Predicting maximal HR in heart failure patients on β-blockade therapy

Accurate Prediction Equations for Ventilatory Thresholds in Cardiometabolic Disease When Gas Exchange Analysis is Unavailable: Development and Validation

AIMS

To develop and validate equations predicting heart rate (HR) at the first and second ventilatory thresholds (VTs) and an optimized range-adjusted prescription for patients with cardiometabolic disease (CMD). To compare their performance against guideline-based exercise intensity domains.

METHODS

Cross-sectional study involving 2,868 CMD patients from nine countries. HR predictive equations for first and second VTs (VT1, VT2) were developed using multivariate linear regression with 975 cycle-ergometer cardiopulmonary exercise tests (CPET). 'Adjusted' percentages of peak HR (%HRpeak) and HR reserve (%HRR) were derived from this group. External validation with 1,893 CPET (cycle-ergometer or treadmill) assessed accuracy, agreement, and reliability against guideline-based %HRpeak and %HRR prescriptions using mean absolute percentage error (MAPE), Bland-Altman analyses, intraclass correlation coefficients (ICC).

RESULTS

HR predictive equations (R²: 0.77 VT1, 0.88 VT2) and adjusted %HRR (VT1: 42%, VT2: 77%) were developed. External validation demonstrated superiority over widely used guideline-directed intensity domains for %HRpeak and %HRR. The new methods showed consistent performance across both VTs with lower MAPE (VT1: 7.1%, VT2: 5.0%), 'good' ICC for VT1 (0.81, 0.82) and 'excellent' for VT2 (0.93). Guideline-based exercise intensity domains had higher MAPE (VT1: 6.8%-21.3%, VT2: 5.1%-16.7%), 'poor' to 'good' ICC for VT1, and 'poor' to 'excellent' for VT2, indicating inconsistencies related to specific VTs across guidelines.

CONCLUSION

Developed and validated HR predictive equations and the optimized %HRR for CMD patients for determining VT1 and VT2 outperformed the guideline-based exercise intensity domains and showed ergometer interchangeability. They offer a superior alternative for prescribing moderate intensity exercise when CPET is unavailable.

2023 TAMIS/TSOC/TACVPR Consensus Statement for Patients with Acute Myocardial Infarction Rehabilitation

Cardiac rehabilitation is a comprehensive intervention recommended in international and Taiwanese guidelines for patients with acute myocardial infarction. Evidence supports that cardiac rehabilitation improves the health-related quality of life, enhances exercise capacity, reduces readmission rates, and promotes survival in patients with cardiovascular disease. The cardiac rehabilitation team is comprehensive and multidisciplinary. The inpatient, outpatient, and maintenance phases are included in cardiac rehabilitation. All patients admitted with acute myocardial infarction should be referred to the rehabilitation department as soon as clinically feasible. Pre-exercise evaluation, including exercise testing, helps physicians identify the risks of cardiac rehabilitation and organize appropriate exercise prescriptions. Therefore, the Taiwan Myocardial Infarction Society (TAMIS), Taiwan Society of Cardiology (TSOC), and Taiwan Academy of Cardiovascular and Pulmonary Rehabilitation (TACVPR) address this consensus statement to assist healthcare practitioners in performing cardiac rehabilitation in patients with acute myocardial infarction.

Among Patients Taking Beta-Adrenergic Blockade Therapy, Use Measured (Not Predicted) Maximal Heart Rate to Calculate a Target Heart Rate for Cardiac Rehabilitation

PURPOSE

Among patients in cardiac rehabilitation (CR) on beta-adrenergic blockade (βB) therapy, this study describes the frequency for which target heart rate (THR) values computed using a predicted maximal heart rate (HR max ), correspond to a THR computed using a measured HR max in the guideline-based heart rate reserve (HR reserve ) method.

METHODS

Before CR, patients completed a cardiopulmonary exercise test to measure HR max , with the data used to determine THR via the HR reserve method. Additionally, predicted HR max was computed for all patients using the 220 - age equation and two disease-specific equations, with the predicted values used to calculate THR via the straight percent and HR reserve methods. The THR was also computed using resting heart rate (HR) +20 and +30 bpm.

