Abstract
Background
This study aimed to explore the incidence of cardiac complications including myocardial infarction, acute heart failure, and cardiogenic shock and identify associated risk factors during index hospitalization following total knee arthroplasty (TKA) using the National Inpatient Sample (NIS) database, with the goal of providing actionable insights to refine risk stratification protocols and optimize perioperative clinical decision-making.
Methods
This national retrospective cohort study analyzed adults undergoing primary TKA between 2010 and 2019, excluding patients with preexisting cardiac conditions or prior knee surgeries to mitigate confounding. Utilizing the NIS, we identified risk factors for postoperative cardiac complications including myocardial infarction, acute heart failure, and cardiogenic shock occurring during index hospitalization following primary TKA through multivariate logistic regression analysis of demographics, hospital characteristics, preoperative comorbidities, and postoperative complications.
Results
A total of 1,283,093 patients undergoing TKA were included in the analysis. The overall incidence of cardiac complications after TKA was 2.78% (n = 35,723). Advanced age, male sex, Black race, larger hospital size, teaching hospital status, and non-elective admissions were significant risk factors. Comorbidities, such as chronic pulmonary disease, hypertension, and chronic renal failure, were strongly associated with cardiac complications. Additionally, the occurrence of cardiac complications was associated with postoperative complications such as pneumonia, deep vein thrombosis, and arrhythmias.
Conclusions
Cardiac complications after TKA were influenced by both patient-specific factors, such as age, sex, race, and comorbidities, and hospital-related factors, including hospital size and teaching status. Our analysis highlights the need for preoperative risk assessments and perioperative care, especially for high-risk patients with multiple comorbidities.
Keywords: Total knee arthroplasty, Cardiac complications, Risk factors, National inpatient sample
Total knee arthroplasty (TKA) is one of the most commonly performed orthopedic procedures, with over 700,000 surgeries conducted annually in the United States alone.1) It remains the most effective treatment for alleviating pain and improving function in patients with advanced knee osteoarthritis.2) Despite its procedural success and enhanced patient outcomes, TKA is associated with a range of perioperative complications, notably cardiovascular events, which contribute significantly to morbidity and mortality in the postoperative period.2,3)
While TKA is associated with diverse perioperative complications, including venous thromboembolism, renal failure, and pulmonary embolism, cardiac events remain a leading cause of morbidity and mortality.2) Cardiac complications, including myocardial infarction, acute heart failure, and cardiogenic shock, are among the most serious postoperative events. These complications not only prolong hospitalization but also increase the likelihood of adverse long-term outcomes.2,3) Given the aging population and the rising prevalence of comorbidities such as hypertension, diabetes, and obesity, the incidence of cardiac events after TKA is expected to rise.3)
Previous studies by Chokshi et al.4) have identified several risk factors for cardiac complications following TKA, such as advanced age, male sex, prior cardiovascular disease, and the presence of systemic comorbidities. However, a comprehensive analysis using large national databases is required to better quantify these risks and avoid confounding factors due to the complexity of patients and the diversity of surgical techniques.5)
In this study, we utilized the National Inpatient Sample (NIS) database to explore the incidence and risk factors of major cardiac complications following TKA. By utilizing the NIS’s nationally representative data, our analysis aimed to generate evidence-based insights that directly inform risk stratification frameworks and perioperative management strategies, ultimately improving outcomes for high-risk TKA patients.
METHODS
Due to the retrospective, de-identified nature of the NIS data, the requirement for individual patient consent was waived. All analyses adhered to the data use agreement set forth by the Healthcare Cost and Utilization Project (HCUP). The study received an exempt determination from the Institutional Review Board of Affiliated Meizhou Hospital of Shantou University Medical College owing to the exclusive use of fully deidentified patient records from the NIS dataset.
Study Design and Data Source
This retrospective cohort study utilized the NIS database, the largest publicly available all-payer inpatient health care database in the United States. The NIS is part of the HCUP, sponsored by the Agency for Healthcare Research and Quality (AHRQ). It contains data from over 7 million hospital stays each year, encompassing a wide range of information on patient demographics, hospital profiles, clinical diagnoses, procedures, and economic costs associated with inpatient care.4,5,6,7) This study included adult patients undergoing primary TKA from 2010 to 2019, excluding those with prior knee surgeries or preexisting cardiac conditions to focus on new-onset cardiac complications.
