There’s a new clue about why women are more likely than men to die after heart bypass surgery.
The finding, published in the Archives of Internal Medicine, isn’t tied to the heart. Instead, it focuses on infections anywhere in the body.
The University of Michigan’s Mary Rogers, PhD, and colleagues studied more than 9,200 Medicare patients in Michigan who had heart bypasses. Participants were followed for 100 days after surgery.
--16 percent of women had infections, compared to 10 percent of men.
--Patients with infections had higher death rates after heart bypass.
--Women’s higher death rates after bypass surgery were largely explained by their higher prevalence of infection.
About the Operation
Heart bypass surgery, or coronary artery bypass graft surgery, is one of America’s most common operations. Every year, more than half a million heart bypasses are done in the U.S., write Rogers and colleagues.
The goal of the operation is to do an end-run around blocked coronary arteries. The coronary arteries supply heart muscle with blood. When those arteries get narrow or clogged, blood can’t get through.
In a bypass, doctors create an alternate route to restore blood flow to the heart muscle that should have been fed by the blocked artery. Surgeons take blood vessels from the patient’s chest, legs, or arms and graft them into place. It’s like building a new exit ramp off the main highway because the original road is blocked.
During hospitalization for heart bypass, women have a greater risk of death than men. The reasons for that gap aren’t clear, the researchers write.
Other experts have studied artery size and other health problems as possible explanations. However, “this issue remains controversial,” write Rogers and colleagues.
Infections in Women, Men
A small percentage of the patients in Roger’s study were diagnosed with infections during their stay in the hospital (1,122 people, or about 12 percent).
Infections were more common among women than men, both in hospital and after being discharged from hospital. However, more infected men died than infected women.
For men, infection tripled the risk of dying in the 100 days after heart bypass surgery. For women, infection nearly doubled the risk of death during the same period.
No particular area of infection stood out. The most common infections involved the respiratory, urinary, and digestive tracts.
The data don't show when and how the infections started, and the findings should be confirmed, write Rogers and colleagues.
“Clearly, infection is an important factor when evaluating the association between sex and mortality after [heart bypass] surgery,” they write.
In bypass patients, any infection is a “direct indicator of patient safety” that deserves “additional investigation” as a possible contributor to death, the researchers note.
By Miranda Hitti, reviewed by Louise Chang, MD
SOURCES: Rogers, M. Archives of Internal Medicine, Feb. 27, 2006; vol 166: pp 437-443. WebMD Medical Reference in collaboration with The Cleveland Clinic: “Heart Failure: Treating Heart Disease: Coronary Artery Bypass Surgery.” News release, JAMA/Archives.