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ARTICLES: Cardiac Surgery Outcomes

Factors Associated With Frailty in Patients Undergoing Cardiac Surgery

A Longitudinal Study

Chen, Wei-Yi MSN, RN; Liu, Chieh-Yu PhD; Shih, Chun-Che MD; Chen, Yih-Sharng MD; Cheng, Hsiao-Wei MSN, RN; Chiou, Ai-Fu PhD, RN

Author Information
The Journal of Cardiovascular Nursing: 5/6 2022 - Volume 37 - Issue 3 - p 204-212
doi: 10.1097/JCN.0000000000000787
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Abstract

Frailty is a specific geriatric syndrome characterized by a decreased physiological reserve and increased vulnerability to stressors due to multiple impairments across different systems, including cardiovascular diseases and issues related to cardiac surgery.1,2 Fried and colleagues3 defined frailty as a clinical syndrome that occurs when 3 or more of the following criteria are present: unintentional weight loss, self-reported exhaustion, weakness, a slow walking speed, and low physical activity levels. These criteria are based on data from the Cardiovascular Health Study, which included 5317 older adults. Frailty is an important condition in older adults and patients undergoing cardiac surgery. The prevalence of frailty and prefrailty in older adults ranges from 4.9% to 27.3% and from 34.6% to 57.6%, respectively.4,5 Patients undergoing cardiac surgery have an increased vulnerability to frailty because the biological mechanisms of frailty are similar to those of other conditions, including inflammation; higher levels of factor VIII, D-dimer, and C-reactive protein; and thrombosis.6,7 Furthermore, cardiac surgery might increase the risk of frailty, as frailty has been reported to occur in 25% to 50% of older patients after cardiac surgery.8

Frailty is associated with limitations in activities of daily living (ADL), falls, admission to the emergency room, and a poor quality of life. In particular, frail patients undergoing cardiac surgery are more affected by the complexity of the surgical process and have an increased risk of postoperative major adverse cardiac and cerebrovascular events, such as delirium, bleeding, or stroke; moreover, they exhibit poor recovery after surgery as well as longer hospitalization stays, higher mortality rates, and greater long-term care needs.8,9 The development of frailty is a progressive process that may be reversible at the early stage. A decrease in the severity of frailty is beneficial for improving clinical outcomes and decreasing healthcare utilization and costs.10 The early assessment of frailty is important for identifying cardiac surgery patients at risk of frailty and then administering interventions to reduce the progression of frailty and improve clinical outcomes. Therefore, it is necessary to identify the prevalence of frailty and its associations in patients undergoing cardiac surgery.

According to previous studies, frailty is associated with older age, the female sex, a low level of education, a low economic status, poor health, a poor functional status, comorbidities, and psychosocial conditions such as cognitive decline, depression, and lower levels of social support in older adults or patients with cardiac disease.3,7,9,10 However, few studies have focused on the prevalence of frailty and its associations in patients undergoing cardiac surgery. In addition, frailty can be a key criterion for selecting the appropriate surgical treatment while considering the net clinical benefit of surgery. For example, frail patients undergoing cardiac surgery were more likely to choose minimally invasive direct coronary artery bypass to prevent surgical complications and a delay of recovery. The combination of a frailty assessment with clinical risk assessments such as the European System for Cardiac Operative Risk Evaluation (EuroSCORE) provides important information on the risk of cardiac surgery and helps healthcare providers and their patients perform shared decision making.8 A longitudinal assessment of frailty may provide a better understanding of the trajectory of frailty development after cardiac surgery and lead to the development of effective interventions for preventing frailty and maintaining the quality of life and functional independence of patients undergoing cardiac surgery.8 Therefore, the aim of this study was to investigate the prevalence of frailty and its associated factors in patients before cardiac surgery and at 1 and 3 months after cardiac surgery.