Study Population
This national cohort included adult patients undergoing primary TKA between 2010 and 2019. Cases were identified using International Classification of Diseases (ICD)-9-CM procedure code 81.54 and ICD-10-CM codes 0SRC0JZ (right knee) and 0SRD0JZ (left knee). Exclusion criteria included patients with prior knee surgeries, preexisting cardiac conditions, non-primary or non-elective procedures, and other contraindications (see Fig. 1 for the full exclusion workflow). Bilateral procedures (ICD-10 codes 0SRC0JZ/0SRD0JZ with modifier 50) were excluded to focus on primary unilateral TKA cases.
Fig. 1. Patient exclusion process for those undergoing total knee arthroplasty with cardiac complications. ICD: International Classification of Diseases.
Variables
Dependent variables
Cardiac complications were defined as new-onset events during the index hospitalization for TKA, including myocardial infarction (ICD-9: 410.x; ICD-10: I21-I22), acute heart failure (ICD-9: 428.x; ICD-10: I50), and cardiogenic shock (ICD-9: 785.51; ICD-10: R57.0). A composite outcome, termed “overall cardiac complications,” encompassed these 3 categories.
Independent variables
Independent variables for logistic regression analysis were grouped into 3 main categories: patient demographics, hospital characteristics, and comorbidities (Table 1).
Table 1. Variables Used in Binary Logistic Regression Analysis.
| Variable category | Specific variable |
|---|---|
| Patient demographics | Age (≤ 64 yr and ≥ 65 yr), sex (male and female), race (White, Black, Hispanic, Asian or Pacific Islander, Native American and Other) |
| Hospital characteristics | Type of admission (non-elective, elective), bed size of hospital (small, medium, large), teaching status of hospital (nonteaching, teaching), location of hospital (rural, urban), type of insurance (Medicare, Medicaid, private insurance, self-pay, no charge, other), location of the hospital (northeast, Midwest or north central, south, west) |
| Comorbidity | AIDS, alcohol abuse, deficiency anemia, rheumatoid diseases, chronic blood loss anemia, chronic pulmonary disease, coagulopathy, depression, diabetes (uncomplicated), diabetes (with chronic complications), drug abuse, hypertension, hypothyroidism, liver disease, lymphoma, fluid and electrolyte disorders, metastatic cancer, neurological disorders, obesity, paralysis, peripheral vascular disorders, psychoses, pulmonary circulation disorders, renal failure, solid tumor without metastasis, peptic ulcer disease, valvular disease, and weight loss |
AIDS: acquired immunodeficiency syndrome.
Statistical Analysis
Statistical analyses were performed using IBM SPSS software version 25 (IBM Corp). Wilcoxon rank test was applied to assess continuous data, while chi-square test was used for comparing categorical data to compare baseline characteristics between patients who did and did not develop cardiac complications. Multivariable logistic regression was employed to identify independent risk factors for cardiac complications after TKA, with results presented as odds ratios (ORs) with 95% CIs. A p-value of less than 0.01 was considered statistically significant. The logistic regression analysis included all variables from NIS, covering patient demographics, hospital characteristics, and comorbidities (Table 1).
RESULTS
Study Population and Data Cleansing
The initial dataset consisted of 1,313,178 patients scheduled for TKA from 2010 to 2019. After rigorous data cleansing to address missing values and inconsistencies, the study focused on 1,283,093 patients (Fig. 1). Our cleansing ensured the reliability of subsequent analyses focusing on risk factors associated with cardiac complications following TKA.
Patient Characteristics and Outcomes after Cardiac Complications
Out of the cleansed dataset, 35,723 patients (2.78%) experienced cardiac complications. The median age of patients with complications was significantly higher at 72 years, compared to 67 years for those without complications (p < 0.001) (Table 2). Males comprised 43.60% of those with complications, a higher proportion than their representation among those without complications (37.60%, p < 0.001) (Table 2). Analysis by race indicated a higher incidence of cardiac complications among Black patients (11.20% vs. 7.50%, p < 0.001) (Table 2). The median length of stay (LOS) was equal, but the interquartile range was still larger in the cardiac complications groups (2 days to 4 days) than in the control group (2 days to 3 days), suggesting that the occurrence of cardiac complications slightly prolonged hospitalization (Table 2). As expected, cardiac complications increased medical expenditure despite the slightly longer LOS. There was a significant increase of $7,265 in total hospital charges with the presence of cardiac complications ($56,677 vs. $48,950, p < 0.001) (Table 2).
