Effect of high-volume and -intensity endurance training in heart transplant recipients

Cardiac rehabilitation for heart transplant patients: Considerations for exercise training

Heart transplantation (HT) is the treatment of choice for eligible patients with end-stage chronic heart failure (HF). One-year survival world-wide is >85%. Many patients experience a reasonable functional ability post-HT, but episodes of acute rejection, as well as multiple co-morbidities such as hypertension, diabetes, chronic kidney disease and cardiac allograft vasculopathy are common. Immunosuppression with prednisone frequently results in increased body fat and skeletal muscle atrophy. Exercise capacity is below normal for most patients with a mean peak oxygen uptake (VO₂) of approximately 60% of expected. HT recipients have abnormal exercise physiology findings related to surgical cardiac denervation, diastolic dysfunction, and the legacy of reduced skeletal muscle oxidative capacity and impaired vasodilatory ability resulting from pre-HT chronic HF. The heart rate response to exercise is blunted. Cardiac reinnervation resulting in partial normalization of the heart rate response to exercise occurs in approximately 40% of HT recipients months to years after HT. Supervised exercise training in cardiac rehabilitation (CR) programs is safe and is recommended by professional societies both before (pre-habilitation) and after HT. Exercise training does not require alteration in immunosuppressants. Exercise training in adults after HT improves peak VO₂ and skeletal muscle strength. It has also been demonstrated to reduce the severity of cardiac allograft vasculopathy. In addition, CR exercise training is associated with reduced stroke risk, percutaneous coronary intervention, hospitalization for either acute rejection or HF, and death. There are only limited data for exercise training in the pediatric population.

Improvements in exercise capacity following cardiac transplantation in a patient born with double inlet left ventricle

A 32-year-old man born with double inlet left ventricle (DILV) and other significant cardiac abnormalities underwent surgical palliation at 1 day, 2 years and 20 years, before receiving a donor heart at 29 years. To our knowledge, there are no case reports or cohort studies of the effect of exercise training on exercise capacity and peak oxygen uptake (VO2peak) following heart transplantation (HTx) for individuals born with DILV. The patient accessed our clinical exercise physiology service for assessment, advice and support for exercise training over a 7-year period spanning pre-HTx and post-HTx. An individualised exercise plan, together with careful assessment and monitoring, and the patient's own motivation have contributed to him achieving an outstanding post-HTx doubling of VO2peak and exercise capacity.

Exercise-based cardiac rehabilitation in heart transplant recipients

BACKGROUND

Heart transplantation is considered to be the gold standard treatment for selected patients with end-stage heart disease when medical therapy has been unable to halt progression of the underlying pathology. Evidence suggests that aerobic exercise training may be effective in reversing the pathophysiological consequences associated with cardiac denervation and prevent immunosuppression-induced adverse effects in heart transplant recipients.

OBJECTIVES

To determine the effectiveness and safety of exercise-based rehabilitation on the mortality, hospital admissions, adverse events, exercise capacity, health-related quality of life, return to work and costs for people after heart transplantation.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (Ovid), Embase (Ovid), CINAHL (EBSCO) and Web of Science Core Collection (Thomson Reuters) to June 2016. We also searched two clinical trials registers and handsearched the reference lists of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of parallel group, cross-over or cluster design, which compared exercise-based interventions with (i) no exercise control (ii) a different dose of exercise training (e.g. low- versus high-intensity exercise training); or (iii) an active intervention (i.e. education, psychological intervention). The study population comprised adults aged 18 years or over who had received a heart transplant.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all identified references for inclusion based on pre-specified inclusion criteria. Disagreements were resolved by consensus or by involving a third person. Two review authors extracted outcome data from the included trials and assessed their risk of bias. One review author extracted study characteristics from included studies and a second author checked them against the trial report for accuracy.