METHODS

Participants and Setting

A longitudinal design was used in this study. A convenience sample of 154 patients undergoing cardiac surgery was recruited from the cardiovascular units of 2 large medical centers in northern Taiwan. The inclusion criteria were patients who were (1) 20 years or older; (2) hospitalized for cardiac surgeries including valve repair or replacement, coronary artery bypass grafting, and aneurysm dissection surgery; and (3) able to communicate and speak in Mandarin or Taiwanese. The exclusion criteria were patients who (1) had a Mini-Mental State Examination (MMSE) score of 24 or lower; (2) underwent unexpected cardiac surgery or heart transplantation or had an unstable condition requiring devices such as a left ventricular assist device; or (3) were diagnosed with a mental illness such as depression, anxiety disorders, or schizophrenia by a psychiatrist. We excluded these patients because our study variables were evaluated using a structured questionnaire, a hand grip dynamometer, and a walking test, which required patients to have normal cognitive function, stable conditions, and a healthy mental status to complete the tasks and ensure the accuracy of our results.

During the study period from June 2017 to June 2018, 169 patients from the cardiovascular units of the study hospitals were screened for eligibility according to the inclusion criteria. Of these patients, 15 were excluded (10 refused to participate, 2 had a mental illness, and 3 had MMSE scores of ≤24). A total of 154 patients signed the consent form and completed the questionnaire before cardiac surgery. At 1 month after surgery, 3 patients were lost to follow-up because of loss of contact. At 3 months after surgery, 6 patients were lost to follow-up because of rehospitalization (n = 2), loss of contact (n = 1), or relocation (n = 3). Of the 154 participants, 145 completed the entire study (Figure). A post hoc statistical power analysis was performed using the repeated-measures, within-factors analysis of variance (ANOVA) setting in the G-Power software, with an α of 0.05 and effect size of 0.15; a sufficient power of 0.98 could be attained with a sample size of 145.

F1
FIGURE:
Flowchart of the subject inclusion process.

Ethical Considerations and Procedure

This study was conducted in accordance with the principles of the Declaration of Helsinki. The institutional review boards of the study hospitals approved the study. A researcher explained to all eligible patients the study purpose and procedure and that the participants had the right to voluntarily withdraw from the study. All participants who signed the consent form were asked to complete a structured questionnaire to obtain baseline data before cardiac surgery; the questionnaire included items on demographic and clinical information, the short-form of the International Physical Activity Questionnaire for older adults, the Hospital Anxiety and Depression Scale, and the Social Support Scale. The questionnaire was administered again at 1 and 3 months after surgery. Clinical data, including the New York Heart Association (NYHA) functional classification, left ventricular ejection fraction, Canadian Cardiovascular Society grade for angina pectoris, chronic diseases, medications, and body mass index; laboratory data, including hemoglobin and albumin levels; and operative-related data, including the EuroSCORE score, type of surgery, need for cardiopulmonary bypass, anesthesia time, duration of endotracheal tube and extracorporeal circulation usage, and intensive care unit and hospital stays, were retrieved from the patients' medical charts by the researcher.

Measurements

Frailty was measured by assessing the frailty phenotype proposed by Fried and colleagues3 with the following 5 criteria: unintentional weight loss in the past year, self-reported exhaustion, weak grip strength, slow walking speed, and a low physical activity level (Table 1). Patients were classified as frail if they met 3 or more criteria, as prefrail if they met 1 or 2 criteria, and as robust (nonfrail) if they met none of the criteria.

TABLE 1 - Criteria Used to Define Frailty
Criteria Methods Cutoff for Positive Results
Weight loss Self-reported unintentional weight loss ≥3 kg or 5% weight loss over the past year
Low grip strength Grip strength of the dominant hand (mean of 3 serial measurements) adjusted for sex and body mass index The lowest 20th percentile
Exhaustion Evaluation of 2 items from the CES-D (a) I felt everything I did was an effort
(b) I could not get going
at least 1 condition was present for 3 days or more over the past week
Slow gait speed Timed walk over 4 m, adjusted by sex and height The longest 20th percentile
Low physical activity Physical activity level over past 2 weeks using international physical activity questionnaire for older adults The weekly levels of physical activity were converted to equivalent kilocalories of expenditure
The lowest 20th percentile
One point was assigned for each criterion that was met, with a score of 3 or higher indicating frailty and a score of 1 or 2 indicating prefrailty.
Abbreviation: CES-D, Center for Epidemiological Studies–Depression Scale.

