A Review of High-Intensity Interval Training in Heart Transplant Recipients: Current Knowledge and Future Perspectives.

OBJECTIVE: This review reports how exercise-based rehabilitation strategies have developed over the past decades, and it specifically focuses on the effectiveness, safety, and implementation of high-intensity interval training (HIIT). It provides an overview of the historical progression, main research findings, and considerations surrounding HIIT as the preferred exercise modality for recipients of heart transplant (HTx). REVIEW METHODS: The review includes a timeline of studies spanning from 1976-2023. The 2017 Cochrane systematic review on exercise-based cardiac rehabilitation in recipients of HTx serves as the main knowledge base (≥2015). Additionally, literature searches in PubMed/Medline and ClinicalTrials.gov have been performed, and all reviews and studies reporting the effects of moderate- to high-intensity exercise in recipients of HTx, published in 2015 or later have been screened. SUMMARY: High-intensity interval training has gained prominence as an effective exercise intervention for recipients of HTx, demonstrated by an accumulation of performed studies in the past decade, although implementation in clinical practice remains limited. Early restrictions on HIIT in HTx recipients lacked evidence-based support, and recent research challenges these previous restrictions. High-intensity interval training results in greater improvements and benefits compared with moderate-intensity continuous training in the majority of studies. While HIIT is now regarded as generally suitable on a group level, individual assessment is still advised. The impact of HIIT involves reinnervation and central and peripheral adaptations to exercise, with variations in recipent responses, especially between de novo and maintenance recipients, and also between younger and older recipients. Long-term effects and mechanisms behind the HIIT effect warrant further investigation, as well as a focus on optimized HIIT protocols and exercise benefits.

Factors Associated With Sinoatrial Reinnervation After Heart Transplantation.

Background: Factors associated with sympathetic and parasympathetic sinoatrial reinnervation after heart transplantation (HTx) are inadequately studied. Methods: Fifty transplant recipients were examined at 7 to 12 wk (index visit), 6, 12, 24, and 36 mo after HTx. Supine rest heart rate variability in the low-frequency (LF) domain (sympathetic and parasympathetic sinoatrial reinnervation) and the high-frequency (HF) domain (parasympathetic sinoatrial reinnervation) were measured repeatedly and related to selected recipient, donor, and perisurgical characteristics. We primarily aimed to identify index visit factors that affect the sinoatrial reinnervation process. Secondarily, we examined overall associations between indices of reinnervation and repeatedly measured recipient characteristics to generate new hypotheses regarding the consequences of reinnervation. Results: LF and HF variability increased time dependently. In multivariate modeling, a pretransplant diagnosis of nonischemic cardiomyopathy (P = 0.038) and higher index visit handgrip strength (P = 0.028) predicted improved LF variability. Recipient age, early episodes of rejection, and duration of extracorporeal circulation were not associated with indices of reinnervation. Study average handgrip strength was positively associated with LF and HF variability (respectively, P = 0.005 and P = 0.029), whereas study average C-reactive protein was negatively associated (respectively, P = 0.015 and P = 0.008). Conclusions: Indices of both sympathetic and parasympathetic sinoatrial reinnervation increased with time after HTx. A pretransplant diagnosis of nonischemic cardiomyopathy and higher index visit handgrip strength predicted higher indices of mainly sympathetic reinnervation, whereas age, rejection episodes, and duration of extracorporeal circulation had no association. HTx recipients with higher indices of reinnervation had higher average handgrip strength, suggesting a link between reinnervation and improved frailty. The more reinnervated participants had lower average C-reactive protein, suggesting an inhibitory effect of reinnervation on inflammation, possibly through enhanced function of the inflammatory reflex. These potential effects of reinnervation may affect long-term morbidity in HTx patients and should be scrutinized in future research.

Kinetics of Torque Teno virus in heart transplant patients.

