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A systematic review of rehabilitation in chronic heart failure: evaluating the reporting of exercise interventions

Abstract A large body of research supports the use of exercise to improve symptoms, quality of life, and physical function in patients with chronic heart failure. Previous reviews have focused on reporting outcomes of exercise interventions such as cardiorespiratory fitness. However, none have critically examined exercise prescription. The aim of this review was to evaluate the reporting and application of exercise principles in randomised control trials of exercise training in patients with chronic heart failure. A systematic review of exercise intervention RCTs in patients with CHF, using the Consensus on Exercise Reporting Template (CERT), was undertaken. The Ovid Medline/PubMed, Embase, Scopus/Web of Science, and Cochrane Library and Health Technology Assessment Databases were searched from 2000 to June 2020. Prospective RCTs in which patients with CHF were randomized to a structured exercise programme were included. No limits were placed on the type or duration of exercise structured exercise programme or type of CHF (i.e. preserved or reduced ejection fraction). We included 143 studies, comprising of 181 different exercise interventions. The mean CERT score was 10 out of 19, with no study achieving a score of 19. Primarily, details were missing regarding motivational strategies, home‐based exercise components, and adherence/fidelity to the intervention. Exercise intensity was the most common principle of exercise prescription missing from intervention reporting. There was no improvement in the reporting of exercise interventions with time (R 2 = 0.003). Most RCTs of exercise training in CHF are reported with insufficient detail to allow for replication, limiting the translation of evidence to clinical practice. We encourage authors to provide adequate details when reporting future interventions. Where journal word counts are restrictive, we recommend using supplementary material or publishing trial protocols prior to beginning the study.


Introduction
Chronic heart failure (CHF) is characterized by the reduced ability of the heart to pump and or fill with blood, resulting in fatigue, dyspnoea, and exercise intolerance. 1 It is a significant healthcare challenge affecting around 26 million people worldwide, 2 with a prevalence of 1-3% of the general population increasing to around 10% in those aged 70 and over. 3 Patients with CHF often have reduced functional capacity and decreased quality of life. 4 A range of pharmacological (angiotensin II receptor blockers, diuretics, beta-blockers, cardiac glycosides, and anticoagulants), medical (cardiac resynchronization therapy), and lifestyle (smoking cessation and reduced salt intake) interventions can help improve quality of life and reduce hospital admissions in CHF. 5 In addition, structured exercise training is recommended and should be an integral part of the treatment pathway.
There is evidence for the benefits of exercise training in New York Heart Association class I-III CHF patients, with numerous randomized controlled trials reporting improvements in health-related quality of life, cardiorespiratory function, and physical activity participation. 6-8 These benefits have been identified using a range of exercise training intervention modalities such as high intensity interval training, 9 moderate intensity training, 10 and resistance training. 11 Despite evidence of the therapeutic role of exercise training in CHF populations, the heterogeneity of interventions limits understanding of the most effective prescription. A range of exercise frequencies, intensities, modalities, and durations have been reported in the management of CHF. The plethora of exercise intervention models available for the treatment of CHF requires that frequency, intensity, time, and type of exercise be accurately reported, as proposed in the consensus on exercise reporting template (CERT). 12 These criteria, which are often inadequately reported in exercise clinical trials, are fundamental for translation, interpretation, and implementation within clinical practice. 13 To date, no review has fully evaluated the reporting of exercise interventions in CHF, risking sub-therapeutic exercise prescription despite proposed efficacy of treatment. This review, therefore evaluated using the CERT criteria, randomized controlled trials of exercise interventions in patients with CHF in relation to (i) the principles of exercise prescription (i.e. frequency, intensity, time, and type) and (ii) the reporting of intervention components related to exercise prescription.

Methods
This review was conducted in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidance. 14 As we did not report any specific health care outcomes, we could not prospectively register this review on PROSPERO.

