Abstract
Background:
Poor psychological health and cardiorespiratory fitness prior to open heart surgery (OHS) might be predictors of postoperative pulmonary complications that lead to morbidity and mortality. Assessment of physical and psychological conditions should be considered for patients receiving OHS, to possibly prevent these complications. This study investigates how inspiratory muscle strength (IMS) and functional capacity (FC) relate to the psychological health of preoperative cardiac surgery patients.
Method:
A cross-sectional study was designed before OHS; the 6-minute walk test and IMS were performed on patients who were admitted for OHS. All participants were requested to complete Hospital Anxiety and Depression Scale. Pearson correlation and hierarchal regression analysis were performed to determine the relationships between IMS and FC and psychological conditions (anxiety and depression).
Results:
Overall, 36 males and 28 females aged 56.89±10.23 years were recruited. Significant relationships were observed between IMS and anxiety and depression symptoms (r = –0.33 and r = –0.27, respectively). Anxiety was negatively related to FC (r = –0.25). These relationships remained significant after adjustment for age, sex, and body mass index (BMI) (∆R2 = 0.11 and ∆R2 = 0.09). In addition, anxiety was also related to FC after controlling for age, sex, and BMI (∆R2 = 0.09).
Conclusion:
Among patients undergoing OHS, those with a higher level of depression or anxiety had a lower cardiorespiratory fitness than those with a low level of depression or anxiety.
Keywords: Open heart surgery, cardiac surgical procedures, functional capacity, 6-minute walk test, inspiratory muscle, anxiety, depression
Key Messages:
Depression and anxiety symptoms in patients who underwent open heart surgery were inversely associated with inspiratory muscle strength. Anxiety symptoms were negatively associated with functional capacity. These relationships remained significant even after controlling for age, sex, and BMI.
World Health Organization showed that 17.8 million people died from cardiovascular disease (CVD) in 2017, and the global mortality rate was 31%.1 In 2016, CVD had caused over 17.9 million deaths for a global mortality rate of approximately 31.0%. Further, 85% of these deaths were from CVD (i.e., heart attack and stroke).2 In addition, it was reported that 56.7% of patients aged ≥ 65 years had received a coronary artery bypass graft (CABG); this number is eventually projected to increase to 67.3%.3 The total cost for patients of a CABG is over $30,0004; therefore, medical care costs are significant for patients undergoing CABG.
Poor inspiratory muscle strength (IMS), functional capacity (FC), and psychological health (e.g., symptoms of anxiety, depression) are associated with adverse outcomes after open heart surgery (OHS) and are risk factors for post-surgical morbidity and mortality.5–11 FC is the ability to perform regular activities requiring aerobic metabolism and is a combination of an individual’s performance and cardiovascular, respiratory, and skeletal muscle health.12
Decreased IMS and FC (as assessed with the 6-minute walk test, 6-MWT) have been observed in patients after operative cardiac surgery.5–8 Respiratory muscle dysfunction and the loss of ability to generate force in patients with OHS leads to pulmonary complications such as breathlessness, impaired airway clearance, and poor pulmonary ventilation.13, 14 Therefore, these factors should be assessed and treated before OHS to prevent poor respiratory muscle function and pulmonary ventilation. In addition, symptoms of depression and anxiety prior to OHS are significant predictors of morbidity and mortality in short- and long-term follow-up consultations.9–11, 15–19 For example, patients with moderate to severe depression before heart operations had a higher mortality rate than those without depression.15 Tully et al.19 reported that patients suffering from anxiety tended to experience major adverse cardiovascular and cerebrovascular events (e.g., myocardial infarction, stroke) after CABG surgery. Symptoms of depression were also related to a lack of physical function (assessed using the Short Form-36) before cardiac surgery.20 In addition, patients undergoing cardiac surgery should be assessed in a more comprehensive manner that includes assessments of IMS, FC, and psychological health (i.e., anxiety and depression) to prevent postoperative pulmonary complications (e.g., pneumonia, lung atelectasis, prolonged ventilation). Therefore, this study examined the relationships between psychological health and cardiorespiratory fitness (i.e., IMS and FC) in patients undergoing preoperative OHS.
Materials and Methods
A cross-sectional study was designed with 64 preoperative OHS participants (i.e., receiving valve replacement or coronary artery bypass grafting) at Thammasat University Hospital between December 2015 and December 2016. The participants were aged 35–70 years and consisted of both males and females. An information sheet was given to the participants prior to participation in the study. The study protocol was approved by the ethics committee board from Thammasat University and Thammasat University Hospital. Written informed consent was obtained from all the participants. In addition, the study was registered in the Thai Clinical Trials Registry (TCTR); the identification number is TCTR 20151215002.
