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Cardiac Rehabilitation in Patients With Left Ventricular Assist Device: A SYSTEMATIC REVIEW AND META-ANALYSIS

Mahfood Haddad, Toufik MD; Saurav, Alok MD; Smer, Aiman MBBCh; Azzouz, Muhammad S. MD; Akinapelli, Abhilash MBBS; Williams, Mark A. PhD; Alla, Venkata M. MD

Journal of Cardiopulmonary Rehabilitation and Prevention: November 2017 - Volume 37 - Issue 6 - p 390–396
doi: 10.1097/HCR.0000000000000254
Scientific Review

Purpose: Exercise-based cardiac rehabilitation (EBCR) has been demonstrated to improve functional capacity in heart failure (HF). However, there are limited data on the effect of EBCR in patients with advanced HF and left ventricular assist devices (LVADs). This meta-analysis sought to evaluate the effects of EBCR on functional capacity in patients with LVAD.

Methods: PubMed, Web of Science, CINAHL, and Cochrane Library databases were searched for randomized studies assessing the impact of EBCR in patients following LVAD implantation compared with standard therapy (ST). Using pre-defined criteria, appropriate studies were identified and selected. Data from selected studies were extracted in a standardized fashion and a meta-analysis was performed using a random-effects model with DerSimonian Liard weighting. Analysis employed weighted mean difference (WMD) as the effect size and intention-to-treat (ITT) principle. Study quality, publication bias, and heterogeneity were assessed.

Results: Six trials with a total of 183 patients (EBCR: 125; ST: 58) were identified. Mean age was 51 years and 83% were males. The initiation of EBCR varied from LVAD implantation during the index hospitalization to 10 mo post-LVAD implantation. The median rehabilitation period ranged from 6 to 10 wk. Exercise-based cardiac rehabilitation was associated with improved peak oxygen uptake (

O2) in all trials. Quantitative analysis was performed on 3 randomized studies involving 61 patients (EBCR = 39, ST = 22). Exercise-based cardiac rehabilitation was associated with significantly greater peak

O2 (WMD: 3.00 mL/kg/min; 95% CI: 0.64-5.35, P = .001). Similarly, 6-minute walk distance (6MWD) showed significantly greater improvement in the EBCR group than in the ST group (WMD: 60.06 m; 95% CI, 22.61-97.50, P = .002). Heterogeneity was low among the included trials. Exclusion sensitivity and per-protocol analysis demonstrated results consistent with ITT analysis. None of the included studies reported serious adverse events related to EBCR, which supports the safety of EBCR after LVAD implantation.

Conclusion: This systematic review and meta-analysis demonstrated that EBCR following LVAD implantation is associated with greater improvement in functional capacity compared with ST as reflected by improved peak

O2 and 6MWD. However, given the small number of patients, further research into the clinical impact of EBCR in LVAD patients is necessary.

Supplemental Digital Content is Available in the Text.Systematic review and meta-analysis were performed evaluating the impact of exercise-based cardiac rehabilitation (EBCR) on left ventricular assist device recipients. Using data from 3 randomized controlled trials, EBCR is associated with greater improvement in functional capacity compared with standard therapy, reflected by improved peak oxygen uptake and 6-minute walk distance.

Division of Cardiology, Creighton University School of Medicine, Omaha, Nebraska.

Correspondence: Toufik Mahfood Haddad, MD, Division of Cardiology, 3006 Webster St, Omaha, NE 68131 (Toufikmahfoodhaddad@creighton.edu).

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's website (www.jcrpjournal.com).

The authors declare no conflicts of interest.

Left ventricular assist devices (LVADs) are being increasingly used to support patients with advanced heart failure (HF), both as a bridge to recovery and as destination therapy.1,2 It is well-known that LVADs improve survival, functional capacity, and quality of life (QOL) in patients with advanced HF.3,4 However, compared with recipients of heart transplants, many patients with LVADs continue to experience exercise intolerance.5 Exercise-based cardiac rehabilitation (EBCR) has been shown to be safe and effective in patients with HF.6,7 Exercise-based cardiac rehabilitation improves peak oxygen uptake (

O2), functional capacity, and QOL and reduces HF symptoms and hospitalizations.6–8 However, there are very limited data on the safety and efficacy of EBCR in patients with LVADs. We therefore systematically reviewed the literature and performed a meta-analysis to evaluate the impact of EBCR in LVAD recipients.

