Predictive factors of maximal aerobic capacity after cardiac transplantation

Cardiac rehabilitation program improves exercise capacity in heart transplantation recipients regardless of marginal donor factors

Cardiac rehabilitation (CR) is recommended to improve exercise capacity after heart transplantation (HTx); however, the effects of marginal donor factors are unclear. Forty-one recipients participated in a 3-month CR program early after HTx (mean age 39 ± 14 years; 88% male). Patients were divided into marginal (≥ 2 marginal donor factors; n = 24) and control groups (< 2 marginal donor factors; n = 17). We examined donor and recipient factors related to change in peak oxygen uptake (peak VO₂) during the CR program using multiple linear regression analysis. Baseline characteristics were similar between groups, although the mean age was higher in the marginal group (43 ± 13 vs. 34 ± 14 years, p = 0.043). Peak VO₂ and knee extensor muscular strength (KEMS) improved significantly in both groups (p < 0.05), but there were no observed inter-group differences. Multiple analysis revealed change in KEMS (β = 0.52, 95% CI = 0.023-1.01) as an independent predictor of change in peak VO₂ after adjustment for recipients' age, sex, and CR attendance frequency (adjusted R² = 0.25, p = 0.0084), whereas marginal donor factors were not a predictor (p = 0.76). The CR program improved exercise capacity in HTx recipients regardless of marginal donor factors, suggesting that recipients of marginal donor hearts should be referred to CR programs.

Exercise-based rehabilitation strategies in heart transplant recipients: Focus on high-intensity interval training

Despite progressive improvement in medical therapy and standard care, the exercise capacity of heart transplant recipients is reduced compared with age-matched healthy individuals. Exercise-based rehabilitation programs have been shown to improve the exercise capacity of transplant patients through a multifactorial effect. In this context, high-intensity interval exercise is a growing field of research, with current evidence suggesting a major benefit in heart transplant recipients compared with a conventional training protocol. Therefore, this study aimed to provide an overview of the mechanisms involved in the reduced exercise capacity of heart transplant patients and a review of current rehabilitation strategies with a special focus on the mechanisms and clinical effects of high-intensity interval training exercise.

Increased aortic augmentation index is associated with reduced exercise capacity after heart transplantation

OBJECTIVE

Exercise capacity is often reduced after heart transplantation. We aimed to investigate the association between aortic stiffness and exercise capacity after heart transplantation.

METHODS

We retrospectively analyzed the data of patients who underwent a cardiopulmonary exercise test and central hemodynamic measurements over 1 year following heart transplantation, from Janary 2011 to June 2018.

RESULTS

A total of 54 patients (mean age, 49 years; 72% men) were analyzed. The median peak oxygen uptake level was 21.1 ml/kg per min at a median time of 13 months after heart transplantation. In univariate linear regression, recipient age, pulmonary arterial pressure, pulmonary capillary wedge pressure, hemoglobin level, estimated glomerular filtration rate, aortic augmentation index, and pulse wave velocity were significant predictors for peak oxygen uptake level. After adjustment for other confounding variables, heart rate-corrected aortic augmentation index was a significant predictor for peak oxygen uptake (β = -0.141, 95% confidence interval, -0.263 to -0.058, P = 0.003).

CONCLUSION

In the present study, increased aortic augmentation index was associated with reduced exercise capacity after heart transplantation. Therefore, this simple measurement of aortic stiffness should be periodically used for the evaluation of exercise capacity after heart transplantation.

Clinical and Rehabilitative Predictors of Peak Oxygen Uptake Following Cardiac Transplantation