Assessment of FC was conducted via 6-MWT, following the protocol from the American Thoracic Society.21 IMS was tested using an RPM01 (Micro Medical Ltd., United Kingdom). According to the American Thoracic Society/European Respiratory Society (ATS/ERS) recommendations on respiratory muscle testing, IMS was measured at residual volume.21 To evaluate IMS, the participants were instructed to exhale slowly and completely, and then inhale deeply and sustain the pressure for 1.5 seconds. Each participant was asked to perform the 3–5 IMS maneuver, with the highest two readings within 10 cmH2O recorded.
In addition, the participants were asked to complete the Hospital Anxiety and Depression Scale (HADS). The Thai translation of HADS has reliability and validity for both anxiety and depression subscales. The sensitivity of anxiety subscales of the Thai HADS subscale was 100% and specificity was 86.0%. For the depression subscale, sensitivity was 85.71% and specificity was 91.3%. Additionally, the Thai version of the HADS had demonstrated good internal consistencies, with Cronbach’s alpha coefficients of 0.86 for the anxiety scale and 0.83 for the depression scale.22 The total scores range from 0 to 21 for both HADS-anxiety and HADS-depression; higher scores indicate greater depression or anxiety.23 To define an individual with depressive or anxiety symptoms, a cut-off of ≥ 8 on the anxiety and depression subscales was used.24
The measurements were performed within 48 hours prior to the cardiac operation. Body mass index (BMI) was calculated using weight/height (meter).2 According to the World Health Organization, normal BMI is defined as 18.5–23.0 kg/m2 in the Asian populations.25
Statistical Analysis
Percentages (%), means, and standard deviations (SD) were calculated. A normality of distribution test (the Kolmogorov–Smirnov Goodness of Fitness Test) was performed to verify the distribution data. ANOVA was then conducted to compare psychological health conditions and types of cardiac operations. Pearson correlation coefficients were calculated between psychological health conditions (i.e., anxiety and depression) and IMS and FC. Additionally, a linear regression was applied to evaluate the relationship between HADS anxiety and depression scores, and IMS and 6-MWT.
Results
A total of 64 eligible patients were evaluated in terms of IMS and FC (i.e., 6-MWT). The characteristics of the participants are presented in Table 1. Their mean age±SD was 56.89±10.23 years. There were 36 males and 28 females. Thirty-six participants (56.25%) were overweight, with a BMI of ≥ 23.0 kg/m2, whereas 28 (43.75%) were categorized as having a normal BMI. In the current study, the average IMS value of patients was 68.25±25.67 cmH2O, indicating inspiratory muscle weakness (defined as the ATS/ERS guideline with IMS values of < 80 cmH2O).
Table 1. Demographic Data in Patients Who Attended the Open Heart Surgery at Baseline (n = 64).
| Number (%) | Mean± SD | ||
| Gender | Female/ | 28 (43.75) | |
| Male | 36 (56.25) | ||
| Type of heart disease | CAD | 28 (43.75) | |
| Valvular disease | 33 (51.56) | ||
| Both CAD and valvular disease | 3 (4.69) | ||
| Age (years) | 56.89 ±10.23 |
||
| BMI (kg/m2) |
23.55 ±3.35 |
||
| 6-MWD (meters) | 328.16 ±126.64 |
||
| IMS (cmH2O) |
68.28 ±25.67 |
||
| HADS (scores) | Anxiety | 4.55 ±4.06 |
|
| Depression | 3.38 ±3.35 |
||
CAD: coronary artery disease, BMI: body mass index, 6-MWD: 6-minute walk distance, IMS: inspiratory muscle strength, HADS: Hospital Anxiety and Depression Scale.
Symptoms of Anxiety and Depression
ANOVA was conducted to compare depression and anxiety scores between patients diagnosed with coronary artery disease (CAD), valvular disease, or both. Patients diagnosed with both CAD and valvular disease had higher scores for both anxiety (9.33±4.51 vs. 3.32±3.40; F (2, 63) = 4.09; P = 0.022) and depression (9.00±5.29 vs. 2.50±2.06; F (2, 63) = 6.10, P = 0.004) than those with only CAD. However, no significant difference was observed between CAD and valvular disease in terms of anxiety or depression scores (5.15±4.20 vs. 3.32±3.40, P=0.070 and 3.61±3.62 vs. 2.50±2.06, P=0.158, respectively).
Using the HADS score of 8 as the cutoff point for both the depression and the anxiety categories, 13 (20.31%) participants were categorized as anxious. Similarly, 12 (18.75%) were categorized as depressed and 11 (17.19%) were categorized as having mixed anxiety and depressive symptoms. There was no significant group difference in age and BMI in anxiety and depression (P > 0.05). Differences in FC and IMS were observed in patients who had both anxiety and depressive symptomatology: higher the depression or anxiety scores, lower the FC and IMS (Table 2).