End-stage heart failure often requires heart transplantation as a life-prolonging treatment. Immunosuppressive therapy is necessary to avoid rejection, but is associated with serious adverse effects. New approaches are needed to monitor immune function in heart transplant patients. We here report the kinetics of Torque Teno Virus (TTV) after transplantation in a large cohort of heart transplant patients and examine its possible role in predicting rejection. We included 106 patients from Aarhus University Hospital and Oslo University Hospital. Patients were followed for 3 years with clinical assessments, biopsies, TTV measurements, and flowcytometric phenotyping. We observed TTV levels reaching a maximum 3 months after transplantation for all 106 patients, after which levels gradually declined. 38 patients (38 %) had biopsy-proven rejection within the first year. We did not find evidence of an association between TTV and serum trough levels, events of rejection, nor flow cytometric immunophenotype. We report data on a large cohort of heart transplant patients and contribute to the understanding of how TTV behaves in transplant patients. Despite not finding an association with rejection, our results provide important insights into the kinetics of TTV levels after transplantation, which may be useful in future studies of immune function in heart transplant patients.

Effects of high-intensity interval training on cardiac remodelling, function and coronary microcirculation in de novo heart transplant patients: a substudy of the HITTS randomised controlled trial.

Objectives: High-intensity interval training (HIT) improves peak oxygen consumption (VO2peak) in de novo heart transplant (HTx) recipients. It remains unclear whether this improvement early after HTx is solely dependent on peripheral adaptations, or due to a linked chain of central and peripheral adaptations. The objective of this study was to determine whether HIT results in structural and functional adaptations in the cardiovascular system. Methods: Eighty-one de novo HTx recipients were randomly assigned to participate in either 9 months of supervised HIT or standard care exercise-based rehabilitation. Cardiac function was assessed by echocardiogram and the coronary microcirculation with the index of microcirculatory resistance (IMR) at baseline and 12 months after HTx. Results: Cardiac function as assessed by global longitudinal strain was significantly better in the HIT group than in the standard care group (16.3±1.2% vs 15.6±2.2%, respectively, treatment effect = -1.1% (95% CI -2.0% to -0.2%), p=0.02), as was the end-diastolic volume (128.5±20.8 mL vs 123.4±15.5 mL, respectively, treatment effect=4.9 mL (95% CI 0.5 to 9.2 mL), p=0.03). There was a non-significant tendency for IMR to indicate improved microcirculatory function (13.8±8.0 vs 16.8±12.0, respectively, treatment effect = -4.3 (95% CI -9.1 to 0.6), p=0.08). Conclusion: When initiated early after HTx, HIT leads to both structural and functional cardiovascular adaptations. Trial registration number: NCT01796379.

Predictors of Hypertension Development 1 Year After Heart Transplantation.

BACKGROUND: Hypertension after heart transplantation (HTx) is common. We investigated predictors of and mechanisms for hypertension development during the first year after HTx, with particular attention toward immunosuppressive agents, reinnervation processes, and donor/recipient sex. METHODS: Heart transplant recipients (HTxRs) were consecutively enrolled 7 to 12 wk after surgery and followed prospectively for 12 mo. Ambulatory blood pressure recordings and autonomic cardiovascular control assessments were performed at baseline and follow-up. Possible predictors of posttransplant hypertension development were investigated in bivariate linear regression analyses followed by multiple regression modeling. RESULTS: A total of 50 HTxRs were included; 47 attended the follow-up appointment at 12 mo. Mean systolic and diastolic blood pressure increased significantly during the observational period (systolic blood pressure from 133 to 139 mm Hg, P = 0.007; diastolic blood pressure from 81 to 84 mm Hg, P = 0.005). The blood pressure increment was almost exclusively confined to HTxRs with a female donor heart, doubling the cases of systolic hypertension (from 6 to 13/14; 46% to 93%, P = 0.031) and diastolic hypertension (from 7 to 14/14; 54% to 100%, P = 0.031) in this subgroup. Autonomic cardiovascular control assessments suggested tonically constricted resistance and capacitance vessels in recipients with female donor hearts. Immunosuppressive agents and reinnervation markers were not associated with hypertension development. CONCLUSIONS: Blood pressures increase during the first year after HTx, with female donor sex as a strong predictor of recipient hypertension development. The underlying mechanism seems to be enhanced peripheral vasoconstriction caused by attenuated cardiovascular homeostasis capabilities. Further studies are needed to confirm the results.