Search strategy
The Ovid Medline/PubMed, Embase, Scopus/Web of Science, Cochrane Library, and Health Technology Assessment Databases were searched from 2000 to June 2020. Only full text articles involving adults over 18 years of age and published in the English language were considered. Search terms included 'heart failure', 'exercise training', and 'rehabilitation'. Titles and abstracts identified were independently interrogated for inclusion by two reviewers (A. E. H. and S. R.). The full texts of any potentially eligible articles were then screened against the inclusion/exclusion criteria.

Inclusion criteria
We included prospective randomized controlled trials in which patients with CHF were randomized to a structured exercise programme. No limits were placed on the type or duration of exercise structured exercise programme. We also placed no limits on type of CHF (i.e. preserved or reduced ejection fraction).

Exclusion criteria
Alternative interventions such as yoga, Pilates, or Tai Chi, as well as specific therapeutic interventions (such as drug therapies) were excluded. In addition, randomized controlled trials in which the intervention was exclusively behavioural were excluded. We also excluded duplicate papers whereby the pilot and subsequent randomized trial reported the same exercise intervention. Studies published before 2000 were excluded due to them predating the publication of the European Society of Cardiology clinical exercise guidelines which outlined specific exercise prescription recommendations. 15

Data extraction
Data extraction was performed by two reviewers (A. E. H. and S. R.) using a standardized form. Data pertaining to search results, duplicates, and included and excluded (with explanation) studies were recorded.
Data extraction included study characteristics (country, design, and appropriate information to assess the quality of the study), sample size, and a detailed description of the intervention according to the 'FITT principle'; defined as the Frequency, Intensity, Time, and Type. Studies were rated for each of the principles of exercise training based on the reported application of the principle within the paper. Application of a specific principle was assigned a '1', whereas '0' was assigned if the principle was not reported. Where data were unclear, or if the principle was reported but used inconsistently, we also assigned a '0'. In addition, we used the 'Consensus on Exercise Reporting Template' 12 to provide each paper with an objective score out of 19.

Consensus on exercise reporting
The 'Consensus on Exercise Reporting' (CERT) template is a 16-item checklist designed to evaluate the completeness of exercise intervention reporting and spans the 'who', 'what', 'when', 'where', and 'how'. We utilized the CERT 'Explanation and Elaboration Statement' to ensure methodological quality of scoring. 12 Each item of the CERT was scored '1' (adequately reported) or '0' (not adequately reported, Exercise rehabilitation in heart failure 3459 unclear, or not reported at all). A maximum score of 19 can be achieved. Where studies cited methodology from previous work or referenced protocols or supplementary materials, we also checked information from these sources and included them in the scoring as appropriate. Due to the volume of studies included, four authors (A. E. H., S. R., N. C. O., and S. M.) scored studies, with A. E. H. and S. R. verifying all scores independently in cases of uncertainty.

Data synthesis
Data were synthesized, and studies rated based on the application of exercise training principles and the CERT template. The percentage of studies meeting each criterion; application of the principles of exercise training; reporting of the components of prescription using the aforementioned FITT principles; and the CERT were calculated. To determine whether improvements/differences occurred over time, an R 2 test was utilized.

Included studies
The search yielded a total of 53 429 records, of which, 575 full-text articles were assessed for eligibility. Of these, we included 143 studies, comprising 181 different exercise interventions ( Figure 1).  In total, there were 11 752 participants of which 6429 were randomized to an exercise intervention with 5787 (90%) completed the intervention.

Application of the principles of exercise training
The application of the principles of exercise training is outlined in Figure 2. The FITT principle in CHF interventions was very well reported. However, at least one component was not reported in 24 (17%) of the 143 interventions, [23][24][25]28,30,34,49,55,61,66,72,75,79,83,89,90,92,100,111,114,118,151,152,155 and in two studies, none of the principles of exercise training was reported. 25, 75 The most poorly (or 'worst') reported principle of exercise training was intensity which was not reported in 12 out of 181 interventions. 23,25,28,49,66,72,75,114,118,151,152,155 All studies where intensity was not reported were centre-based programmes and across all exercise modalities -aerobic, 23,28,49,66,72,151,155 resistance, 75,114,152 or mixed interventions. 25,118

