Living with advanced heart failure (HF) and a left ventricular assist device (LVAD) is complex, stressful, and commonly burdensome.1 The number of individuals living with an LVAD is increasing, underscoring the importance of examining psychological as well as physiological and clinical outcomes such as health-related quality of life (HRQOL), exercise capacity, and healthcare utilization.2 Emotional and psychological sequelae occur because of challenges of LVAD self-care (eg, adapting to dependence on a power source and manipulation of the device), impaired sleep, pain, limitations on activities of daily living, and management of complex medication regimens.3
Stress has been defined as the experience of appraising events as threatening, due to exceeding personal resources.4 Psychological stress response may be characterized by perceived stress, depressive symptoms, and fatigue due to common causal pathways.5,6 Although little is known about the psychological stress experienced by LVAD patients, perceived stress and depression have been associated with poor health outcomes among cardiac patients.7,8 In a study by Arnold et al7 comparing cardiac patients by level of perceived stress, those with higher perceived stress had worse 2-year mortality compared with those with low perceived stress even after controlling for clinical factors such as depression. Perceived stress and the relationship between stress and outcomes have not been studied among patients living with an LVAD.
Coping, the cognitive and behavioral efforts to respond to stressful events and chronic stress, can take adaptive and maladaptive forms.4 Maladaptive coping strategies, such as denial and avoidance, are associated with worse outcomes in HF patients.9 One important adaptive coping strategy evaluated by transplant committees is social support. Typically, LVAD patients must have caregivers, identified before implantation; however, the caregiver-patient relationship, as demonstrated in qualitative studies, can be strained by changes in levels of independence, roles, and relationships.3,10,11 Higher levels of social support have been associated with better outcomes including HRQOL and HF self-care in HF studies but have not been studied among LVAD patients.12,13
To our knowledge, no studies to date have taken a comprehensive view of psychological indicators of stress and have related these indicators to social support and outcomes. Therefore, the purpose of this study was to describe and examine the relationships between indicators of psychological stress, coping, social support, and clinical outcomes including HRQOL, exercise capacity, and healthcare utilization. Our aims were to (1) describe indicators of psychological stress among LVAD patients; (2) compare indicators of stress, social support, and outcomes by level of perceived stress; (3) examine the relationships between indicators of psychological stress response and outcomes; and (4) test the role of social support as a moderator of the relationships between psychological stress response and outcomes.
A cross-sectional study design was used to describe indicators of psychological stress, coping, social support, and outcomes among patients living with an LVAD. The conceptual framework for this study is an adaptation of the Lazarus and Folkman4 Stress Model (see Figure 1). Poor outcomes result from the inability to respond to the demands of stress. In this conceptual framework, individual characteristics of LVAD patients (ie, implant strategy, emergent implantation, time since implant, stressful life events) influence indicators of psychological stress response (ie, perceived stress, depressive symptoms, fatigue, and coping). In particular, we wanted to examine the relationships between perceived stress and other indicators of psychological stress response. Psychological stress response is related to LVAD patient outcomes (ie, HRQOL, exercise capacity, and healthcare utilization). Based on the literature and clinical experience of the investigators, we hypothesized that social support would moderate the relationship between indicators of psychological stress and outcomes.12–14
Setting and Sampling
Patients living with an LVAD and served by the LVAD clinic at 2 large tertiary care centers in the mid-Atlantic region of the United States were included in the study. Convenience sampling was used to recruit patients living with an LVAD from both centers. Institutional review board approval was obtained, and informed consent was obtained in person during clinic visits. We recruited outpatients with an LVAD at greater than 2 months postimplant. The timing of recruitment was based on an understanding that early surgical recovery is very stressful with functional and HRQOL improvements that change rapidly.15 Eligibility criteria included patients with continuous-flow LVAD treated in an outpatient clinic and who were older than 21 years, had a Montreal Cognitive Assessment score of 17 or greater (no severe cognitive impairment),16 and could speak and understand English. Patients were excluded if being treated in inpatient rehabilitation or acutely hospitalized with the assumption that stress during inpatientstays would be different than outpatient stress.
A power analysis was conducted to determine the sample size needed based on covariates in the model and estimated effect sizes. Because of the limited literature demonstrating relationships between our key variables in this population, we used a small effect size (f 2 = 0.2) in our calculations.17–19 Based on the power analysis for linear regression, an estimated effect size of f 2 = 0.2, α = .05, and a power of 80%, we planned to recruit 80 patients.
Study Procedures and Measurement
Patients were recruited on scheduled clinic visit days. Surveys were administered on paper and collected at the end of the visit if completed but often were completed at a subsequent clinic visit. Demographic characteristics and instruments assessing study variables were self-administered. Widely validated instruments were selected based on their use with HF populations and relevance to the conceptual model for the variables of interest (Table 1).