Table 2. Patient Characteristics and Outcomes after Cardiac Complications (2010–2019).
| Characteristics | No cardiac complication | Cardiac complication | p-value | |
|---|---|---|---|---|
| Total number | 1,247,370 | 35,723 | - | |
| Total incidence (%) | - | 2.78 | - | |
| Age (yr), median (range) | 67 (60–73) | 72 (65–78) | < 0.001 | |
| Age group (yr), % | < 0.001 | |||
| 18–44 | 1.50 | 0.40 | ||
| 45–64 | 40.30 | 23.40 | ||
| 65–74 | 37.40 | 37.40 | ||
| ≥ 75 | 20.90 | 38.80 | ||
| Sex (%) | < 0.001 | |||
| Male | 37.60 | 43.60 | ||
| Female | 62.40 | 56.40 | ||
| Race (%) | < 0.001 | |||
| White | 76.60 | 75.30 | ||
| Black | 7.50 | 11.20 | ||
| Hispanic | 36.50 | 16.90 | ||
| Asian or Pacific Islander | 1.20 | 0.90 | ||
| Native American | 0.40 | 0.50 | ||
| Other | 8.80 | 8.10 | ||
| Number of comorbidities (%) | < 0.001 | |||
| 0 | 36.50 | 16.00 | ||
| 1 | 34.50 | 28.10 | ||
| 2 | 18.70 | 26.40 | ||
| ≥ 3 | 10.30 | 29.60 | ||
| Length of stay (day) | 3 (2–3) | 3 (2–4) | < 0.001 | |
| Total charge ($), median (range) | 48,538 (35,755–68,385) | 55,803 (40,007–81,279) | < 0.001 | |
| Type of insurance (%) | < 0.001 | |||
| Medicare | 55.80 | 77.00 | ||
| Medicaid | 3.80 | 3.90 | ||
| Private insurance | 36.50 | 16.90 | ||
| Self-pay | 0.50 | 0.30 | ||
| No charge | 0.10 | 0 | ||
| Other | 3.30 | 1.90 | ||
| Bed size of hospital (%) | < 0.001 | |||
| Small | 26.80 | 22.80 | ||
| Medium | 27.20 | 27.30 | ||
| Large | 45.90 | 49.90 | ||
| Elective admission (%) | 95.60 | 93.50 | < 0.001 | |
| Location of hospital (urban, %) | 89.00 | 88.40 | 0.001 | |
| Type of hospital (teaching %) | 53.50 | 57.30 | < 0.001 | |
| Region of hospital (%) | < 0.001 | |||
| Northeast | 17.60 | 15.40 | ||
| Midwest or North Central | 26.90 | 31.40 | ||
| South | 37.00 | 38.20 | ||
| West | 18.60 | 15.00 | ||
| Died (%) | 0 | 0.60 | < 0.001 | |
Risk Factors of Cardiac Complications for TKA
We identified several significant factors influencing the incidence of cardiac complications following TKA (Tables 2 and 3). As illustrated in Table 3, advanced age demonstrated a graded association with increased risk, with patients aged 45–64, 65–74, and ≥ 75 years exhibiting progressively higher odds of experiencing cardiac complications compared to younger counterparts (ages 45–64: OR = 1.94, 95% CI = 1.64–2.29, p < 0.001; ages 65–74: OR = 2.26, 95% CI = 1.91–2.67, p < 0.001; ages ≥ 75: OR = 3.63, 95% CI = 3.06–4.30, p < 0.001). Conversely, female sex (OR = 0.67, 95% CI = 0.66–0.69, p < 0.001) conferred protective effects against these complications (Table 3). Black race (OR = 1.40, 95% CI = 1.35–1.46, p < 0.001) was also identified as a predisposing factor, while Hispanic (OR = 0.80, 95% CI = 0.75–0.84, p < 0.001) and Asian or Pacific Islander races (OR = 0.78, 95% CI = 0.7–0.88, p < 0.001) showed comparatively lower risks (Table 3).
