Cardiorespiratory Fitness (Peak Oxygen Uptake): Safe and Effective Measure for Cardiovascular Screening Before Kidney Transplant

Measurement properties of performance-based measures to assess physical function in chronic kidney disease: recommendations from a COSMIN systematic review

Background

There is wide heterogeneity in physical function tests available for clinical and research use, hindering our ability to synthesize evidence. The aim of this review was to identify and evaluate physical function measures that could be recommended for standardized use in chronic kidney disease (CKD).

Methods

MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, CINAHL, Scopus and Web of Science were searched from inception to March 2022, identifying studies that evaluated a clinimetric property (validity, reliability, measurement error and/or responsiveness) of an objectively measured performance-based physical function outcomes using the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) based recommendations. Studies with individuals of all ages and of any stage of CKD were included.

Results

In total, 50 studies with 21 315 participants were included. Clinimetric properties were reported for 22 different physical function tests. The short physical performance battery (SPPB), Timed-up-and-go (TUG) test and Sit-to-stand tests (STS-5 and STS-60) had favorable properties to support their use in CKD and should be integrated into routine use. However, the majority of studies were conducted in the hemodialysis population, and very few provided information regarding validity or reliability.

Conclusion

The SPPB demonstrated the highest quality of evidence for reliability, measurement error and construct validity amongst transplant, CKD and dialysis patients. This review is an important step towards standardizing a core outcome set of tools to measure physical function in research and clinical settings for the CKD population.

Cardiopulmonary exercise testing in patients with end-stage kidney disease: principles, methodology and clinical applications of the optimal tool for exercise tolerance evaluation

Chronic kidney disease (CKD), especially end-stage kidney disease (ESKD), is associated with an increased risk for cardiovascular events and all-cause mortality. Exercise intolerance as well as reduced cardiovascular reserve is extremely common in patients with CKD. Cardiopulmonary exercise testing (CPET) is a non-invasive, dynamic technique that provides an integrative evaluation of cardiovascular, pulmonary, neuropsychological and metabolic function during maximal or submaximal exercise, allowing the evaluation of functional reserves of these systems. This assessment is based on the principle that system failure typically occurs when the system is under stress and thus CPET is currently considered to be the gold standard for identifying exercise limitation and differentiating its causes. It has been widely used in several medical fields for risk stratification, clinical evaluation and other applications, but its use in everyday practice for CKD patients is scarce. This article describes the basic principles and methodology of CPET and provides an overview of important studies that utilized CPET in patients with ESKD, in an effort to increase awareness of CPET capabilities among practicing nephrologists.

The Comparison of High-Intensity Interval Training Versus Moderate-Intensity Continuous Training after Coronary Artery Bypass Graft: A Systematic Review of Recent Studies

Currently, no international consensus on cardiac rehabilitation exists, leading to great variability in the intensity recommendations for training programs for cardiac patients, including those undergoing coronary artery bypass graft surgery (CABG). While some countries prefer the high-intensity interval training (HIIT) method to improve cardiorespiratory fitness, other countries opt for moderate-intensity continuous training (MICT). The aim of this systematic review was to compare the effects of HIIT and MICT on aerobic fitness and quality of life (QoL) in patients undergoing CABG with the intention of providing support for a consensus on exercise therapy.

METHODS

A systematic review of randomized controlled trials (RCTs) was conducted using the online publication databases PubMed, the Cochrane Library and the Bibliothèque nationale du Luxembourg (BnL) covering the last ten years to July 2022. Relevant identified studies respecting the inclusion/exclusion criteria were selected, screened and extracted by four reviewers. Furthermore, the methodological quality of the clinical trials was assessed using the PEDro scale, which was reinforced using the Cochrane Risk of Bias Tool for Randomized Trials (RoB2) for the evaluation of the risk of bias to provide more detail in the evaluation. The certainty of the evidence analysis was established using different levels of evidence in accordance with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework.

