Research in Cardiovascular Medicine

ORIGINAL ARTICLE
Year
: 2017  |  Volume : 6  |  Issue : 4  |  Page : 38--44

Changes in exercise capacity and psychosocial factors in hospitalized cardiac surgery patients


Masato Ogawa1, Kazuhiro P Izawa2, Aki Kitamura3, Seimi Satomi-Kobayashi4, Yasunori Tsuboi5, Kodai Komaki6, Yoshitada Sakai7, Hiroshi Tanaka3, Yutaka Okita3,  
1 Division of Rehabilitation Medicine, Kobe University Hospital; Department of International Health, Kobe University Graduate School of Health Sciences, Kobe, Japan
2 Department of International Health, Kobe University Graduate School of Health Sciences, Kobe, Japan
3 Department of Surgery, Division of Cardiovascular Surgery, Kobe University Graduate School of Medicine, Kobe, Japan
4 Department of Internal Medicine, Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
5 Division of Rehabilitation Medicine, Kobe University Hospital; Department of Internal Medicine, Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
6 Division of Rehabilitation Medicine, Kobe University Hospital, Kobe, Japan
7 Division of Rehabilitation Medicine, Kobe University Graduate School of Medicine, Kobe, Japan

Correspondence Address:
Dr. Kazuhiro P Izawa
Department of International Health, Kobe University Graduate School of Health Sciences, 7-10-2, Tomogaoka, Suma-Ku, Kobe, Hyogo 654-0142,
Japan

Abstract

Background: After cardiac valve surgery, postoperative exercise capacity and psychosocial parameters of patients change significantly and both affect prognosis. This study aimed to analyze and clarify the relationship between changes in perioperative exercise capacity and psychosocial factors in the early phase after valvular surgery. Materials and Methods: We enrolled 48 consecutive patients who underwent valvular surgery and studied their exercise capacity, health-related quality of life (HRQOL), anxiety disorders, depression symptoms, blood samples, and echocardiograms preoperatively and 14-day postoperatively. Results: At the preoperative evaluation, the peak maximal oxygen consumption was 17.7 ± 5.9 ml/kg/min and decreased by 14.3 ± 4.4 ml/kg/min after the surgery (P < 0.0001). With regard to the HRQOL, the physical component summary (PCS) score and the role component summary scores decreased significantly after surgery (P < 0.05 for each). However, the mental component summary score increased significantly after surgery (51.9 ± 11.6 to 55.2 ± 10.4; P = 0.04). The ratios of the above the cut-off value for postoperative anxiety and depression scores were 29.1%, and 43.7%, respectively. Postoperative changes in exercise capacity were associated with variations in right ventricular function, chronotropic response during exercise, and the PCS score (P < 0.05 for each). Conclusions: Exercise capacity was reduced approximately 20% during the postoperative period in patients who underwent valvular surgery, and changes in exercise capacity were related to changes in psychosocial factors, not only cardiac functions. Therefore, it is important to evaluate not only perioperative exercise capacity but also psychosocial indicators during postoperative cardiac rehabilitation programs.



How to cite this article:
Ogawa M, Izawa KP, Kitamura A, Satomi-Kobayashi S, Tsuboi Y, Komaki K, Sakai Y, Tanaka H, Okita Y. Changes in exercise capacity and psychosocial factors in hospitalized cardiac surgery patients.Res Cardiovasc Med 2017;6:38-44


How to cite this URL:
Ogawa M, Izawa KP, Kitamura A, Satomi-Kobayashi S, Tsuboi Y, Komaki K, Sakai Y, Tanaka H, Okita Y. Changes in exercise capacity and psychosocial factors in hospitalized cardiac surgery patients. Res Cardiovasc Med [serial online] 2017 [cited 2022 Aug 9 ];6:38-44
Available from: https://www.rcvmonline.com/text.asp?2017/6/4/38/223778


Full Text



 Introduction



The efficacy of multidisciplinary cardiac rehabilitation (CR) programs has already been proven.[1],[2] CR programs not only include exercise training but also customized for a specific individual, aiming to improve the quality of life by reducing risk factors and providing psychological support, nutritional care, and guidance on how to resume daily life activities, such as returning to work.[1],[2] The benefits of CR include a reduction in mortality rates, symptom relief, improved exercise capacity, risk factor modification, and improved overall psychosocial well-being.[3]

However, cardiac valve replacement results in a decline in postoperative exercise capacity despite the postoperative improvements in hemodynamic parameters.[4],[5] Le Tourneau et al.[6] reported no improvement in exercise capacity even at 1 year after the surgery. Importantly, postoperative physical activity levels are positively associated with higher survival rates.[7] Therefore, it is very important to begin multidisciplinary CR as early as possible after surgery. It has been reported that early CR succeeded in improving exercise performance in postcardiac surgery patients,[8] and for every 1-day delay in starting CR, patients were 1% less likely to improve across all fitness-related measures.[9]