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METHODS

LITERATURE SEARCH

A systemic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.9 Two authors separately searched PubMed, Web of Science, CINAHL, and Cochrane Library databases for studies assessing the effect of cardiac rehabilitation in patients following LVAD implantation from January 1966 through May 2016. We used the following key words in various combinations: heart assist device; ventricular assist device; assistive device; and cardiac rehabilitation. Additional details of search terms and strategy are provided in the Supplemental Appendix (Supplemental Digital Content 1, available at http://links.lww.com/JCRP/A52). The bibliographies of selected manuscripts and review articles were also manually searched for additional studies that were not identified in the original search. Titles and abstracts were screened to identify studies for full-text review. Studies assessing the effect of EBCR in patients following LVAD implantation and fulfilling the pre-defined inclusion and exclusion criteria were selected for inclusion in the review and quantitative analysis. Search strategy and results are depicted in Figure 1.

Figure 1

Figure 1

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STUDY SELECTION

Studies were included in the systematic review and meta-analysis if they (1) assessed the impact of EBCR in LVAD recipients; (2) included a standard therapy (ST) group for comparison; and (3) enrolled adult subjects (>18 years of age). Exclusion criteria included (1) non-English language publication; (2) published abstract without full-text publication; (3) studies assessing the effect of cardiac rehabilitation on LVAD recipients without an ST group; (4) studies assessing the effect of different treatment strategies of cardiac rehabilitation without an ST group; and (5) studies lacking endpoint measures such as peak

O2 and 6-minute walk distance (6MWD). Standard therapy was defined as LVAD recipients who were not given any individualized/structured exercise prescription apart from advice to walk regularly by their physicians (30-45 min/d). The EBCR group was defined as participation in a structured cardiac rehabilitation program with a clearly defined protocol.

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DATA EXTRACTION AND OUTCOME ASSESSMENT

Two independent authors performed the search in duplicate, selected studies for inclusion and extracted data in a standardized fashion. Differences were resolved by consensus or after review with a third author. The following data from selected studies were extracted: (1) general characteristics, including study design, sample size, year of publication; (2) patient characteristics, including mean age, gender; (3) duration between LVAD insertion and study start date; (4) definition of outcomes and duration of follow-up; (5) type of LVAD used; and (6) summary findings. Quality assessment was performed using the Newcastle-Ottawa Scale method10 for nonrandomized controlled studies and Jadad scale11 for randomized controlled studies.

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STATISTICAL ANALYSIS

Data from selected studies were extracted and a meta-analysis of randomized trials was performed comparing EBCR versus ST using the random effects model with DerSimonian Liard weighting.12 Analysis employed weighted mean difference (WMD) as the effect size and intention-to-treat (ITT) principle. Publication bias was analyzed visually using funnel plot. The Cochrane Q statistic was calculated and used to determine the heterogeneity of included studies for each endpoint. I2 index values of 25% to 50%, 51% to 75%, and >75% were considered as low, moderate, and high heterogeneity, respectively. An exclusion sensitivity analysis was performed when necessary and a 2-sided P value of < .05 was considered statistically significant for all analyses.

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RESULTS

A total of 6 studies involving 183 patients (EBCR = 125; ST = 58) were included in the review.13–18 The most common indication for LVAD was bridging to heart transplantation and the most common device used was a second-generation axial continuous-flow pump. Study characteristics are summarized in the Table. The mean age was 51 years (EBCR = 51 years; ST = 51 years) and 83% of subjects were males. Exercise-based cardiac rehabilitation was associated with improved peak

O2 compared with ST in all but 2 trials14,17 and showed QOL improvement in all trials except one.15 The duration of follow-up was variable across the studies, ranging from 1 to 18 mo. Initiation of exercise rehabilitation ranged from initiation during the index hospitalization (for LVAD implantation) to 10 mo post-LVAD implantation and the median rehabilitation period varied from 6 to 10 wk. Cardiac rehabilitation training session frequency ranged from 3 to 5 times weekly.