MAIN RESULTS

We included 10 RCTs that involved a total of 300 participants whose mean age was 54.4 years. Women accounted for fewer than 25% of all study participants. Nine trials which randomised 284 participants to receive exercise-based rehabilitation (151 participants) or no exercise (133 participants) were included in the main analysis. One cross-over RCT compared high-intensity interval training with continued moderate-intensity training in 16 participants. We reported findings for all trials at their longest follow-up (median 12 weeks).Exercise-based cardiac rehabilitation increased exercise capacity (VO_2peak) compared with no exercise control (MD 2.49 mL/kg/min, 95% CI 1.63 to 3.36; N = 284; studies = 9; moderate quality evidence). There was evidence from one trial that high-intensity interval exercise training was more effective in improving exercise capacity than continuous moderate-intensity exercise (MD 2.30 mL/kg/min, 95% CI 0.59 to 4.01; N = 16; 1 study). Four studies reported health-related quality of life (HRQoL) measured using SF-36, Profile of Quality of Life in the Chronically Ill (PLC) and the World Health Organization Quality Of Life (WHOQoL) - BREF. Due to the variation in HRQoL outcomes and methods of reporting we were unable to meta-analyse results across studies, but there was no evidence of a difference between exercise-based cardiac rehabilitation and control in 18 of 21 HRQoL domains reported, or between high and moderate intensity exercise in any of the 10 HRQoL domains reported. One adverse event was reported by one study.Exercise-based cardiac rehabilitation improves exercise capacity, but exercise was found to have no impact on health-related quality of life in the short-term (median 12 weeks follow-up), in heart transplant recipients whose health is stable.There was no evidence of statistical heterogeneity across trials for exercise capacity and no evidence of small study bias. The overall risk of bias in included studies was judged as low or unclear; more than 50% of included studies were assessed at unclear risk of bias with respect to allocation concealment, blinding of outcome assessors and declaration of conflicts of interest. Evidence quality was assessed as moderate according to GRADE criteria.

AUTHORS' CONCLUSIONS

We found moderate quality evidence suggesting that exercise-based cardiac rehabilitation improves exercise capacity, and that exercise has no impact on health-related quality of life in the short-term (median 12 weeks follow-up), in heart transplant recipients. Cardiac rehabilitation appears to be safe in this population, but long-term follow-up data are incomplete and further good quality and adequately-powered trials are needed to demonstrate the longer-term benefits of exercise on safety and impact on both clinical and patient-related outcomes, such as health-related quality of life, and healthcare costs.

Exercise-based cardiac rehabilitation in heart transplant recipients

BACKGROUND

Heart transplantation is considered to be the gold standard treatment for selected patients with end-stage heart disease when medical therapy has been unable to halt progression of the underlying pathology. Evidence suggests that aerobic exercise training may be effective in reversing the pathophysiological consequences associated with cardiac denervation and prevent immunosuppression-induced adverse effects in heart transplant recipients.

OBJECTIVES

To determine the effectiveness and safety of exercise-based rehabilitation on the mortality, hospital admissions, adverse events, exercise capacity, health-related quality of life, return to work and costs for people after heart transplantation.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (Ovid), Embase (Ovid), CINAHL (EBSCO) and Web of Science Core Collection (Thomson Reuters) to June 2016. We also searched two clinical trials registers and handsearched the reference lists of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of parallel group, cross-over or cluster design, which compared exercise-based interventions with (i) no exercise control (ii) a different dose of exercise training (e.g. low- versus high-intensity exercise training); or (iii) an active intervention (i.e. education, psychological intervention). The study population comprised adults aged 18 years or over who had received a heart transplant.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all identified references for inclusion based on pre-specified inclusion criteria. Disagreements were resolved by consensus or by involving a third person. Two review authors extracted outcome data from the included trials and assessed their risk of bias. One review author extracted study characteristics from included studies and a second author checked them against the trial report for accuracy.

MAIN RESULTS

We included 10 RCTs that involved a total of 300 participants whose mean age was 54.4 years. Women accounted for fewer than 25% of all study participants. Nine trials which randomised 284 participants to receive exercise-based rehabilitation (151 participants) or no exercise (133 participants) were included in the main analysis. One cross-over RCT compared high-intensity interval training with continued moderate-intensity training in 16 participants. We reported findings for all trials at their longest follow-up (median 12 weeks).Exercise-based cardiac rehabilitation increased exercise capacity (VO2peak) compared with no exercise control (MD 2.49 mL/kg/min, 95% CI 1.63 to 3.36; N = 284; studies = 9; moderate quality evidence). There was evidence from one trial that high-intensity interval exercise training was more effective in improving exercise capacity than continuous moderate-intensity exercise (MD 2.30 mL/kg/min, 95% CI 0.59 to 4.01; N = 16; 1 study). Four studies reported health-related quality of life (HRQoL) measured using SF-36, Profile of Quality of Life in the Chronically Ill (PLC) and the World Health Organization Quality Of Life (WHOQoL) - BREF. Due to the variation in HRQoL outcomes and methods of reporting we were unable to meta-analyse results across studies, but there was no evidence of a difference between exercise-based cardiac rehabilitation and control in 18 of 21 HRQoL domains reported, or between high and moderate intensity exercise in any of the 10 HRQoL domains reported. One adverse event was reported by one study.Exercise-based cardiac rehabilitation improves exercise capacity, but exercise was found to have no impact on health-related quality of life in the short-term (median 12 weeks follow-up), in heart transplant recipients whose health is stable.There was no evidence of statistical heterogeneity across trials for exercise capacity and no evidence of small study bias. The overall risk of bias in included studies was judged as low or unclear; more than 50% of included studies were assessed at unclear risk of bias with respect to allocation concealment, blinding of outcome assessors and declaration of conflicts of interest. Evidence quality was assessed as moderate according to GRADE criteria.