Reporting of exercise intervention components
The reporting of the exercise intervention components is summarized in Figure 3. None of the studies scored by CERT achieved 100%. Further, the mean CERT score in all 181 interventions was 10 out of a possible score of 19. The lowest CERT score was 2/19 with all information missing with the exception of 'setting' and 'whether the intervention was delivered as planned'. The highest CERT score was 18/19, which was obtained by two studies with two details not reported: 'description of home components' and 'description or expertise of instructors', respectively. The least reported components included 'detailed description of motivation strategies','detailed description of any home programme component', and 'description of how adherence or fidelity to the exercise intervention is assessed/measured'. The best reported outcomes included 'description of whether exercise is supervised or unsupervised and how they are delivered' and whether exercises were 'generic (one size fits all) or tailored to the individual'.
○ Question 1: Detailed description of the type of exercise equipment Most studies described the mode (i.e. treadmill walking or cycling) but did not provide an adequate description of the make and/or model of the exercise equipment. Particularly regarding resistance exercise, very few descriptions beyond 'resistance machines' or 'dumbbells' were provided.
○ Question 2: Detailed description of the qualifications, expertise, and/or training Only 31% of interventions provided information on the specific professional disciplines delivering the intervention. Those disciplines included physiotherapists, nurses, and exercise physiologists. Generally, there were no details about qualifications, but phrases such as 'highly trained' or 'experienced' were used.  format. For those interventions that were unsupervised, all were home-based exercise programmes.

○ Question 5: Detailed descriptions of how adherence to exercise is measured and reported
The methodology for reported adherence to exercise was poor, with only 37% of interventions reporting this adequately. Where it was measured, it was usually recorded as attendance to training via diaries, telephone calls, and physical monitoring of attendance.
○ Question 6: Detailed description of motivational strategies Only 14% (26/181) of interventions provided details regarding motivational strategies. Where strategies were employed, motivational interviewing, educational support, and regular support were the most common.
○ Question 7a: Detailed description of the decision rule(s) for determining exercise progression; 7b: Detailed description of how the exercise programme was progressed The decision rule(s) for progression were only identified in 28% (52/181) of included interventions. Mostly the decision to progress was based on rating of perceived exertion or heart rate responses. Despite only 28% of interventions provided decisions rules for progression, 47% did provide descriptions of how programmes were actually progressed. Progression was administered in a number of ways including increasing the intensity and duration of exercise.
○ Question 8: Detailed description of each exercise to enable replication Detailed descriptions of exercise were evident in 58% (110/181) of interventions. Predominantly, information was missing in instances where aerobic circuit-based training sessions were utilized, but individual exercises were not reported. ○

Improvement over time
We assessed if reporting of exercise interventions improved over time from 2000 to 2020. There was no significant relationship (R 2 = 0.003) between year of study and quality of study reporting (Figure 4).