RESULTS

Mean predicted HR max using the 220 - age equation (161 ± 11 bpm) and the disease-specific equations (123 ± 9 bpm) differed ( P < .001) from measured HR max (133 ± 21 bpm). Also, THR computed using predicted HR max resulted in values that were infrequently within the guideline-based HR reserve range calculated using measured HR max . Specifically, 0 to ≤61% of patients would have had an exercise training HR that fell within the guideline-based range of 50-80% of measured HR reserve . Use of standing resting HR +20 or +30 bpm would have resulted in 100% and 48%, respectively, of patients exercising below 50% of HR reserve .

CONCLUSIONS

A THR computed using either predicted HR max or resting HR +20 or +30 bpm seldom results in a prescribed exercise intensity that is consistent with guideline recommendations for patients in CR.

Old and new equations for maximal heart rate prediction in patients with heart failure and reduced ejection fraction on beta-blockers treatment: results from the MECKI score data set

AIMS

Predicting maximal heart rate (MHR) in heart failure with reduced ejection fraction (HFrEF) still remains a major concern. In such a context, the Keteyian equation is the only one derived in a HFrEF cohort on optimized β-blockers treatment. Therefore, using the Metabolic Exercise combined with Cardiac and Kidney Indexes (MECKI) data set, we looked for a possible MHR equation, for an external validation of Keteyien formula and, contextually, for accuracy of the historical MHR formulas and their relationship with the HR measured at the anaerobic threshold (AT).

METHODS AND RESULTS

Data from 3487 HFrEF outpatients on optimized β-blockers treatment from the MECKI data set were analyzed. Besides excluding all possible confounders, the new equation was derived by using HR data coming from maximal cardiopulmonary exercise test. The simplified derived equation was [109-(0.5*age) + (0.5*HR rest) + (0.2*LVEF)-(5 if haemoglobin <11 g/dL)]. The R2 and the standard error of the estimate were 0.24 and 17.5 beats min-1 with a mean absolute percentage error (MAPE) = 11.9%. The Keteyian equation had a slightly higher MAPE = 12.3%. Conversely, the Fox and Tanaka equations showed extremely higher MAPE values. The range 75-80% of MHR according to the new and the Keteyian equations was the most accurate in identifying the HR at the AT (MAPEs = 11.3-11.6%).

CONCLUSION

The derived equation to estimate the MHR in HFrEF patients, by accounting also for the systolic dysfunction degree and anaemia, improved slightly the Keteyian formula. Both formulas might be helpful in identifying the true maximal effort during an exercise test and the intensity domain during a rehabilitation programme.

Estimating VO2peak in 18–90 Year-Old Adults: Development and Validation of the FitMáx©-Questionnaire

Purpose

Cardiorespiratory fitness (CRF) plays an essential role in health outcomes and quality of life. However, it is often not assessed nor estimated. Objective CRF assessment is costly, labour intensive and not widely available. Patient-reported outcome measures estimate CRF more cost-efficiently, but current questionnaires lack accuracy. The aim of this study is to develop a new self-reported questionnaire to estimate CRF.

Materials and Methods

The FitMáx©-questionnaire, consisting of only three questions assessing walking, stair climbing, and cycling capacity, was compared with the commonly used Duke Activity Status Index (DASI) and Veterans Specific Activity Questionnaire (VSAQ). These questionnaires were compared to peak oxygen uptake (VO_2peak) as measured with cardiopulmonary exercise testing. This study included 759 cardiac, pulmonary and oncologic patients and healthy persons aged 18‒90.

Results

FitMáx© strongly correlated (r = 0.94 (0.92‒0.95) SEE = 4.14 mL∙kg⁻¹∙min⁻¹) with measured VO_2peak. Bias between predicted and measured VO_2peak was −0.24 (−9.23‒8.75; 95% limits of agreement) mL·kg⁻¹·min⁻¹. The FitMáx© scored superiorly on correlation and SEE compared with the DASI and VSAQ, r = 0.75 (0.68‒0.80) SEE = 4.62 mL∙kg⁻¹∙min⁻¹ and r = 0.87 (0.83‒0.90) SEE = 6.75 mL∙kg⁻¹∙min⁻¹, respectively.