RESULTS

A total of 379 patients from five RCTs diagnosed with coronary artery disease, including patients undergoing CABG, performed aerobic exercise over different time periods and were assessed based on peakVO2, VO2max and QoL. Overall, both training methods provided improvements in cardiorespiratory fitness and quality of life, with greater changes in HIIT groups.

CONCLUSION

Both trainings methods provide improvements in cardiorespiratory fitness and QoL, with greater increases from HIIT. The moderate quality of evidence supports the use of HIIT and MICT to improve cardiorespiratory fitness and QoL.

Prognostic Value of Exercise Capacity in Kidney Transplant Candidates

Background Exercise stress testing for cardiovascular assessment in kidney transplant candidates has been shown to be a feasible alternative to pharmacologic methods. Exercise stress testing allows the additional assessment of exercise capacity, which may have prognostic value for long-term cardiovascular outcomes in pre-transplant recipients. This study aimed to evaluate the prognostic value of exercise capacity on long-term cardiovascular outcomes in kidney transplant candidates. Methods and Results We retrospectively evaluated exercise capacity in 898 consecutive kidney transplant candidates between 2013 and 2020 who underwent symptom-limited exercise stress echocardiography for pre-transplant cardiovascular assessment. Exercise capacity was measured by age- and sex-predicted metabolic equivalents (METs). The primary outcome was incident major adverse cardiovascular events, defined as cardiac death, non-fatal myocardial infarction, and stroke. Cox proportional hazard multivariable modeling was performed to define major adverse cardiovascular events predictors with transplantation treated as a time-varying covariate. A total of 429 patients (48%) achieved predicted METs. During follow-up, 93 (10%) developed major adverse cardiovascular events and 525 (58%) underwent transplantation. Achievement of predicted METs was independently associated with reduced major adverse cardiovascular events (hazard ratio [HR] 0.49; [95% CI 0.29-0.82], P=0.007), as was transplantation (HR, 0.52; [95% CI 0.30-0.91], P=0.02). Patients achieving predicted METs on pre-transplant exercise stress echocardiography had favorable outcomes that were independent (HR, 0.78; [95% CI 0.32-1.92], P=0.59) and of similar magnitude to subsequent transplantation (HR, 0.97; [95% CI 0.42-2.25], P=0.95). Conclusions Achievement of predicted METs on pre-transplant exercise stress echocardiography confers excellent prognosis independent of and of similar magnitude to subsequent kidney transplantation. Future studies should assess the benefit on exercise training in this population.

Outcomes and Health Care Utilization After Early Hospital Dismissal in Kidney Transplantation: An Analysis of 1001 Consecutive Cases

OBJECTIVE

To understand whether reduced lengths of stay after kidney transplantation were associated with excess health care utilization in the first 90 days or long-term graft and patient survival outcomes.

BACKGROUND

Reducing length of stay after kidney transplant has an unknown effect on post-transplant health care utilization. We studied this association in a cohort of 1001 consecutive kidney transplants.

METHODS

We retrospectively reviewed 2011-2015 data from a prospectively-maintained kidney transplant database from a single center.

RESULTS

A total of 1001 patients underwent kidney transplant, and were dismissed from the hospital in 3 groups: Early [≤2 days] (19.8%), Normal [3-7 days] (79.4%) and Late [>7 days] (3.8%). 34.8% of patients had living donor transplants (Early 51%, Normal 31.4%, Late 18.4%, P < 0.001). Early patients had lower delayed graft function rates (Early 19.2%, Normal 32%, Late73.7%, P = 0.001). By the hospital dismissal group, there were no differences in readmissions or emergency room visits at 30 or 90 days. Glomerular filtration rate at 12 months and rates of biopsy-proven acute rejection were also similar between groups. The timing of hospital dismissal was not associated with the risk-adjusted likelihood of readmission. Early and Normal patients had similar graft and patient survival. Late dismissal patients, who had higher rates of cardiovascular complications, had significantly higher late mortality versus Normal dismissal patients in unadjusted and risk-adjusted models.