The measurement of peak oxygen uptake (VO_2peak) is an important metric for evaluating cardiac transplantation (HTx) eligibility. However, it is unclear which factors (e.g., recipient demographics, clinical parameters, cardiac rehabilitation (CR) participation) influence VO_2peak following HTx. Consecutive HTx patients with cardiopulmonary exercise testing (CPET) between 2007–2016 were included. VO_2peak was measured from CPET standard protocol. Regression analyses determined predictors of the highest post-HTx VO_2peak (i.e., quartile 4: VO_2peak > 20.1 mL/kg/min). One hundred-forty HTx patients (women: n = 41 (29%), age: 52 ± 12 years, body mass index (BMI): 27 ± 5 kg/m²) were included. History of diabetes (Odds Ratio (OR): 0.17, 95% Confidence Interval (CI): 0.04–0.77, p = 0.021), history of dyslipidemia (OR: 0.42, 95% CI: 0.19–0.93, p = 0.032), BMI (OR: 0.90, 95% CI: 0.82–0.99, p = 0.022), hemoglobin (OR: 1.29, 95% CI: 1.04–1.61, p = 0.020), white blood cell count (OR: 0.81, 95% CI: 0.66–0.98, p = 0.033), CR exercise sessions (OR: 1.10, 95% CI: 1.04–1.15, p < 0.001), and pre-HTx VO_2peak (OR: 1.17, 95% CI: 1.07–1.29, p = 0.001) were significant predictors. Multivariate analysis showed CR exercise sessions (OR: 1.10, 95% CI: 1.03–1.16, p = 0.002), and pre-HTx VO_2peak (OR: 1.16, 95% CI: 1.04–1.30, p = 0.007) were independently predictive of higher post-HTx VO_2peak. Pre-HTx VO_2peak and CR exercise sessions are predictive of a greater VO_2peak following HTx. These data highlight the importance of CR exercise session attendance and pre-HTx fitness in predicting VO_2peak post-HTx.

Cholinesterase levels predict exercise capacity in cardiac recipients early after transplantation

PURPOSE

Although cardiac rehabilitation is recommended for patients early after heart transplantation (HTx), adequate exercise effect cannot always be obtained, partly because in patients with chronic heart failure, exercise capacity is reduced due to malnutrition while waiting for HTx. This study aimed to investigate the relationships between exercise capacity and clinical variables, including nutritional indicators, early after HTx.

PATIENTS AND METHODS

Forty-three HTx recipients were studied. The mean age at HTx was 38 ± 14 years, and 86% were male. We assessed the relationships between peak oxygen uptake (VO₂ ) and clinical variables, including plasma B-type natriuretic peptide (BNP), isometric knee extensor muscle strength (KEMS), and nutritional indicators within 1 week of their respective discharges.

RESULTS

Peak VO₂ correlated positively with isometric KEMS (r = .63, P < .0001) and negatively with BNP level (r = -.37, P = .015). Of the nutritional indicators, only cholinesterase levels had a significant relationship with peak VO₂ (r = .34, P = .028), whereas the Geriatric Nutritional Risk Index and the Controlling Nutritional Status scores did not. In multiple linear regression analysis, cholinesterase levels and isometric KEMS were independent predictors of peak VO₂ .

CONCLUSION

Cholinesterase levels predicted exercise capacity early after HTx.

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.

Adrenergic Receptor Polymorphism and Maximal Exercise Capacity after Orthotopic Heart Transplantation

Background

Maximal exercise capacity after heart transplantion (HTx) is reduced to the 50–70% level of healthy controls when assessed by cardiopulmonary exercise testing (CPET) despite of normal left ventricular function of the donor heart. This study investigates the role of donor heart β₁ and β₂- adrenergic receptor (AR) polymorphisms for maximal exercise capacity after orthotopic HTx.

Methods

CPET measured peak VO₂ as outcome parameter for maximal exercise in HTx recipients ≥9 months and ≤4 years post-transplant (n = 41; mean peak VO₂: 57±15% of predicted value). Donor hearts were genotyped for polymorphisms of the β₁-AR (Ser49Gly, Arg389Gly) and the β₂-AR (Arg16Gly, Gln27Glu). Circumferential shortening of the left ventricle was measured using magnetic resonance based CSPAMM tagging.

Results

Peak VO₂ was higher in donor hearts expressing the β₁-Ser49Ser alleles when compared with β₁-Gly49 carriers (60±15% vs. 47±10% of the predicted value; p = 0.015), and by trend in cardiac allografts with the β₁-AR Gly389Gly vs. β₁-Arg389 (61±15% vs. 54±14%, p = 0.093). Peak VO2 was highest for the haplotype Ser49Ser-Gly389, and decreased progressively for Ser49Ser-Arg389Arg > 49Gly-389Gly > 49Gly-Arg389Arg (adjusted R² = 0.56, p = 0.003). Peak VO₂ was not different for the tested β₂-AR polymorphisms. Independent predictors of peak VO₂ (adjusted R² = 0.55) were β₁-AR Ser49Gly SNP (p = 0.005), heart rate increase (p = 0.016), and peak systolic blood pressure (p = 0.031). Left ventricular (LV) motion kinetics as measured by cardiac MRI CSPAMM tagging at rest was not different between carriers and non-carriers of the β₁-AR Gly49allele.

