Coronary heart disease-related fatigue:risk factors,assessment and treatments

Yao-Yao Hu,Lu Yu,Jing Zhang,Fang-Ying Mao,Qing Wu,Lin Liu

1School of Nursing,Soochow University,Jiangsu Province,Suzhou,China.2Department of Cardiology,Soochow University,Jiangsu Province,Suzhou,China.

Abstract Coronary atherosclerotic heart disease is a disease of myocardial ischemia and hypoxia,which often presents as chest pain,dyspnea,cold sweat and fatigue.Fatigue is the subjective experience of patients,which is easy to be ignored,and will lead to the decline of patients’quality of life and physical activity level,etc.,with a high incidence and great harm.The purpose of this paper was to review the concept,risk factors,assessment tools and intervention measures of coronary atherosclerotic heart disease fatigue in order to provide a reference for identifying and improving the fatigue of coronary atherosclerotic heart disease.

Keywords:coronary atherosclerotic heart disease;fatigue;risk factors;tools;CHD

Introduction

Coronary atherosclerotic heart disease is an acute myocardial ischemia and hypoxia heart disease caused by coronary artery stenosis or occlusion,which is referred to as coronary heart disease(CHD)[1].It is one of the non-communicable diseases with the highest mortality in the world[2].According to the summary of the China Cardiovascular Disease Report 2018,it is estimated that the number of people with cardiovascular disease in China is 290 million,including 11 million with CHD[3].Fatigue is a common and easily overlooked symptom of patients with CHD,with a high incidence of about 40%～76%,which can be seen in the occurrence and development of the disease and can exist for a long time[4-6].Although studies on CHD fatigue have increased in recent years,the pathophysiological mechanism of fatigue of CHD has not been clearly defined.Currently,possible biological mechanisms related to fatigue include inflammation,hypothalamicpituitary-adrenal axis dysfunction,and automatic nervous system activation.Due to the complexity and multidimensional nature of fatigue,its definition has not been unified.In the study of chronic diseases,fatigue is defined as a kind of continuous physical and mental discomfort,which is mainly manifested in subjective tiredness,inability to concentrate,weakness of muscles in the body,decline of work efficiency in behavior,which cannot be alleviated through rest and sleep[7-8].CHD fatigue refers to a kind of continuous physical and mental discomfort caused by many factors(such as disease itself,social psychology and other factors,etc.),which is often accompanied by physical strength decline,mental burnout,memory decline and activity decline,etc.[9].Studies have reported that fatigue can reduce the quality of life of patients with CHD[10-11].The study by Ji et al.reported that fatigue reduces self-management in patients with CHD,which in turn affects the effectiveness of secondary prevention of CHD[12].In addition,a study by Ekmann et al.noted that fatigue can also increase readmission rates in patients with CHD[13].More seriously,fatigue can also induce sudden death in patients with CHD[14].Therefore,timely recognition of fatigue and intervention is of great importance to patients with CHD.At present,domestic and international studies on fatigue in CHD have made some progress.Therefore,this review aimed to summarize the concepts,risk factors and assessment tools of fatigue in patients with coronary heart disease,to provide input for clinical care practice.

Risk Factors of CHD Fatigue

Demographic Factors

Age.The exact relationship between CHD fatigue and age is not clear from the studies.A survey by Crane of 98 elderly patients with myocardial infarction showed that 76% of patients had fatigue[5].A study showed that patients with CHD aged 60 years were prone to fatigue[15].Possible causes of fatigue in elderly patients are the decline in their own body functions and the damage to their heart muscle,which makes them prone to fatigue.However,a study of 282 patients with acute coronary syndrome noted that it was younger patients who reported being most affected by fatigue[16].Young and middle-aged people are the main source of income for their families,under pressure from all sides,may be more prone to fatigue.In addition,other studies indicate that fatigue is still at a high level in young and middle-aged CHD patients[17-18].However,one study noted that the age of patients with CHD was statistically different only in terms of physical fatigue[19].Although the above research results are inconsistent,it is undeniable that fatigue is widespread in patients with CHD of all ages.

Sex.The relationship between gender and CHD fatigue is also unclear.Women with coronary artery disease are more likely to experience fatigue than men,and the degree of fatigue is greater[6,15,20].Fatigue is also a common precursor symptom and acute-phase symptom for female patients with CHD[21].It is possible that female patients are more emotional,delicate and sensitive,and are more prone to adverse psychological reactions,so the reactions to fatigue were more sensitive[22].However,Fennessy et al.showed that the fatigue level of male patients with myocardial infarction did not decrease after discharge,while the fatigue level of females decreased,suggesting that female patients’ fatigue is prone to fluctuate[23].However,Crane et al.pointed out that there is no difference in the incidence of fatigue in terms of gender[5].Inconsistent findings may be due to different sample sizes,different research tools and cultural differences.Therefore,in future studies,we look forward to multicenter,large sample studies to confirm the relationship between gender and CHD fatigue.