Table 3. Risk Factors Associated with Cardiac Complications after Total Knee Arthroplasty.
| Variable | Multivariate logistic regression | |||
|---|---|---|---|---|
| OR | 95% CI | p-value | ||
| Age group (yr), % | ||||
| 18–44 | Reference | - | - | |
| 45–64 | 1.94 | 1.64–2.29 | < 0.001 | |
| 65–74 | 2.26 | 1.91–2.67 | < 0.001 | |
| ≥ 75 | 3.63 | 3.06–4.30 | < 0.001 | |
| Female | 0.67 | 0.66–0.69 | < 0.001 | |
| Race | ||||
| White | Reference | - | - | |
| Black | 1.40 | 1.35–1.46 | < 0.001 | |
| Hispanic | 0.80 | 0.75–0.84 | < 0.001 | |
| Asian or Pacific Islander | 0.78 | 0.7–0.88 | < 0.001 | |
| Native American | 1.07 | 0.91–1.25 | 0.444 | |
| Other | 0.95 | 0.91–0.99 | 0.008 | |
| Number of comorbidities | ||||
| 0 | Reference | - | - | |
| 1 | 1.30 | 1.25–1.36 | < 0.001 | |
| 2 | 1.58 | 1.48–1.68 | < 0.001 | |
| ≥ 3 | 1.77 | 1.6–1.95 | < 0.001 | |
| Type of insurance | ||||
| Medicare | Reference | - | - | |
| Medicaid | 1.05 | 0.99–1.12 | 0.118 | |
| Private insurance | 0.58 | 0.56–0.6 | < 0.001 | |
| Self-pay | 0.85 | 0.7–1.02 | 0.076 | |
| No charge | 0.43 | 0.21–0.87 | 0.019 | |
| Other | 0.64 | 0.59–0.69 | < 0.001 | |
| Bed size of hospital | ||||
| Small | Reference | - | - | |
| Medium | 1.11 | 1.07–1.14 | < 0.001 | |
| Large | 1.16 | 1.13–1.19 | < 0.001 | |
| Elective admission | 0.75 | 0.72–0.79 | < 0.001 | |
| Teaching hospital | 1.14 | 1.12–1.17 | < 0.001 | |
| Urban hospital | 0.88 | 0.84–0.91 | < 0.001 | |
| Region of hospital | ||||
| Northeast | Reference | - | - | |
| Midwest or North Central | 1.29 | 1.25–1.34 | < 0.001 | |
| South | 1.19 | 1.15–1.23 | < 0.001 | |
| West | 1.02 | 0.98–1.07 | 0.281 | |
OR: odds ratio.
In addition to demographic traditional risk factors, other hospital characteristics were analyzed to determine their influence on the occurrence of cardiac complications. Patients in teaching hospitals had a higher risk of complications (OR = 1.14, 95% CI = 1.12–1.17) (Table 3). As shown, larger hospital size was also associated with increased risk, with medium hospitals (OR = 1.11, 95% CI = 1.07–1.14, p < 0.001) and large hospitals (OR = 1.16, 95% CI = 1.13–1.19, p < 0.001) exhibiting higher risk compared to small hospitals (Table 3). Insurance type significantly affected outcomes, with private insurance linked to a lower risk of complications (OR = 0.58, 95% CI = 0.56–0.60, p < 0.001) compared to Medicare and other types of insurance (Table 3). Elective surgeries were associated with higher complication risks (OR = 0.75, 95% CI = 0.72–0.79, p < 0.001) (Table 3). Geographic location played a role, with urban hospitals showing lower odds of complications compared to rural hospitals (OR = 0.88, 95% CI = 0.84–0.91, p < 0.001) (Table 3). Regional variations indicated higher risks in the Midwest/North Central (OR = 1.29, 95% CI = 1.25–1.34, p < 0.001) and South (OR = 1.19, 95% CI = 1.15–1.23, p < 0.001) compared to the Northeast (Table 3).
