Incidence and Timing of Myocardial Infarction After Total Joint Arthroplasty

The Journal of Arthroplasty Vol. 21 No. 6 2006

Incidence and Timing of Myocardial Infarction After Total Joint Arthroplasty Rajiv Gandhi, MD,* Danielle Petruccelli, MLIS,y Philip J. Devereaux, MD,z§ Anthony Adili, MD, PEng, FRCSC,t Matthias Hubmann, MD,b and Justin de Beer, MD, FRCSCy

Abstract: Retrospective review of 3471 patients who underwent total joint arthroplasty (TJA) (1479 hips, 1992 knees) to determine the incidence and timing of inhospital myocardial infarction (MI) after TJA. Sixty-three patients (1.8%; 95% CI, 1.4%-2.4%) suffered a perioperative MI occurring at a mean of 3 days post surgery. In multivariate analysis, increased age, body mass index, bilateral TJA, diabetes, and American Society of Anesthesiologists rating 3 were associated with perioperative MI. Our data cautions against hospital discharge within 3 days of surgery. Key words: total joint arthroplasty, myocardial infarction, surgery, incidence, perioperative. n 2006 Elsevier Inc. All rights reserved.

Perioperative cardiovascular complications are the most frequent serious complications post TJA [1,2], and MI is the most common event. Given the advances in surgical and anesthetic techniques throughout the last decade, some surgeons may assume that the risk of perioperative MI has decreased to the point that early hospital discharge is not a concern. Several concurrent changes challenge this assumption. First, there have been major advances in the treatment of coronary artery disease [3]. As a result, patients with high burdens of coronary artery disease are now surviving to develop conditions that require surgical consideration, including severe osteoarthritis of the hip or knee. Second, there has been a cultural shift toward advanced medical care (including surgery) for the elderly. Because of the changes in the patient population undergoing TJA and the surgical and anesthetic advances, there exists uncertainty as to the current incidence and timing of perioperative MIs in patients undergoing TJA. We undertook a study to evaluate these issues.

Recently, surgeons have increased their focus on the goal of faster recovery times with associated emphasis on shorter hospital stays for elective total joint arthroplasty (TJA). This refocusing has occurred because of the advent of so-called bminimally invasiveQ (MIS) surgical procedures as well as pressures to minimize hospital costs. Although there are potential advantages associated with rapid hospital discharges post TJA, we must ensure that this process is safe.

From the *Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada; y Hamilton Arthroplasty Group, Hamilton Health Sciences Henderson Hospital, Hamilton, Ontario, Canada; z Department of Medicine, McMaster University, Hamilton, Ontario, Canada; § Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada; t St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and b Faculty of Medicine, Karl-Franzens University Graz, Graz, Austria. Dr PJ Devereaux is supported by a Canadian Institute of Health Research, Senior Research. Submitted January 6, 2005; accepted October 17, 2005. No benefits or funds were received in support of the study. Reprint requests: Danielle Petruccelli, MLIS, Hamilton Arthroplasty Group, Hamilton Health Sciences Henderson Hospital, 711 Concession St., Hamilton, Ontario, Canada L8V 1C3. n 2006 Elsevier Inc. All rights reserved 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.10.007

Methods We included all patients who underwent an elective TJA at a single tertiary care orthopedic

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Perioperative Myocardial Infarction Post TJA ! Gandhi et al 875

center between April 1998 and April 2003. All procedures were performed through conventional/ standard single-incision surgical exposure. We identified these patients through our prospective arthroplasty database that records information on all patients who undergo TJA at our hospital. We identified patients who suffered a perioperative MI after surgery in our arthroplasty database and confirmed our results through evaluation of our hospital Canadian Institute for Health Information database. Myocardial infarction (MI) was defined as a clinical event associated with a significant troponin rise, as diagnosed and recorded by the attending medical internist [4]. All patients underwent preoperative consultation with an anesthetist who assessed medical comorbidity and classified patients according to the extent of their systemic disease using the American Society of Anesthesiologists’ classification rating (ASA) [5] of physical status. All categorical data were analyzed using descriptive statistics and the v 2 or Fisher exact test, where appropriate. Continuous data, including age, body mass index (BMI), and hospital length of stay, were analyzed using descriptive statistics and compared using independent samples t test. Demographic and surgical data points including sex, age, BMI, ASA rating, preoperative medical comorbidities, TJA (hip or knee), surgical procedure; primary vs revision, unilateral vs sequential bilateral, and hospital length of stay were compared between the MI cohort and non-MI cohort of arthroplasty patients using the v 2 or Fisher exact test for proportions and the independent samples t test. Correlations were performed using Pearson correlation. Univariate regression was then performed on all demographics and cardiac risk factors to determine variables predictive of perioperative MI. Multiple logistic regression was performed on all variables that were statistically significant in the univariate analyses. For the univariate analysis, a value of P b .1 was considered statistically significant; for all other tests, a value of P b .05 was considered statistically significant. All statistical analyses were performed using SPSS version 10.