Table C

Table C

Quantitative analysis was performed on 3 randomized studies involving 61 patients (EBCR = 39; ST = 22).13–15 Exercise-based cardiac rehabilitation was associated with significantly greater peak

O2 (WMD = 3.00 mL/kg/min; 95% CI, 0.64-5.35, P = .001) (Figure 2). Similarly, 6MWD improved to a greater extent in the EBCR group than in the ST group (WMD = 60.06 m; 95% CI, 22.61-97.50, P = .002) (Figure 3). Quantitative analysis was not performed on QOL measures as the tools used to evaluate the QOL varied between studies (Minnesota Living with Heart Failure Questionnaire [MLWHFQ], Kansas City Cardiomyopathy Questionnaires, and 36-item Short Form Health Survey). Heterogeneity was low among the included trials with an I2 value of 25.6% in the analysis of

O2 and 0% in the analysis of 6MWD. Exclusion sensitivity and per-protocol analysis demonstrated results consistent with main (ITT) analysis.

Figure 2

Figure 2

Figure 3

Figure 3

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DISCUSSION

Our analysis suggests that EBCR results in significant improvements in functional capacity as measured by 6MWD and peak

O2 in patients with advanced HF who undergo LVAD implantation. In our review, the mean baseline peak

O2 and 6MWD of patients were 13 mL/kg/min and 380 m, respectively. In patients who were prescribed EBCR, the peak

O2 and 6MWD increased to 17 mL/kg/min (23% increase from baseline) and 490 m (28% increase), respectively, compared with 13.8 mL/kg/min and 429 m in the control group. The baseline values of peak

O2 and 6MWD are consistent with published data on LVAD recipients. In a systematic review of patients receiving continuous-flow LVADs, the average baseline 6MWD ranged from 180 to 200 m and increased to 320 to 350 during 3- to 6-mo follow-up,19 highlighting the dramatic improvements in functional capacity with LVAD implantation. The additional improvements noted in our study provide evidence that patient participation in EBCR after LVAD implantation can provide substantial improvements in functional capacity above the dramatic improvements that occur with LVAD implantation alone. To the best of our knowledge, this is the first systematic review/meta-analysis assessing the benefits of EBCR in LVAD recipients.

In the pivotal HF-ACTION study (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training) randomized controlled trial, 2331 stable outpatients with systolic HF were randomized to supervised exercise program or usual care. During a median follow-up of 30 mo, patients randomized to EBCR had an 11% reduction in the primary endpoint of all-cause mortality or hospitalization and a 15% reduction in the secondary endpoint of cardiovascular mortality or HF hospitalization after adjustment for other predictors.6,7 The majority of these patients had New York Heart Association class II or III symptoms. Baseline

O2 and 6MWD in the ST and EBCR groups were 14.5 mL/kg/min and 373 m and 14.4 mL/kg/min and 366 m, respectively. At 3 mo, EBCR was associated with an increase in peak

O2 of 0.6 mL/kg/min (15%) and an increase in 6MWD of 20 m compared with 0.2 mL/kg/min and 5 m, respectively, in the usual care group.6 Despite the modest improvements in measures of functional capacity, significant clinical benefits were noted. The relative improvements noted in our analysis appear larger than those observed in the HF-ACTION study. This is likely due to the following factors: (1) our analysis included a small number of patients, which might have resulted in an overestimation of the impact of EBCR; (2) patients in our study had more advanced HF and worse functional capacity (peak

O2) at baseline; thus, larger percentage improvements are likely to be observed even with small changes; and (3) patients receiving LVADs or transplant generally get more intense teaching and closer follow-up, which may result in better adherence to pharmacologic and exercise prescriptions compared to general HF populations. Of note, only 30% of those in the HF-ACTION trial exercise-arm exercised at or above the target number of minutes per week.20 Unfortunately, none of the studies in our review assessed the impact of EBCR on major clinical outcomes such as mortality or hospitalization although it has previously been shown that even modest improvements in functional capacity can predict improvements in long-term clinical outcomes.21

