July 23rd, 2012

Elevated Risk for Acute MI After Total-Hip or -Knee Replacement Surgery

A large study reports a high increased risk for acute MI (AMI) in the first 6 weeks after total-hip replacement (THR) or total-knee replacement (TKR) surgery. Analyzing a nationwide cohort from Denmark that included 95,227 patients who underwent THR or TKR and matched controls, Arief Lalmohamed and colleagues calculated the adjusted hazard ratios (HR) for AMI. Their results are published in the Archives of Internal Medicine.

The risk for AMI was significantly higher in the first two postoperative weeks for both THR and TKR, but the risk was higher only in the THR group for weeks 2 through 6.

Adjusted HR, Weeks 1 to 2:

  • THR: 25.5 (95% CI, 17.1-37.9)
  • TKR: 30.9 (95% CI, 11.1-85.5)

Adjusted HR, Weeks 2 to 6:

  • THR: 5.05 (95% CI, 3.58-7.13)
  • TKR: 0.81 (95% CI, 0.37-1.77)

At 6 weeks, the absolute rate of AMI was 0.51% in the THR group and 0.21% in the TKR group. The only significant effect modifier identified by the investigators was age, with the greatest excess risk found in patients age 80 or older. By contrast, no increase in risk was found in patients younger than 60 years.

In an accompanying commentary, Arthur Wallace writes that the 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.” Risk can be reduced with the appropriate use of preoperative beta-blockers, clonidine, statins, and aspirin, he writes. Despite level 1 evidence supporting the use of antiischemic agents, many physicians discontinue their use in the perioperative period, he notes.

5 Responses to “Elevated Risk for Acute MI After Total-Hip or -Knee Replacement Surgery”

  1. Robin Motz, M.D., Ph.D. says:

    Based on this study, where over 90% of the study participants received thromboprophylaxis post-op, what does this tell us about the value of low-dose thromboprophylaxis in preventing an acute MI in patients?

  2. Robin Motz, M.D., Ph.D. says:

    I note that the authors suggest that marrow embolization might have been the cause of the MI, because the generation of fat emboli is impervious to anti-coagulation. I recall an article in Lancet over 20 years ago: a clinical study showed that one amp of D50W in the ER given to all hip fx. patients decreased the incidence of fat emboli. Perhaps a study should be done to look at this.

  3. JOSEPH BARRY, BS, MD says:

    I need to know what depth of pre op screening was done to find coronary plaques about to rupture. It appears to me that the issue falls back to
    how inefficient we are in diagnosis of coronary heart disease in asymptomatic Seniors
    I am in my 80s and have had 2 knees done.The pre op exam was shall I say, WORTHLESS. JOSEPH BARRY,MD, FACP

  4. Karen Politis, MD says:

    This study seems to confirm a gut feeling I have had for many years: these are not operations to be taken lightly. They involve extensive trauma, which sets off a reaction that perhaps we cannot comprehend yet. A senior with limited reserves would be at high risk. I cringe at the sight of an obese 80-year-old patient’s large surgical site, oozing blood, and the orthopaedic surgeon hacking and sawing the femur and the pelvis. Indeed we should be meticulous in the preoperative workup, and of course during and after the operation. This is major, not “peripheral” surgery.

  5. Judith Andersen, AB, MD says:

    I agree with all of the above concerns. This study, a retrospective cohort study that compares each of 95,227 Danish patients who underwent either THR (66,524) or TKR (28,703) with 3 normal controls over a 10 yr period from 1/1/1998 through12/31/2007, reveals that both procedures were associated with increased post-operative risk of AMI. THR HR was 25.5 in the first 2 post-op wks and remained elevated (HR 5.05) for 2-6 wks, whereas HR for TKR was 30.9 in the first 2 wks, but did not differ from controls thereafter. Age, male gender, prvs (particularly recent) MI and prior history of CV disease were associated with increased risk, as was the use of NSAIDS, nitrates, K+-sparing diuretics, and beta -blockers — these latter associations supporting the contribution of pre-existing cardiac disease to perioperative susceptibility to MI. Dr Politis’ comment that, although increasingly common and effective in alleviating the ravages of osteoarthropathy, “these are not operations to be taken lightly” is particularly apt, and suggests that the burden of protecting patients contemplating such surgery has not been taken seriously enough.

    Most major surgeries increase risk of perioperative venous thrombosis by a variety of mechanisms, and routine use use of preventive measures has become a US national surgical (SCIP) quality measure. THR and TKR have been a particular prevention target because of the high risk of perioperative VTE, and there are now clear guidelines and several highly effective agents for VTE prevention in orthopedic surgery. That these strategies were routinely employed in the operated patients in the Danish study and did not abrogate the occurrence of AMI tells us that we have been ignoring important contributors to perioperative arterial thrombosis, with serious consequences. The data from the Danish study suggest that advanced age, prior cardiac events, need for ongoing treatment of cardiac dysfunction, and the use of (or the need for) NSAIDS all increase the risk of THR and TKR-associated MI. Those of us who provide clearance for patients about to undergo such surgeries thus must carefully evaluate our elderly patients with cardiac disease — and re-assess some of the standard perisurgical strategies that involve discontinuing agents such as aspirin, thienopyridines and other platelet function inhibitors. Orthopedic surgery continues to evolve toward less “rip and tear” strategies, and improved surgical techniques will doubtless make this issue less troublesome, but our current and future responsibility will continue to be to carefully evaluate each patient’s pre-operative status, postponing elective surgery in high risk patients until cardiac instability can be minimized, and giving careful thought to perioperative antithrombotic/anti-infarction strategies. And convincing our enthusiastic orthopedic colleagues to work with us .