Results We identified 3471 patients who underwent TJA (1479 hip and 1992 knee arthroplasties) during our study period. Of these patients, a total of 63 (1.8%; 95% CI, 1.4%-2.4%) suffered a clinically evident perioperative MI. Table 1 presents patient demo-

Table 1. Demographics MI cohort (SD) (n = 63) Sex Male Female Age BMI ASA rating ASA1 ASA2 ASA3 ASA4 TJA Total hip Total knee TJA procedure Primary Revision Unilateral Bilateral

28 (44.4%) 35 (55.6%) 76.2 (6.4) 33.9 (12.2) – 23 (36.5%) 38 (60.3%) 2 (3.2)

Non-MI cohort (SD) (n = 3408)

1322 2086 69.8 31.5

(39%) (61%) (9.9) (7.4)

4.3% 70% 24.6% 1.1%

26 (41.3%) 37 (58.7%)

1453 (42.6%) 1955 (57.4%)

53 10 53 10

3019 389 3125 283

(84.1%) (15.9%) (84.1%) (15.9%)

(88.6%) (11.4%) (91.7%) (8.3%)

P

.362 b.0001 .168 .112 b.0001 b.0001 .092 0.828 .272 .032

graphics for the individuals who did and did not suffer a perioperative MI. Of 63 patients with MI, 22 (34.9%) were younger than 75 years and 3 (4.8%) were younger than 65 years. The proportion of total hip and total knee procedures among the cohorts were comparable, comprising 58.7% knees and 41.3% hips in the MI cohort and 57.4% knees and 42.6% hips in the non-MI cohort ( P = .828). Proportions of primary and revision procedures were comparable, with 84.1% primary and 15.9% revision TJAs in the MI cohort and 88.6% primary and 11.4% revision TJAs in the non-MI cohort ( P = .272). There was, however, a significantly greater proportion of bilateral total knee arthroplasties in the MI cohort, 15.9%, as compared with the non-MI cohort with 8.3% ( P = .032) (Table 1). Univariate logistic regression identified patient age, preoperative BMI, and procedure (unilateral or bilateral) as significant predictors of perioperative MI ( P b .1). Table 2 contrasts the cardiac risk factors among patients who did and did not suffer a perioperative MI. Univariate logistic regression identified ASA rating 2 and 3, angina, diabetes, heart disease, and previous MI as predictive of perioperative MI ( P b .1). When the significant demographic and cardiac risk factors identified in the univariate analyses were put into the multiple logistic regression model, age (OR, 1.11; 95% CI, 1.06-1.15), BMI (OR, 1.04; 95% CI, 1.01-1.06), procedure (unilateral or bilateral) (OR, 0.349; 95% CI, 0.157-0.777), ASA 3 (OR, 12.2; 95% CI, 1.64-90.24), and diabetes (OR, 2.63;

876 The Journal of Arthroplasty Vol. 21 No. 6 September 2006 95% CI, 1.39-4.96) were identified as significant predictors of perioperative MI. As expected, there was a high incidence of known cardiac risk factors among the MI cohort. However, it should be noted that 18 (28.6%) of 63 patients did not present with any known cardiac risk factors. Number of per-patient cardiac risk factors and inhospital fatal MI after TJA were not significantly correlated ( P = .786). Mean time to MI from the day of surgery, defined as day 0, was 3 days (F3.3), (range, 018). Eighty-three percent of the MI cohort suffered a myocardial infarct by postoperative day 3. Ninety-one percent of the MI events had occurred by postoperative day 5 (Fig. 1). The overall inhospital mortality rate for the MI cohort was 11.1%, including 5 men and 2 women ( P = .226). Nine of 63 patients within the MI cohort, 9 (14.3%) had suffered a previous MI at a mean of 4.8 (F3.6) years before TJA, with 2 of these patients suffering inhospital fatal MI after TJA. Mean hospital length of stay for the MI cohort was 17.5 days (F12.7), including 5.9 days (F5.3) in the intensive care/cardiac care unit. Of 63 patients, 37 (58.7%) were discharged home with homecare, 13 (20.6%) to an inhospital rehabilitation ward, 3 (4.8%) to a cardiac unit, 3 (4.8%) to a nursing facility, and 7 (11.1%) died in hospital. Mean hospital length of stay for the non-MI cohort was 6.7 days (F4.6), as compared with the MI cohort ( P b .0001). In contrast to the MI cohort, 94.3% ( P b .0001) of the non-MI cohort was discharged home with homecare, 4.2% ( P b .0001) to a rehabilitation ward, 1.3% to a nursing facility ( P = .059), and 0.2% ( P b .0001) died in hospital. Of the non-MI cohort, 3.3% were discharged home within 3 days post surgery. Of these patients, 57% were men and 48% were women. Mean age