Table 2. Baseline Characteristics of the Study Population Assessed by HADS Depression and Anxiety Scores.
| Participants (%) | |||||
| Anxiety symptoms | Depression symptoms | ||||
| Anxiety (n = 13) |
Nonanxiety (n = 51) |
Depression (n = 12) |
Nondepression (n = 52) |
||
| Sex | Female (n = 28) | 6 (9.38%) | 22 (34.38%) | 4 (6.25%) | 24 (37.50%) |
| Male (n = 36) | 7(10.94%) | 29 (45.31%) | 8 (12.50%) | 28 (43.75%) | |
| Heart disease | CAD (n = 28) | 4 (6.25%) | 24 (37.50%) | 3 (4.69%) | 25 (39.06%) |
| Valvular disease (n = 33) | 7 (10.94%) | 26 (40.63%) | 7 (10.94%) | 26 (40.63%) | |
| CAD and valvular disease (n = 3) | 2 (3.13%) | 1 (1.56%) | 2 (3.13%) | 1 (1.56%) | |
| Mean ± SD | Mean ± SD | ||||
| Age (years) | 57.08±9.73 | 56.84±10.44 | 55.58±11.44 | 57.19±10.03 | |
| BMI (kg/m2) | 23.41±4.97 | 23.58±3.62 | 23.45 ± 5.16 | 23.57 ± 3.60 | |
| IMS (cmH2O) | 57.23 ± 23.92 | 71.10± 25.56 | 56.92±23.08 | 70.90±25.72 | |
| 6-MWD (meters) | 242.23±119.10 | 350.07±119.97 | 264.17±131.24 | 342.93±122.10 | |
HADS: Hospital Anxiety and Depression Scale, CAD: coronary artery disease, BMI: body mass index, 6-MWD: 6-minute walk distance, IMS: inspiratory muscle strength.
Relationship of IMS and FC with Psychological Conditions
The impact of heart disease in cardiorespiratory function, specifically IMS and FC, was observed in participants who received OHS (see Table 3). HADS anxiety scores were inversely correlated with both FC and IMS. In addition, depression scores were negatively related to IMS but not correlated to FC.
Table 3. Correlation Between Cardiorespiratory Fitness and HADS Scores.
| Functional Capacity | Inspiratory Muscle Strength | |||
| Pearson correlation r | P value | Pearson correlation r | P value | |
| Anxiety | –0.25 | 0.046* | –0.33 | 0.007** |
| Depression | –0.15 | 0.241 | –0.27 | 0.033* |
HADS: Hospital Anxiety and Depression Scale, *P < 0.05, **P < 0.01.
Hierarchical regression was then performed to determine how depression and anxiety were correlated with IMS and FC.
When comparing IMS and FC with the HADS (anxiety and depression) scores, patients who underwent OHS had high anxiety scores and lower IMS and FC. Hierarchical regression revealed that, after controlling for age, sex, and BMI, lower IMS remained correlated to higher anxiety and depression scores (β = –0.34, P = 0.001, and β = –0.30, P < 0.001, respectively), explaining 35.4% and 33.0% of the variance, respectively (Table 4). Furthermore, after hierarchical regression, anxiety scores and 6-MWT scores were still associated after controlling for age, sex, and BMI (β = –0.31, P = 0.001), explaining 32.6% of the variance (Table 5). Multicollinearity was not a concern (anxiety scores and IMS values, variance inflation factor (VIF) = 1.05; depression scores and IMS values, VIF = 1.05; anxiety scores and 6-MWT, VIF = 1.05) (see Tables 4 and 5)
Table 4. A Hierarchical Regression Outcomes Between Inspiratory Muscle Strength and HADS Scores.
| β | T | VIF | R 2 | F | ∆R2 | ∆F | |
| Step 1 | 0.25 | 6.47* | 0.25 | 6.47* | |||
| Age | –0.33 | –2.72* | |||||
| Sex | –0.37 | –3.00* | |||||
| Body mass index | 0.34 | 3.01* | |||||
| Step 2.1 | 0.35 | 8.06** | 0.11 | 10.04* | |||
| Anxiety scores | –0.34 | –3.17* | 1.05 | ||||
| Step 2.2 | 0.33 | 7.28** | 0.09 | 7.57* | |||
| Depression scores | –0.30 | –2.75* | 1.05 |
HADS: Hospital Anxiety and Depression Scale, VIF: variance inflation factor. *P = 0.001, **P < 0.001.
