In many cases, replacing damaged joints gives people with osteoarthritis a dramatically improved quality of life – with reduction or even elimination of pain and improved mobility. But a new study found that hip and knee replacement surgery may boost the risk of heart attack during the early recovery period.

“We found that total hip and knee replacements substantially increase the risk of heart attack during the first two weeks, in particular in patients older than 60,” says lead study author Arief Lalmohamed, a researcher in the department of pharmaceutical sciences at Utrecht University in the Netherlands. “We learned from this study that we need to focus more on preventing cardiac outcomes following this major surgery.”

The study, which appeared in the Archives of Internal Medicine, relied on national registry data on about 95,000 Danish patients who underwent total hip replacement or total knee replacement surgeries between 1998 and 2007. The average age of the hip patients was 72, while the average age of the knee patients was 67. The researchers found that during the two weeks immediately following each surgery, heart attack risk rose sharply – 25-fold for hip patients and 31-fold for knee patients, compared with similar people in the Danish registries who did not have these surgeries.

After two weeks, heart attack risk dropped dramatically – although the overall risk of heart attack after hip replacement surgery remained elevated for six weeks. Researchers also found that the association between hip and knee replacement surgeries and heart attack was strongest in those 80 years or older. They found no significantly increased risk in patients younger than 60.

This study adds weight to previous research suggesting that certain groups are at increased risk of heart trouble following joint surgery. For example, a study in Annals of the Rheumatic Diseases in 2011 found an increased risk for cardiac complications following joint replacement surgery in older patients and in those who had pre-existing heart disease, deep vein thrombosis or pulmonary embolism.
 

“Although the [new] findings are in line with previous reports, I was still quite surprised by the magnitude of increased risk,” says Lalmohamed. “Even though these patients are typically older, they are screened for surgical fitness. These are indeed common surgeries in older individuals, and therefore the findings underline that we need more focus on preventing these cardiac events in the future.”

The American College of Cardiology and the American Heart Association published guidelines in 2007 that outlined surgeries considered most risky to the heart. Orthopaedic surgeries fell into the intermediate category. An example of a low-risk surgery is cataract removal, whereas aortic surgery is considered high risk.

“The increased risk [of heart attack following joint replacement surgery] is probably the result of both the stressful time during the perioperative period, as well as a direct effect of [hip replacement] and [knee replacement] surgery itself,” says Lalmohamed, referring to such effects as loss of blood, arrhythmias and a reduction in oxygen getting to the heart. These effects are also associated with other, major surgeries.

With hip replacement surgery, there is another potential risk factor for heart attacks, Lalmohamed says: the leakage of bone marrow from the femur into the bloodstream, which can cause blockage of a vessel.

Although the results of this study might cause some concern among those considering joint replacement surgery, Lalmohamed says it’s important to consider the long-term benefits of having the procedure done.

Simply being disabled by a hip or a joint that needs to be replaced can increase patients' risk of cardiovascular events, compared with those who aren't disabled. “It is therefore very plausible, although not confirmed, that joint replacement may reduce long-term cardiovascular risk in these patients," Lalmohamed says. "It is important to stress that although there are some short-term risks with these major surgeries, the long-term benefit is well established and should be taken into account when discussing risks and benefits."
 

Prospective surgical patients concerned about the data in this study ought to talk with their doctors to put the information into perspective, says Thomas Vail, MD, president of the American Association of Hip and Knee Surgeons in Rosemont, Ill.

“This study is very useful from the standpoint of raising awareness,” Dr. Vail says. “As it relates to an individual patient, what one has to do is take this background information provided in a large population and ask yourself, ‘Well, how might this apply to my circumstances? For example, do I have specific cardiac risk factors?’”

Arthur Wallace, MD, an attending anesthesiologist at the San Francisco VA Medical Center wrote an accompanying commentary to the study. He says steps must be taken beyond just recognizing risk. “Just knowing your risk is high doesn’t help,” he says. “What are you going to do, just worry more? You need to reduce the risk.”

At the hospital where Dr. Wallace works – and at many others – risk reduction for joint replacement surgery can include the use of cardiac medications, such as beta blockers and statins, during the perioperative period. Patients who already take them continue doing so, and patients with a combination of known but untreated risk factors – such as hypertension, elevated cholesterol and/or diabetes – are started on them before the surgery.

"There is good evidence that this is not only safe, but also best practice," says Dr. Vail.

About 40,000 surgical patients at the San Francisco VA Medical Center have followed this protocol since 1998, reducing their overall risk of cardiac complications by about 35 percent, Dr. Wallace says. “That’s pretty good.”