Increased Heart Attack Risk Associated with Hip and Knee Replacement

A new study published in the Archives of Internal Medicine claims that people over the age of 60 who have had total hip replacement (THR) and total knee replacement (TKR) surgeries were more inclined to acute myocardial infarction (AMI, or heart attack). The risk remains high for up to six weeks after surgical procedures.

The study noticed the occurrence of heart attack common in people in their 80's and people under the age group of 60 were no more likely to have heart attacks.

THR and TKR are effective for treating patients who are suffering with osteoarthritis. The study reveals that nearly 1.8 million similar procedures are performed annually.

"This study demonstrated an increased risk of AMI during the first two weeks after THR (25-fold) and TKR (31-fold) surgery compared with matched controls. The risk of AMI sharply decreased after this period, although it remained significantly elevated in the first six weeks for THR patients. The association was strongest in patients 80 years or older, whereas we could not detect a significantly increased risk in patients younger than 60 years," Arief Lalmohamed, Pharm.D., of Utrecht University, the Netherlands, and colleagues said.

The study collected data from the Danish National registries. All patients who underwent a primary THR or TKR (n = 95 227) surgery from Jan. 1, 1998, through Dec. 31, 2007, were selected and matched to three controls by age, sex, and geographic region. They didn't consider THR or TKR. All study participants were followed up for AMI, and disease- and medication history-adjusted hazard ratios (HRs) were calculated.

 The researchers noticed that during the first two weeks, the risk of AMI was substantially increased in THR patients compared with matched controls. The risk remained elevated for two to six weeks after surgery and then decreased to baseline levels. The absolute six-week risk of AMI was 0.51 percent in THR patients and 0.21 percent in TKR patients.

"Furthermore, a previous AMI in the six months before surgery increased the risk of new AMI during the first six weeks after THR and TKR surgery but did not modify the relationship between THR or TKR and AMI," the authors concluded.

Previous studies have shown that joint replacements increase a patient's risk for dangerous blood clots that can lodge in the legs or lungs. For that reason, joint replacement patients are routinely prescribed blood thinners to prevent those kinds of events.

The study shows that the risk of AMI substantially increases in the first two weeks after THR and TKR surgery compared with controls. It also reinforces the importance and significance of the cardiac risk and the need to prevent perioperative cardiac morbidity and mortality.