Furthermore, preoperative comorbidities including rheumatoid arthritis/collagen vascular diseases (OR = 1.13, 95% CI = 1.07–1.19, p < 0.001), chronic pulmonary disease (OR = 1.82, 95% CI = 1.75–1.88, p < 0.001), coagulopathy (OR = 1.37, 95% CI = 1.29–1.46, p < 0.001), depression (OR = 1.09, 95% CI = 1.05–1.13, p < 0.001), diabetes without complications (OR = 1.51, 95% CI = 1.47–1.55, p < 0.001), diabetes with chronic complications (OR = 2.06, 95% CI = 1.98–2.14, p < 0.001), drug abuse (OR = 1.28, 95% CI = 1.14–1.44, p < 0.001), hypertension (OR = 2.03, 95% CI = 1.96–2.1, p < 0.001), fluid and electrolyte disorders (OR = 1.42, 95% CI = 1.36–1.48, p < 0.001), other neurological disorders (OR = 1.29, 95% CI = 1.22–1.36, p < 0.001), obesity (OR = 1.28, 95% CI = 1.23–1.32, p < 0.001), paralysis (OR = 1.50, 95% CI = 1.27–1.79, p < 0.001), peripheral vascular disorders (OR = 1.57, 95% CI = 1.49–1.65, p < 0.001), pulmonary circulation disorders (OR = 4.43, 95% CI = 4.19–4.68, p < 0.001), renal failure (OR = 2.55, 95% CI = 2.48–2.63, p < 0.001), valvular disease (OR = 2.71, 95% CI = 2.60–2.83, p < 0.001), and weight loss (OR = 2.23, 95% CI = 1.98–2.52, p < 0.001) were also confirmed as significant risk factors for cardiac complications after TKA (Table 4).
Table 4. Relationship between Cardiac Complications and Preoperative Comorbidities.
| Comorbidity | Univariate analysis | Multivariate logistic regression | |||||
|---|---|---|---|---|---|---|---|
| No cardiac complication | Cardiac complication | p-value | OR | 95% CI | p-value | ||
| Preoperative comorbidity | |||||||
| Acquired immune deficiency syndrome | 874 (0.10) | 32 (0.10) | < 0.001 | 0.88 | 0.61–1.27 | 0.501 | |
| Alcohol abuse | 10,714 (0.90) | 457 (1.30) | < 0.001 | 1.06 | 0.96–1.17 | 0.267 | |
| Deficiency anemia | 83,432 (6.70) | 3,801 (10.60) | < 0.001 | 1.03 | 0.98–1.07 | 0.249 | |
| Rheumatoid arthritis/collagen vascular diseases | 49,872 (4.00) | 1,961 (5.50) | < 0.001 | 1.13 | 1.07–1.19 | < 0.001 | |
| Chronic blood loss anemia | 11,270 (0.90) | 499 (1.40) | < 0.001 | 1.07 | 0.97–1.18 | 0.153 | |
| Chronic pulmonary disease | 186,502 (15.00) | 10,997 (30.80) | < 0.001 | 1.82 | 1.75–1.88 | < 0.001 | |
| Coagulopathy | 21,987 (1.80) | 1,630 (4.60) | < 0.001 | 1.37 | 1.29–1.46 | < 0.001 | |
| Depression | 173,393 (13.90) | 6,281 (17.60) | < 0.001 | 1.09 | 1.05–1.13 | < 0.001 | |
| Diabetes, uncomplicated | 227,682 (18.30) | 9,732 (27.20) | < 0.001 | 1.51 | 1.47–1.55 | < 0.001 | |
| Diabetes with chronic complications | 43,455 (3.50) | 4,726 (13.20) | < 0.001 | 2.06 | 1.98–2.14 | < 0.001 | |
| Drug abuse | 7,201 (0.60) | 355 (1.00) | < 0.001 | 1.28 | 1.14–1.44 | < 0.001 | |