Conclusion

FitMáx© is a valid and accessible questionnaire to estimate CRF expressed as VO_2peak in clinical practice and shows substantial improvement compared to currently used questionnaires.

Harnessing Neuroplasticity to Promote Brain Health in Aging Adults: Protocol for the MOVE-Cog Intervention Study

Background

Extensive evidence supports a link between aerobic exercise and cognitive improvements in aging adults. A major limitation with existing research is the high variability in cognitive response to exercise. Our incomplete understanding of the mechanisms that influence this variability and the low adherence to exercise are critical knowledge gaps and major barriers for the systematic implementation of exercise for promoting cognitive health in aging.

Objective

We aimed to provide an in-person and remotely delivered intervention study protocol with the main goal of informing the knowledge gap on the mechanistic action of exercise on the brain by characterizing important mechanisms of neuroplasticity, cardiorespiratory fitness response, and genetics proposed to underlie cognitive response to exercise.

Methods

This is an open-label, 2-month, interventional study protocol in neurologically healthy sedentary adults. This study was delivered fully in-person and in remote options. Participants underwent a total of 30 sessions, including the screening session, 3 pretest (baseline) assessments, 24 moderate-to-vigorous aerobic exercise sessions, and 3 posttest assessments. We recruited participants aged 55 years and above, sedentary, and cognitively healthy. Primary outcomes were neuroplasticity, cognitive function, and cardiorespiratory fitness. Secondary outcomes included genetic factors, endothelium function, functional mobility and postural control, exercise questionnaires, depression, and sleep. We also explored study feasibility, exercise adherence, technology adaptability, and compliance of both in-person and remote protocols.

Results

The recruitment phase and data collection of this study have concluded. Results are expected to be published by the end of 2021 or in early 2022.

Conclusions

The data generated in these studies will introduce tangible parameters to guide the development of personalized exercise prescription models for maximal cognitive benefit in aging adults. Successful completion of the specific aims will enable researchers to acquire the appropriate expertise to design and conduct studies by testing personalized exercise interventions in person and remotely delivered, likely to be more effective at promoting cognitive health in aging adults.

Trial Registration

ClinicalTrials.gov NCT03804528; http://clinicaltrials.gov/ct2/show/NCT03804528

International Registered Report Identifier (IRRID)

RR1-10.2196/33589

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

Exercise based cardiac rehabilitation (CR) is recognized internationally as a class 1 clinical practice recommendation for patients with select cardiovascular diseases and heart failure with reduced ejection fraction. Over the past decade, several meta-analyses have generated debate regarding the effectiveness of exercise-based CR for reducing all-cause and cardiovascular mortality. A common theme highlighted in these meta-analyses is the heterogeneity and/or lack of detail regarding exercise prescription methodology within CR programs. Currently there is no international consensus on exercise prescription for CR, and exercise intensity recommendations vary considerably between countries from light-moderate intensity to moderate intensity to moderate-vigorous intensity. As cardiorespiratory fitness [peak oxygen uptake (VO₂peak)] is a strong predictor of mortality in patients with coronary heart disease and heart failure, exercise prescription that optimizes improvement in cardiorespiratory fitness and exercise capacity is a critical consideration for the efficacy of CR programming. This review will examine the evidence for prescribing higher-intensity aerobic exercise in CR, including the role of high-intensity interval training. This discussion will highlight the beneficial physiological adaptations to pulmonary, cardiac, vascular, and skeletal muscle systems associated with moderate-vigorous exercise training in patients with coronary heart disease and heart failure. Moreover, this review will propose how varying interval exercise protocols (such as short-duration or long-duration interval training) and exercise progression models may influence central and peripheral physiological adaptations. Importantly, a key focus of this review is to provide clinically-relevant recommendations and strategies to optimize prescription of exercise intensity while maximizing safety in patients attending CR programs.

Adherence to High-Intensity Interval Training in Cardiac Rehabilitation: A REVIEW AND RECOMMENDATIONS

PURPOSE

High-intensity interval training (HIIT) is gaining popularity as a training approach for patients attending cardiac rehabilitation (CR). While the literature has focused on the efficacy of HIIT for improving cardiorespiratory fitness (CRF), particularly when compared with moderate intensity exercise, less emphasis has been placed on adherence to HIIT. The aim of this review was to summarize the current literature regarding adherence to HIIT in CR patients with coronary artery disease.