Along with changes in exercise capacity, psychosocial parameters also reported to change significantly before and after cardiac surgery.[10],[11] Importantly, there is an association between a low health-related quality of life (HRQOL) score and rehospitalization and mortality in heart failure patients.[12] Khoueiry et al. reported that the HRQOL score returned to the baseline value at 9 months after surgery or improved as compared to the preoperative value.[11] However, these previous studies focused on long-term changes, and therefore, there is a specific need to investigate changes in exercise capacity and psychosocial indicators in the early phase after cardiac surgery to implement early multidisciplinary CR, including exercise training, life coaching, and counseling.

Based on the previous studies mentioned above, we hypothesized that both exercise capacity and psychosocial factors are impaired during the early postoperative period. This study aimed to reveal the changes in exercise capacity and psychosocial factors in the early phase after valvular surgery and to clarify the relationship between the changes in perioperative exercise capacity and psychosocial factors.

 Materials and Methods



Study population

Between December 2013 and January 2016, 223 consecutive patients who underwent valvular surgery were included in this study. Patients were excluded from the study if they required emergency surgery (n = 19), had severe clinical instability that would prevent them from performing the exercise test (n = 130), and refused to participate (n = 4). All patients received postoperative rehabilitation from the day after the surgery, according to the Japanese Circulation Society guidelines for rehabilitation in patients with cardiovascular disease.[3] Fourteen days after the surgery, we obtained repeat measurements for the cardiopulmonary exercise test and resting echocardiography. Twenty-two patients were not included in the final analysis because 10 of them developed surgical complications and 12 could not reach the maximal exercise level due to orthopedic reasons. The remaining patients had completed the preoperative and postoperative exercise tests and were included in the final analysis. This study complied with the principles of the Declaration of Helsinki regarding investigations in humans and was approved by the local institutional board at Kobe University. Written informed consent was obtained from each patient.

Data collection

Patient characteristics were evaluated from electronic medical records. The baseline characteristics evaluated included age, sex, body mass index, comorbidities, brain natriuretic peptide levels, New York Heart Association (NYHA) functional classification, and European System for Cardiac Operative Risk Evaluation (EuroSCORE) II.[13] Laboratory data collection and two-dimensional and Doppler echocardiography were performed within 1 week before the surgery and 14 days after the surgery. The laboratory data collected included estimated glomerular filtration rate (eGFR), serum hemoglobin, C-reactive protein (CRP), and serum albumin levels. Echocardiography was performed using a commercially available echocardiography system with a 3.5-MHz transducer (Vivid 7; GE Vingmed Ultrasound, Horten, Norway). The left ventricular ejection fraction (LVEF) was determined using the modified biplane Simpson's method.[14] Tricuspid annular plane systolic excursion (TAPSE) was determined from an apical four-chamber view with an M-mode cursor through the lateral tricuspid annulus to determine conventional right ventricular systolic function. Knee extensor muscle strength (KEMS) was measured using a handheld dynamometer (MicroFET2; Hoggan Health Industries, Salt Lake City, UT, USA). Measurements were obtained for both legs at maximum isometric contraction,[15] and we calculated the average of the highest values (N) of the sum of the KEMS of the right and left knees as N/2/body weight (BW) = % BW.[16]

Cardiopulmonary exercise test

Patients performed the exercise test on a cycle ergometer (Strength Ergo 8; Mitsubishi Electric Engineering, Tokyo, Japan), in accordance with the protocol described in the American Thoracic Society guideline.[17] Preoperative assessments were performed within 10 days of the surgery, and postoperative assessments were performed 14 days after the surgery. The exercise test was a continuous protocol test with a progressive increase of 10 W/min. Exercise was finished at the point when the patient could not to continue because of dyspnea or leg fatigue. Blood pressure (BP) was measured with an electronic sphygmomanometer every minute during the exercise test. Heart rate (HR) was registered using a 12-lead electrocardiogram continuously, and HR recovery at 1 min was registered. The predicted value of maximal oxygen consumption (VO2) was estimated using the Wasserman equation, normalizing VO2 for weight, age, height, and gender.[18] Ventilatory efficiency during exercise was expressed as the slope of minute ventilation (VE) versus carbon dioxide production (VCO2) over the linear component of the plot of VE versus VCO2(VE/VCO2 slope). Chronotropic response was measured as HR reserve (HR reserve = [peak HR – rest HR]/[age-predicted maximal HR – rest HR]).[19] Age-predicted maximal HR was calculated using the formula: (220 – age).[19] The rate of increase in VO2 relative to workload (WR) (ΔVO2/ΔWR) has been interpreted as an indicator of cardiovascular efficiency and aerobically generated adenosine triphosphate. The ΔVO2/ΔWR slope was automatically calculated using a method as described elsewhere.[20]