The improvements noted with EBCR in our analysis appear comparable to those observed with other common interventions in advanced systolic HF such as cardiac resynchronization therapy. In a substudy of COMPANION (The Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure),22 trial patients who underwent cardiac resynchronization therapy had an average improvement of 1.26 mL/kg/min (from a baseline of 12.7 mL/kg/min) in peak

O2 and an increase of 43.0 m (baseline of 292 m) in 6MWD. While heart transplantation is associated with larger improvements in functional capacity ranging from 3 to 4.5 mL/kg/min increase in

O2,23–25 the continuing organ donor shortage precludes this option for the majority of patients with advanced systolic HF. Left ventricular assist devices therefore represent a significant advancement in the therapy of patients with stage D HF with reduced ejection fraction.26 Significant technological advances in LVAD design have improved the durability and safety of these devices, resulting in increased use of LVAD as destination therapy. However, despite these advancements, QOL and exercise tolerance remain lower than that reported in recipients of heart transplants.5,27

The persistent functional impairment, despite adequate hemodynamic support after LVAD implantation, may be related to other peripheral mechanisms such as skeletal muscle deconditioning and apoptosis associated with advanced HF.28 Derangement of skeletal muscle structure and metabolic function is associated with exercise intolerance and fragility. These changes correlate poorly with central hemodynamics.29 Recruitment of skeletal muscle fibers during exercise is known to increase oxygen transport and uptake by skeletal muscles, upregulation of anabolic enzymes, and decrease in the catabolic catalysts. These favorable changes lead to an increase in peak muscle strength and could contribute to the additive benefits of EBCR in LVAD recipients.30 Furthermore, none of the included studies in our review reported serious adverse events related to EBCR. In 1 recent retrospective study, Marko et al18 identified only 1 training-related adverse event in 41 LVAD recipients undergoing a total of 1600 training sessions. Thus, participation in EBCR shortly after LVAD implantation appears safe, despite the limited nature of the available evidence.31 In addition, there are very limited data comparing the benefits of traditional EBCR to home-based rehabilitation programs in this patient population. Cinar et al32 demonstrated a greater improvement in peak

O2, 6MWD, and QOL (MLWHFQ) with a hospital exercise program compared with home exercise program. However, it is important to emphasize that these patients provide new challenges to the staff and there is a great variance in exercise training programs for this population.33,34 The duration and intensity of EBCR should be aimed to achieve a level of physical fitness appropriate to each patient's needs. Monitoring each patient's capability to exercise and tailoring it to individual needs is the key to ensuring safe prescription of EBCR in LVAD recipients.35

There were limitations with this review and analysis. As with any meta-analysis, our study inherits the intrinsic limitations of each of the included studies. Second, the limited number of studies (3 for meta-analysis and 6 for the review) and the overall small number of subjects limit the general applicability of our findings. In addition, we could not accurately assess the impact of EBCR on QOL in this cohort due to discrepancies between studies in the tools used for assessing QOL. Finally, all included studies were single-center trials and there was heterogeneity in the type of LVADs used and the protocols of EBCR among the included trials. This highlights the need for larger well-designed, multicenter studies on the impact of EBCR in LVAD recipients using standardized CR protocols.

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SUMMARY

This meta-analysis and systematic review suggest that EBCR in advanced HF patients receiving LVADs is associated with significant improvement in exercise capacity as assessed by peak

O2 and 6MWD. Therefore, LVAD recipients should be encouraged to participate in supervised EBCR. However, given the small number of patients, there is an urgent need for large well-designed multicenter studies assessing the clinical benefits of EBCR in the burgeoning population of HF patients with LVADs.

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ACKNOWLEDGMENT

We thank Kate Hayes, digital repository and reference librarian, at Creighton University Health Sciences Library for her support in conducting the search and article procurement.

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Keywords:

cardiac rehabilitation; heart failure; left ventricular assist device; meta-analysis

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