Discussion
There are a multitude of studies examining the benefits of exercise training for patients with CHF. These studies have provided a vast amount of evidence relating to the safety, feasibility, and health benefits of exercise in this population. 7 However, there has been no evaluation of the application of the basic principles of exercise training or the quality of study reporting. We used the CERT criteria to evaluate 143 randomized controlled trials of exercise interventions in patients with CHF. Our review had two main aims: (i) to assess the application of the principles of exercise prescription (i.e. frequency, intensity, time, and type) and (ii) to assess the reporting of exercise intervention components.
Our main finding was that the overall reporting of exercise interventions (as assessed by the CERT) was poor. The mean CERT score was 10 out of 19, with 80/181 (45%) of interventions scoring less than the mean. The worst reported components included 'detailed description of motivation strategies', 'detailed description of any home programme component', and 'description of how adherence or fidelity to the exercise intervention is assessed/measured'. Poor reporting of exercise interventions may impact on the ability to translate research findings into meaningful clinical interventions and may ultimately impact any potential benefits for patients.
Motivational strategies were poorly reported overall and could only be identified in 14% of all interventions (26/181). Good adherence to exercise and general physical activity, health and wellbeing behaviours may be achieved via effective behaviour change. 93,159,160 The most common form of motivational strategy in the included studies was an education group or the use of standard verbal encouragement during exercise sessions. Other forms of behaviour change strategies that were used include patient diaries and goal setting. 161 It is likely that improving this component of exercise interventions will improve adherence and may lead to better patient outcomes. Indeed, the 'Rehabilitation Enablement in Chronic Heart Failure' (REACH-HF) trial demonstrated that those who received a behaviour change intervention had superior quality of life outcomes following 12 weeks of cardiac rehabilitation and that the intervention was feasible and well accepted by both patients and caregivers. 162 A similar remotely delivered physical activity behaviour change intervention demonstrated that 'lifestyle coaching' enabled patients to reduce fear of physical activity and improved motivation and confidence. 163 It is evident that behaviour change constitutes a vital component of exercise interventions, and therefore, good quality reporting is essential to allow for replication and translation from research to clinical practice.
The methodology for recording and reporting 'adherence or fidelity to the exercise intervention' was also poorly reported, and we only identified 23% (43/181) of interventions where this was appropriately measured. When measured, it was predominantly related to the percentage of exercise sessions attended. In a small minority of studies, fidelity was monitored through the measurement of heart rate during the sessions (related to intensity), but data were not provided by the authors. Intervention fidelity is important in determining the validity of randomized controlled trials. 164,165 There are several different components to intervention fidelity. In exercise trials, information about compliance with exercise prescription is particularly important and is integral to quantifying the intended dose of exercise and the dose that participants actually received. 166 Most studies adequately described the principles of exercise training (including frequency, intensity, time, and type). Previous analysis of the principles of exercise training inn other clinical cohorts have demonstrated heterogeneity in results. For instance, a review of exercise in breast cancer patients demonstrated poor reporting, 167 while another review in pulmonary hypertension demonstrated excellent reporting. 168 The principle of exercise training that was least reported in both reviews was intensity. This is of great concern given that intensity is an integral component of any exercise intervention, particularly in relation to specificity and progression. Even where exercise intensity was reported, parameters were highly variable including rating of perceived exertion, anaerobic threshold, % of peak oxygen consumption (VO 2 ), % of peak heart rate, % of heart rate reserve, and so forth. This variation in markers of exercise intensity is likely to cause challenges in identifying the most appropriate methods in this cohort. Indeed, while not necessarily related to poor reporting, evidence has emerged demonstrating that a large proportion of patients undertaking cardiac rehabilitation do not exercise at a sufficient intensity to improve cardiorespiratory fitness. 169 Understanding and ensuring that intensity is well-defined, monitored during exercise, and clearly reported are essential.
Finally, we wanted to address whether the reporting of exercise interventions has improved over time (Figure 3). Our analysis indicated that the quality of reporting has not improved with time which corresponds to previous research in patients undergoing cardiac rehabilitation. 170 It may be that tight restrictions on word count within journals limits authors' ability to provide adequate descriptions of exercise interventions. However, authors should be able to provide further information in the form of supplementary material or published protocols.

Conclusion
There is a wealth of evidence to support the use of exercise training for patients with chronic heart failure. Our study found that most randomized controlled trials of exercise training in this population did not report their interventions with enough detail. The major areas of weakness included intervention adherence and fidelity, exercise intensity, motivational strategies, and home-based components of the intervention. These inadequacies in reporting may limit application to clinical practice and future research. We would encourage all authors to provide adequate details when reporting interventions in the future, in line with the CERT criteria. Where journal publication criteria are restrictive, we recommend using supplementary material or publishing protocols prior to the beginning of the study.
Pfeffer MA, Investigators C. Characterization of health-related quality of life in heart failure patients with preserved versus low ejection fraction in CHARM. Eur J Heart Fail 2007; 9: 83