Table 5. A Hierarchical Regression Outcomes Between Functional Capacity (6-MWT) and HADS Scores.
| β | T | VIF | R 2 | F | ∆R2 | ∆F | |
| Step 1 | 0.24 | 6.15* | 0.24 | 6.15* | |||
| Age | –0.50 | –4.08** | |||||
| Sex | –0.17 | –1.36 | |||||
| Body mass index | 0.154 | 1.33 | |||||
| Step 2 | |||||||
| Anxiety scores | –0.310 | –2.83* | 1.05 | 0.33 | 7.15** | 0.09 | 7.99* |
6-MWT: 6minute walk test, HADS: Hospital Anxiety and Depression Scale, VIF: variance inflation factor. *P = 0.001, **P < 0.001.
Discussion
We evaluated how IMS and FC are related to depressive and anxiety symptoms in patients who underwent OHS. This is the first study to explore the relationships between psychological health (i.e., anxiety and depression) and cardiorespiratory fitness (i.e., IMS and FC) in patients undergoing OHS. We found that anxiety scores are negatively correlated with IMS and FC. In addition, depression scores were inversely related to IMS. Finally, these negative relationships remained significant even after adjusting for age, sex, and BMI.
In the present study, 20.3% of the patients showed symptoms of anxiety, and 18.8% showed symptoms of depression. Several studies had reported that patients show high anxiety and depression scores during the preoperative period; however, these studies did not focus on the patient’s physiological condition (e.g., pulmonary function, functional capacity).18, 26–34 Poole et al.34 found depression and anxiety symptoms in patients who had undergone OHS; in addition, patients who had higher anxiety also had more negative physical symptoms (e.g., numbness, swelling) after the operation. Similarly, Rodrigues et al.30 found that patients with greater anxiety and depression symptoms before OHS had a higher frequency of complications (e.g., hemodynamic instability, prolonged intubation) after OHS during their stay in the intensive care unit. Anxiety and depression might affect the severity of a patient’s symptoms, leading to a poorer quality of life for the patients.35, 36
One explanation might be that these patients required cardiac surgery because they either had intractable angina from CAD or extreme dyspnea from valvular disease. It is possible that the more severe their disease, the worse their preoperative symptoms were, and the less they were able to perform daily activities. Therefore, these severe symptoms would have caused the anxiety and depression. However, it should be noted that only three patients were diagnosed with both CAD and valvular disease. Thus, the interpretations regarding the severity of the symptoms of the heart disease should be taken cautiously. Navarro-Garcia et al.37 had found that 32% of patients showed preoperative anxiety, and 19% showed symptoms of depression; they also reported that a prolonged preoperative hospital stay was associated with both the conditions. In addition, Geulayov et al.31 found that symptoms of depression and anxiety one year after cardiac surgery were positively associated with mortality. Therefore, further studies should explore the relationships among preoperative psychological conditions and length of hospital stay after operations as well as longitudinal changes in anxiety and depression symptoms post operation.
The mean walking distance in the present study was 328.16±126.64 meters, which corresponds to the findings of Fiorina et al.6 who reported a mean walking distance of 304±89 meters in 1370 patients. Shuldham et al.38 evaluated the FC in older women with and without mitral valve disease. Using a set of questionnaires (i.e., the SF-36 Health Status questionnaire and the Functional Limitations Profile), they found that higher depression and anxiety levels are related to limited FC in patients with mitral valve stenosis compared to participants without mitral valve stenosis or other heart conditions.
In addition, IMS values were negatively correlated with anxiety and depression in preoperative heart surgery. Similarly, Demir et al.35 reported that IMS and FC are negatively associated with quality of life (e.g., emotional dimension) among patients with atrial fibrillation. Therefore, a poor IMS and low FC are associated with poor psychological health conditions, and also cardiorespiratory fitness is one of the predictors of mortality in patients with OHS.39, 40 In addition, individuals with negative psychological health (i.e., symptoms of anxiety and depression) are associated with the risk factor of mortality and morbidity in OHS.34, 37
Several limitations of this study have been noted. Firstly, it was a cross-sectional study that explored an event at a singular point in time rather than over the development of the condition; a prospective cohort study might determine the relationships between psychological conditions and IMS and FC in a patient who underwent OHS. In addition, the study had a relatively small sample size. Furthermore, the duration of the preoperative hospital stay, history of functional class (e.g., New York Heart Association (NYHA) Functional Classification) prior to the operation, the severity of the heart disease, and the demographic data (e.g., education, socioeconomic status, marital status, occupation, family type or domicile) were not recorded, that limit the generalizability of the results. A future study needs to explore these relationships with a large sample size and a prospective cohort design.
Conclusion
Patients undergoing OHS had a high level of depression or anxiety as well as lower FC and IMS. Depressive and anxiety symptoms were inversely correlated with IMS; additionally, anxiety symptoms were negatively correlated with FC. These relationships remained significant even after controlling for age, sex, and BMI. Therefore, it might be beneficial for health professionals to assess psychological health conditions including cardiorespiratory fitness in patients undergoing OHS.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
This article was supported by the Thammasat Medical Hospital Foundation (grant number 2558).
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