Conclusion

Similar LV cardiac motion kinetics at rest in donor hearts carrying either β₁-AR Gly49 or β₁-Ser49Ser variant suggests exercise-induced desensitization and down-regulation of the β₁-AR Gly49 variant as relevant pathomechanism for reduced peak VO₂ in β₁-AR Gly49 carriers.

Design and rationale of the HITTS randomized controlled trial: Effect of High-intensity Interval Training in de novo Heart Transplant Recipients in Scandinavia

There is no consensus on how, when, and at what intensity exercise should be performed and organized after heart transplantation (HTx). Most rehabilitation programs are conducted in HTx centers, which might be impractical and costly. We have recently shown that high-intensity interval training (HIT) is safe, well tolerated, and efficacious in maintenance HTx recipients, but there are no studies among de novo patients, and whether HIT is feasible and superior to moderate training in HTx recipients is unclear. A total of 120 clinically stable HTx recipients older than 18 years will be recruited from 3 Scandinavian HTx centers. Participants are randomized to HIT or moderate training, shortly after surgery. All exercises are supervised in the patients' local communities. Testing at baseline and follow-up includes the following: VO2peak (primary end point), muscle strength, body composition, quality of life, myocardial performance, endothelial function, biomarkers, and progression of cardiac allograft vasculopathy. A subgroup (n = 90) will also be tested at 3-year follow-up to assess long-term effects of exercise. So far, the HIT intervention is well tolerated, without any serious adverse events. We aim to test whether decentralized HIT is feasible, safe, and superior to moderate training, and whether it will lead to significant improvement in exercise capacity and less long-term complications.

Parasympathetic reinnervation accompanied by improved post-exercise heart rate recovery and quality of life in heart transplant recipients

Although sympathetic reinnervation is accompanied by the improvement of exercise tolerability during the first years after heart transplantation (HTx), little is known about parasympathetic reinnervation and its clinical impact. We enrolled 21 recipients (40 ± 16 years, 71% male) who had received successive cardiopulmonary exercise testing at 6 months, and 1 and 2 years after HTx. Exercise parameters such as peak oxygen consumption or achieved maximum load remained unchanged, whereas recovery parameters including heart rate (HR) recovery during 2 minutes and the delay of peak HR, which are influenced by parasympathetic activity, improved significantly during post-HTx 2 years (P < 0.05 for both). HR variability was analysed at post-HTx 6 months in 18 recipients, and high frequency power, representing parasympathetic activity, was significantly associated with the 2 recovery parameters (P < 0.05 for all). We also assessed quality of life using the Minnesota Living with Heart Failure (HF) Questionnaire at post-HTx 6 months and 2 years in the same 18 recipients, and those with improved recovery parameters enjoyed a better HF-specific quality of life (P < 0.05 for both). In conclusion, parasympathetic reinnervation emerges along with improved post-exercise recovery ability of HR and quality of life during post-HTx 2 years.

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.

High-intensity interval training improves peak oxygen uptake and muscular exercise capacity in heart transplant recipients

Heart transplant (HTx) recipients usually have reduced exercise capacity with reported VO(2peak) levels of 50-70% predicted value. Our hypothesis was that high-intensity interval training (HIIT) is an applicable and safe form of exercise in HTx recipients and that it would markedly improve VO(2peak.) Secondarily, we wanted to evaluate central and peripheral mechanisms behind a potential VO(2peak) increase. Forty-eight clinically stable HTx recipients >18 years old and 1-8 years after HTx underwent maximal exercise testing on a treadmill and were randomized to either exercise group (a 1-year HIIT-program) or control group (usual care). The mean ± SD age was 51 ± 16 years, 71% were male and time from HTx was 4.1 ± 2.2 years. The mean VO(2peak) difference between groups at follow-up was 3.6 [2.0, 5.2] mL/kg/min (p < 0.001). The exercise group had 89.0 ± 17.5% of predicted VO(2peak) versus 82.5 ± 20.0 in the control group (p < 0.001). There were no changes in cardiac function measured by echocardiography. We have demonstrated that a long-term, partly supervised and community-based HIIT-program is an applicable, effective and safe way to improve VO(2peak) , muscular exercise capacity and general health in HTx recipients. The results indicate that HIIT should be more frequently used among stable HTx recipients in the future.