Self-reported exhaustion was measured using 2 items (“I felt everything I did was an effort” and “I could not get going”) from the Center for Epidemiological Studies–Depression Scale.11 Patients were asked to rate the frequency of occurrence during the past week using the following scores: 0 = rarely or none of the time, 1 = some or a little of the time, 2 = a moderate amount of the time, or 3 = most of the time. The patients who responded with a score of 2 or 3 to either of these questions were categorized as positive for exhaustion. Grip strength was assessed using a digit hand grip dynamometer (Camry EH101 200 lb/90 kg); as the patients squeezed it, the dynamometer measured their grip strength in kilograms. The mean of 3 serial measurements was calculated. The results were interpreted with respect to the patient's sex and body mass index, and the 20th percentile of patients with the lowest values were considered positive for weak grip strength. Walk time was measured as the time that patients spent walking 4 m. The results were adjusted by the patient's sex and height, and the 20th percentile of patients with the longest times was considered positive for slow walk time.

Physical activity was measured by using the short-form of the International Physical Activity Questionnaire for older adults.12 The International Physical Activity Questionnaire asked the participants about the duration and frequency of their physical activity over the past 7 days, including vigorous-, moderate-, and light-intensity activity; walking for at least 10 minutes; sitting; and sleeping. The weekly levels of physical activity were converted to the equivalent kilocalories of expenditure. Low physical activity was defined by the lowest 20th percentile of physical activity values adjusted by sex. The International Physical Activity Questionnaire has been shown to have good test-retest reliability (r = 0.67), a content validity index of 0.98, and a concurrent validity index of 0.84.12

Anxiety and depression were measured using the 14-item Hospital Anxiety and Depression Scale, which consists of anxiety and depression subscales.13 Each item score ranged from 0 to 3. Each subscale had a total possible score of 21, with high scores indicating high levels of anxiety and depression. For both subscales, scores of 0 to 7 indicated no anxiety/depression, scores of 8 to 10 indicated doubtful cases, and scores of 11 or more indicated anxiety and depression. The reliability index of the overall Hospital Anxiety and Depression Scale was reported to be 0.84 in patients with heart failure.14 In the present study, the Cronbach's α for the overall Hospital Anxiety and Depression Scale was 0.81.

Social support was measured using the 15-item Social Support Scale, including 2 subscales: social support from family/friends and healthcare professionals.15 Patients rated their perceived level of social support on a scale from 0 (no support) to 3 (always supported). The total possible score ranged from 0 to 90, with high scores indicating high levels of social support. A content validity index of 0.94 and a Cronbach's α of 0.91 have been reported in patients with heart failure.15 In this study, the Cronbach's α was 0.95.

The Barthel Index of Activities of Daily Living16 and Lawton's instrumental ADL (IADL) scale17 were used to measure patients' functional abilities. The Barthel index consists of 10 items: feeding, bathing, grooming, dressing, bowel control, bladder control, toileting, chair transfer, ambulation, and stair climbing. The total score ranges from 0 to 100, with higher scores indicating higher levels of independence in ADL. The scale had a test-retest r of 0.89 and an intercoder reliability of 0.95. The Lawton IADL scale includes items on 8 complex activities: using a telephone, shopping, food preparation, housekeeping, laundry, transportation, handling finances, and taking medications. The total score ranges from 0 (low function) to 8 (high function). The reliability and validity of the Chinese versions of the Barthel index and Lawton's IADL scale have been shown to be adequate in Taiwanese patients.18

Data Analysis

Data were analyzed by SPSS 22 using descriptive statistics, χ2 tests, 1-way ANOVA, multinomial logistic regression, and generalized estimating equations. Generalized estimating equations were used to compare the changes in frailty from baseline to 1 and 3 months. χ2 Tests and 1-way ANOVA were used to analyses the associations between frailty and demographic, clinical, and psychosocial variables. Multinomial logistic regression was used to identify the predictors of frailty. A P value <.05 was considered statistically significant.