CONCLUSION

Dismissing patients from the hospital 2 days after kidney transplant is safe, feasible, and improves value. It is not associated with excess health care utilization or worse short or long-term transplant outcomes.

Association of physical function and performance with peak VO2 in elderly patients with end stage kidney disease

BACKGROUND

Physical function is impaired in end stage renal disease (ESRD). Various instruments have been used to assess the functional capabilities and health status of patients with ESRD, but it is not known which has the best association with peak VO₂.

AIMS

To assess the association between functional measures in ESRD.

METHODS

Thirty nine elderly ESRD patients were evaluated with commonly used functional, health status, and quality of life measures, including maximal cardiopulmonary exercise testing (CPET), 6-min walk (6MWT), sit-to-stand test (STS), Veterans Specific Activity Questionnaire (VSAQ), upper and lower body strength, pulmonary function tests, and body composition determined by dual X-ray absorptiometry. The association between performance on these functional tools, clinical variables, and exercise test responses was assessed, and a non-exercise test multivariate model was developed to predict peak VO₂.

RESULTS

Peak VO₂ was modestly related to VSAQ score (r = 0.59, p < 0.01), indices of upper and lower body strength (r = 0.45, p < 0.01 for both), and FEV₁ (r = 0.51, p < 0.01). Functional and quality of life questionnaires were generally poorly related to one another and to peak VO₂. In a multivariate model, 6MWT performance, forced expiratory volume in 1 s (FEV₁), and VSAQ score were the best predictors of peak VO₂, yielding a multiple R = 0.82, accounting for 67% of the variance in peak VO₂.

CONCLUSION

Exercise capacity can be reasonably estimated using non-exercise test variables in patients with ESRD, including a symptom questionnaire (VSAQ), 6MWT and FEV₁.

CLINICAL TRIAL INFORMATION

ClinicalTrials.gov identifier: NCT01990495. Registered Nov 21, 2013.

Making Cardiopulmonary Exercise Testing Interpretable for Clinicians

ABSTRACT

Cardiopulmonary exercise testing (CPET) is a dynamic clinical tool for determining the cause for a person's exercise limitation. CPET provides clinicians with fundamental knowledge of the coupling of external to internal respiration (oxygen and carbon dioxide) during exercise. Subtle perturbations in CPET parameters can differentiate exercise responses among individual patients and disease states. However, perhaps because of the challenges in interpretation given the amount and complexity of data obtained, CPET is underused. In this article, we review fundamental concepts in CPET data interpretation and visualization. We also discuss future directions for how to best use CPET results to guide clinical care. Finally, we share a novel three-dimensional graphical platform for CPET data that simplifies conceptualization of organ system-specific (cardiac, pulmonary, and skeletal muscle) exercise limitations. Our goal is to make CPET testing more accessible to the general medical provider and make the test of greater use in the medical toolbox.

Performance versus Risk Factor-Based Approaches to Coronary Artery Disease Screening in Waitlisted Kidney Transplant Candidates

INTRODUCTION

Current screening algorithms for coronary artery disease (CAD) before kidney transplantation result in many tests but few interventions.

OBJECTIVE

The aim of this study was to study the utility of 6-minute walk test (6MWT), an office-based test of cardiorespiratory fitness, for risk stratification in this setting.

METHODS

We enrolled 360 patients who are near the top of the kidney transplant waitlist at our institution. All patients underwent CAD evaluation irrespective of 6MWT results. We examined the association between 6MWT and time to CAD-related events (defined as cardiac death, revascularization, nonfatal myocardial infarction, and removal from the waitlist for CAD), treating noncardiac death and waitlist removal for non-CAD reasons as competing events.