AUTHORS' CONCLUSIONS

We found moderate quality evidence suggesting that exercise-based cardiac rehabilitation improves exercise capacity, and that exercise has no impact on health-related quality of life in the short-term (median 12 weeks follow-up), in heart transplant recipients. Cardiac rehabilitation appears to be safe in this population, but long-term follow-up data are incomplete and further good quality and adequately-powered trials are needed to demonstrate the longer-term benefits of exercise on safety and impact on both clinical and patient-related outcomes, such as health-related quality of life, and healthcare costs.

High-intensity interval training evokes larger serum BDNF levels compared with intense continuous exercise

Exercise can have a positive effect on the brain by activating brain-derived neurotrophic factor (BDNF)-related processes. In healthy humans there appears to be a linear relationship between exercise intensity and the positive short-term effect of acute exercise on BDNF levels (i.e., the highest BDNF levels are reported after high-intensity exercise protocols). Here we performed two experiments to test the effectiveness of two high-intensity exercise protocols, both known to improve cardiovascular health, to determine whether they have a similar efficacy in affecting BDNF levels. Participants performed a continuous exercise (CON) protocol at 70% of maximal work rate and a high-intensity interval-training (HIT) protocol at 90% of maximal work rate for periods of 1 min alternating with 1 min of rest (both protocols lasted 20 min). We observed similar BDNF kinetics in both protocols, with maximal BDNF concentrations being reached toward the end of training (experiment 1). We then showed that both exercise protocols significantly increase BDNF levels compared with a rest condition (CON P = 0.04; HIT P < 0.001), with HIT reaching higher BDNF levels than CON (P = 0.035) (experiment 2). These results suggest that shorter bouts of high intensity exercise are slightly more effective than continuous high-intensity exercise for elevating serum BDNF. Additionally, 73% of the participants preferred the HIT protocol (P = 0.02). Therefore, we suggest that the HIT protocol might represent an effective and preferred intervention for elevating BDNF levels and potentially promoting brain health.

Exercise after heart transplantation: An overview

While life expectancy is greatly improved after a heart transplant, survival is still limited, and compared to the general population, the exercise capacity and health-related quality of life of heart transplant recipients are reduced. Increased exercise capacity is associated with a better prognosis. However, although several studies have documented positive effects of exercise after heart transplantation (HTx), little is known about the type, frequency and intensity of exercise that provides the greatest health benefits. Moreover, the long-term effects of exercise on co-morbidities and survival are also unclear. Exercise restrictions apply to patients with a denervated heart, and for decades, it was believed that the transplanted heart remained denervated. This has since been largely disproved, but despite the new knowledge, the exercise restrictions have largely remained, and up-to-date guidelines on exercise prescription after HTx do not exist. High-intensity, interval based aerobic exercise has repeatedly been documented to have superior positive effects and health benefits compared to moderate exercise. This applies to both healthy subjects as well as in several patient groups, such as patients with metabolic syndrome, coronary artery disease or heart failure. However, whether the effects of this type of exercise are also applicable to heart transplant populations has not yet been fully established. The purpose of this article is to give an overview of the current knowledge about the exercise capacity and effect of exercise among heart transplant recipients and to discuss future exercise strategies.

Muscular exercise capacity and body fat predict VO(2peak) in heart transplant recipients

BACKGROUND

Heart transplant (HTx) recipients usually have reduced exercise capacity, with reported VO2peak levels of 50-70% of predicted values. This study aimed to evaluate central and peripheral factors predictive of VO2peak.