RESULTS

Patient Characteristics at Baseline

The mean age of the participants was 63.15 years. Most participants were male (68.2%), were married (78.6%), were unemployed (57.8%), had an NYHA class of I or II (76.6%), had a Canadian Cardiovascular Society grade of angina of I or II (88.3%), and needed to undergo cardiopulmonary bypass (88.3%). Valvular surgery was the most common surgery (48.7%), followed by coronary artery bypass grafting (29.9%). Significant differences in the demographic and clinical characteristics were observed among the nonfrail, prefrail, and frail groups, except for age, sex, marital status, education level, religion, and left ventricular ejection fraction (Tables 2 and 3). Frail or prefrail patients were more likely to be unemployed (χ2 = 11.88, P = .018), have gout (χ2 = 8.82, P = .012), have dysrhythmia before surgery (χ2 = 6.99, P = .030), have higher NYHA classes (χ2 = 7.68, P = .021), have lower ADL (F = 10.72, P < .001) and IADL (F = 14.78, P < .001) scores, have higher EuroSCORE scores (F = 7.72, P < .001), need to undergo cardiopulmonary bypass (χ2 = 9.54, P = .008), have longer anesthesia times (F = 9.25, P < .001), have longer endotracheal tube (F = 13.71, P < .001) and extracorporeal circulation (F = 6.99, P < .001) times, have longer intensive care unit (F = 10.78, P < .001) and hospital (F = 15.30, P < .001) stays, and have lower hemoglobin (F = 15.42, P < .001) and albumin (F = 10.96, P < .001) levels. In addition, higher anxiety (F = 4.46, P = .013) and depression levels (F = 14.94, P < .001) and lower MMSE scores (F = 6.37, P = .002) were found in frail patients than in nonfrail and prefrail patients.

TABLE 2 - Subjects' Characteristics and the Differences in Frailty
Variables All (N = 154) Robust (n = 60) Prefrail (n = 69) Frail (n = 25) χ 2 P
Sex 6.04 .049
 Male 105 (68.2) 45 (75.0) 48 (69.6) 12 (48.0)
 Female 49 (31.8) 15 (25.0) 21 (30.4) 13 (52.0)
Marital status 4.79 .570
 Single/others 33 (21.4) 11 (18.3) 16 (23.2) 6 (24.0)
 Married 121 (78.6) 49 (81.7) 53 (76.8) 19 (76.0)
Education 5.01 .286
 ≤9 y 59 (38.3) 19 (31.7) 29 (42.0) 11 (44.0)
 >9 y 95 (61.7) 41 (68.3) 40 (58.0) 14 (56.0)
Religious 1.51 .959
 No 39 (25.3) 17 (28.3) 17 (24.6) 5 (20.0)
 Yes 115 (74.7) 43 (71.7) 52 (75.4) 20 (80.0)
Work status 11.88 .018
 Unemployed 89 (57.8) 27 (45.0) 41 (59.4) 21 (84.0)
 Employed 65 (42.2) 33 (55.0) 28 (40.6) 4 (16.0)
Comorbidity
 Gout 28 (18.2) 5 (8.6) 18 (25.7) 4 (20.0) 8.82 .012
Dysrhythmia before surgery 6.99 .030
 No 122 (79.2) 51 (85.0) 56 (81.2) 15 (60.0)
 Yes 32 (20.8) 9 (15.0) 13 (18.8) 10 (40.0)
NYHA class 7.68 .021
 I, II 118 (76.6) 53 (88.3) 47 (68.1) 18 (72.0)
 III, IV 36 (23.4) 7 (11.7) 22 (31.9) 7 (28.0)
Cardiopulmonary bypass 9.54 .008
 No 18 (11.7) 13 (21.7) 4 (5.8) 1 (4.0)
 Yes 136 (88.3) 47 (78.3) 65 (94.2) 24 (96.0)
LVEF 0.07 .967
 ≦30% 5 (3.2) 2 (3.3) 2 (2.9) 1 (4.0)
 >31% 148 (96.1) 58 (96.7) 66 (97.1) 24 (96.0)
Data are presented as n (%).
Abbreviations: NYHA, New York Heart Association; LVEF, left ventricular ejection fraction.