Individual Characteristics

Negative Emotions.The common negative emotions of patients with coronary heart disease mainly include anxiety and depression.A survey found that patients with acute myocardial infarction who had higher levels of depression were prone to higher levels of fatigue and that depression was an independent factor affecting fatigue levels in patients with acute myocardial infarction(OR= 1.217;95%CI,1.088 - 6.8780)[6].Crane et al.also found that depression was a predictive risk factor for fatigue of elderly patients with myocardial infarction[5].However,Alsén et al.investigated 204 patients with myocardial infarction and found that 33% of them only had fatigue but no depression.Over time,the degree of depression also decreased in patients with decreased fatigue[20].The study also pointed out that fatigue is an important symptom of CHD with or without depression.Although the relationship between fatigue and negative emotions is controversial,one study has proved that psychological intervention can reduce patients’ anxiety,depression and fatigue[24].A study by Tang et al.also showed that higher levels of hope and positive emotions were negatively associated with fatigue[25].Therefore,clinical medical staff should pay attention to psychological nursing for patients with CHD to reduce the occurrence of fatigue or improve the level of fatigue.

Sleep Disorders.Sleep disorders are also common in patients with CHD[26].Poor sleep quality,the body cannot get enough rest,and fatigue may occur[27].Previous studies have noted that sleep disturbances are associated with CHD fatigue[28-29].Gao’s study also noted that Pittsburgh Sleep Quality Index scores were significantly higher in patients with CHD in the fatigue group than in the non-fatigue group[15].However,Fredriksson-Larsson et al.found that fatigue of patients with myocardial infarction was related to sleep quality in university analysis,but sleep was not included in statistical analysis in multivariate analysis[30].Despite the inconsistent findings,sleep disorders are closely related to the onset,development and prognosis of CHD,and measures such as music therapy,aromatherapy and Chinese medicine can be used to improve the phenomenon of sleep disorders in patients.More high-quality studies are needed in the future to confirm the relationship between sleep and CHD fatigue.

Stress and Coping Style.Stress is the psychological distress caused by various factors in life.One study reported that fatigue was associated with decreased cardiovascular function during anticipated mental stress challenges[31].Alsén et al,through a survey of 74 patients with myocardial infarction,found that the more stressful the patient,the more fatigued they felt[32].Similar to the findings of Fredriksson-Larsson et al.[30].This study also showed that active coping strategies were negatively associated with fatigue[30].It may be that stress affects the hypothalamuspituitary-adrenal axis and autonomic nerve function,which leads to the relative disorder of neuroendocrine reaction and immune response,resulting in fatigue[33].Coping strategies are the efforts made by individuals in the face of perceived threats.Positive coping makes health develop positively.Coping strategies are influenced by many factors such as educational level and disease cognition.Therefore,clinical medical staff can explain diseases,fatigue and other related knowledgeto enrich patients’ coping resources and improve their coping ability.In addition,it is necessary to evaluate the patient’s stress level in time and relieve the stress through effective intervention.

Disease-related Factors

Inflammatory Factors.At present,inflammatory factors have become the research focus of the fatigue mechanism.Common inflammatory factors include C-reactive protein(CRP),interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α).One study noted that patients with CHD had high hs-CRP,IL-6 and TNF-levels compared to the healthy population[34].A follow-up study of 4847 people also showed that CRP and IL-6 were related to fatigue[35].Alsén et al.also showed that CPR was associated with the somatic fatigue dimension and the reduced motivation dimension of fatigue in patients with CHD[19].Analysis of the possible causes is that inflammatory factors act centrally and thus induce fatigue[36].Fortunately,related studies have reported that anti-inflammatory treatment or anti-inflammatory diets can improve fatigue in patients,which provides new ideas for future research[37-38].

Drugs.The relationship between drugs and fatigue cannot be ignored.Kalra et al.found that β-blockers can cause fatigue in patients with CHD,which is consistent with the research results of Alsén[19,39].Another study found that statins also caused fatigue in patients with CHD,and those female patients were most severely affected[40].In addition,a related study has pointed out that the cumulative effect of drugs can cause patients to experience greater fatigue[41].It is necessary to focus on the intervention of patients who use β-blockers and statins.