Ischemic time as a predictor of physical recovery in the first months after heart transplantation

Functional results after heart transplantation range from modest to spectacular improvement. Little is known about factors to predict functional result. This study aimed to identify these factors. We present a prospective study including all consecutive transplant recipients (n = 55) in a two-year period whose survival was greater than two months. Perioperative, donor, and recipient issues were systematically analyzed. Exercise capacity was assessed by symptom-limited treadmill exercise testing two months after transplantation. Exercise capacity was classified as satisfactory or poor depending on achieving or not 4.5 METs (metabolic equivalents), respectively. Thirty-three patients (60%) showed a good exercise capacity (>4.5 METs), whereas the remaining twenty-two patients (40%) were unable to exceed this threshold. The variables which correlated with exercise capacity in univariate analysis were recipient age, inotropic treatment, ischemic time, ventricular assist device, etiology, urgent transplant, and INTERMACS score. Among them only recipient age and ischemic time were proved to be correlated with exercise capacity in the multiple regression analysis. Thus, younger patients and those who had received an organ with shorter ischemic time showed greater exercise capacity after transplant. These findings strengthen the trend toward reducing ischemic time as much as possible to improve both survival and clinical recovery.

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.

Increased metaboreflex activity is related to exercise intolerance in heart transplant patients

Heart transplantation does not normalize exercise capacity or the ventilatory response to exercise. We hypothesized that excessive muscle reflex activity, as assessed by the muscle sympathetic nerve activity (MSNA) response to handgrip exercise, persists after cardiac transplantation and that this mechanism is related to exercise hyperpnea in heart transplant recipients (HTRs). We determined the MSNA, ventilatory, and cardiovascular responses to isometric and dynamic handgrips in 11 HTRs and 10 matched control subjects. Handgrips were followed by a post-handgrip ischemia to isolate the metaboreflex contribution to exercise responses. HTRs and control subjects also underwent recordings during isocapnic hypoxia and a maximal, symptom-limited, cycle ergometer exercise test. HTRs had higher resting MSNA ( P < 0.01) and heart rate ( P < 0.01) than the control subjects. Isometric handgrip increased MSNA in HTRs more than in the controls ( P = 0.003). Dynamic handgrip increased MSNA only in HTRs. During post-handgrip ischemia, MSNA and ventilation remained more elevated in HTRs ( P < 0.05). The MSNA and ventilatory responses to hypoxia were also higher in HTRs (both P < 0.04). In HTRs, metaboreflex overactivity was related to the ventilatory response to exercise, characterized by the regression slope relating ventilation to CO2 output ( r = +0.8; P < 0.05) and a lower peak ventilation ( r = +0.81; P < 0.05) during cycle ergometer exercise tests. However, increased chemoreflex sensitivity ( r = +0.91; P < 0.005), but not metaboreflex activity, accounted for the lower peak ventilation during exercise in a stepwise regression analysis. In conclusion, heart transplantation does not normalize muscle metaboreceptor activity; both increased metaboreflex and chemoreflex control are related to exercise intolerance in HTRs.

Why does chronic heart failure cause breathlessness and fatigue?

Traditional explanations for the symptoms of fatigue and breathlessness experienced by patients with chronic heart failure (CHF) focus on how reduced cardiac output on exercise leads to impaired skeletal muscle blood supply, thus causing fatigue, and on how the requirement for a raised left ventricular filling pressure to maintain cardiac output results in reduced pulmonary diffusion owing to interstitial edema, thus causing breathlessness. However, indices of left ventricular function relate poorly to exercise capacity and symptoms, suggesting that the origin of symptoms may lie elsewhere. There is a specific heart failure myopathy that is present early in the condition which may contribute largely to the sensation of fatigue. Receptors present in skeletal muscle sensitive to work (ergoreceptors) are overactive in patients with CHF, presumably as a consequence of the myopathy, and their activity is related both to the ventilatory response to exercise and breathlessness, and to the sympathetic overactivity of CHF. In the present paper, we review the systemic consequences of left ventricular dysfunction to understand how they relate to the symptoms of heart failure.

Functional Status One Year After Heart Transplant

PURPOSE

Although heart transplantation (HT) increases survival of heart failure patients, many patients still experience problems afterward that affect functioning.

PURPOSES

(1) to compare the functional status of HT patients before transplant versus 1 year after transplant, (2) to identify functional problems 1 year post-transplant, and (3) to identify which variables predicted worse functional status 1 year later.