METHODS AND RESULTS

Fifty-one clinically stable HTx recipients >18 years old and 1-8 years after HTx, underwent maximal exercise testing on a treadmill. Clinical laboratory, haemodynamic and echocardiographic data, lung function, and isokinetic muscle strength and muscular exercise capacity were recorded. The mean ± SD age was 52 ± 16 years, 71% were male, and time from HTx was 4.1 ± 2.2 years. The patients were assigned to one of two groups: VO2peak ≤or >27.3 ml/kg/min, which was the median value, corresponding to 80% of predicted value. The group with the higher VO2peak had significantly lower body mass index, body fat, and triglycerides, and significantly higher body water, muscular exercise capacity, high-density lipoprotein (HDL) cholesterol, lung function, mitral annular velocity, peak ventilation, O2 pulse, and VE/VCO2 slope. Donor age, recipient age, sex, medication, ischaemic time, cardiac dimensions, systolic function, and chronotropic responses during exercise were similar. Multiple regression analysis showed that muscular exercise capacity and body fat were the strongest VO2peak predictors.

CONCLUSIONS

Chronotropic incompetence is not a limiting factor for exercise capacity in a population of relatively fit HTx patients. The most significant predictors, representing only peripheral factors, are similar to those often determining VO2peak in healthy, non-athletic individuals. Our findings emphasize the importance of a low percentage of body fat and high muscular exercise capacity in order to attain a sufficient VO2peak level after HTx.

Exercise therapy for cardiac transplant recipients

Heart transplantation (HT) is an attractive treatment for patients with terminal heart failure from a variety of causes. Survival at 1- and 5 years after HT averages 90% and 70%, respectively. The physiologic response to exercise is abnormal after HT presumably because the transplanted heart is surgically denervated, although a minority of patients demonstrate signs of partial cardiac reinnervation several months after surgery. The heart rate response to exercise is typically blunted, and exercise capacity is below average for most HT recipients. Multiple studies have demonstrated the benefits of exercise training (ET) after HT. Peak exercise oxygen uptake improves by an average of 24% after 2 to 3 months of ET. Resistance training results in increased skeletal muscle mass and strength. Early mobilization and low-level ET may begin in the hospital after extubation. Outpatient ET, ideally in a supervised environment for at least several weeks, should begin immediately after hospital dismissal. Exercise prescription for HT patients is similar to that for other patients who have undergone cardiothoracic surgery, with the exception of a target heart rate. Ratings of perceived exertion are useful for prescribing exercise intensity. Exercise training does not affect the frequency or severity of episodes of acute rejection. There are no data regarding the effect of ET on survival after HT.

Left ventricular torsion and untwisting during exercise in heart transplant recipients

Left ventricular (LV) rotation is the dominant deformation during relaxation and links systole with early diastolic recoil. LV torsion and untwisting rates during submaximal exercise were compared between heart transplant recipients (HTRs), young adults and healthy older individuals to better understand impaired diastolic function in HTRs. Two dimensional and colour M-mode echocardiography with speckle-tracking analysis were completed in eight HTRs (age: 61 +/- 9 years), six recipient age-matched (RM, age: 60 +/- 11 years), and five donor age-matched (DM, age: 35 +/- 8 years) individuals (all males) at rest and during submaximal cycle exercise. LV peak torsion, peak rate of untwisting and peak intraventricular pressure gradients (IVPGs) were examined. LV torsion increased with exercise in DMs (6.5 +/- 5.6 deg, P < 0.05), but not in RMs (-2.6 +/- 7.0 deg) or HTRs (-0.9 +/- 4.4 deg). The change from rest to exercise in the peak rate of untwisting was significantly greater for DMs (-2.1 +/- 0.5 rads s(-1), P < 0.05) compared to RMs (-0.7 +/- 1.3 rads s(-1)) and HTRs (-0.2 +/- 0.9 rads s(-1)). The amount of untwisting occurring prior to mitral valve opening substantially declined with exercise in RMs and HTRs only. The change in IVPGs was 1.3-fold greater in DMs versus HTRs or RMs (P > 0.05). Peak LV torsion and untwisting are blunted during exercise in HTRs and RMs compared to DMs. These factors may contribute to the impaired diastolic filling found in HTRs during exercise. Similarities between HTRs and RMs during exercise suggest functional accelerated ageing of the cardiac allograft.