A randomized clinical study using optical coherence tomography to evaluate the short-term effects of high-intensity interval training on cardiac allograft vasculopathy: a HITTS substudy.

Cardiac allograft vasculopathy (CAV) remains a leading cause of long-term mortality after heart transplantation. Both preventive measures and treatment options are limited. This study aimed to evaluate the short-term effects of high-intensity interval training (HIT) on CAV in de novo heart transplant (HTx) recipients as assessed by optical coherence tomography (OCT). The study population was a subgroup of the 81-patient HITTS study in which HTx recipients were randomized to HIT or moderate intensity continuous training (MICT) for nine consecutive months. OCT images from baseline and 12 months were compared to assess CAV progression. The primary endpoint was defined as the change in the mean intima area. Paired OCT data were available for 56 patients (n = 23 in the HIT group and n = 33 in the MICT group). The intima area in the entire study population increased by 25% [from 1.8±1.4 mm2 to 2.3±2.0 mm2 , P < .05]. The change was twofold higher in the MICT group (.6±1.2 mm2 ) than in the HIT group (.3±.6 mm2 ). However, the treatment effect of HIT was not significant (treatment effect = -.3 mm2 , 95% CI [-.825 to .2 mm2 ] P = .29). These results suggest that early initiation of HIT compared with MICT does not attenuate CAV progression in de novo HTx recipients.

Strong evidence for parasympathetic sinoatrial reinnervation after heart transplantation.

BACKGROUND: Heart transplantation (HTx) surgically denervates the heart. We examined indices of sinoatrial reinnervation, with emphasis on (1) the occurrence and timing of parasympathetic reinnervation, and (2) the consequences of reinnervation for heart rate (HR) responsiveness and arterial baroreceptor sensitivity. METHODS: Fifty HTx recipients were prospectively followed for 36 months after surgery. Hemodynamic variables and heart rate variability were continuously recorded at supine rest, 60 degrees head-up-tilt, during the Valsalva maneuver and during handgrip isometric exercise. RESULTS: Suggesting parasympathetic reinnervation: at baseline rest, root of the mean squared differences of successive RR intervals increased from median 3.9(5.9) to 7.1(5.1) ms (p < 0.001); high-frequency power increased from 4.0(12) to 5.7(18.9) ms2 (p = 0.018); and baroreceptor sensitivity increased from 0.04(0.36) to 1.3(2.4) ms/mmHg (p < 0.001). Suggesting sympathetic reinnervation: at baseline rest low-frequency power increased from 0.49(2.5) to 7.5(18.1) ms2 (p < 0.001); and HR responses to sympathetic stimulation during (1) head-up tilt increased from 1.9(4.2) to 9.1(8.2) bpm (p < 0.001), (2) Valsalva increased from 1.6(1.4) to 8.3(10.8) bpm (p < 0.001) and (3) handgrip increased from 0.3(0.6) to 1.9(5.1) bpm (p < 0.001). Signs of sympathetic reinnervation emerged within 6 months, while signs of parasympathetic reinnervation emerged by 24 months. CONCLUSIONS: Root of the mean squared differences of successive RR intervals, high-frequency and low-frequency variability, HR responsiveness and arterial baroreflex sensitivity all increased after HTx, suggesting functional parasympathetic and sympathetic sinoatrial reinnervation. Accordingly, the pathological regulatory state present in heart transplant recipients, which is responsible for a host of functional and clinical abnormalities, is being partially offset over time by restored autonomic control of the heart in many heart transplant recipients.

Prognostic value of comprehensive intracoronary physiology assessment early after heart transplantation.