Table 2. Preoperative Cardiac Risk Factors

Anemia Angina Diabetes Heart disease* Hypertension Stroke Previous MI No cardiac risk factors

MI cohort (%) (n = 63)

Non-MI cohort (%) (n = 3408)

P

7.9 22.2 27 28.6 50.8 4.8 14.3 28.6

7.1 10.8 12 18.7 48.2 6.1 8.1 54.3

.802 .004 b.0001 .048 .684 .457 .074 b.0001

*Heart disease is defined as a history of arrhythmia or valvular disease.

Fig. 1. Timing of inhospital MI after TJA.

was 64 years and mean BMI was 32.6 kg/m2. The group composed of 61% knees, one of which was bilateral, and 39% hips. Seven percent were rated as ASA 1, 73% as ASA 2, and 20% as ASA 3. Eighty-two percent underwent primary TJA, whereas 18% underwent revision TJA. There were no documented intraoperative hypoxic events, hypotensive events (blood pressure drop z20 mm Hg), or arrhythmias among the MI cohort.

Discussion In our study, the incidence of perioperative MI was 1.8% and the inhospital mortality rate from MI was 0.2%. This correlates with the findings of Gill et al [6] who reported the death rate from cardiac causes to be between 0.2% and 0.29%. They identified increased age and history of cardiovascular disease as the major risk factors for mortality. Moreover, Mantilla et al [1] attributed increased frequency of perioperative MI with older age (N70 years) and male sex, reporting an overall MI rate of 0.4%, increasing to 1.6% for patients 80 years or older. Our incidence of 1.8% is more than 4 times that reported by Mantilla et al [1] and more in line with a rate of 1.9% reported by Marsch et al [2]. The methods used to confirm a diagnosis of postoperative MI differed between these 2 studies and ours, and this may account for the differences reported. Marsch et al conducted a prospective study on only 52 patients undergoing total hip arthroplasty (THA) and used perioperative Holter monitoring. Mantilla et al, as in our study, conducted a retrospective review (of N10 000 patients) and used creatine kinase levels or MB fractions thereof, whereas our study used serum troponin levels in addition to electrocardiogram changes for diagnosis. Of 63 patients within our MI cohort, 45 (71.4%) presented with one or more cardiac risk factors. Multivariate analysis identified diabetes

Perioperative Myocardial Infarction Post TJA ! Gandhi et al 877

and an ASA rating of 3 as significant predictors of perioperative MI. As has previously been reported, we found a significantly greater incidence of MI among elderly patients with known cardiac risk factors undergoing sequential bilateral total knee arthroplasties [7]. Of 63 MI patients, 18 (28.6%) did not present with any known cardiac risk factors. Thirty-seven percent of the MI cohort had a preoperative BMI below 30; 34.9% younger than 75 and 4.8%, younger than 65 years. The relevance of the patients fitting these latter criteria is that they may potentially be considered for an accelerated discharge protocol after TJA, especially if a so-called MIS-type procedure has been performed. A factor driving interest in MIS is the potential to dramatically shorten hospital length of stay. Berger [8] has reported an average hospital length of stay of 1.9 days for mini-incision arthroplasty vs 3.5 days for a standard incision. Berger and Duwelius [9] have also introduced a bsame day pathwayQ for discharge after 2-incision technique for THA. However, TJA, especially THA, involves surgical invasion of the medullary canal of the femur with potential for marrow embolization and consequent cardiac stress [10,11]. Obesity is a known risk factor for ischemic heart disease, but there is, as yet, no clear consensus on obesity and MIS surgery. Sculco et al [12] suggest a guideline of a BMI below 30 kg/m2, whereas Goldstein et al [13] have extended their inclusion criteria to include all patients except the bmost obese.Q The trend toward decreasing inhospital length of stay is attractive to patients, surgeons, and hospital administrators. It should, however, be noted that most of patients undergoing TJA are older and often have multiple medical comorbidities. We have shown that delaying discharge until postoperative day 3 will identify 83% of cardiac events that could potentially occur in hospital. A limitation of our study is that it was a retrospective design, and postoperative electrocardiograms and troponin measurements were uncommon. These limitations suggest, if anything, that we have underestimated the true incidence of perioperative MI. Furthermore, we would caution against underestimating the concern related to the safety of performing major orthopedic reconstructive surgery, in conjunction with a predetermined focus on dramatically shortened hospital length of stay.

Acknowledgment The authors thank Arne Rungi, MSc-School of Medicine, Faculty of Health Sciences, Queen’s University, Kingston, Ontario, Canada, for assistance with the literature review.

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