METHODS

The sample was 237 adult HT recipients who completed the 1-year post-transplant study booklet. Functional ability was assessed by the Sickness Impact Profile. Paired t tests compared Sickness Impact Profile scores before and after transplant. Medical and demographic data plus patient questionnaire data on Sickness Impact Profile, symptoms, stressors, and compliance were used in the regression.

RESULTS

Sickness Impact Profile functional scores improved significantly from pre-transplant (23.0%) to post-transplant (13.4%); however, many HT recipients still reported problems in 12 functional areas 1 year after surgery. Major problem areas were the following: work (90% of patients), eating (due to dietary restrictions, 87%), social interaction (70%), recreation (63%), home management (62%), and ambulation (54%). Only 26% were working 1 year after transplant; 59% of those working reported health-related problems performing their job. Predictors of worse functional status were greater symptom distress, more stressors, more neurologic problems, depression, female sex, older age, and lower left ventricular ejection fraction (worse cardiac function).

CONCLUSIONS

Many HT recipients were still having functional problems and had not reached their full rehabilitation potential by the 1-year anniversary after transplant.

Comparison of cardiac and peripheral arterial stiffening and ventriculovascular uncoupling in patients with uncomplicated hypertension versus patients with hypertension after heart transplantation

Despite normal ejection fractions, patients who undergo heart transplantation (HT) have low peak aerobic capacity and reduced arterial compliance, suggesting "ventriculovascular uncoupling." To what extent this is related to post-transplantation hypertension versus the unique characteristics of the donor-recipient relation remains poorly understood. Echocardiograms were retrospectively reviewed from 126 normal subjects, 309 patients with uncomplicated hypertension (UH), and 58 consecutive patients with HT >1 year after the procedure who were stable without evidence of rejection. Left ventricular (LV) end-systolic elastance (Ees), a measure of LV systolic performance; effective arterial elastance (Ea), a measure of vascular stiffness; and Ea/Ees, a parameter describing ventriculovascular coupling, were obtained. Compared with normal subjects, tandem increases in Ea (+24% and +85%, all p values <0.0001) and Ees (+23% and +33%, all p values <0.0001) were observed in patients with UH and HT, respectively, with patients with HT having significantly higher values than those with UH (both p values <0.05). Although the Ea/Ees ratio remained similar between normal subjects and patients with UH, patients with HT exhibited increases in the Ea/Ees ratio (all p values <0.01) and reduced stroke volume indexes (-20% and -22%, respectively, all p values <0.05). These changes were associated with a doubling of LV concentric remodeling in patients with HT compared with those with UH (67% vs 34%, p <0.0001). In conclusion, HT is associated with increases in Ees, Ea, and the Ea/Ees ratio, suggesting ventriculovascular uncoupling and maximal LV stroke work. These aberrations, which determine cardiovascular performance in the setting of HT, are not simply explained by vascular age or post-transplantation hypertension but may adversely affect functional capacity.

[Exercise training in cardiac patients: usefulness of the cardiopulmonary exercise test]

Exercise training is currently including in the treatment of coronary arterial disease patients, in patients with left ventricular dysfunction as well as in patients who underwent cardiac transplantation or cardiac surgery. However methods of prescribing exercise-training programs are difficult to determine and must be adapted for each patient Exercise test with gas analysis through the determination of anaerobic threshold may help to understand the physiopathological mechanism related to exercise limitation in these patients. Exercise test may help to precise exercise intensity during cardiac rehabilitation and may assess the benefits on exercise tolerance.

Physical functional outcomes after cardiothoracic transplantation

The study of patient healthcare outcomes after cardiothoracic transplantation has increased substantially over the last 2 decades. Physical function after heart, lung, and heart-lung transplantation has been studied using both subjective and objective measures. The majority of reports in the literature on physical function after cardiothoracic transplantation are descriptive and observational. The purposes of the article are to review and critique the existing literature on cardiothoracic recipients' subjective and objective physical function, including respiratory function for heart-lung and lung transplant recipients. In addition, the literature on sexual function in cardiothoracic recipients is examined, the gaps in the literature are identified, and recommendations are given for future research.