AIMS: We evaluated the long-term prognostic value of invasively assessing coronary physiology after heart transplantation in a large multicentre registry. METHODS AND RESULTS: Comprehensive intracoronary physiology assessment measuring fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) was performed in 254 patients at baseline (a median of 7.2 weeks) and in 240 patients at 1 year after transplantation (199 patients had both baseline and 1-year measurement). Patients were classified into those with normal physiology, reduced FFR (FFR ≤ 0.80), and microvascular dysfunction (either IMR ≥ 25 or CFR ≤ 2.0 with FFR > 0.80). The primary outcome was the composite of death or re-transplantation at 10 years. At baseline, 5.5% had reduced FFR; 36.6% had microvascular dysfunction. Baseline reduced FFR [adjusted hazard ratio (aHR) 2.33, 95% confidence interval (CI) 0.88-6.15; P = 0.088] and microvascular dysfunction (aHR 0.88, 95% CI 0.44-1.79; P = 0.73) were not predictors of death and re-transplantation at 10 years. At 1 year, 5.0% had reduced FFR; 23.8% had microvascular dysfunction. One-year reduced FFR (aHR 2.98, 95% CI 1.13-7.87; P = 0.028) and microvascular dysfunction (aHR 2.33, 95% CI 1.19-4.59; P = 0.015) were associated with significantly increased risk of death or re-transplantation at 10 years. Invasive measures of coronary physiology improved the prognostic performance of clinical variables (χ2 improvement: 7.41, P = 0.006). However, intravascular ultrasound-derived changes in maximal intimal thickness were not predictive of outcomes. CONCLUSION: Abnormal coronary physiology 1 year after heart transplantation was common and was a significant predictor of death or re-transplantation at 10 years.

Intravenous iron supplement for iron deficiency in cardiac transplant recipients (IronIC): A randomized clinical trial.

AIMS: Heart transplant recipients have reduced exercise capacity despite preserved graft function. The IronIC trial was designed to test the hypothesis that intravenous iron therapy would improve peak oxygen consumption in these patients. METHODS AND RESULTS: This randomized, placebo-controlled, double-blind trial was performed at our national center for heart transplantation. One hundred and 2 heart transplant recipients with a serum ferritin <100 µg/liter or 100 to 300 µg/liter, in combination with transferrin saturation of <20%, and hemoglobin level >100 g/liter were enrolled ≥1 year after transplantation. A cardiopulmonary exercise test was performed before administration of the study drug and at 6 months follow-up. The primary endpoint was peak oxygen consumption. Key secondary outcomes included iron status, handgrip strength, quality of life, and safety. Fifty-two patients were randomized to receive ferric derisomaltose 20 mg/kg, and 50 to placebo. The between-group difference in baseline-adjusted peak oxygen consumption was 0.3 ml/kg/min (95% confidence interval -0.9 to 1.4, p = 0.66). In patients with a baseline ferritin <30 µg/liter, peak oxygen consumption was significantly higher in the ferric derisomaltose arm. At 6 months, iron stores were restored in 86% of the patients receiving ferric derisomaltose vs 20% in patients receiving placebo (p < 0.001). Quality of life was significantly better in patients receiving ferric derisomaltose. Twenty-seven adverse events occurred in the intravenous iron group vs 30 in the placebo group (p = 0.39). CONCLUSION: Intravenous iron treatment did not improve peak oxygen consumption in heart transplant recipients with ferritin <100 µg/liter or 100 to 300 µg/liter in combination with transferrin saturation <20%. TRIAL REGISTRATION NUMBER: http//www.clinicaltrials.gov identifier NCT03662789.

Functional evidence of low-pressure cardiopulmonary baroreceptor reinnervation 1 year after heart transplantation.

PURPOSE: Heart transplantation (HTx) implies denervation of afferent neural connections. Reinnervation of low-pressure cardiopulmonary baroreceptors might impact the development and treatment of hypertension, but little is known of its occurrence. The present prospective study investigated possible afferent reinnervation of low-pressure cardiopulmonary baroreceptors during the first year after heart transplantation. METHODS: A total of 50 heart transplant recipients (HTxRs) were included and were evaluated 7-12 weeks after transplant surgery, with follow-up 6 and 12 months later. In addition, a reference group of 50 healthy control subjects was examined once. Continuous, non-invasive recordings of cardiovascular variables were carried out at supine rest, during 15 min of 20° head-up tilt, during Valsalva maneuver and during 1 min of 30% maximal voluntary handgrip. In addition, routine clinical data including invasive measurements were used in the analyses. RESULTS: During the first year after HTx, the heart rate (HR) response to 20° head-up tilt partly normalized, a negative relationship between resting mean right atrial pressure and HR tilt response developed, low-frequency variability of the RR interval and systolic blood pressure at supine rest increased, and the total peripheral resistance response to Valsalva maneuver became stronger. CONCLUSION: Functional assessments suggest that afferent reinnervation of low-pressure cardiopulmonary receptors occurs during the first year after heart transplantation, partially restoring reflex-mediated responses to altered cardiac filling.