Comorbidities.CHD is a chronic disease,often complicated with various diseases,such as diabetes,hypertension and hyperlipidemia.A study by Horne et al.found that the number of comorbidities was associated with CHD fatigue and noted that patients with coronary artery disease with more than five comorbidities needed to be screened for fatigue[42].A study by Gao et al.showed that patients with CHD in the fatigue group had a statistically significant difference in the history of hypertension,history of diabetes,and history of myocardial infarction compared to patients with CHD in the non-fatigue group[15].Patients with a high number of comorbidities may be more prone to fatigue as they are less able to cope with their physical functions and have to manage themselves to control clinical symptoms,resulting in a combination of physical and mental stress.Therefore,in clinical nursing work,it is necessary to pay more attention to patients with more complications and give corresponding care in time to help them manage their blood pressure,blood sugar,blood lipid,etc.,to reduce the occurrence of fatigue or improve fatigue.

Other Diseases Related Factors.The relationship between body mass index(BMI)and CHD fatigue is also unclear.Related research found that,the overall fatigue degree of CHD patients with MBI <18.5 kg/m2was the highest,followed by those with BMI >27kg/m2[14].However,Crane et al.showed that there was no relationship between BMI and fatigue[5].Although the results are inconsistent,one study suggested that keeping BMI within the normal range is beneficial to the prognosis of patients with coronary heart disease[43].Therefore,clinical care workers need to focus on underweight and overweight patients to help them maintain a normal BMI.Additionally,it has also been found that mean arterial pressure is associated with fatigue and that lower mean arterial pressure is predictive of fatigue[5,14].Thus,in clinical work,we should pay attention to the evaluation of patients’ blood pressure and correct bad blood pressure in time.In addition,we need to teach patients to self-test their blood pressure and record it,and to come to the hospital for regular reviews.

Fatigue Assessment Tool

The Multidimensional Fatigue Index-20(MFI-20)

The scale was developed by Smets et al.and has 20 entries with 5 dimensions(general fatigue,somatic fatigue,mental fatigue,reduced activity and decreased motivation)[44].The scale is primarily used to assess the patient’s fatigue over the last 2 weeks.However,the dimensions of the scale may be different for different people.Han et al.Chineseized the scale and divided it into 3 dimensions by measuring it in oncology patients[45].Tang Nan used the 3-dimensional scale in patients with CHD and measured a Cronbach’sαcoefficient of 0.837 for the scale[14].Each entry on the MFI-20 is scored on a scale of 1 to 5,with a total scale score ranging from 20 to 100.Depending on the total score,fatigue is classified into four levels:mild,moderate,severe and very severe.MFI-20 is widely used at home and abroad,but this scale can only evaluate the fatigue degree and divide the fatigue dimension.It does not tell if a patient is tired.

Revised Piper Fatigue Scale(RPFS)

The scale was developed by Piper et al.and includes 22 items and 4 dimensions(behavior,emotion,cognition/emotion and body)[46].Each item is scored with 0-10 points,and the final score of the scale is the sum of all items divided by the number of items.According to the final score,fatigue can be divided into four grades:0 is no fatigue,1～3 is mild fatigue,4～6 is moderate fatigue,and 7～10 is severe fatigue.Crane et al.applied the scale to patients with myocardial infarction,and Cronbach’sαcoefficient was 0.95[5].RPFS is widely used to measure fatigue of CHD abroad,but it has not been involved in the CHD field in China.

Fatigue Assessment Instrument(FAI)

This scale was developed by Schwartz et al.[47].The scale mainly evaluates the fatigue characteristics and degree of patients in the first 2 weeks,explores situational fatigue,and distinguishes normal fatigue from abnormal fatigue.There are 29 items in FAI,each item is divided into 7 grades from “totally disagree” to “totally agree”,and all of them adopt the scoring method of 1-7 points,with a total score ranging from 29 to 203 points.The higher the total score,the more serious the fatigue.FAI has good reliability and is widely used in the field of CHD[48].When Chinese scholar Yu used this scale to distinguish the fatigue of CHD from the general population[18].

Fatigue Symptom Inventory(FSI)

The scale was developed by Hann et al.and was originally used to assess fatigue in cancer patients last week[49].FSI includes 13 items and 3 dimensions(namely fatigue degree,fatigue duration and fatigue influence).Each FSI entry is scored on a scale of 0 to 10,with higher total scores on the scale indicating more severe fatigue.The average score of FSI ≥3 is the best dividing line for identifying clinically meaningful fatigue[50].This scale was applied to the CHD field,and its Cronbach’sαcoefficient was 0.86 ～0.93[4].When Ji et al.used this scale to study the fatigue of patients with the acute coronary syndrome,40.71% of the fatigue patients were screened out.However,this scale cannot classify fatigue[8].

