o months, one year and two years after MI by the first author as well as to complete the follow-up questionnaires. The inclusion criteria were ≤75 years of age and meeting the diagnostic criteria for MI. The exclusion criteria were communicative disabilities, cognitive disorientations and other severe diseases  .
SPSS statistical software version 21 was used. Imputation was used to replace missing variables with the average value for the item. Six variables were missing across all questionnaires. Descriptive statistics are presented as means and standard deviations (SD), and analytic statistics comprise correlation analyses. Both parametric and nonparametric (Spearman) correlations were calculated, however, no major discrepancies were found. To identify predictors of fatigue and to what extent they predict fatigue one year post-MI, a regression analysis was performed.
2.6. Ethical Considerations
The Regional Ethical Review Board in Gothenburg (720-10) approved the study. The participants were informed about the study aim and procedures both in writing and verbally and were given adequate time to consider participation during the first week in hospital. Data collection was performed by trained research nurses. Informed written consent was obtained from those who wished to participate.
3.1. Background Characteristics
One year after myocardial infarction, 125 persons of the 165 persons from baseline completed the questionnaire package. The majority were men (77%), and the mean age was 63.8 ± 7, range 44 - 75. Thirty-nine percent were employed and 83 percent were cohabiting one year post-MI. Demographics and clinical data are presented in (Table 1).
3.2. Descriptive Statistic
The mean of Post-Myocardial Infraction Fatigue (PMIF) scale was 15.99 ± 12.42 and Cardiac Self-efficacy 34.39 ± 7.53. Descriptive statistics for variables included in the univariate analysis are presented in (Table 2).
3.3. Univariate Analysis
The univariate analyses identified associations between fatigue and the independent variables stress (p = 0.790), breathlessness (p = 0.509), physical activity (p = −0.319) and self-efficacy (p = −0.611). The p-values from the univariate analysis for fatigue are listed in (Table 3).
3.4. Multiple Regression Analysis
The multivariate regression analyses aimed at identifying how much of the variance in fatigue could be explained by the regression model, which included cardiac self-efficacy (r2 = 0.373), symptoms of breathlessness (r2 = 0.259) and stress (r2 = 0.623). The regression model summary explained 72.4 percent of the variance in fatigue.
The stress variable made the greatest unique contribution (Standardize beta coefficients = 0.593), although cardiac self-efficacy (Standardize beta coefficients = −0.218) and breathlessness (Standardized beta coefficients = 0.204) also made a statistically significant contribution to explaining the variance in fatigue. The R-square and Standardized beta coefficients are presented in (Table 4).
Stress had the greatest influence; each unit increase in stress increases fatigue by 0.79 units, while each unit of cardiac self-efficacy decreases fatigue by −0.61 units. Also, breathlessness was identified as being associated with and increasing fatigue by 0.51 units.
**Correlation is significant at the 0.01 level (2-tailed); *Correlation is significant at the 0.05 level (2-tailed).
The study showed a clear association between fatigue and stress, cardiac self-efficacy, physical activity and breathlessness one year post-MI. Physical activity and cardiac self-efficacy showed a negative correlation with fatigue, which means higher levels of self-efficacy and physical activity could decrease fatigue one year post-MI.
Physical activity is important in secondary coronary heart disease (CHD) prevention  . It is also important when persons, post-MI, experience anxiety and fear another MI again  . Fatigue significantly influenced physical activity post-MI  , and 22% - 40% persons do not meet the physical activity recommendations for cardiovascular benefits  . Our results did not find physical activity to associate with fatigue one year post-MI, Physical activity is a measure on its own, but due to the combination of other factors its effect disappears in the regression analysis. However, physical activity is an “easy measure to perform”, and our results show that it is associated with decreased fatigue, breathlessness and stress as well as increased self-efficacy.
According to European guidelines, health and medical care professionals need to consider whether there is sufficient focus on patients’ psychosocial condition during the rehabilitation process  , though there are no recommendations in the guidelines for measures to prevent post-MI fatigue. It is important to implement psychological interventions in rehabilitation therapy, the aim of such interventions being to improve patients’ quality of life by managing their illness representations and strengthening their sense of personal control in adhering to intervention activities. Studies have indicated that factors related to a subject’s perception are more likely to be associated with self-efficacy than with disease knowledge  which underscores the importance of considering illness representations and cardiac self-efficacy beliefs in efforts to improve well-being among cardiovascular disease patients  . The present study indicates that cardiac self-efficacy is the only variable that predicted fatigue (in a negative correlation) and is an important factor for fatigue relief post-MI. Also in the present study, cardiac self-efficacy shows associations in the univariate analysis with decreased stress and breathlessness, both of which are significant as regards developing fatigue symptoms post-MI.
The study showed an association between stress and fatigue two months post-MI, but also a significant difference in fatigue level between persons who experienced high stress and persons with low stress  . Our regression analysis one year post-MI revealed that stress and breathlessness were associated with fatigue. The univariate analyses showed that stress and symptoms of breathlessness decreased when cardiac self-efficacy was high. Also, physical activity level decreased with higher levels of stress. Earlier studies have shown that improvements in cardiac self-efficacy one year after cardiovascular disease enable better self-management of cardiovascular lifestyle with regard to physical activity and food choice  and that self-efficacy can be changed through nursing interventions  . Early intervention, continuous monitoring and support of persons’ ability to manage their symptoms are important in promoting their confidence in long-term management of long-term management of lifestyle changes  and significant improvements in behavioral outcomes  , which could be important steps in a fatigue-relief strategy.
In cardiac rehabilitation programs today there are typically few or no recommendations at all concerning strategies for dealing with fatigue post-MI. The present findings indicated that post-MI fatigue-relief support may rely not only on identification of fatigue and other concurrent symptoms, but also on identification of cardiac self-efficacy.
In the present study, the inclusion criteria were having received a diagnosis of myocardial infarction and being younger than 75 years of age. Today the proportion of older people is increasing and thus, persons older than 75 years must be tested further. Moreover, the present study was cross-sectional, which could be seen as a limitation. Despite these limitations, the present results contribute to our understanding of self-efficacy and its association with post-MI fatigue.
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