A study published on July 23 in the Archives of Internal Medicine found that the "risk of acute myocardial infarction (AMI) is substantially increased in the first two weeks following total hip replacement (THR) and total knee replacement (TKR) surgery compared with controls."

 

There is currently limited evidence that suggests the risk of AMI may be increased shortly after THR and TKR surgery, as well as a lack of research comparing the risk of matched controls not undergoing surgery. This new study evaluates the timing of AMI after THR and TKR surgery to evaluate potential side effect modifiers of this relationship and identify determinants of AMI in THR and TKR patients.

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This retrospective, nationwide cohort study using Danish national registries targeted patients who underwent a primary THR or TKR surgery, with controls based on age, sex and geographic region. All patients were followed up for AMI, and disease- and medication history-adjusted hazard ratios were calculated.

 

The authors found that "during the first two postoperative weeks, the risk of AMI was substantially increased in THR patients compared with controls (adjusted HR, 25.5; 95 percent CI, 17.1-37.9). The risk remained elevated for two to six weeks after surgery (adjusted HR, 5.05; 95 percent CI, 3.58-7.13) and then decreased to baseline levels. For TKR patients, AMI risk was also increased during the first two weeks (adjusted HR, 30.9; 95 percent CI, 11.1-85.5) but did not differ from controls after the first two weeks. The absolute six-week risk of AMI was 0.51 percent in THR patients and 0.21 percent in TKR patients."

Overall, the study is the first to find "THR (25-fold) and TKR patients (31-fold) are at increased risk of AMI during the first two weeks after surgery." The study authors noted that "elevated risk was sustained for six weeks after THR and for two weeks after TKR," and "the effect of surgery on AMI risk was strongest in patients 80 years or older."

"Risk assessment of AMI should be considered during the first six weeks after THR surgery and during the first two weeks after TKR surgery," add the authors.

"The risk factors for perioperative cardiac morbidity and mortality have been established for many years, and although different studies find slightly different risk factors, there is remarkable consistency over time," notes Arthur W. Wallace, MD, PhD, from the Department of Anesthesiology, University of California, San Francisco in an editorial comment. "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."

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