Children with advanced heart failure (HF) often have significant deconditioning with impaired functional capacity and quality of life.1–4 The use of ventricular assist devices (VAD) to support children with advanced HF either as a bridge to transplant or as destination therapy has rapidly increased, which has led to improved survival in this high risk pediatric population.5,6 As morbidity and mortality associated with VADs improve, it has become important to optimize the functional capacity and quality of life for patients.
Exercise and musculoskeletal strength training aim to improve functional capacity by decreasing frailty, strengthening respiratory muscles, and increasing musculoskeletal reserve. In adult VAD recipients, exercise training through cardiac rehabilitation (CR) has been shown to be safe and associated with decreased mortality, decreased rehospitalization rates, increased aerobic fitness, and improved quality of life.7,8 Cardiac rehabilitation is now universally recommended for adult VAD recipients based on the recent 2019 European Association for Cardio-Thoracic Surgery Expert Consensus and should be provided in a center familiar with patients on VAD support.9
For children with HF supported with VAD as a bridge to heart transplantation, optimizing musculoskeletal conditioning is an important component of rehabilitation because functional status may be a modifiable risk factor for post-transplant outcomes as has been shown in the adult heart transplant population.10–12 Doing so may improve post-transplant outcomes by decreasing time to extubation and ambulation as well as hospitalization length of stay. Exercise training has been shown to be safe and feasible in children with HF receiving inotropic or VAD support.13,14 However, data on exercise testing and CR in pediatric VAD recipients have not been reported to date. With the recent development of the Advanced Cardiac Therapies Improving Outcomes Network (ACTION, www.actionlearningnetwork.org), a collaborative learning network focused on outcomes in pediatric VAD recipients, there is now an available opportunity to evaluate variation in CR to better understand existing gaps in CR care.15 We aimed to describe variation in CR practices and understand barriers to exercise testing and CR among children supported with a durable, continuous-flow VAD across pediatric VAD centers in North America.
Materials and Methods
A survey was broadly administered to sites participating in ACTION. Pediatric cardiology providers with an expertise in pediatric VAD management were invited to complete an online questionnaire. Respondents were asked to identify their professional role and describe their attitudes and practices around exercise testing and rehabilitation at their center. Responders provided details regarding the type and frequency of exercise testing and training. Questions were developed in Survey Monkey according to guidelines for reporting survey-based research. Survey questions were predominantly in multiple-choice format with some options for open-ended responses. No incentives were offered for survey participation. A copy of the full survey is attached in the Appendix, Supplemental Digital Content, https://links.lww.com/ASAIO/A580.
A multidisciplinary cohort of 52 respondents from 28 major pediatric VAD centers participating in ACTION across North America completed the survey. The survey response rate was 68% among all ACTION centers. Respondents included pediatric cardiologists (45%), VAD coordinators (25%), pediatric cardiac intensivists (11%), pediatric HF advanced fellows (2%), pediatric cardiothoracic surgeons (2%), physical or occupational therapists (4%), and clinical research coordinators (4%).
Regarding use of exercise testing in pediatric patients after implantation of a durable continuous-flow VAD, only 38% of respondents (n = 20) reported performing exercise testing (Figure 1). Some respondents reported performing multiple types of testing at their center with the 6 minute walk test being the most common exercise test performed after VAD implantation while cycle ergometry or graded treadmill exercise testing was much less commonly performed. Even among centers who did conduct either cycle ergometry or graded treadmill tests after VAD implantation, referral for testing was uncommon (Figure 2). Regarding timing of cycle ergometer or graded treadmill exercise testing after VAD implantation, there was significant variability with 42% performed at 4 weeks, 16% at 6 weeks, and 26% at >6 weeks. Additionally, among those who perform treadmill or cycle ergometry exercise tests, only 15% performed testing before hospital discharge. Age at referral for either cycle ergometer or graded treadmill testing also varied among respondents and ranged from 6 to 12 years old (Figure 3).
Regarding barriers to routinely performing exercise testing (including cycle ergometer or graded treadmill), responders cited lack of expertise to interpret exercise testing results (21%), lack of resources to conduct exercise testing (11%), concerns about the safety of exercise testing (5%), and perceived lack of utility of exercise testing (21%).
Exercise Training and Cardiac Rehabilitation
The survey then asked respondents to describe their practices regarding exercise training and CR after durable continuous-flow VAD implantation. All respondents referred children to physical therapy after VAD implant with most (90%) referring patients within 2 weeks of VAD implant. In contrast, only 53% referred VAD recipients to either musculoskeletal exercise training or CR (Figure 4). In terms of testing location, most reported using the hospital center with only a quarter using a home-based program. Of respondents that did refer children with VADs to a CR program, the timing of referral varied, with 37% referring at 2 weeks after VAD implantation, 37% at 4 weeks, and 25% at >6 weeks. Fifty-five percent of respondents referred patients to exercise training and CR before hospital discharge.