TABLE 3 - Subjects' Characteristics and the Differences in Frailty (n = 154)
Variables All Robust Prefrail Frail F P
Age, y 63.15 (11.16) 61.33 (993) 64.39 (11.17) 65.08 (13.56) 1.32 .272
ADL score 98.93 (5.45) 100.00 (0) 99.57 (2.54) 94.60 (12.16) 10.72 <.001
IADL score 7.81 (0.68) 8.00 (0) 7.87 (0.48) 7.20 (1.35) 14.78 <.001
EuroSCORE score, % 2.64 (2.55) 2.22 (2.59) 2.37 (2.14) 4.39 (2.85) 7.72 <.001
Surgery time, h 5.22 (1.71) 4.93 (1.57) 5.07 (1.53) 6.32 (2.11) 6.80 <.001
Anesthesia time, h 6.71 (1.86) 6.29 (1.70) 6.58 (1.60) 8.07 (2.31) 9.25 <.001
Endotracheal tube time, h 21.92 (35.93) 12.32 (14.06) 18.98 (23.39) 53.05 (70.21) 13.71 <.001
Extracorporeal circulation time, h 2.47 (1.38) 2.03 (1.45) 2.59 (1.16) 3.17 (1.43) 6.99 <.001
ICU stay, d 4.89 (7.18) 3.79 (3.66) 3.77 (2.15) 10.64 (15.55) 10.78 <.001
Hospitalization, d 20.10 (12.99) 17.30 (8.80) 18.25 (9.24) 32.42 (21.82) 15.30 <.001
Hemoglobin level, g/dL 13.15 (2.04) 13.89 (1.62) 13.15 (1.95) 11.42 (2.19) 15.42 <.001
Albumin level, mg/dL 4.11 (0.42) 4.26 (0.35) 4.09 (0.40) 3.80 (0.47) 10.96 <.001
Anxiety score 4.75 (3.80) 3.82 (3.08) 4.96 (4.02) 6.40 (4.22) 4.46 .013
Depression score 3.57 (3.16) 2.08 (2.40) 4.16 (3.21) 5.52 (3.12) 14.94 <.001
MMSE score 29.07 (1.20) 29.27 (1.02) 29.17 (1.19) 28.32 (1.38) 6.37 .002
Social support score 74.06 (13.28) 75.83 (12.20) 73.03 (14.01) 72.64 (13.80) 0.88 .415
Data are provided as mean (SD).
Abbreviations: ADL, activities of daily living; IADL, instrumental activities of daily living; EuroSCORE, European System for Cardiac Operative Risk Evaluation; ICU, intensive care unit; MMSE, Mini-Mental State Examination.

Changes in Frailty From Baseline (Before Surgery) to 3 Months After Surgery

As shown in Table 4, the prevalence of frailty in patients undergoing cardiac surgery was 16.2%, 20.5%, and 16.6% before surgery and at 1 and 3 months after surgery, respectively. The prevalence of prefrailty was 44.8%, 41.1%, and 43.4%, before surgery and at 1 month and 3 months after surgery, respectively. Generalized estimating equation analysis showed that the number of positive responses to the frailty criteria increased from before surgery to 1 month after surgery (B = 0.11, P = .317) and increased at 3 months after surgery (B = 0.03, P = .787), but no statistically significant differences were found.