REVIEW METHODS

A review identified 36 studies investigating HIIT in CR patients with coronary artery disease. Methods and data were extracted for exercise or training adherence (to attendance, intensity, and duration), feasibility of protocols, and CRF. The review summarizes reporting of adherence; adherence to HIIT and comparator/s; the influence of adherence on changes in CRF; and feasibility of HIIT.

SUMMARY

Adherence to the attendance of HIIT sessions was high and comparable with moderate-intensity exercise. However, adherence to the intensity and duration of HIIT was variable and underreported, which has implications for determining the treatment effect of the exercise interventions being compared. Furthermore, additional research is needed to investigate the utility of home-based HIIT and long-term adherence to HIIT following supervised programs. This review provides recommendations for researchers in the measurement and reporting of adherence to HIIT and other exercise interventions to facilitate a sufficient and consistent approach for future studies. This article also highlights strategies for clinicians to improve adherence, feasibility, and enjoyment of HIIT for their patients.

Responses to exercise training in patients with heart failure. Analysis by oxygen transport steps

BACKGROUND

Exercise training (ET) increases exercise tolerance, improves quality of life and likely the prognosis in heart failure patients with reduced ejection fraction (HFrEF). However, some patients do not improve, whereas exercise training response is still poorly understood. Measurement of cardiac output during cardiopulmonary exercise test might allow ET response assessment according to the different steps of oxygen transport.

METHODS

Fifty-three patients with HFrEF (24 with ischemic cardiomyopathy (ICM) and 29 with dilated cardiomyopathy (DCM) had an aerobic ET. Before and after ET program, peak oxygen consumption (VO_2peak) and cardiac output using thoracic impedancemetry were measured. Oxygen convection (QO_2peak) and diffusion (DO₂) were calculated using Fick's principle and Fick's simplified law. Patients were considered as responders if the gain was superior to 10%.

RESULTS

We found 55% VO_2peak responders, 62% QO_2peak responders and 56% DO₂ responders. Four patients did not have any response. None baseline predictive factor for VO_2peak response was found. QO_2peak response was related to exercise stroke volume (r = 0.84), cardiac power (r = 0.83) and systemic vascular resistance (SVR_peak) (r = -0.42) responses. Cardiac power response was higher in patients with ICM than in those with DCM (p < 0.05). Predictors of QO2_peak response were low baseline exercise stroke volume and ICM etiology. Predictors of DO₂ response were higher baseline blood creatinine and prolonged training.

CONCLUSION

The analysis of the response to training in patients with HFrEF according to the different steps of oxygen transport revealed different phenotypes on VO_2peak responses, namely responses in either oxygen convection and/or diffusion.

Role of Cardiac Rehabilitation After Ventricular Assist Device Implantation

Patients with heart failure suffered by a complex syndrome, where the filling of the ventricle or ejection of the blood is impaired. In this setting, the exercise capacity decreases for many reasons, one of them being the insufficient oxygen transfer due to reduced cardiac output and anemia. Ventricular assist device has emerged as a durable and safe therapy for patients with end-stage heart failure. The benefits of cardiac rehabilitation in ventricular assist device patients are enormous: the first aim is to progressively reduce the physical and functional impairments of these patients, so that they will be able to resume meaningful daily activities.

Limiting factors of peak and submaximal exercise capacity in LVAD patients

AIMS

Although patients supported with a Continuous-Flow Left Ventricular Assist Device (CF-LVAD) are hemodynamically stable, their exercise capacity is limited. Hence, the aim of this work was to investigate the underlying factors that lead to peak and submaximal exercise intolerance of CF-LVAD supported patients.

METHODS

Seven months after CF-LVAD implantation, eighty three patients performed a maximal cardiopulmonary exercise test and a six minute walk test. Peak oxygen uptake and the distance walked were measured and expressed as a percentage of the predicted value (%VO2p and %6MWD, respectively). Preoperative conditions, echocardiography, laboratory results and pharmacological therapy data were collected and a correlation analysis against %VO2p and %6MWD was performed.

