Elderly patients who have total knee or hip replacement surgeries are at substantially greater risk of a heart attack within the first two weeks of surgery, according to a large new study of Danish patients.
Hip and knee replacement surgeries are widely used to treat patients with moderate to severe osteoarthritis, reducing pain and restoring mobility. About 1.8 million of the surgeries are performed worldwide annually and that number is expected to increase as baby boomers enter their retirement years.
Researchers at Utrecht University in the Netherlands studied Danish national registries of over 95-thousand patients who had either knee or hip replacement surgery between 1998 and 2007. The average age of patients who had their knees replaced was 67, compared 72 for those who had total hip replacement.
In the first two weeks after surgery, researchers found a 25 times greater risk of an acute myocardial infarction, or heart attack, in the hip replacement patients and a 31 times greater risk in the knee patients; when compared to people of the same sex and age who did not have either surgery.
The risk of a heart attack decreased after two weeks, but remained significantly elevated in the hip replacement patients for six weeks.
Patients less than 60 years of age did not have an increased risk of heart attack, but patients aged 80 and older had the greatest risk.
“The perioperative (postoperative) period is stressful to patients… The present study once again confirms that the perioperative period increases cardiac risk. Physicians must go further than establishing risk factors; physicians must actively work to reduce perioperative risk,” said Arthur W. Wallace, MD, of the University of California, San Francisco in a commentary on the study published in the Archives of International Medicine. “It is important for physicians caring for patients in the perioperative period to recognize the potential for cardiac morbidity and mortality and then appropriately use the armamentarium of medical therapies we now have to reduce cardiac risk.”
Specifically, researchers learned that one in 200 people who underwent total hip replacement had a heart attack within six weeks of surgery, while one in 500 people who had surgery for a total knee replacement had a heart attack within six weeks.
Possible explanations for the increased risk of a heart attack include cardiac stress caused by surgery, blood loss, fluid shifts, arrhythmia, hypoxia and the effects of anesthesia.
The researchers say the data suggests that elective hip replacement surgery not be performed on patients who had a heart attack in the last 12 months before surgery.