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

Study Questions:

What are the timing and potential determinants of acute myocardial infarction (AMI) in patients undergoing total hip replacement (THR) and total knee replacement (TKR)?

Methods:

This was a retrospective cohort study conducted using Danish national registries. All patients who underwent primary THR or primary TKR from January 1, 1998, through December 31, 2007, were included in the study. Post-THR and TKR patients were matched to three controls (no THR or TKR) by age, sex, and geographic region. All patients were followed up for death and both nonfatal and fatal AMI.

Results:

The risk of AMI after THR and TKR was substantially increased in the first two postoperative weeks. Adjusted hazard ratios (HRs) were 25.5 (95% confidence interval [CI], 17.1-37.9) for THR and 30.9 (95% CI, 11.1-85.5) for TKR. This escalated risk normalized after 2 weeks post-TKR, but persisted for up to 6 weeks in THR patients (2-6 weeks: adjusted HR, 5.05; 95% CI, 3.58-7.13). The effect of THR on AMI was highest in the oldest patients (≥80 years old; adjusted HR, 25.3; 95% CI, 17.7-36.2). A significantly increased risk was not detected in patients younger than 60 years. A four-fold increase in six-week risk for AMI following THR and TKR was observed in patients who had had a previous MI in the 6 months before surgery.

Conclusions:

Compared with matched controls, post-THR and post-TKR have a 25-fold and 31-fold escalated risk for AMI, respectively, in the first two postoperative weeks. This risk remained significantly elevated up to 6 weeks for THR patients, and was particularly highest in the most elderly.

Perspective:

While limited by a retrospective collection of data, the current study adds to the evidence base on timing of AMI after THR and TKR. Risk for AMI is substantially increased in the first two postoperative weeks following THR and TKR, an observation that has implications for early postoperative risk assessment. The present study also establishes the impact of a previous MI on AMI risk following THR and TKR, potentially informing the rationale for postponing elective orthopedic surgery in those with AMI in the 12 months preceding surgery.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention

Keywords: Registries, Myocardial Infarction, Cardiovascular Diseases, Orthopedic Procedures, Confidence Intervals, Orthopedics, Risk Assessment, Cardiac Surgical Procedures, Postoperative Period


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