RESULTS

CF-LVAD patients showed a relatively higher submaximal exercise capacity (%6MWD = 64±16%) compared to their peak exertion (%VO2p = 51±14%). The variables that correlated with %VO2p were CF-LVAD parameters, chronotropic response, opening of the aortic valve at rest, tricuspid insufficiency, NT-proBNP and the presence of a cardiac implantable electronic device. On the other hand, the variables that correlated with %6MWD were diabetes, creatinine, urea, ventilation efficiency and CF-LVAD pulsatility index. Additionally, both %6MWD and %VO2p were influenced by the CF-LVAD implantation timing, calculated from the occurrence of the cardiac disease.

CONCLUSION

Overall, both %6MWD and %VO2p depend on the duration of heart failure prior to CF-LVAD implantation. %6MWD is primarily determined by parameters underlying the patient's general condition, while %VO2p mostly relies on the residual function and chronotropic response of the heart. Moreover, since %VO2p was relatively lower compared to %6MWD, we might infer that CF-LVAD can support submaximal exercise but is not sufficient during peak exertion. Hence concluding that the contribution of the ventricle is crucial in sustaining hemodynamics at peak exercise.

Effect of Physical Exercise Training in Patients With Chagas Heart Disease (from the PEACH STUDY)

Chagas heart disease (HD) is a chronic fibrosing myocarditis with high mortality. The PEACH study aimed to evaluate if exercise training can improve the functional capacity of Chagas HD patients with left ventricular dysfunction and/or heart failure. The PEACH study was a single center, parallel-group, clinical trial that randomized 30 clinical stable Chagas HD patients with left ventricular ejection fraction <45% or heart failure symptoms to either supervised exercise training 3 times/week for 6 months or a control group. Both groups had the same monthly pharmaceutical and nutritional counseling and usual care. Primary end point was functional capacity assessed by peak exercise oxygen consumption (peak VO₂) obtained by cardiopulmonary exercise test. Secondary end points included other cardiopulmonary exercise test variables, cardiac function by echocardiography, body composition, muscle respiratory strength, and metabolic biomarkers. Peak VO₂ increased among patients in exercise group from 17.60 ± 4.65 mlO₂ kg^-1 min^-1 to 19.40 ± 5.51 mlO₂ kg^-1 min^-1 while decreased in controls from 15.40 ± 6.30 mlO₂ kg^-1 min^-1 to 12.96 ± 4.50 mlO₂ kg^-1 min^-1, resulting in significant difference in change in peak VO₂ between groups after 6 months (β = +4.6, p = 0.004). There were significant differences between groups in changes in anaerobic threshold (β = 3.7, p = 0.05), peak oxygen pulse (β = +2.7, p = 0.032) and maximum minute ventilation (β = +13.9, p < 0.0001) after 6 months of intervention. In conclusion, exercise training improved functional capacity of chronic Chagas HD patients with left ventricular dysfunction and/or heart failure.

Predictors of Exercise Capacity in Patients with Hypertrophic Obstructive Cardiomyopathy