Early Signs of Sinoatrial Reinnervation in the Transplanted Heart.

BACKGROUND: Heart transplantation (HTx) surgically transects all connections to the heart, including the autonomic nerves. We prospectively examined signs, timing and consequences of early sympathetic and parasympathetic sinoatrial reinnervation, as well as explored indirect evidence of afferent cardiopulmonary reinnervation. METHODS: Fifty HTx recipients were assessed at 2.5, 6, and 12 mo after HTx. For comparison, 50 healthy controls were examined once. Continuous, noninvasive recordings of hemodynamic variables and heart rate variability indices were performed at supine rest, 0.2 Hz controlled breathing, 60° head-up-tilt, during the Valsalva maneuver and during handgrip isometric exercise. RESULTS: In HTx recipients, supine low-frequency heart rate variability gradually increased; supine high-frequency variability did not change; heart rate variability indices during controlled breathing remained unaltered; heart rate responses during tilt and isometric exercise gradually increased; the tachycardia response during Valsalva maneuver increased, while the bradycardia response remained unchanged; and indices of baroreflex sensitivity improved. Responses remained low compared to healthy controls. A negative correlation between indices of preload and heart rate response during head-up tilt emerged at 12 mo. CONCLUSIONS: Results suggest that sympathetic reinnervation of the sinoatrial node starts within 6 mo after HTx and strengthens during the first year. No evidence of early parasympathetic reinnervation was found. Indirect signs of afferent reinnervation of cardiopulmonary low-pressure baroreceptors emerged at 12 mo. Better sympathetic sinoatrial control improved heart rate responsiveness to orthostatic challenge and isometric exercise, as well as heart rate buffering of blood pressure fluctuations.

High-intensity interval training and health-related quality of life in de novo heart transplant recipients - results from a randomized controlled trial.

BACKGROUND: Studies on the effect of high-intensity interval training (HIT) compared with moderate intensity continuous training (MICT) on health-related quality of life (HRQoL) after heart transplantation (HTx) is scarce. No available studies among de novo HTx recipients exists. This study aimed to investigate the effect of HIT vs. MICT on HRQoL in de novo recipients. METHODS: The HITTS study randomized eighty-one de novo HTx recipients to receive either HIT or MICT (1:1). The HIT intervention were performed with 2-4 interval bouts with an intensity of 85-95% of maximal effort. The MICT group exercised at an intensity of 60-80% of their maximal effort with a duration of 25 min. HRQoL was assessed by the Short Form-36 version 2 (SF-36v2) and the Hospital Anxiety and Depression Scale, mean 11 weeks after surgery and after a nine months' intervention. The participants recorded their subjective effect of the interventions on their general health and well-being on a numeric visual analogue scale. Clinical examinations and physical tests were performed. Differences between groups were investigated with independent Student t-tests and with Mann-Whitney U tests where appropriate. Within-group differences were analyzed with Paired-Sample t-tests and Wilcoxon Signed Rank tests. Correlations between SF-36 scores and VO2peak were examined with Pearson's correlations. RESULTS: Seventy-eight participants completed the intervention. Both exercise modes were associated with improved exercise capacity on the physical function scores of HRQoL. Mental health scores remained unchanged. No differences in the change in HRQoL between the groups occurred except for Role Emotional subscale with a larger increase in the HIT arm. Better self-reported physical function was associated with higher VO2peak and muscle strength. CONCLUSION: HIT and MICT resulted in similar mean changes in HRQoL the first year after HTx. Both groups experienced significant improvements in the physical SF-36v2. TRIAL REGISTRATION: ClinicalTrials.gov number: NCT01796379 Registered 18 February 2013.