In addition to survey data, the Six Minute Walk was administered according to the American Thoracic Society Protocol. This test has a reported reliability of 0.8628–30 and is used in “standard of care” in many LVAD centers. Healthcare utilization was operationalized as number of outpatient visits, number of days hospitalized, and number of outpatient procedures. Relevant data were captured from the electronic medical record for the 6 months before the date of survey completion or since the date of LVAD implant. Because of the complicated nature of these patients, only 78% were able to complete the survey; Figure 2 to demonstrate completion rates.31
Data were checked for quality and consistency. All statistical analyses were completed with STATA version 14 (StataCorp, College Station, Texas). Descriptive statistics and graphical displays were used to summarize overall data (aim 1) and by perceived stress level (aim 2). We examined the distribution of perceived stress and ranked low (0–11) and moderate and high (12–40), using approximately the upper 2 quartiles to designate moderate and high stress.7 t Tests were used to compare high- and low-stress groups. We also examined differences between clinic settings. A correlation matrix was created to examine relationships between continuous variables. Categorical variables were examined for their bivariate association using χ2 tests. A multiple linear regression model was then fit using only variables with P < .20 from the bivariate correlation analysis (aim 3). This analysis was followed by tests for multicollinearity between model variables using variance inflation factor. The assumptions of this parametric analysis were met. The final model includes only variables with P < .05.
The moderation of social support was tested using 2 additional models (aim 4). To test these relationships, we dichotomized social support at the median of 20. Interaction terms were created for (1) social support and perceived stress and then (2) social support and fatigue. Building on the multiple linear regression models, social support and interaction terms were tested.
The 62 patients who completed the survey were predominantly male (78%), black (47%), and married (66%), with a mean age of 56.7 ± 13.0 years (see Table 2). Patients were nearly evenly distributed by implant strategy (destination therapy, 49%; bridge to transplant, 51%), and the mean length of LVAD support was 25.3 ± 24.5 months (see Table 3). Forty-nine percent were Intermacs Profiles 1 and 2, implanted emergently. On the Holmes and Rahe stressful life event inventory, patients reported frequent stressful life events with an average life event score of 111.9 ± 91.8 (Table 3); 17 participants (27%) had a summed weighted score greater than 150, the high-risk threshold.
Mean perceived stress for the sample was 11.7 ± 7 (Table 4). The overall sample had a moderate stress profile: moderate perceived stress (mean, 11.7 ± 7), few depressive symptoms (mean, 3.2 ± 3.9), and moderate fatigue (mean, 14.3 ± 9.1). Both adaptive and maladaptive coping strategies were commonly used by all participants. Patients reported very high social support (mean, 19.9 ± 5.4).
Overall HRQOL was rated good (mean, 73 ± 14.6). Regarding HRQOL domains, LVAD patients reported little interference of HF symptom frequency (88 ± 14.7), but social limitation was more severely limiting (64.4 ± 20.3). Mean six minute walk test distance was 287 ± 193 m overall, demonstrating a low level of exercise capacity. Participants spent an average of 6.5 ± 4.6 days or 8% of days in the 6 months before the study in the hospital or attending outpatient visits. There were no significant differences by clinic setting for any variables studied.
Higher Perceived Stress Is Related to Depressive Symptoms, Fatigue, and Health-related Quality of Life
When comparing psychological stress response by perceived stress level using t tests, the higher-stress group had more depressive symptoms (P < .01) and more fatigue (P < .001), used more maladaptive coping (P < .003), and had less social support (P < .003). In addition, overall HRQOL was worse in the higher-stress group (P < .01); social limitation and quality of life domains were worse in the higher-stress group (P < .01), whereas the physical limitation and symptom frequency domains trended toward significance (P = .05). There were no demographic differences between groups, but the higher-stress group included 6 of 31 participants with a history of depression compared with none in the lower-stress group (P = .01). There were also no differences between groups by implant strategy, emergent implantation, time since implant, stressful life events, six minute walk test distance, or healthcare utilization.
In multivariate regression analysis, perceived stress and fatigue were independent predictors of worse HRQOL. Using the model for HRQOL, we tested social support as a moderator of the relationships between psychological stress response and HRQOL. High social support moderated the relationship between perceived stress and HRQOL when controlling for fatigue (R 2 = 0.49, P < .001) (see Table 5 and Figure 3). Variance inflation factors were less than 2 on the final models, indicating low likelihood of collinearity. Regression analysis showed no significant multivariate models for exercise capacity or healthcare utilization.
We found that most LVAD patients had a moderate level of perceived stress, mild depressive symptoms, and moderate fatigue. Those with higher perceived stress had worse depressive symptoms and fatigue and more frequently used maladaptive coping compared with those with lower stress. In multivariate analysis, high perceived stress and fatigue were associated with lower HRQOL, and this relationship was moderated by social support.
The perceived stress mean score was similar to the age-adjusted normal value of 12, which has been reported for the general population and similar to those reported in other cardiac populations.22 Higher perceived stress has been related to higher mortality in myocardial infarction patients.7 Further investigation is warranted to examine the role of perceived stress in LVAD patients, the mechanisms for these effects, and the possible impact on adverse events and survival. These findings suggest that enhanced clinical assessment of psychosocial factors is important for understanding LVAD outcomes. This is a challenge because LVAD patient visits are frequently full, including physical examinations and equipment checks. However, early referral for psychological counseling and even palliative care symptom management may reduce the burden felt by patients and providers.