Hypertrophic obstructive cardiomyopathy (HOCM) patients exhibit compromised peak exercise capacity (VO₂peak). Importantly, severely reduced VO₂peak is directly related to increased morbidity and mortality in these patients. Therefore, we sought to determine clinical predictors of VO₂peak in HOCM patients. HOCM patients who performed symptom-limited cardiopulmonary exercise testing between 1995 and 2016 were included for analysis. Peak VO₂ was reported as absolute peak VO₂, indexed to body weight and analyzed as quartiles, with quartile 1 representing the lowest VO₂peak. Step-wise regression models using demographic features and clinical and physiologic characteristics were created to determine predictors of HOCM patients with the lowest VO₂peak. We included 1177 HOCM patients (age: 53 ± 14 years; BMI: 24 ± 12 kg/m²) with a VO₂peak of 18.0 ± 5.6 mL/kg/min. Significant univariate predictors of the lowest VO₂peak included age, female sex, New York Health Association (NYHA) class, BMI, left atrial volume index, E/e’, E/A, hemoglobin, N-terminal pro b-type natriuretic peptide (NT-proBNP), and a history of diabetes, hypertension, stroke, atrial fibrillation, or coronary artery disease. Independent predictors of the lowest VO₂peak included age (OR, CI: 1.03, 1.02–1.06; p < 0.0001), women (4.66, 2.94–7.47; p = 0.001), a history of diabetes (2.05, 1.17–3.60; p = 0.01), BMI (0.94, 0.92–0.96; p < 0.0001), left atrial volume index (1.07, 1.05–1.21; p = 0.04), E/e’ (1.05, 1.01–1.08; p = 0.004), hemoglobin (0.76, 0.65–0.88; p = 0.0004), and NT-proBNP (1.72, 1.42–2.11; p < 0.0001). These findings demonstrate that demographic factors (i.e., age and sex), comorbidities (e.g., diabetes and obesity), echocardiography indices, and biomarkers (e.g., hemoglobin and NT-proBNP) are predictive of severely compromised VO₂peak in HOCM patients.

Obesity and hemoglobin content impact peak oxygen uptake in human heart failure

Background

Exercise intolerance, obesity, and low hemoglobin (hemoglobin<13 and <12 g/dl, men/women, respectively) are common features of heart failure. Despite serving as potent contributors to metabolic dysfunction, the impact of obesity and low hemoglobin on exercise intolerance is unknown. This study tested the hypotheses, compared with non-obese (NO) heart failure with normal hemoglobin, (a) counterparts with low hemoglobin and obesity or non-obesity will demonstrate reduced peak exercise oxygen uptake; (b) obese with normal hemoglobin will demonstrate decreased peak exercise oxygen uptake; (c) compared across stratifications, obese with low hemoglobin will demonstrate the sharpest decrement in peak exercise oxygen uptake.

Methods

Adults with heart failure ( n = 315; left ventricular ejection fraction≤40%; 77% men) (Group 1: normal hemoglobin and non-obese, n = 137; Group 2: low hemoglobin and non-obese, n = 51; Group 3: normal hemoglobin+obesity, n = 89; Group 4, n = 38: low hemoglobin+obesity; body mass index = 26 ± 3, 26 ± 2, 34 ± 4, 34 ± 4 kg/m2, respectively) completed treadmill cardiopulmonary exercise testing as part of routine clinical management. Peak exercise oxygen uptake was measured via standard metabolic system.

Results

There were no group-wise differences for heart failure class, gender, left ventricular ejection fraction, and resting cardiopulmonary function. Group 1 demonstrated increased peak exercise oxygen uptake versus Groups 2–4 (20 ± 6 versus 17 ± 6, 17 ± 5, 13 ± 4 ml/kg/min, respectively; all p < 0.001); whereas Group 4 peak exercise oxygen uptake was reduced versus all groups ( p < 0.001). Additionally, both body mass index (R2 = 0.10) and hemoglobin (R2 = 0.12) were significant predictors of peak exercise oxygen uptake in Group 1; which were relationships not mirrored for Groups 2–4.

Conclusion

These data suggest obesity together with low hemoglobin are potent contributors to impaired peak exercise oxygen uptake and, hence, oxidative metabolic capacity. In diverse populations of heart failure where obesity and/or low hemoglobin are present, it is important to consider these features together when interpreting peak exercise oxygen uptake and underlying exercise limitations.

Heart rate response and functional capacity in patients with chronic heart failure with preserved ejection fraction

Aims

The mechanisms of exercise intolerance in heart failure with preserved ejection fraction (HFpEF) are not yet elucidated. Chronotropic incompetence has emerged as a potential mechanism. We aimed to evaluate whether heart rate (HR) response to exercise is associated to functional capacity in patients with symptomatic HFpEF.

