“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."