TABLE 4 - Changes in Frailty Over Time Determined Using the Generalized Estimating Equation (n = 154)
Preop (n = 154) 1 Mo (n = 151) 3 Mo (n = 145)
n % n % n %
Robust 60 39.0 58 38.4 58 40.0
Prefrail 69 44.8 62 41.1 63 43.4
Frail 25 16.2 31 20.5 24 16.6
B SE 95% CI Wald X 2 P
Lower Upper
Intercept 1.17 0.10 0.97 1.38 134.10 <.001
Preop Reference
Postop 1 mo 0.11 0.11 −0.10 0.32 1.00 .317
Postop 3 mo 0.03 0.10 −0.18 0.23 0.07 .787
Abbreviations: Preop, preoperation; Postop, postoperation; 95% CI, 95% confidence interval.

Predictors of Frailty

Multinomial logistic regression analysis showed that the significant predictors of prefrailty were the presence of gout (odds ratio [OR], 4.44; 95% confidence interval [95% CI], 1.38–14.32; P = .013), higher NYHA classes (OR, 3.26; 95% CI, 1.24–8.56; P = .013), lower ADL scores (OR, 0.11; 95% CI, 0.10–0.13; P < .001), lower hemoglobin levels (OR, 0.67; 95% CI, 0.51–0.89; P = .005), and higher levels of depression (OR, 1.32; 95% CI, 1.10–1.59; P = .003). In addition, frailty was significantly predicted by unemployment (OR, 5.19; 95% CI, 1.55–17.42; P = .008), lower hemoglobin levels (OR, 0.47; 95% CI, 0.31–0.71; P < .001), and higher levels of depression (OR, 1.53; 95% CI, 1.17–2.00; P = .002) (Table 5).

TABLE 5 - Predictors of Frailty Determined Using the Multinomial Logistic Regression Analysis (n = 154)
Variables Prefrail Frail
B SE OR 95% CI P B SE OR 95% CI P
Unemployed 0.42 0.38 1.53 0.73–3.20 .264 1.65 0.62 5.19 1.55–17.42 .008
Gout 1.49 0.60 4.44 1.38–14.32 .013 1.27 0.73 3.57 0.86–14.82 .080
NYHA classes III and IV 1.18 0.49 3.26 1.24–8.56 .013 0.80 0.64 2.23 0.64–7.76 .206
Dysrhythmia before surgery 0.02 0.51 1.02 0.38–2.77 .964 1.02 0.58 2.78 0.90–8.62 .070
ADL score −2.20 0.06 0.11 0.10–0.13 <.001
EuroSCORE score −0.15 0.11 0.86 0.69–1.07 .170 −0.07 0.14 0.94 0.71–1.24 .640
Anesthesia time −0.02 0.19 0.98 0.68–1.42 .912 0.42 0.30 1.52 0.85–2.74 .160
Endotracheal tube time 0.03 0.02 1.03 0.99–1.06 .128 0.04 0.02 1.04 1.00–1.07 .054
Extracorporeal circulation time 0.38 0.24 1.47 0.93–2.32 .101 0.08 0.40 1.08 0.49–2.36 .846
Hospitalization −0.03 0.03 0.97 0.93–1.02 .294 −0.01 0.03 0.10 0.95–1.05 .876
Hemoglobin level −0.40 0.14 0.67 0.51–0.89 .005 −0.76 0.21 0.47 0.31–0.71 <.001
Albumin level −0.59 0.65 0.55 0.15–1.99 .365 −0.97 1.01 0.38 0.05–2.71 .333
Anxiety score 0.01 0.07 1.00 0.87–1.16 .953 0.04 0.11 1.04 0.84–1.29 .716
Depression score 0.28 0.09 1.32 1.10–1.59 .003 0.42 0.14 1.53 1.17–2.00 .002
MMSE score 0.06 0.21 1.06 0.71–1.60 .763 −0.18 0.29 0.83 0.47–1.47 .526
Abbreviations: NYHA, New York Heart Association; ADL, activities of daily living; EuroSCORE, European System for Cardiac Operative Risk Evaluation; MMSE, Mini-Mental State Examination.