We did not see a relationship between coping strategies and HRQOL; however, we did find that more frequent use of adaptive and maladaptive coping strategies was associated with worse perceived stress. This is consistent with the Lazarus and Folkman32 description of the economics of stress—as stress increases, the demand for coping increases. Thus, those with higher levels of perceived stress also reported more frequent use of both maladaptive and adaptive coping strategies because more coping is required when more stress is experienced. The Brief COPE does not evaluate effectiveness of coping strategies, only frequency of use. Understanding how individuals living with an LVAD cope with stress is important for understanding issues of adherence and self-management and for determining ways to support patients and families throughout LVAD therapy.
Overall, this sample of community-dwelling LVAD patients appears similar in HRQOL and exercise capacity compared with previous research. Kansas City Cardiomyopathy Questionnaire-12 item HRQOL average scores 12 months after implant range between 66 and 75.15,33,34 Health-related quality of life in this study was within this range, which is nearly double the reported KCCQ values before LVAD implant and exceeds the minimal clinically important difference for the Kansas City Cardiomyopathy Questionnaire (12-item).33,35,36 Exercise capacity was also within range of findings from Intermacs.2,33 Hospital length of stay has been reported in the literature, but we did not identify any other studies that considered outpatient visits in LVAD healthcare utilization. The frequency of outpatient visits may vary by region and LVAD program as a function of the distance from the patient's home to clinic, use of outreach strategies, and stability of the patient, which we did not capture in this study.
Social support was reported at a comparable level with previously reported cardiac populations who were partnered.26 This was expected because LVAD patients are required to have caregivers available for initial implant care to support clinic attendance and to manage LVAD care. Multivariate modeling and moderation analysis revealed that, when comparing those with the same level of perceived stress, those with high social support had a higher HRQOL than those with low social support after controlling for fatigue. This moderation analysis provides evidence for the importance placed on social support when considering advanced HF patients for LVAD implantation. However, it was not possible to determine in this study whether the caregiver, healthcare team, or other sources are responsible for the perceived level of social support. Support is provided by LVAD programs through 24/7 access to providers. Yet, patients and caregivers have reported variable levels of satisfaction with the support provided by LVAD programs, suggesting a need to explore additional ways to increase the type(s) and level of support provided.37 Specifically, it is not clear how programs are assessing patient stress or helping patients manage stress. Resources vary between institutions, although some offer support groups and other activities for LVAD patients and caregivers. Support strategies that are tailored to the individual patients' needs may be most effective.
Strengths and Limitations
To our knowledge, this is the first study to examine indicators of psychological stress, coping, and social support in a moderate-size continuous-flow LVAD patient sample, providing important intervention targets for future work. In addition, we evaluated important psychosocial factors and their impact on outcomes in a diverse, multicenter population. Finally, we have introduced evidence that supports LVAD program policies related to social support. To expand these findings, the next step will be to conduct a longitudinal study to examine how psychosocial factors change over time and to establish approaches to tailoring future interventions.
This study has several limitations. As a cross-sectional study, no causal relationships can be drawn from this analysis. Furthermore, we had several challenges in completion rates. Long patient clinic visits and frequent complications often resulted in patients who consented being unable to complete the survey. This may have resulted in a self-selection bias and in the underestimation of variables related to stress and overestimation of HRQOL compared with the total LVAD population. This concern is consistent with other survey data collected from the LVAD population.38 In addition, our statistical approach may not have captured all possible confounders. In addition, the patients in our sample had an average of almost 2 years of LVAD support, which also may have resulted in lower reported stress and higher HRQOL than the overall LVAD population. Another limitation is that we used a HF-specific measure for HRQOL. This measure is not specific to having a LVAD; however, as of yet, there are no VAD-specific measures of HRQOL. Finally, our conceptual framework incorporated coping as a component of psychological stress response, due to the nature of the Brief COPE, which measures frequency of coping strategy use. Others have described coping as a mediator of stress and outcomes, and another instrument that incorporates a measure of coping effectiveness may provide a clearer understanding of coping as a mediator of stress in this population.
Increased perceived stress was related to worse depressive symptoms, fatigue, maladaptive coping, and worse HRQOL. Furthermore, the influence of high levels of social support on HRQOL, despite fatigue, confirms the need to continually assess the social support available to LVAD patients. Thorough, ongoing assessment by healthcare providers and social workers may uncover stressful conditions requiring increased monitoring and possible intervention. Future studies to test the effects of interventions designed to enhance stress management via adaptive coping may improve HRQOL and other LVAD outcomes.
What's New and Important?
- Increased perceived stress was reported by nearly half of LVAD patients and was related to worse depression, fatigue, maladaptive coping, and worse HRQOL; perceived stress and fatigue were related to quality of life in multivariate analysis.
- The moderating influence of high levels of social support on the relationship between perceived stress and health-related quality of life, despite fatigue, confirms the need to continually assess the social support available to LVAD patients, a common concern among nurses and providers caring for these patients.
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Keywords:Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved
heart assist device; quality of life; stress, psychological