| Hypertension | 841,583 (67.50) | 31,387 (87.90) | < 0.001 | 2.03 | 1.96–2.10 | < 0.001 | |
| Hypothyroidism | 207,660 (16.60) | 7,413 (20.80) | < 0.001 | 0.99 | 0.95–1.03 | 0.622 | |
| Liver disease | 16,647 (1.30) | 811 (2.30) | < 0.001 | 1.08 | 1.00–1.17 | 0.06 | |
| Lymphoma | 2,550 (0.20) | 158 (0.40) | < 0.001 | 1.33 | 1.12–1.58 | 0.001 | |
| Fluid and electrolyte disorders | 85,365 (6.80) | 5,744 (16.10) | < 0.001 | 1.42 | 1.36–1.48 | < 0.001 | |
| Metastatic cancer | 912 (0.10) | 51 (0.10) | < 0.001 | 1.20 | 0.89–1.62 | 0.236 | |
| Other neurological disorders | 32,620 (2.60) | 1,793 (5.00) | < 0.001 | 1.29 | 1.22–1.36 | < 0.001 | |
| Obesity | 330,379 (26.50) | 13,338 (37.30) | < 0.001 | 1.28 | 1.23–1.32 | < 0.001 | |
| Paralysis | 24,398 (2.00) | 2,415 (6.80) | < 0.001 | 1.50 | 1.27–1.79 | < 0.001 | |
| Peripheral vascular disorders | 25,574 (2.10) | 1,073 (3.00) | < 0.001 | 1.57 | 1.49–1.65 | < 0.001 | |
| Psychoses | 257 (2.2) | 29 (2.4) | < 0.001 | 1.12 | 1.04–1.20 | 0.002 | |
| Pulmonary circulation disorders | 8,886 (0.70) | 2,579 (7.20) | < 0.001 | 4.43 | 4.19–4.68 | < 0.001 | |
| Renal failure | 60,822 (4.90) | 8,020 (22.50) | < 0.001 | 2.55 | 2.48–2.63 | < 0.001 | |
| Solid tumor without metastasis | 5,757 (0.50) | 273 (0.80) | < 0.001 | 0.96 | 0.84–1.09 | 0.532 | |
| Peptic ulcer disease excluding bleeding | 1,791 (0.10) | 85 (0.20) | < 0.001 | 1.05 | 0.84–1.32 | 0.672 | |
| Valvular disease | 37,907 (3.00) | 4,912 (13.80) | < 0.001 | 2.71 | 2.60–2.83 | < 0.001 | |
| Weight loss | 2,699 (0.20) | 383 (1.10) | < 0.001 | 2.23 | 1.98–2.52 | < 0.001 | |
Values are presented as number (%).
OR: odds ratio.
Other Complications Associated with Cardiac Complications during TKA
Univariate analysis indicated that patients undergoing TKA with the occurrence of cardiac complications were more likely to experience pneumonia, convulsions, deep vein thrombosis (DVT), peripheral vascular disease, postoperative delirium, arrhythmias, and blood transfusions. As shown in Table 5, multivariate analysis showed that cardiac complications following TKA were independently associated with pneumonia (OR = 6.85, 95% CI = 6.37–7.37, p < 0.001), convulsions (OR = 1.48, 95% CI = 1.25–1.74, p < 0.001), DVT (OR = 1.43, 95% CI = 1.25–1.63, p < 0.001), peripheral vascular disease (OR = 2.94, 95% CI = 2.81–3.08, p < 0.001), postoperative delirium (OR = 2.88, 95% CI = 2.66–3.11, p < 0.001), cardiac arrhythmias (OR = 1.65, 95% CI = 1.5–1.81, p < 0.001), and blood transfusion (OR = 2.03, 95% CI = 1.96–2.1, p < 0.001) (Table 5).
Table 5. Relationship between Cardiac Complications and Postoperative Complications.