RESULTS

The 6MWT-based approach designated approximately 45% of patients as "low risk," whereas a risk factor- or symptom-based approach designated 14 and 81% of patients as "low risk," respectively. The 6MWT-based approach was not significantly associated with CAD-related events within 1 year (subproportional hazard ratio [sHR] 1.00 [0.90-1.11] per 50 m) but was significantly associated with competing events (sHR 0.70 [0.66-0.75] per 50 m). In a companion analysis, removing waitlist status from consideration, 6MWT result was associated with the development of CAD-related events (sHR 0.92 [0.84-1.00] per 50 m).

CONCLUSIONS

The 6MWT designates fewer patients as high risk and in need of further testing (compared to risk factor-based approaches), but its utility as a pure CAD risk stratification tool is modulated by the background waitlist removal rate. CAD screening before kidney transplant should be tailored according to a patient's actual chance of receiving a transplant.

Efficacy of aerobic exercise on the cardiometabolic and renal outcomes in patients with chronic kidney disease: a systematic review of randomized controlled trials

BACKGROUND

Several randomized controlled trials (RCTs) have demonstrated the cardiometabolic effects of aerobic exercise in the general population and in patients with cardiovascular diseases. However, the efficacy of aerobic exercise in patients with chronic kidney disease (CKD) remains to be elucidated.

METHODS

RCTs comparing aerobic exercise with no aerobic exercise in patients with CKD not requiring kidney replacement therapy were identified through PubMed using RobotAnalyst, a web-based software system that combines text-mining and machine learning algorithms for organizing references. Cardiometabolic and renal outcomes of interest included body mass index (BMI); systolic blood pressure (SBP); hemoglobin A1c (HbA1c), total cholesterol (TCHO), low- and high- density lipoprotein cholesterol (LDLC and HDLC, respectively), and urinary protein (UP) levels/concentration; peak oxygen uptake (Vo₂peak); and glomerular filtration rate (GFR) at the end of the follow-up period. The standardized mean difference (SMD) of each outcome was estimated using the DerSimonian-Laird random-effect model with inverse-variance weighting.

RESULTS

A total of 15 trials, including 622 patients, were included. Their follow-up periods were 3-4, 6-12, and > 12-months in 7 (46.7%), 7 (46.7%), and 1 (6.7%) trial(s), respectively. Meta-analyses showed that aerobic exercise significantly decreased BMI (SMD, -0.19 [95% confidence interval, -0.38, -0.00]) and SBP (-0.75 [-1.24, -0.26]) and increased Vo₂peak (0.54 [0.29, 0.78]); however, no significant association was observed in HbA1c, TCHO, HDLC, LDLC, GFR, and UP. Meta-regression models suggested that aerobic exercise was more likely to improve Vo₂peak in patients with younger age, no diabetes, and lower BMI.

CONCLUSION

Aerobic exercise of 3-12 months' duration improved obesity, high blood pressure, and low exercise capacity in overweight/obese patients with CKD, but it had no significant effect on GFR and proteinuria. Well-designed large RCTs with a longer follow-up period are needed to evaluate the efficacy of aerobic exercise in patients with CKD.

Assessing physical activity and function in patients with chronic kidney disease: a narrative review

Physical activity potentially improves health outcomes in patients with chronic kidney disease (CKD) and recipients of kidney transplants. Although studies have demonstrated the beneficial effects of physical activity and exercise for primary and secondary prevention of non-communicable diseases, evidence for kidney patients is limited. To enlarge this evidence, valid assessment of physical activity and exercise is essential. Furthermore, CKD is associated with a decline in physical function, which may result in severe disabilities and dependencies. Assessment of physical function may help clinicians to monitor disease progression and frailty in patients receiving dialysis. The attention on physical function and physical activity has grown and new devices have been developed and (commercially) launched on the market. Therefore the aims of this review were to summarize different measures of physical function and physical activity, provide an update on measurement instruments and discuss options for easy-to-use measurement instruments for day-to-day use by CKD patients. This review demonstrates that large variation exists in the different strategies to assess physical function and activity in clinical practice and research settings. To choose the best available method, accuracy, content, preferable outcome, necessary expertise, resources and time are important issues to consider.