The Profile of Mood States-Fatigue Scale(POMS-F)

The scale has the advantages of fewer items and simple operation,including 7 items,each item adopts a 0 ～4 scoring method,and the total score ranges from 0 to 28 points.The higher the total score,the heavier the fatigue degree.Nyenhuis et al.applied this scale to healthy people,and the average score of the healthy norm was 7.3 ± 5.7 for men and 8.7 ± 6.1 for women[51].The scale has been used in the CHD field at home and abroad,and its Cronbach’sαcoefficient is 0.89 ～0.91[23].However,the scale can only reflect emotional fatigue,but cannot evaluate the physical fatigue of patients.

The Brief Fatigue Inventory(BFI)

The scale was developed by Mendoza et al.,includes 9 items and 2 dimensions(fatigue degree and fatigue distress)[52].Each item adopts a line segment scoring method of 0～10,where 0 means no fatigue and 10 means the most serious fatigue.The final score is obtained by adding the total score of the 10 entries and dividing by 10 to obtain the average score.Based on the average score,fatigue is classified as light(1 to 3 points),medium(4 to 6 points)and heavy(7 to 10 points).The Chinese version of the simplified fatigue scale has good reliability and validity,with Cronbach’sαcoefficient of fatigue strength dimension being 0.92 and Cronbach’sαcoefficient of fatigue distress dimension being 0.90[53].Jin Zhi et al.applied BFI in the study of fatigue in patients with acute myocardial infarction[6].The results showed that 61.7% of patients with acute myocardial infarction had fatigue,and the degree of fatigue was higher in women and patients with higher levels of depression.

Intervention Measures

Intervention Based on Cardiac Rehabilitation

A study by Van et al,a foreign academic,showed that cardiac rehabilitation can reduce fatigue in patients with CHD[54].The cardiac rehabilitation program is mainly based on exercise,and patients receive exercise training twice a week for 75 minutes,lasting from 4 weeks to 13 weeks.Training programs include warm-up exercise,gymnastics exercise,aerobic exercise(combining fast walking with jogging and increasing jogging time with time),cooling activities,etc.In addition to sports training,the cardiac rehabilitation program also provides stress management,diet guidance,smoking cessation programs and other courses.Patients can choose their courses according to their actual needs.The study indicated that after cardiac rehabilitation,the incidence of fatigue in patients with CHD decreased from 38.9% at baseline to 10.5%,and the incidence of severe fatigue decreased from 10.6% at baseline to 8.15%.In addition to that,cardiac rehabilitation also improved the patient’s aerobic metabolic capacity and reduced depression levels.The distance walked during the 6-min walk test(6MWT)increased from 581m at baseline to 622m,depression scores decreased from 3.57 at baseline to 2.87.Nevertheless,this study pointed out that after patients’ severe fatigue rate is still very high,and psychological and emotional aspects(depression)have a great relationship with CHD fatigue,so it is necessary to identify CHD fatigue as early as possible and carry out an intervention.In addition,Ter et al.pointed out that 3 months’ heart rehabilitation based on exercise combined with 9 months’ face-to-face group consultation can effectively improve patients’ severe fatigue degree and fatigue incidence[55].This shows that psychosocial factors should not be overlooked when developing interventions for patients,and further research is needed to explore more effective intervention options for fatigue in patients with CHD in China.

Intervention based on health education

Domestic scholar Tang[14]has implemented health education based on forgetting curve for patients with CHD(i.e.,health education for patients on the first day,the second day,the third day,the fourth day,the eighth day and one month after discharge,including explaining the concept,classification,clinical characteristics,hazards and relief methods of fatigue),which has significantly improved patients’ awareness of fatigue and reduced fatigue.It is suggested that health education can help patients with CHD increase their knowledge reserve and improve fatigue.In addition,different methods,such as the Teach-back method,mind map method and WeChat public platform,can be adopted in health education for patients.

Conclusion

Fatigue has a high incidence,great harm and many influencing factors in coronary heart disease,and lacks corresponding specialized evaluation tools and targeted intervention measures.It is suggested that a special tool for the fatigue assessment of CHD should be developed.Finally,based on the concept of evidence-based nursing,the fatigue intervention program for CHD with a specific cultural background can be formulated to help patients with coronary heart disease reduce fatigue and improve prognosis.