Effect of high-intensity interval training in young heart transplant recipients: results from two randomized controlled trials.

BACKGROUND: Little is known about the effect of exercise in young heart transplant recipients, and results on group level is lacking. This study summarizes the findings of the youngest participants in two previous randomized controlled trials. METHOD: This is a hypothesis-generating study reporting the main results from the youngest participants in two larger randomized controlled trials investigating the effect of high-intensity interval training (HIT). The article summarizes the main results from 28 young participants (< 40 year of age) who have participated in two previous studies which evaluated the effect of HIT vs. controls in adult heart transplant recipients. One of the studies included de novo heart transplant recipients and the other included maintenance heart transplant recipients.All study tests were performed in-hospital, in the specialist health care setting, but the exercise intervention was carried out locally, in cooperation with the primary health care. In both studies the exercise intervention lasted for 9-12 months. In one study, HIT (85-95% of peak effort) was compared to controls (no specific intervention), and in the other study HIT was compared to moderate, continuous exercise (MICT, 60-80% of peak effort). The main outcome measure was peak oxygen uptake (VO2peak) and a secondary endpoint was muscle strength. RESULTS: The summarized findings from the youngest heart transplant recipients in these two studies demonstrated mainly that the improvement in peak oxygen uptake among the younger recipients (< 40 years) was much larger (4.7 vs. 1.2 ml/kg/min and 7.0 vs. 2.2 ml/kg/min) compared to the improvement among the older recipients (≥ 40 years), and in accordance with results from adult heart transplant populations: HIT, compared to MICT, induced the largest improvement in peak oxygen consumption, also in the younger heart transplant recipients. CONCLUSIONS: These results suggest that young heart transplant recipients have a greater effect of HIT than of MICT and may also suggest that younger recipients benefit more from high-intensity interval training than their older co-patients. However, larger randomized studies focusing on the young heart transplant population is strongly needed to confirm this hypothesis. TRIAL REGISTRATION: Clinical trial registrations: NCT01796379 and NCT01091194.

Long-term effects of high-intensity training vs moderate intensity training in heart transplant recipients: A 3-year follow-up study of the randomized-controlled HITTS study.

The randomized controlled High-Intensity Interval Training in De Novo Heart Transplant Recipients in Scandinavia (HITTS) study compared 9 months of high-intensity interval training (HIT) with moderate intensity continuous training in de novo heart transplant recipients. In our 3-year follow-up study, we aimed to determine whether the effect of early initiation of HIT on peak oxygen consumption (VO2peak ) persisted for 2 years postintervention. The study's primary end point was the change in VO2peak (mL/kg/min). The secondary end points were muscle strength, body composition, heart rate response, health-related quality of life, daily physical activity, biomarkers, and heart function. Of 78 patients who completed the 1-year HITTS trial, 65 entered our study and 62 completed the study tests. VO2peak increased from baseline to 1 year and leveled off thereafter. During the intervention period, the increase in VO2peak was larger in the HIT arm; however, 2 years later, there was no significant between-group difference in VO2peak . However, the mean change in the anaerobic threshold and extensor muscle endurance remained significantly higher in the HIT group. Early initiation of HIT after heart transplantation appears to have some sustainable long-term effects. Clinical trial registration number: NCT01796379.

Autonomic cardiovascular control changes in recent heart transplant recipients lead to physiological limitations in response to orthostatic challenge and isometric exercise.