Psychosocial assessment

Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS).[21] The HADS is a self-report questionnaire, which has been validated as a screening instrument to assess the presence or severity of anxiety disorders and depression symptoms.[22] The HADS questionnaire consists of 14 items, 7 for each of the 2 subscales – anxiety and depression. Each subscale is rated from 0 to 3, resulting in a maximum sum score of 21 for each subscale. In general, a cut-off value of >8 indicates anxiety or depression.[22] HRQOL was investigated with the Japanese version of the Medical Outcomes Study 36-Item Short-Form General Health Survey Version 2.0 (SF-36; v2).[23] The validity and reliability of this questionnaire has already been proved in the previous study.[23] SF-36 was measured on a scale from 0 to 100, with higher scores representing a higher HRQOL. To evaluate in detail, the SF-36 subscales were combined into the 3-component model: the role component summary (RCS) score, the physical component summary (PCS) score, and the mental component summary (MCS) score.[24] Each component score is converted to an average of 50 and a standard deviation of 10, according to the population standard in Japan.[25] A score of <50 indicates that the specific health concept is below the normal value for the Japanese population.

Statistical analysis

Results are expressed as the mean ± standard deviation for continuous data and as a ratio for categorical data. We conducted statistical analyses after confirming that the data were normally distributed using the Shapiro–Wilk test. The paired t-test was used to compare values before and after surgery. To compare the preoperative and postoperative values, percentage changes were obtained for continuous variables, and univariate linear regression analysis was applied to calculate the correlations between various parameters by determining the Pearson correlation coefficients. The overall statistical significance level was set at 0.05. All statistical analyses were performed using JMP11.0 J software (SAS Institute Japan, Tokyo, Japan).

 Results



Baseline characteristics

Of the 223 patients, 175 were excluded from the study based on the exclusion criteria. Thus, 48 patients with the mean age of 65.1 ± 13.3 years were included in this study. The baseline demographic characteristics are shown in [Table 1]. Two patients were NYHA class I, 32 were NYHA class II, and 14 were NYHA class III.{Table 1}

Preoperative and postoperative characteristics

The preoperative and postoperative echocardiography findings, laboratory data, and medication data are shown in [Table 2]. Preoperative LVEF was 61.3% ±7.9% and decreased by 54.8% ±10.8% (P = 0.0024). TAPSE decreased significantly postoperatively (P< 0.0001). The hemoglobin and serum albumin levels decreased significantly postoperatively; however, CRP levels and eGFR increased significantly (P< 0.05 for each). At the baseline, 39.5% of the patients were treated with β-blockers, and the ratio remained unchanged after the surgery (P = 0.37). In contrast, the ratio of patients treated with angiotensin-converting enzyme (ACE) inhibitors or angiotensin-II receptor blockers (ARBs) decreased significantly postoperatively (P = 0.0020). With regard to muscle strength, KEMS decreased significantly from 4.4 ± 1.0 to 4.3 ± 0.9 after the surgery (P = 0.04).{Table 2}

Cardiopulmonary exercise test

At the preoperative evaluation, the peak VO2 was 17.7 ± 5.9 ml/kg/min, which corresponded to the standard value for 69.5% of the population [Table 3]. At the postoperative evaluation, the peak VO2 decreased by 14.3 ± 4.4 ml/kg/min, which corresponded to the standard value for 57.2% of the population (P< 0.0001). Similarly, the peak WR, ΔVO2/ΔWR slope, HR reserve, HR recovery at 1 min, and peak systolic BP decreased significantly after surgery (P< 0.05 for each). The VE/VCO2 slope significantly increased from 27.5 ± 6.5 to 32.9 ± 9.4 after surgery. Whereas, there was no statistically significant difference in the respiratory exchange ratio (RER) before and after surgery (1.3 ± 0.2 to 1.3 ± 0.2; P = 0.20).{Table 3}