Finally, the survey assessed each respondent’s interest in the implementation of a standardized exercise training and CR program after VAD implantation. A total of 92% indicated they would be interested. Perceived barriers to implementing such a program included inadequate implementation logistics knowledge (46%), inadequate staff to supervise CR (70%), inadequate resources for exercise testing (24%) or training (42%), concerns over the safety of CR (18%), and concern about patients ability to regularly commute to CR facility (55%) (Table 1).
Table 1. -
Survey Responses to the Question “What Potential Barrier(S) Would You Anticipate if You Were to Implement a Standardized Cardiac Rehabilitation Program at Your Pediatric VAD Center?”
N = 33 (%)
|Inadequate knowledge of how to implement cardiac rehabilitation program
|Concerns about safety
|Inadequate staff to supervise cardiac rehabilitation
|Inadequate equipment to do exercise testing
|Inadequate equipment to do exercise training
|Lack of dedicated space
|Lack of interest among VAD team members
|Lack of patient/family commitment
|Inability for patient/family to travel to cardiac rehabilitation facility
VAD, ventricular assist devices.
Our data, collected from a multicenter survey of ACTION pediatric centers specializing in VAD support across North America, represent the most detailed description of the landscape of CR in children on VAD support to date. We found significant variability in CR practices for children with advanced HF supported by durable, continuous-flow VADs. Despite many perceived barriers for exercise testing and CR, the vast majority of pediatric VAD centers are interested in implementing a standardized CR program for pediatric VAD recipients. In light of these findings, ACTION is developing a standardized CR protocol for all pediatric VAD centers as a quality improvement initiative. We hope to determine the impact of standardized CR with VAD therapy on both transplant waitlist and post-transplant outcomes in this population.
Exercise training through CR has been shown to be safe in both children and adults with advanced HF on both inotropic or VAD support.13,14,16 Given that some patients are not be able to cooperate with exercise testing requiring maximal effort due to age or developmental limits, it would be not expected that all children complete such testing. There are no standardized age requirements for completing formal exercise stress testing in children after VAD implant, although some centers report safely performing exercise stress testing (either via treadmill or cycle ergometry) in as young as 6–8 years. Alternative methods for to assess functional capacity in younger children with VADs include 6 minute walk tests. However, further standardization of functional capacity assessment in children with HF of all ages, particularly in young children who are unable to complete formal exercise stress testing, is needed. Similarly, it is recognized that exercise training strategies (i.e., frequency, intensity, timing, type) will have to be developmentally appropriate to allow for uptake and enjoyment of the intervention.
In adults with VADs, there is evidence that participation in CR is associated with increased aerobic fitness, quality of life, decreased mortality, and decreased rehospitalization rates compared to standard post-VAD care.7,8,16–21 The recent 2019 European Association for Cardio-Thoracic Surgery Expert Consensus statement and the 2019 Heart Failure Association of the European Society of Cardiology now recommend that CR should be included in routine post-VAD care in adults.9,20 However, there are no standardized guidelines for post-VAD care in children which likely explains the significant variation in rehabilitation practice demonstrated in the current study.
Children with advanced HF who receive durable VAD support are often significantly deconditioned, as acute cardiogenic shock and progressive decompensated HF lead to decreased functional status, sarcopenia, and malnutrition.1,3,22–24 Even before the VAD implantation surgery itself, 21% of patients are intubated and 10% are paralyzed due to critical illness.5 Ventricular assist devices have been shown to improve functional capacity and quality of life in pediatric recipients, and this improvement plateaus by 3 months postimplant.25,26 According to the Pedimacs registry, approximately 50% of children with durable continuous-flow VAD support undergo heart transplantation within 3 months after VAD implant, before reaching a plateau in functional recovery. Additionally, approximately 50% of pediatric durable continuous-flow VAD recipients are not discharged home after VAD implant.5 Interestingly, a recent analysis from the United Network for Organ Sharing database suggested longer VAD support before transplant improves outcomes, as children supported with VAD for greater than 2 months had longer post-transplant survival compared to those supported less than 2 months.26 Some centers have adopted a policy of an “inactive on the transplant list” grace period after VAD implant (typically 3 months or more) to maximal the opportunity for improving functional status. If more time with VAD support became standard, this would enable more time for potential discharge to home for ongoing functional recovery as well as CR before transplantation, which might have additive value to improve patients before heart transplantation. Duration of VAD support is a modifiable risk factor for children with advanced HF, and further study is needed to evaluate the optimal duration of durable VAD support before transplantation to improve both functional capacity, quality of life and post-transplant outcomes.