Cardiovascular responses to incremental and sustained submaximal exercise in heart transplant recipients

The cardiovascular response to exercise in heart transplant recipients (HTR) has been compared with that of healthy individuals matched to the recipient age (RM controls). However, no study has compared HTR with donor age-matched (DM) controls. Moreover, the cardiovascular response to sustained submaximal exercise in HTR requires further evaluation. We therefore examined cardiovascular responses during incremental exercise and sustained (1 h) submaximal aerobic exercise in 9 clinically stable HTR [63 +/- 10 yr of age, 24.2 +/- 10.9 ml x kg(-1) x min(-1) peak O(2) uptake (Vo(2peak))] and 11 healthy age-matched controls (60 +/- 11 yr of age and 36.3 +/- 10.7 ml.kg(-1) x min(-1) Vo(2peak) for 6 RM controls and 35 +/- 8 yr of age and 51.1 +/- 10.4 ml x kg(-1) x min(-1) Vo(2peak) for 5 DM controls). Heart rate (HR) and left ventricular systolic and diastolic volumes (2-dimensional echocardiography) indexed to body surface area [end-systolic and end-diastolic volume indexes (EDVI and ESVI)], cardiac output (CI), ejection fraction (EF), systemic vascular resistance (SVRI), end-systolic elastance index, and arterial elastance index were determined. Although systolic function was maintained during incremental exercise, peak CI was significantly reduced (6.7 +/- 2.4 vs. 11.6 +/- 1.4 l x min(-1) x m(-2)), secondary to blunted HR, EDVI, and increased peak SVRI, in HTR compared with DM controls. The lower peak CI in HTR than in RM controls was due to blunted peak EDVI (54.1 +/- 13.2 vs. 68.6 +/- 5.7 ml/m(2)). During sustained submaximal exercise, HTR exhausted their preload reserve, a response for which changes in ESVI, HR, or EF did not fully compensate. Thus it appears that HTR are limited by impaired preload reserve, HR reserve, and vascular reserve during exercise conditions.

Comparison of hospital-supervised exercise versus home-based exercise in patients after orthotopic heart transplantation: effects on functional capacity, quality of life, and psychological symptoms

In heart transplant patients it is common to observe a reduced exercise capacity and diminished quality of life. The objective of this study was to compare the effectiveness of a hospital-based exercise program versus that of a home-based exercise program on the functional capacity, quality of life, and psychological symptoms among heart transplant patients.

METHODS

Thirty-eight heart transplant patients were randomly placed into two groups: a hospital-based exercise program (group 1, n = 15) or a home-based exercise program (group 2, n = 13). All patients performed flexibility, stretching, aerobic, strengthening, breathing, and relaxation exercise programs for 8 weeks. We performed estimates of functional capacity (maximal oxygen consumption-pVO2), quality of life (Short Form-36-SF36), and psychological symptoms (Beck Depression Inventory-BDI, the State-Trait Anxiety Inventory-STAI).

RESULTS

In group 1, significant increases were observed in pVO2 and all SF36 subgroups, with the exception of vitality and social function subgroups (P < .05). Significant increases were not observed on the BDI or STAI (P > .05). Group 2 failed to show significant improvements in any variable, with the exception of the score on the bodily pain subgroup of the SF36 (P > .05).

CONCLUSION

Based on our clinical results, we recommend a well-organized exercise program performed in a rehabilitation unit to improve postoperative exercise capacity and quality of life among heart transplant patients.

Adherence to the Therapeutic Regimen in Heart, Lung, and Heart-Lung Transplant Recipients

Optimal outcome after heart, lung, and heart-lung transplantation can only be obtained if patients are supported in adhering to a lifelong therapeutic regimen. The transplant patient's therapeutic regimen consists of a lifelong medication regimen, including immunosuppressive drugs; monitoring for signs and symptoms related to complications; avoidance of risk factors for cardiovascular disease and cancer (ie, diet and exercise prescriptions, nonsmoking); avoidance of abuse/dependence of alcohol or illegal drugs, as well as attending regular clinical checkups. Nonadherence to all aspects of this regimen is substantial. Nonadherence has been related to negative clinical outcome in view of acute rejections, graft vasculopathy, higher costs, and mortality. This review focuses on the prevalence, correlates, and consequences of nonadherence to the therapeutic regimen in heart, lung, and heart-lung transplantation. The current state of the-art on adherence-enhancing interventions is reported. Priorities for future research are outlined.