Physical Activity Patterns in Heart Transplant Women

Maintaining regular, long-term physical activity is critical to achieve favorable effects of heart transplantation. Yet, at present, little is known about the physical activity patterns of transplant recipients, especially women. The study was conducted to (1) describe levels and types of physical activity using actigraphy and self-report, (2) determine the association between physical activity and sociodemographic variables, and (3) assess the relationship between physical activity, quality of life (QOL), and relevant health indicators (hypertension, hyperlipidemia, and obesity) among female heart transplant recipients. Twenty-seven women (average age, 57 +/- 13 years, primarily Caucasian [82%], retired [89%], married [67%], average time since transplant 2.1 +/- 1.3 years) from a single heart transplant facility were asked to report amount and types of physical activity and overall QOL and wear an actigraph for 1 week to measure physical activity level. Physical activity levels by actigraphy averaged 280,320 +/- 52,416 counts for the week (range, 206,784-354,144); self-reported physical activity level on a 0 to 10 scale was 4.3 +/- 0.37 (range, 0-7). The actigraph and self-reported measures were significantly correlated (r = 0.661, P = .000). It was found that women were more likely to engage in household tasks and family activities than occupational activities or sports. Significant differences in physical activity (F = 6.319, P = .006) were observed in participants who reported fair (n = 13), good (n = 9), and very good (n = 5) overall QOL. The only demographic factor associated with physical activity was age; younger women were more active than older women (r = -0.472, P = .013). A negative correlation was found between levels of physical activity and presence of hypertension, hyperlipidemia, and obesity. It was found that a majority of female transplant recipients remains sedentary. Given the association between physical activity and overall QOL and relevant health indicators, measures to enhance physical activity need to be developed and tested; these strategies may be beneficial in improving overall outcomes.

Time course of physical reconditioning during exercise rehabilitation late after heart transplantation

BACKGROUND

Exercise rehabilitation improves physical capacity in heart transplant recipients. The time course of physical reconditioning and skeletal muscle adaptation late after transplantation are unknown.

METHODS

Twenty-one heart transplant recipients, at 5.2 +/- 2.1 years after transplantation, completed 1 year of an individually tailored home ergometer-training program (2.1 +/- 0.7 sessions weekly with matched heart rates, intensity at 10% below anaerobic threshold). We analyzed time course of physical reconditioning data for each home-training session (n = 2,396). Constant-load tests with consistent blood lactate concentrations were performed quarterly (n = 105) to estimate the time course of skeletal muscle adaptation. Nine heart transplant recipients served as a control group (CG).

RESULTS

After 12 months, exercise capacity for matched heart rates (112 +/- 11 beats/min; CG, 114 +/- 8 beats/min) increased by 35% +/- 19% (from 43 +/- 14 to 58 +/- 18 W; p < 0.001; CG, 53 +/- 18 to 54 +/- 18 W); 24% of the increase was caused by improved skeletal muscle function and 11% by central functioning. Physical reconditioning showed its greatest increase within the first 3 months (+18%; p < 0.001); 50% of the increase consisted of better skeletal muscle or central functioning. Between the 4(th) and 12(th) months, exercise capacity increased continuously (+15%; p < 0.001), mainly because of better skeletal muscle functioning.

CONCLUSIONS

The persistent improvement in exercise capacity along with consistent lactate concentrations during 12 months of training indicates that exercise training could counteract the negative side effects of immunosuppressive treatment on skeletal muscles. Even late after heart transplantation, physical training should be performed regularly to prevent the accelerated decrease in exercise capacity and in skeletal muscle function.

Ventricular-vascular uncoupling increases expression of B-type natriuretic peptide in heart transplantation

BACKGROUND

Allograft adaptation to a foreign circulation is imperfect as noted from persistent limitations to stress. Effective arterial elastance (Ea), a measure of afterload, provides an estimate of aortic impedance. End systolic elastance (Ees) is a load-independent measure of ventricular performance as well as its interaction in the periphery. The ratio (Ea to Ees) characterizes ventricular-vascular coupling; a value close to unity signifies poor mechanical efficiency. The purpose of this investigation was to correlate mechanical efficiency of work with expression of B-type natriuretic peptide BNP, a specific marker of ventricular stress and strain.

METHODS

We measured BNP levels in 40 consecutive stable heart transplant recipients free from rejection. In addition, echocardiography was performed to obtain Ea, Ees, and their ratio (Ea to Ees) by the single-beat method. We examined correlates of BNP expression by assessing Ea to Ees, while correcting for mean arterial pressure, body mass index, left ventricular mass index, ejection fraction, and serum creatinine.