Although recommendations for exercise training protocols have been published in pediatric HF, there is no published literature for pediatric VAD recipients, and no standard exists across pediatric VAD institutions.13,14 Our data identify several barriers to implementing such a standard. First, integration of metabolic data into exercise testing is rare, with only approximately 15% of pediatric VAD centers routinely doing so often due to inadequate knowledge or resources and perceived lack of utility. Second, some respondents expressed concerns about the safety of exercise testing. Importantly, data have demonstrated that exercise testing, particularly using cycle ergometry, is safe and feasible in both adults and children.16,17 Third, many centers do not have the resources to perform maximal exercise testing due to limited expertise or resources. For these centers, approaches to asses baseline exercise capacity and functional status, as well as tailoring exercise recommendations to a perceived level of exertion using a modified Borg scale, may be a feasible alternative. Finally, these data suggest there is a lack of VAD expertise and comfort in those that perform exercise testing and CR.
The recent European guidelines for adult VAD recipients outlines a process to developing individualized exercise training recommendations for CR after VAD implantation.9 Some lessons from the adult VAD rehabilitation experience that may be helpful for addressing the above perceived barriers to implementing pediatric VAD rehabilitation programs at centers include involving health care providers that are familiar with exercise physiology and different exercise modalities as well as VAD functionality.20 This will reduce the risk of adverse events while exercising with VAD support. Recommendations include performing a baseline assessment of clinical risk factors and functional status (e.g., arrhythmias, coagulopathy, HF symptoms, sternotomy precautions and wound healing concerns, and level of exercise capacity before disease state), having clear exercise/rehabilitation contraindications, individualized exercise prescriptions for low-to-moderate intensity exercise training, using a prolonged gradual warm-up and cool-down, avoiding breath hold or Valsalva maneuver, wearing driveline stabilization belt during exercise, and avoiding trauma. Early mobilization after VAD implant is also encouraged. Individualized exercise prescriptions are developed based on data from a baseline maximal cardiopulmonary exercise test, preferably a cycle ergometry to minimize risk of falls. The exercise training regimen is then guided by the perceived level of exertion, and heart rate and work rate corresponding to the anaerobic threshold. Exercise training regimens include both aerobic training and resistance exercises. Exercises to generally avoid in VAD recipients include running, rowing machine, abdominal exercises, bilateral arms above the head with weights, or swimming. Supervision of exercise sessions, particularly in the initial period after VAD implant, is imperative to ensure proper exercise training technique (avoiding Valsalva maneuver or rapid changes from supine to upright positions that reduce venous return and potentially influence VAD flow, encouraging adequate fluid intake, avoiding exercises that result in tension on the driveline). Exercise should stop if patients develop new symptoms (fainting, shortness of breath, chest pain, sustained arrhythmias), VAD alarms or unexpected changes in VAD parameters.
With this high degree of variability in testing, it is likely that collaboration across pediatric VAD centers will allow the identification of feasible approaches to implement exercise training and CR. If protocols can be standardized while still allowing flexibility based on individual center resources, use of exercise training will likely increase. This in turn could improve pediatric VAD recipient rehabilitation and muscle strengthening, and potentially quality of life and survival.
Our study had some limitations. First, the surveyed participants were selected from the ACTION network, and thus responses reflect the opinions of pediatric VAD providers working in academic tertiary care centers. However, most children undergoing VAD implantation in North America are cared for in centers participating in the ACTION network, making the results of this survey generalizable to the greater pediatric VAD community. Second, as this survey was completed on a voluntary basis, there may be selection bias in respondents. Third, responses were retrospective, raising the possibility of recall bias.
With increasing use of VAD support in children with advanced HF, it is imperative to more carefully consider CR to improve musculoskeletal conditioning, aerobic capacity, functional status, and quality of life. To our knowledge, this is the first study on pediatric VAD exercise training practices. We highlight significant variability in exercise testing and training across institutions. Only half of pediatric VAD centers refer patients for exercise testing or CR, citing inadequate resources or staffing, inadequate knowledge on testing and implementation, concerns of patient safety, and questions regarding utility as limiting factors. Despite these perceived barriers, most pediatric VAD centers express interest in implementing a standardized CR program. We plan ongoing efforts through the ACTION collaborative to focus on the development and implementation of standardized CR programs for pediatric VAD centers in an effort to improve pretransplant rehabilitation and post-transplant outcomes.
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