PURPOSE: Heart transplantation causes denervation of the donor heart, but the consequences for cardiovascular homeostasis remain to be fully understood. The present study investigated cardiovascular autonomic control at supine rest, during orthostatic challenge and during isometric exercise in heart transplant recipients (HTxR). METHODS: A total of 50 HTxRs were investigated 7-12 weeks after transplant surgery and compared with 50 healthy control subjects. Continuous, noninvasive recordings of cardiovascular variables were carried out at supine rest, during 15 min of 60° head-up tilt and during 1 min of 30% of maximal voluntary handgrip. Plasma and urine catecholamines were assayed, and symptoms were charted. RESULTS: At supine rest, heart rate, blood pressures and total peripheral resistance were higher, and stroke volume and end diastolic volume were lower in the HTxR group. During tilt, heart rate, blood pressures and total peripheral resistance increased less, and stroke volume and end diastolic volume decreased less. During handgrip, heart rate and cardiac output increased less, and stroke volume and end diastolic volume decreased less. Orthostatic symptoms were similar across the groups, but the HTxRs complained more of pale and cold hands. CONCLUSION: HTxRs are characterized by elevated blood pressures and total peripheral resistance at supine rest as well as attenuated blood pressures and total peripheral resistance responses during orthostatic challenge, possibly caused by low-pressure cardiopulmonary baroreceptor denervation. In addition, HTxRs show attenuated cardiac output response during isometric exercise due to efferent sympathetic denervation. These physiological limitations might have negative functional consequences.

Effect of High-Intensity Interval Training in De Novo Heart Transplant Recipients in Scandinavia.

BACKGROUND: There is no consensus on how, when, or at what intensity exercise should be performed after heart transplantation (HTx). We have recently shown that high-intensity interval training (HIT) is safe, well tolerated, and efficacious in the maintenance state after HTx, but studies have not investigated HIT effects in the de novo HTx state. We hypothesized that HIT could be introduced early after HTx and that it could lead to clinically meaningful increases in exercise capacity and health-related quality of life. METHODS: This multicenter, prospective, randomized, controlled trial included 81 patients a mean of 11 weeks (range, 7-16 weeks) after an HTx. Patients were randomized 1:1 to 9 months of either HIT (4×4-minute intervals at 85%-95% of peak effort) or moderate-intensity continuous training (60%-80% of peak effort). The primary outcome was the effect of HIT versus moderate-intensity continuous training on the change in aerobic exercise capacity, assessed as the peak oxygen consumption (Vo2peak). Secondary outcomes included tolerability, safety, adverse events, isokinetic muscular strength, body composition, health-related quality of life, left ventricular function, hemodynamics, endothelial function, and biomarkers. RESULTS: From baseline to follow-up, 96% of patients completed the study. There were no serious exercise-related adverse events. The population comprised 73% men, and the mean±SD age was 49±13 years. At the 1-year follow-up, the HIT group demonstrated greater improvements than the moderate-intensity continuous training group; the groups showed significantly different changes in the Vo2peak (mean difference between groups, 1.8 mL·kg-1·min-1), the anaerobic threshold (0.28 L/min), the peak expiratory flow (11%), and the extensor muscle exercise capacity (464 J). The 1.8-mL·kg-1·min-1 difference was equal to ≈0.5 metabolic equivalents, which is regarded as clinically meaningful and relevant. Health-related quality of life was similar between the groups, as indicated by results from the Short Form-36 (version 2), Hospital Anxiety and Depression Scale, and a visual analog scale. CONCLUSIONS: We demonstrated that HIT was a safe, efficient exercise method in de novo HTx recipients. HIT, compared with moderate-intensity continuous training, resulted in a clinically significantly greater change in exercise capacity based on the Vo2peak values (25% versus 15%), anaerobic threshold, peak expiratory flow, and muscular exercise capacity. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier NCT01796379.

Clinical features and determinants of VO2peak in de novo heart transplant recipients.

