Timing of Acute Myocardial Infarction in Patients Undergoing Total Hip or Knee Replacement: A Nationwide Cohort Study

Jul 23, 2012
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Authors:
Lalmohamed A, Vestergaard P, Klop C, et al.
Citation:
Arch Intern Med 2012;Jul 23:[Epub ahead of print].
Summary By:
Debabrata Mukherjee, MD, FACC

Study Questions:

What is the timing of acute myocardial infarction (AMI) in patients undergoing total hip replacement (THR) or total knee replacement (TKR) surgery compared with matched controls?

Methods:

This was a retrospective, nationwide cohort study within the Danish national registries. All patients who underwent a primary THR or TKR (n = 95,227) surgery from January 1, 1998, through December 31, 2007, were selected and matched to three controls (no THR or TKR) by age, sex, and geographic region. All study participants were followed up for AMI, and disease- and medication history–adjusted hazard ratios (HRs) were calculated.

Results:

During the first two postoperative weeks, the risk of AMI was substantially increased in THR patients compared with controls (adjusted HR, 25.5; 95% confidence interval [CI], 17.1-37.9). The risk remained elevated for 2-6 weeks after surgery (adjusted HR, 5.05; 95% CI, 3.58-7.13) and then decreased to baseline levels. For TKR patients, AMI risk was also increased during the first 2 weeks (adjusted HR, 30.9; 95% CI, 11.1-85.5), but did not differ from controls after the first 2 weeks. The absolute 6-week risk of AMI was 0.51% in THR patients and 0.21% in TKR patients.

Conclusions:

The authors concluded that the risk of AMI is substantially increased in the first 2 weeks after THR and TKR surgery compared with controls.

Perspective:

This study demonstrated an increased risk of AMI during the first 2 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 6 weeks for THR patients. Furthermore, a previous AMI in the 6 months before surgery increased the risk of new AMI during the first 6 weeks after THR and TKR (fourfold increase) surgery. These data suggest that appropriate risk assessment of AMI should be considered during the first 6 weeks after THR surgery and during the first 2 weeks after TKR surgery, and elective THR surgery should be contraindicated in patients with a previous AMI in the prior 6-12 months before surgery.

Keywords: Registries, Myocardial Infarction, Health Resources, Cardiovascular Diseases, Confidence Intervals, Risk Assessment, Cardiac Surgical Procedures, Postoperative Period, Troponin


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