Psychosocial factors

During the follow-up, the PCS and RCS scores decreased significantly (P< 0.05 for each) [Table 4]. The mean scores for both PCS and RCS were lower than the national standard values even before surgery (45.0 ± 9.1 and 40.6 ± 16.6, respectively, for each). However, the postoperative MCS score increased significantly as compared to the value before surgery (51.9 ± 11.6 to 55.2 ± 10.4; P = 0.04). The preoperative anxiety score was 6.1 ± 3.6 and decreased significantly by 5.2 ± 3.5 after the surgery (P = 0.03). The depression score was 5.7 ± 2.9 at the baseline and increased by 6.9 ± 3.5 after the surgery (P = 0.0037). The ratios of the above the cut-off value for the postoperative anxiety and depression scores were 29.1% and 43.7%, respectively.{Table 4}

Relationship between changes in physiological outcomes and psychosocial outcomes

The matrix of correlation coefficients between changes in physiological outcomes and psychosocial outcomes are presented in [Table 5]. The changes in peak VO2 were associated with variations in TAPSE, HR reserve, KEMS, and PCS (P< 0.05 for each), and the changes in the PCS score were correlated with the changes in TAPSE and KEMS in addition to the peak VO2. There was a statistically significant association between changes in the MCS score and changes in the anxiety score (r = 0.47; P = 0.0054). The change in the RCS score was correlated with age and changes in the depression score (P< 0.05 for each). There are not statistically significant differences in the change of exercise capacity and QOL by surgical procedures.{Table 5}

 Discussion



To the best of our knowledge, this study is the first to examine postoperative changes in exercise capacity and HRQOL assessment over a short period. Our results suggest that exercise capacity reduced by approximately 20% after valvular surgery. With regard to HRQOL, the PCS and RCS scores reduced significantly, whereas the MCS score improved significantly after the surgery.

The peak VO2 was decreased from 17.7 ± 5.9 to 14.3 ± 4.4 ml/kg/min. It has been reported that exercise capacity <15.0 ml/kg/min indicates a poor prognosis and higher mortality.[26] The average of postoperative peak VO2 was falling below this cut-off value, and it is likely that there is a severe limitation in exercise capacity after surgery. We postulate that there are at least three factors related to the decline in postoperative exercise capacity. First, muscle weakness due to postoperative deconditioning can be thought to be related to the decline in postoperative exercise capacity. We found that KEMS and peak WR during the exercise test were significantly reduced after surgery. The previous study demonstrated that even in the absence of perioperative complications, major surgery is associated with a 20% to 40% reduction in physiological capacity after surgery.[27] This reduction may be due to postoperative inflammation and catabolic phase. Kamiya et al. also reported that muscle strength was a predictor of exercise capacity.[28] This study support these reported findings; furthermore, we revealed that the perioperative changes in KEMS were correlated with changes in the peak VO2.

Second, the decrease of postoperative exercise capacity is related to the decrease in cardiac function which appears after valvular surgery using cardiopulmonary bypass (CPB). It is known that the length of CPB and the duration of aortic cross-clamping during cardiac surgery affected the decline of cardiac function.[29] Our findings of deteriorated right and left ventricular function after surgery as indicated by the changes in the LVEF and TAPSE are thought to trigger such a mechanism. On the other hand, the VE/VCO2 slope during the exercise test increased significantly after surgery from 27.5 ± 6.5 to 32.9 ± 9.4. VE/VCO2 slope is single predictors of mortality in heart failure, and VE/VCO2 slope of 34 was a threshold for risk stratification.[30],[31] In this study, the threshold did not exceed even after the surgery; however, it is highly decreased than the healthy controls. Furthermore, we observed that the ΔVO2/ΔWR was significantly deteriorated during the postoperative exercise test. A reduced contractile reserve and transient ischemia after surgery, limits the stroke volume increase as shown by decreased peak systolic blood pressure, and a complete β-receptor blockade reduces the HR reserve, both leading to a diminished cardiac output (CO) response.[32] Our results showed that the deteriorated resting right and left ventricular function after surgery and the insufficient increase in CO during the exercise test both had a strong role to play in exercise intolerance after surgery.

Third, the reduction in cardiovascular autonomic nervous system function could be associated with the decline in exercise capacity. We found that the HR reserve and HR recovery deteriorated significantly after surgery. The attenuated HR recovery after exercise is a marker of reduced parasympathetic activity,[33] and chronotropic incompetence implies a decreased sensitivity of the sinus node to sympathetic stimulation. Nishime et al. demonstrated that the patients with HR recovery under 12 beats was independent predictors of mortality as the same as exercise capacity.[34] In this study, the average of HR recovery was 10.3 ± 10.3 beats, as represented in reduced parasympathetic activity. The studies investigating perioperative exercise capacity after valvular surgery are sparse; nevertheless, it has already been reported that nervous-humoral factors such as the renin-angiotensin-aldosterone (RAS) system and sympathetic activity are enhanced after cardiac surgery.[35] Furthermore, it has also been reported that impaired autonomic nervous function is a predictor of exercise intolerance and mortality.[34],[36] As is evident from the findings mentioned above, postoperative exercise intolerance is probably associated with overactivity of the sympathetic nervous system or attenuation of the parasympathetic nervous system or both. There was no statistical difference in the ratio of patients treated with β-blockers before and after surgery, but there were significant differences in the ratio of patients treated with RAS system inhibitors such as ACE inhibitors or ARBs. It is possible that the reduction in the RAS system inhibitor contributed to the postoperative increase in sympathetic nervous system activity. Further studies will be needed to confirm and generalize these findings.