AIM: To study exercise capacity and determinants of early peak oxygen consumption (VO2peak) in a cohort of de novo heart transplant (HTx) recipients. METHODS: To determine possible central (chronotropic responses, cardiopulmonary and hemodynamic function) and peripheral factors (muscular exercise capacity and body composition) predictive of VO2peak, a number of different measurements and tests were performed, as follows: Cardiopulmonary exercise testing (CPET) was performed mean 11 wk after surgery in 81 HTx recipients > 18 years and was measured with breath by breath gas exchange on a treadmill or bicycle ergometer. Metabolic/respiratory measures include VO2peak and VE/VCO2 slope. Additional measures included muscle strength testing, bioelectrical impedance analysis, echocardiography, blood sampling and health-related quality of life. Based on the VO2peak (mL/kg per minute) median value, the study population was divided into two groups defined as a low-capacity group and a high-capacity group. Potential predictors were analyzed using multiple regression analysis with VO2peak (L/min) as the dependent variable. RESULTS: The mean ± standard deviation (SD) age of the total study population was 49 ± 13 years, and 73% were men. This de novo HTx cohort demonstrated a median VO2peak level of 19.4 mL/kg per min at 11 ± 1.8 wk post-HTx. As compared with the high-capacity group, the low-capacity group exercised for a shorter time, had lower maximal ventilation, O2 pulse, peak heart rate and heart rate reserve, while the VE/VCO2 slope was higher. The low-capacity group had less muscle strength and muscular exercise capacity in comparison with the high-capacity group. In order of importance, O2 pulse, heart rate reserve, muscular exercise capacity, body mass index, gender and age accounted for 84% of the variance in VO2peak (L/min). There were no minor or major serious adverse events during the CPET. CONCLUSION: Although there is great individual variance among de novo HTx recipients, early VO2peak measures appear to be influenced by both central and peripheral factors.

Agreement between PG-SGA category and fat-free mass in colorectal cancer patients.

BACKGROUND AND AIMS: Low fat-free mass (FFM) is associated with adverse outcomes in colorectal cancer (CRC) patients. Patient-Generated Subjective Global Assessment (PG-SGA) is a widely used tool developed to detect patients with malnutrition or at risk of malnutrition. The aim of this study was to investigate the agreement between PG-SGA category and FFM in patients with non-metastatic CRC. METHODS: Ninety-seven patients were included and categorized as well nourished (PG-SGA:A, n = 67) or malnourished (PG-SGA:B, n = 30). No patients were severely malnourished (PG-SGA: C). Bioelectrical impedance analysis (BIA) was used to assess FFM. Low FFM was defined as low fat-free mass index (FFMI) according to cut-off values recently proposed by The European Society for Clinical Nutrition and Metabolism (ESPEN). RESULTS: Twenty-nine percent of the patients were identified with low FFMI. The proportion with low FFMI was significantly higher among patients classified as malnourished by PG-SGA compared to well nourished (p = 0.015). The sensitivity was however low, as the PG-SGA categorization classified only 50.0% of the patients with low FFMI as malnourished (PG-SGA B). Using the PG-SGA scores (cut-off point > 4), the sensitivity increased to 60.7%. Physical examination in the PG-SGA identified only 64.3% of the patients with low FFMI as muscle depleted. CONCLUSION: Our results indicate a low agreement between PG-SGA category and low FFMI among patients with non-metastatic CRC. In clinical practice, PG-SGA should be supplemented by muscle mass assessments by BIA or other methods in order to detect low FFM in this patient group.

Long-term effects of high-intensity interval training in heart transplant recipients: A 5-year follow-up study of a randomized controlled trial.

BACKGROUND: Previous studies have demonstrated that high-intensity interval training (HIT) is superior to moderate-continuous exercise in general and in cardiovascular diseases. Recently, we also found HIT safe and efficient after heart transplantation (HTx). This study reports the 5-year long-term effects. DESIGN AND METHODS: Forty-one HTx patients who had completed the previous 12-month randomized controlled trial, comparing HIT intervention with usual care, were eligible. In particular, we measured VO2peak , muscular capacity, intravascular ultrasound, and questionnaires measuring physical and mental health. RESULTS: The baseline mean±SD values were as follows: age; 49.1±16.5 years, men; 68%, time since HTx: 4.1±2.2 years. Within the HIT group, initial VO2peak increased significantly from 27.7±5.7 to 31.2±5.3 mL/kg/min. However, during the next 4 years, VO2peak decreased to 26.0±6.2 mL/kg/min. The control group showed slightly decreasing VO2peak values during the entire 5-year period. The HIT group reported significantly less anxiety symptoms, but there were no long-term differences in VO2peak , muscular capacity, or cardiac allograft vasculopathy between the groups. The similar VO2peak values correspond to our findings of similar everyday activity. CONCLUSION: Our findings suggest that intermittent periods of HIT may be necessary to maintain the initial benefits gained from the intervention. However, HIT probably reduces the burden of anxiety, which is a frequent health issue following HTx.