RESULTS

BNP levels were significantly and positively correlated (r=0.38, P=.05) with an increased Ea to Ees ratio. By multivariable analysis, this relationship persisted independently (t=2.1, P=.04), while the five other measures were insignificant predictors.

CONCLUSION

This investigation indicated that the transplanted heart demonstrates poor contractile efficiency and operates at maximal left ventricular work. This is paralleled by a tandem increase in BNP, suggesting that elevation in this stress peptide is at least partly explained by ventriculo-vascular uncoupling in heart transplantation, independent of alterations in blood pressure.

Clinical and Exercise Test Determinants of Survival After Cardiac Transplantation *

BACKGROUND

Cardiac transplantation (CTX) is now a viable option for patients with end-stage heart failure, but there remains a paucity of available donor hearts relative to the demand for them. Establishing prognosis after CTX can help direct this resource to patients most likely to benefit, as well as to help guide therapy for CTX recipients. Clinical, exercise, and hemodynamic factors associated with survival after CTX have not been well established.

METHODS

One hundred seventy-four randomly selected patients who underwent heart transplantation between 1983 and 1999 at Rikshospitalet University Hospital were included in the study. Data were collected as a part of routine posttransplantation management a mean of 3.5 +/- 2.1 years (+/- SD) after CTX. Clinical, cardiopulmonary exercise testing, and hemodynamic measures were performed, including measures of peak oxygen uptake (O(2)), ejection fraction, cardiac index, pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure, creatinine, and the presence of coronary artery disease. Patients were followed up for a mean of 7.1 +/- 2.1 years; all-cause mortality was used as the end point for survival analysis.

RESULTS

During the follow-up period, 39 patients died; the average annual mortality was 3.6%. Peak O(2) was 19.6 +/- 5.6 mL/kg/min, representing 70.5 +/- 6.7% of the age-predicted value. Only right atrial pressure and PCWP differed between those who survived and those who died; both were slightly higher among those who died. By Cox proportional hazard analysis, there were no age-adjusted univariate or multivariate predictors of survival among continuous variables. Exploring various cut points revealed that serum creatinine > 118 micromol/L, PCWP > 12 mm Hg, and mean pulmonary artery pressure > 25 mm Hg were significant univariate predictors of mortality. These cut points for PCWP and pulmonary artery pressure generated hazard ratios of 2.3 and 2.9, respectively.

CONCLUSION

Long-term survival after CTX was comparatively high in our cohort, with 5-year survival > 80%. Standard clinical, hemodynamic, and cardiopulmonary exercise test variables were not strong predictors of mortality in CTX patients a mean of 7 years after CTX. The association between elevated hemodynamic pressures and mortality, although weak, suggests that ventricular compliance, pulmonary vascular resistance, or both, may predict long-term survival after CTX.

Exercise after heart transplantation

Exercise intolerance in heart transplant recipients (HTR) has a multifactorial origin, involving complex interactions among cardiac, neurohormonal, vascular, skeletal muscle and pulmonary abnormalities. However, the role of these abnormalities may differ as a function of time after transplantation and of many other variables. The present review is aimed at evaluating the role of cardiac, pulmonary and muscular factors in limiting maximal aerobic performance of HTR, and the benefits of chronic exercise. Whereas pulmonary function does not seem to affect gas exchange until a critical value of diffusing lung capacity is attained, cardiac and skeletal muscle function deterioration may represent relevant factors limiting maximal and submaximal aerobic performance. Cardiac function is mainly limited by chronotropic incompetence and diastolic dysfunction, whereas muscle activity seems to be limited by impaired oxygen supply as a consequence of the reduced capillary network. The latter may be due to either immunosuppressive regimen or deconditioning. Endurance and strength training may greatly improve muscle function and maximal aerobic performance of HTR, and may also reduce side effects of immunosuppressive therapy and control risk factors for cardiac allograft vasculopathy. For the above reasons exercise should be considered an important therapeutic tool in the long-term treatment of heart transplant recipients.

Physical activity patterns and exercise performance in cardiac transplant recipients

BACKGROUND

Cardiac transplantation (CTX) improves exercise tolerance, but CTX recipients still achieve only 50% to 70% of normal values for exercise capacity. Among the factors suggested to explain the reduced exercise tolerance in CTX recipients is deconditioning. Little is known about the relation between physical activity patterns and exercise test responses in CTX patients.