DISCUSSION

Frailty occurred in 16.2% of patients before cardiac surgery, and this number increased to 20.5% at 1 month after surgery and then decreased to 16.6% at 3 months after surgery. Prefrailty was defined in 44.8%, 41.1%, and 43.4% of patients before cardiac surgery and at 1 month and 3 months after surgery, respectively. These findings are similar to a previous report by Marshall et al,19 who found that 14% and 37% of patients undergoing open cardiac surgery were identified as frail and borderline frail, respectively. However, the findings differ from results reported by Chen,20 who reported the prevalence of frailty to be 19%, 35%, and 9.9% before surgery and at 1 and 3 months after cardiac surgery, respectively; moreover, our values are higher than those reported in a previous survey study showing that 4.1% of patients were frail after cardiac surgery.21 This discrepancy might be attributed to the differences in the definition and measurement of frailty. We used Fried's frailty phenotype to measure and define frailty, whereas Lee et al21 defined frailty as any impairment in ADLs or ambulation or a documented history of dementia.

Consistent with the results reported by Chen,20 the prevalence of frailty increased at 1 month after cardiac surgery and decreased to the baseline level at 3 months after surgery in the present study. This finding could be explained by the recovery process after cardiac surgery. At 1 month after surgery, patients still experience pain or exhibit wounds that have not healed, which might prevent patients from performing physical activity or attending social events, which can affect their emotional status. However, most patients recover from cardiac surgery and increase their physical activity by 3 months after surgery. Although patients can recover at 3 months after cardiac surgery, 16.6% of patients still reported frailty, which might have contributed to disability and worse outcomes. Therefore, it is suggested that nurses assess patients' level of frailty before cardiac surgery; provide early preoperative individualized education regarding pain management, wound self-management, and the appropriate type and strength of exercise or physical activity to perform after surgery; and encourage patients to continuously perform physical activity after discharge.

Our results show that frail or prefrail patients undergoing cardiac surgery are more likely to be unemployed, have gout and dysrhythmia before surgery, have higher NYHA classes and a lower functional ability, have higher EuroSCORE scores, need to undergo cardiopulmonary bypass, have longer anesthesia times, have longer endotracheal tube and extracorporeal circulation times, have longer intensive care unit and hospital stays, have lower hemoglobin and albumin levels, have higher levels of anxiety and depression, and have lower MMSE scores. The significant predictors of prefrailty and frailty included unemployment, gout, higher NYHA classes, lower ADL scores, lower hemoglobin levels, and higher levels of depression. We found that unemployed patients had a 5.19-fold higher risk of frailty than did employed patients. No previous studies have reported relationships between frailty and work status. However, employed patients tend to be younger and have higher levels of physical activity, which might reduce the occurrence of frailty. Therefore, older patients who are unemployed may increase their physical activity, such as participating in social activity or volunteer work, to prevent frailty. Patients with a history of gout had a 4.44 times higher risk of prefrailty than did those without gout. These findings can be explained by the limitation in physical activity caused by gout-related pain. Our study also showed that patients with NYHA classes of III/IV or lower ADL scores had a higher risk of prefrailty than did patients with NYHA scores I/II or higher ADL scores. These results were consistent with previous findings.5,22–24 According to Bagshaw et al,25 frail patients also have more severe diseases, poorer mobility, and greater dependence on others in performing ADLs than patients who are not frail. Thus, patients with low cardiac function might have a low functional ability and limited level of physical activity, which can contribute to a high risk for frailty.