Methods and results

We prospectively studied 74 HFpEF patients [35.1% New York Heart Association Class III, 53% female, age (mean ± standard deviation) 72.5 ± 9.1 years, and 59.5% atrial fibrillation]. Functional performance was assessed by peak oxygen consumption (peak VO₂). The mean (standard deviation) peak VO₂ was 10 ± 2.8 mL/min/kg. The following chronotropic parameters were calculated: Delta‐HR (HR at peak exercise − HR at rest), chronotropic index (CI) = (HR at peak exercise − resting HR)/[(220 − age) − resting HR], and CI according to the equation developed by Keteyian et al. (CIK) (HR at peak exercise − HR at rest)/[119 + (HR at rest/2) − (age/2) − 5 − HR at rest]. In a bivariate setting, peak VO₂ was positively and significantly correlated with Delta‐HR (r = 0.35, P = 0.003), CI (r = 0.27, P = 0.022), CIK (r = 0.28, P = 0.018), and borderline with HR at peak exercise (r = 0.22, P = 0.055). In a multivariable linear regression analysis that included clinical, analytical, echocardiographic, and functional capacity covariates, the chronotropic parameters were positively associated with peak VO₂. We found a linear relationship between Delta‐HR and peak VO₂ (β coefficient of 0.03; 95% confidence interval: 0.004–0.05; P = 0.030); conversely, the association among CIs and peak VO₂ was exponentially shaped.

Conclusions

In patients with chronic HFpEF, the HR response to exercise was positively associated to patient's functional capacity.

Reevaluating Modality of Cardiopulmonary Exercise Testing in Patients with Heart Failure and Resynchronization Therapy: Relevance of Heart Rate-Adaptive Pacing

BACKGROUND

Chronotropic incompetence (CI) in heart failure (HF) patients with cardiac resynchronization therapy (CRT) and activity sensors may vary according to exercise modality. We hypothesized that chronotropic response and exercise capacity differ when HF patients with CRT and heart rate (HR) adaptive pacing are exercised on cycloergometer versus treadmill.

METHODS AND RESULTS

This is a crossover study in which stable HF patients with CRT and HR-adaptive pacing triggered by activity sensors underwent maximal symptom-limited cardiopulmonary exercise testing on both a cycloergometer and treadmill. Adjusted percent of HR reserve (%HRR) was calculated as HRR/age-predicted HRR. CI was defined as ≤62% of age-predicted HRR. Among 16 patients (59 ± 10 years, ejection fraction 27 ± 12%, 87% on beta-blockers), prevalence of CI was high irrespective of exercise modality (87.5% on cycloergometer vs 62.5% on treadmill; P = .12). Chronotropic responses were better on the treadmill; %HRR was higher on a treadmill vs cycloergometer (61 ± 26% vs 22 ± 31%; P = .003). Peak oxygen consumption was increased by 24% on a treadmill vs cycloergometer (15.8 vs 12.7 mL/kg/min; P < .0001).

CONCLUSIONS

In HF patients with CRT and HR-adaptive pacing, treadmill cardiopulmonary exercise testing enhances chronotropic response, HRR, and peak oxygen consumption compared with a cycloergometer. These findings may have implications in exercise prescription and thresholds for advanced therapies such as heart transplantation and ventricular assist devices.

Comprehensive analysis of cardiopulmonary exercise testing and mortality in patients with systolic heart failure: the Henry Ford Hospital cardiopulmonary exercise testing (FIT-CPX) project

BACKGROUND

Many studies have shown a strong association between numerous variables from a cardiopulmonary exercise (CPX) test and prognosis in patients with heart failure with reduced ejection fraction (HFrEF). However, few studies have compared the prognostic value of a majority of these variables simultaneously, so controversy remains regarding optimal interpretation.

METHODS AND RESULTS

This was a retrospective analysis of patients with HFrEF (n = 1,201; age = 55 ± 13 y; 33% female) and a CPX test from 1997 to 2010. Thirty variables from a CPX test were considered in separate adjusted Cox regression analyses to describe the strength of the relation of each to a composite end point of all-cause mortality, left ventricular assist device implantation, or heart transplantation. During a median follow-up of 3.8 years, there were 577 (48.0%) events. The majority of variables were highly significant (P < .001). Among these, percentage of predicted maximum V˙O2 (ppMV˙O2; Wald = 203; P < .001; C-index = 0.73) was similar to VE-VCO2 slope (Wald = 201; P < .001; C = 0.72) and peak V˙O2 (Wald = 161; P < .001; C = 0.72). In addition, there was no significant interaction observed for peak respiratory exchange ratio <1 vs ≥1.