METHODS

Forty-seven CTX patients (mean age 47 +/- 12 years; mean 4.8 +/- 3.0 years after CTX) underwent maximal exercise testing and assessment of current and past physical activity patterns using a questionnaire. Energy expenditure from recreational and occupational activities over the last year and for adulthood were expressed in kcal/week and correlated with peak oxygen consumption (VO(2)), VO(2) at the ventilatory threshold, and the percentage of age-predicted peak VO(2) achieved.

RESULTS

The patients reported expending a mean of approximately 1100 kcal/week in recreational activity, suggesting a moderate level of physical activity is maintained after CTX. The mean peak VO(2) achieved for the group was 17.2 +/- 5.2 mL/kg/min, corresponding to 59% +/- 14% of age-predicted exercise capacity. Significant but modest associations were observed between recreational energy expenditure during the last year and percentage of age-predicted peak VO(2) achieved (r = 0.34, P <.01), and VO(2) at the ventilatory threshold (r = 0.45, P <.01). Energy expenditure from blocks walked and stairs climbed per week was modestly associated with peak VO(2) (r = 0.36, P <.05), percentage of predicted peak VO(2) achieved (r = 0.39, P <.01), and VO(2) at the ventilatory threshold (r = 0.42, P <.01). Exercise capacity was poorly related to occupational and recreational activities when expressed as average weekly energy expended throughout adulthood.

CONCLUSION

Post-CTX patients maintain a moderately active lifestyle. Measures of exercise tolerance generally are related to recent daily recreational activities in CTX patients, but these associations are modest. The many physiologic factors unique to CTX recipients likely play a more important role than deconditioning in determining exercise tolerance in these patients.

Relationship between impaired pulmonary diffusion and cardiopulmonary exercise capacity after heart transplantation

STUDY OBJECTIVES

Diffusion impairment and reduced performance in cardiopulmonary exercise testing (CPX) have been found in patients after heart transplantation. The pathogenesis of these abnormalities is unclear. In particular, the contribution of pulmonary interstitial changes has not yet been verified.

DESIGN

We analyzed pulmonary function tests, high-resolution CT (HRCT), echocardiography, left heart catheterization, and CPX in transplanted patients.

PATIENTS

Forty long-term survivors were studied at a median of 47 months (range, 12 to 89 months) after heart transplantation.

RESULTS

Diffusion was impaired in 40% (transfer factor for carbon monoxide) or 82.5% (carbon monoxide transfer coefficient) of the patients. Diffusion impairment was caused by a decreased diffusing capacity of the alveolar capillary membrane in 89% and/or by a decreased blood volume of the alveolar capillaries in 46% of cases. In five patients (12.5%), CT revealed interstitial lung changes. These patients did not have different values of diffusion capacity. Maximal oxygen uptake and ventilatory efficiency during exercise (minute ventilation/carbon dioxide output slope) were impaired in 92% and 46% of the cases, respectively.

CONCLUSIONS

Our data show that the diffusion abnormalities are caused by an impaired diffusion status of the alveolar capillary membrane. Interstitial changes detectable in HRCT were found not to be involved in this process. The reduced performance in CPX in our long-term survivors is caused by pulmonary perfusion abnormalities and low tidal volume, which is due to the deconditioning of respiratory muscle, rather than by interstitial changes or diffusion abnormalities.

Optimal cardiac pacing after heart transplantation

The transplanted heart is characterized physiologically by autonomic denervation, chronotropic incompetence, intermittent episodes of allograft rejection, and frequently by diastolic dysfunction. Sinus node dysfunction resulting in bradycardia is common in the early postoperative period following standard orthotopic cardiac transplantation. Bradycardia tends to remit spontaneously but there are no factors that accurately identify patients who will need long-term pacing. Patients in whom bradycardia persists beyond the second postoperative week despite treatment with theophylline require permanent pacemaker implantation. It has been observed that chronotropic incompetence and diastolic dysfunction are important determinants of exercise capacity following heart transplantation. Pacing that restores chronotropic competence improves exercise capacity, confirming the importance of impaired heart rate response. As in other settings, pacing that preserves atrioventricular (AV) synchrony results in increased cardiac output. For these reasons when pacing is necessary we recommend the DDDR mode (AAIR if intact AV nodal conduction is present) so that the 30%-50% of patients who remain pacemaker-dependent long-term obtain maximal benefit from their transplant.