A low hemoglobin level was an important predictor of prefrailty and frailty. Albumin level was also significantly associated with frailty. These findings are similar to previous studies.22,26,27 Pires Corona et al26 reported a strong association of anemia with frailty (OR, 3.27; 95% CI, 1.89, 5.65; P < .001) and a significant association with low levels of physical activity, weakness, and slowness. Yamamoto et al27 also reported a relationship between low albumin level and higher mortality and suggested that baseline albumin level might be a useful marker for risk stratification before cardiac surgery. A low albumin level may be associated with nutritional and inflammatory factors.28 Thus, the levels of hemoglobin, albumin, and nutrition must be assessed in patients undergoing cardiac surgery, and education on nutritional supplements, particularly regarding protein intake, must be provided to prevent frailty and poor outcomes. In our study, frailty was associated with operative-related factors, including high EuroSCORE scores, needing to undergo cardiopulmonary bypass, longer anesthesia times, longer endotracheal tube and extracorporeal circulation times, and longer intensive care unit and hospital stays. Similar findings have been reported in previous studies, which showed that frail patients undergoing cardiac surgery had EuroSCORE scores higher than II, longer cardiopulmonary bypass times, and long intensive care unit and hospital stays.29–31 Therefore, preoperative assessments and operative data can be used to assess the risk of frailty in patients undergoing cardiac surgery.

In the present study, the risk of prefrailty and frailty increased by 32% to 57% for each point of increase in the depression score. Higher anxiety and lower MMSE scores were also associated with a higher risk of frailty. Mlynarska et al23 also reported higher anxiety and depression scores for frail patients, and anxiety significantly predicted higher levels of frailty syndrome. As shown in our study, approximately 10% to 20% of patients report depression and anxiety before cardiac surgery. In addition, anxiety and depression levels increase significantly from before to after cardiac surgery. Thus, it is necessary to evaluate patients' psychological status before cardiac surgery and provide appropriate mental support or professional counseling to promote patients' mental health and prevent frailty.

Limitations

We used a convenience sample of patients undergoing cardiac surgery recruited from 2 medical centers in northern Taiwan. Therefore, the results cannot be generalized to all cardiac patients. Although we used a longitudinal study design to examine the changes in frailty and its associated factors before surgery to 3 months after surgery, patients should be followed for at least 6 months to explore long-term changes in frailty and capture the extent of deterioration in patients after cardiac surgery. In addition, we used a structured questionnaire to assess study variables, which might contribute to memory bias and affect the validity of the study results. In particular, frailty was measured with Fried's frailty phenotype, which might not be suitable for patients undergoing cardiac surgery. Thus, it is suggested that future studies use brief assessment instruments or develop new frailty scales to measure frailty in patients undergoing cardiac surgery.

CONCLUSIONS

As shown in our study, frailty is a reversible process in patients undergoing cardiac surgery and is significantly predicted by patients' work status, comorbidities, disease severity, functional status, nutrition status, and depression. Thus, patients' preoperative conditions, physical function, and psychosocial status must be evaluated before and after cardiac surgery by multidisciplinary teams to provide appropriate physical treatment and mental support, as well as physical activity programs for the prevention of frailty. Specific clinical interventions for the prevention of frailty in patients undergoing cardiac surgery may include performing an early preoperative assessment of frailty and its risk factors using a suitable frailty scale and comprehensive geriatric assessment instrument; modifying surgical interventions to less invasive approaches for patients at high risk of frailty; managing presenting comorbidities and cardiac symptoms, such as pain or dyspnea; promoting physical activity, exercise, or cardiac rehabilitation to strengthen patients' muscle power and walking ability; and providing diet counseling, such as increasing protein intake, and mental support after surgery.

What’s New and Important

  • The prevalence of frailty in patients undergoing cardiac surgery was 16.2% before surgery, and it increased at 1 month after cardiac surgery and decreased to the baseline level at 3 months after surgery.
  • The significant predictors of prefrailty and frailty included unemployment, gout, higher NYHA classes, lower ADL scores, lower hemoglobin levels, and higher levels of depression.
  • Frailty should be assessed preoperatively. In addition, patients' physical function and psychosocial status must be evaluated before and after cardiac surgery to provide appropriate physical treatments and mental support, as well as physical activity programs for the prevention of frailty.

Acknowledgments

The authors would like to thank all the subjects who participated in our study and all experts and hospitals for supporting this study.

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Keywords:

frailty; cardiac surgery; anxiety; depression; activities of daily living

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