heart surgery

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