| Complication | Univariate analysis | Multivariate logistic regression | |||||
|---|---|---|---|---|---|---|---|
| No cardiac complication | Cardiac complication | p-value | OR | 95% CI | p-value | ||
| Medical complication | |||||||
| Pneumonia | 3,889 (0.30) | 970 (2.70) | < 0.001 | 6.85 | 6.37–7.37 | < 0.001 | |
| Convulsion | 3,217 (0.30) | 153 (0.40) | < 0.001 | 1.48 | 1.25–1.74 | < 0.001 | |
| DVT | 3,607 (0.30) | 261 (0.70) | < 0.001 | 1.43 | 1.25–1.63 | < 0.001 | |
| Peripheral vascular disease | 24,607 (2.00) | 2,162 (6.10) | < 0.001 | 2.94 | 2.81–3.08 | < 0.001 | |
| Postoperative delirium | 7,258 (0.60) | 769 (2.20) | < 0.001 | 2.88 | 2.66–3.11 | < 0.001 | |
| Joint dislocation | 4,483 (0.40) | 192 (0.50) | 0.001 | 1.54 | 1.33–1.78 | < 0.001 | |
| Arrhythmia | 9,534 (0.80) | 502 (1.40) | < 0.001 | 1.65 | 1.50–1.81 | < 0.001 | |
| Surgical complication | |||||||
| Blood transfusion | 73,430 (5.90) | 4,421 (12.40) | < 0.001 | 2.03 | 1.96–2.10 | < 0.001 | |
OR: odds ratio, DVT: deep venous thrombosis
DISCUSSION
This retrospective cohort study offers an extensive evaluation of the incidence and risk factors associated with cardiac complications following TKA from 2010 to 2019. Our large-scale national analysis identified a 2.78% incidence of in-hospital cardiac complications following primary TKA. Advanced age (> 75 years), male sex, Black race, and comorbidities such as chronic pulmonary disease, hypertension, and renal failure were independently associated with elevated risks. Additionally, hospital-related factors, including larger bed size and teaching status, significantly influenced complication rates. The occurrence of postoperative cardiac events correlated strongly with concurrent complications such as pneumonia, arrhythmias, and venous thromboembolism.
We identified that larger hospitals and teaching institutions were associated with an increased risk of cardiac complications, possibly due to the fact that cases in these facilities are commonly more challenging with complex and multiple comorbidities.7) Our study also highlighted regional disparities, with higher risks in the Midwest/North Central and Southern regions. These variations could be influenced by differences in healthcare delivery models, socioeconomic factors, and regional health policies that affect patient outcomes.8) Racial disparities in cardiac complications were pronounced in our logistics analysis, with Black patients experiencing significantly higher odds compared to White patients. These findings underscore the necessity of addressing racial and ethnic disparities in healthcare, which may be influenced by factors such as access to care, socioeconomic status, and the prevalence of comorbid conditions.9,10) In our investigation, male sex emerged as an independent risk factor for cardiac complications. This sex difference aligns with existing studies indicating that men are generally at greater risk for cardiovascular events, potentially due to a combination of biological, behavioral, and socioeconomic factors.10)
Patients with chronic pulmonary disease had markedly higher odds of cardiac complications. This finding aligns with existing literature that identifies respiratory conditions as risk factors for perioperative morbidity and mortality following TKA. Patients with chronic lung disease often have underlying systemic inflammation, which may be further exacerbated after surgical stress, leading to pronounced pulmonary vascular remodeling and pulmonary hypertension, ultimately increasing cardiac burden and the risk of cardiac complications.11,12) Similarly, our analyses found that pulmonary circulation disorders exhibited the highest risk among the preoperative comorbidities. In line with the findings of Bozic et al.,13) impaired pulmonary circulation, including pulmonary hypertension, can potentially place a pressure load on the right ventricle, which significantly increases the risk of cardiogenic shock during and after surgery. We also found that both uncomplicated diabetes and diabetes with chronic complications significantly increased the risk of cardiac complications. The hyperglycemic state in diabetic patients can lead to endothelial dysfunction and increased platelet aggregation, contributing to higher cardiovascular risk.4,6,14) Hypertension was associated with a two-fold increase in the risk of cardiac complications. Chronic hypertension can lead to left ventricular hypertrophy and reduced cardiac compliance, which may predispose patients to adverse outcomes under the hemodynamic stress of surgery.13,14) Furthermore, patients with renal failure exhibited a relatively high risk among cardiac complications. Renal failure is closely associated with cardiovascular complications, possibly due to fluid overload, and uremic conditions leading to cardiac dysfunction.15,16)