With regard to psychosocial factors, we found that the PCS and RCS scores reduced after surgery. In addition, perioperative changes in the PCS score were correlated with the changes in peak VO2 and KEMS. Perrotti et al. demonstrated that the PCS score did not return to the baseline value at 1 month after cardiac surgery;[37] however, they did not investigate physical function along with HRQOL. In this study, the decline in the PCS score was related to postoperative muscle weakness and a decrease in exercise capacity. In addition, it has been reported that postoperative complaints such as wound pain and sleep disorders affect the PCS score.[38] We did not investigate such complaints, but it could be a possible explanation for the decrease in the PCS score observed in our study.

Ours is the first study to demonstrate changes in the RCS score after surgery. It was reported that the RCS represents not only roles in daily lives but also patients' social functioning.[24] Thus, it is inevitable that age is significantly correlated with changes in the RCS score because RCS decreased gradually with age in the general population. Before undergoing surgery, the study participants were living independently in a community setting and their mental state or social functioning was not severely impaired. Even those patients, the RCS score further decreased after cardiac surgery. In a previous study, 13.8% of patients could not return to work even after 12 months after surgery, and negative perception of health was an independent risk factor that inhibited early return to work after surgery.[39] These results from a previous study were compatible with our result that the RCS score was correlated with changes in depression symptoms. Another randomized study showed that the performance of the exercise test after acute coronary syndrome shortened the time to return to work and resulted in community and patient cost savings.[40] Thus, our results emphasize the importance of counseling patients, planning for rehabilitation, evaluating exercise capacity, and providing support to return to work as early as possible after cardiac surgery.

Surprisingly, the MCS and anxiety scored improved significantly after valvular surgery. This was in contrast to the findings of changes in PCS, RCS, and exercise capacity. Our study showed that 30% of the patients had anxiety scores above the cut-off value before surgery, and the ratio remain unchanged after surgery. The previous research showed that strong anxiety levels and a low-MCS score before cardiac surgery were both independent risk factors for postoperative complications and mortality.[41],[42],[43] A possible explanation for the postoperative improvement in the MCS and anxiety scores observed in this study is that anxiety levels reduced because the patients experienced an alleviation of preoperative problems and a feeling of optimism about their health condition. It has been reported that a lack of information or communication from medical staff during the postoperative recovery period triggers anxiety in patients and caregivers.[44] Thus, it is crucial to provide appropriate information, counseling, and psychological interventions for both patients and caregivers in the early phase after surgery.

Depression symptoms increased significantly after the surgery. This result is in accordance with a previous study that reported the ratio of patients with depressive symptoms increased significantly after surgery as compared to that before surgery.[45] Low levels of physical activity before surgery were correlated with not only preoperative depressive symptoms but also postoperative depression symptoms.[46],[47] Our results emphasize the importance of initiating exercise training in the early phase after surgery, evaluating the intensity of physical activity, and providing adequate counseling.

This study had several limitations. First, we used a pre-post design. We could not establish causation because we did not include a control group. Second, we did not analyze sex- or age-related differences or study the impact of social background because the sample size was small. Furthermore, we did not determine whether these short-term changes would have an impact in the long-term period. Thus, a long-term longitudinal study with a large sample size is needed to confirm the changes in physiological and psychosocial factors in the early phase after cardiac valve surgery.

 Conclusion



Our study revealed that exercise capacity reduced by approximately 20% during the postoperative period in patients who underwent cardiac valve surgery and changes in exercise capacity were related to postoperative muscle weakness, autonomic nervous function impairments, right ventricular function, and the PCS score. Among the psychosocial factors, the MCS and anxiety scores improved significantly, whereas the PCS and RCS scores reduced in the postoperative period. Depression symptoms increased significantly after surgery. Therefore, it is important to evaluate not only the perioperative exercise capacity but also psychosocial indicators during multidisciplinary CR after surgery.

Acknowledgment

We thank the staff members of Kobe University Hospital with whom we collaborated with while performing this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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