Moreover, the results of our research indicated that fluid and electrolyte imbalances are also a critical risk factor in the perioperative setting of TKA. The mechanism underlying this process we conjectured is that imbalances such as hyperkalemia and hypokalemia can disrupt cardiac conduction and lead to ventricular arrhythmias.15) Besides, the inability to effectively manage fluid balance can lead to volume overload, increasing the stress on the heart and ultimately to heart failure in patients undergoing TKA.15) Consistent with our analysis, obesity has been identified in the literatures as a significant risk factor for specific comorbidities, including postoperative cardiac complications.17,18,19) Consequently, for morbidly obese patients with end-stage arthritis, minimally invasive techniques are now advocated as the preferred option over joint replacement surgery.18,19) Psychiatric disorders, including depression and anxiety, have been reported to contribute to cardiac risk through autonomic dysregulation, which can lead to arrhythmias and other adverse events.20) Besides, depression has been shown to alter the hypothalamic-pituitary-adrenal axis, leading to increased cortisol levels and sympathetic nervous system activation, which can exacerbate cardiac conditions.20,21) We also identified substance abuse, including the use of tobacco, alcohol, and illicit drugs, as independent risk factors for perioperative cardiac complications. These substances can induce arrhythmias, contribute to hypertension, and lead to structural heart changes, thereby increasing the likelihood of myocardial infarction and sudden cardiac death.22,23)
In addition, significant preoperative weight loss can indicate underlying frailty or cachexia, both of which are associated with reduced cardiac reserve and increased perioperative cardiac risk.24,25) Cardiac valvular disease further adds to the risk by causing hemodynamic instability during surgery, particularly under conditions of fluid shifts and stress, making cardiac complications more likely to occur following TKA.7,19,20) Peripheral vascular disease impairs blood flow and increases arterial stiffness, which predisposes patients to ischemic events during the perioperative period.25,26,27)
Moreover, the following postoperative complications––DVT, pneumonia, convulsions, delirium, arrhythmias, and transfusions––were significantly associated with cardiac events following TKA. DVT is a well-established complication after TKA, especially in older patients.6,20,28) It significantly elevates the risk of pulmonary embolism and increases cardiovascular stress.28,29) Besides, TKA can result in immobilization and an increased risk of DVT, which may further elevating cardiac risks.20) Postoperative pneumonia directly strains the heart by reducing oxygen levels, leading to a higher risk of ischemic events.6,12) Neurological issues like convulsions and postoperative delirium were also linked to higher mortality and cardiac complications, likely due to autonomic dysregulation.30) Arrhythmias, particularly atrial fibrillation, serve as strong predictors of cardiac events, driven by inflammation and hemodynamic shifts.14,18) Blood transfusions contribute to fluid overload and inflammation intensifying the likelihood of adverse cardiac outcomes.20)
While the study presents valuable insights into the risk factors for cardiac complications following TKA, it has several notable limitations. First, the retrospective nature of the study, based on the NIS database, inherently limits the ability to establish causality between identified risk factors and cardiac outcomes.6) The reliance on administrative coding (ICD-9 and ICD-10) for defining complications and comorbidities introduces potential misclassification bias, as coding errors or inconsistencies across hospitals may affect the accuracy of the data. Additionally, the NIS database lacks detailed clinical information, such as perioperative management strategies, medication use, or the specific surgical techniques employed, which could have influenced cardiac outcomes. The exclusion of patients with prior knee surgeries or preexisting cardiac conditions may have led to selection bias, potentially underestimating the real-world incidence of complications in high-risk populations.3,4,5,17) Moreover, the database does not capture long-term postoperative outcomes, limiting the ability to evaluate the enduring effects of perioperative cardiac events on patient mortality or quality of life. Finally, although the study adjusts for multiple demographic and hospital-related factors, residual confounding cannot be ruled out, particularly with unmeasured variables such as lifestyle factors, socioeconomic status, and preoperative
This study identifies advanced age, male sex, Black race, and comorbidities such as chronic pulmonary disease, hypertension, and renal failure as significant risk factors for cardiac complications following TKA. These findings highlight the need for thorough preoperative risk assessments and tailored perioperative care, especially for high-risk patients with multiple comorbidities. Future research should explore interventions to reduce these complications and improve patient outcomes.
ACKNOWLEDGEMENTS
We thank the Healthcare Cost and Utilization Project (HCUP) team for providing access to the National Inpatient Sample (NIS) database, which served as the foundation for this study.
The study was supported by the Cultivation Program of Meizhou People’s Hospital (no. PY-C 2025014).
Footnotes
CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported.
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