CONCLUSIONS

Consistent with prior studies, many CPX test variables were strongly associated with prognosis in patients with HFrEF. The choice of which variable to use is up to the clinician. Renewed attention should be given to ppMV˙O2, which appears to be highly predictive of survival in these patients.

A study of the 200-metre fast walk test as a possible new assessment tool to predict maximal heart rate and define target heart rate for exercise training of coronary heart disease patients

Objective:

To develop a new predictive model of maximal heart rate based on two walking tests at different speeds (comfortable and brisk walking) as an alternative to a cardiopulmonary exercise test during cardiac rehabilitation.

Design:

Evaluation of a clinical assessment tool.

Setting:

A Cardiac Rehabilitation Department in France.

Subjects:

A total of 148 patients (133 men), mean age of 59 ±9 years, at the end of an outpatient cardiac rehabilitation programme.

Main measures:

Patients successively performed a 6-minute walk test, a 200 m fast-walk test (200mFWT), and a cardiopulmonary exercise test, with measure of heart rate at the end of each test. An all-possible regression procedure was used to determine the best predictive regression models of maximal heart rate. The best model was compared with the Fox equation in term of predictive error of maximal heart rate using the paired t-test.

Results:

Results of the two walking tests correlated significantly with maximal heart rate determined during the cardiopulmonary exercise test, whereas anthropometric parameters and resting heart rate did not. The simplified predictive model with the most acceptable mean error was: maximal heart rate = 130 − 0.6 × age + 0.3 × HR200mFWT (R2 = 0.24). This model was superior to the Fox formula (R2 = 0.138). The relationship between training target heart rate calculated from measured reserve heart rate and that established using this predictive model was statistically significant ( r = 0.528, p < 10−6).

Conclusions:

A formula combining heart rate measured during a safe simple fast walk test and age is more efficient than an equation only including age to predict maximal heart rate and training target heart rate.

Effects of Renal Sympathetic Denervation on Exercise Blood Pressure, Heart Rate, and Capacity in Patients With Resistant Hypertension

Renal denervation reduces office blood pressure in patients with resistant hypertension. This study investigated the effects of renal denervation on blood pressure, heart rate, and chronotropic index at rest, during exercise, and at recovery in 60 patients (renal denervation group=50, control group=10) with resistant hypertension using a standardized bicycle exercise test protocol performed 6 and 12 months after renal denervation. After renal denervation, exercise blood pressure at rest was reduced from 158±3/90±2 to 141±3/84±4 mm Hg ( P <0.001 for systolic blood pressure/ P =0.007 for diastolic blood pressure) after 6 months and 139±3/83±4 mm Hg ( P <0.001/ P =0.022) after 12 months. Exercise blood pressure tended to be lower at all stages of exercise at 6- and 12-month follow-up in patients undergoing renal denervation, although reaching statistical significance only at mild-to-moderate exercise levels (75–100 W). At recovery after 1 minute, blood pressure decreased from 201±4/95±2 to 177±4/88±2 ( P <0.001/ P =0.066) and 188±6/86±2 mm Hg ( P =0.059/ P =0.01) after 6 and 12 months, respectively. Heart rate was reduced after renal denervation from 71±3 bpm at rest, 128±5 bpm at maximum workload, and 96±5 bpm at recovery after 1 minute to 66±2 ( P <0.001), 115±5 ( P =0.107), and 89±3 bpm ( P =0.008) after 6 months and to 69±3 ( P =0.092), 122±7 ( P =0.01), and 93±4 bpm ( P =0.032) after 12 months. Mean exercise time increased from 6.59±0.33 to 8.4±0.32 ( P <0.001) and 9.0±0.41 minutes ( P =0.008), and mean workload increased from 93±2 to 100±2 ( P <0.001) and 101±3 W ( P =0.007) at 6- and 12-month follow-up, respectively. No changes were observed in the control group. In conclusion, renal denervation reduced blood pressure and heart rate during exercise, improved mean workload, and increased exercise time without impairing chronotropic competence.

Association between resting heart rate, chronotropic index, and long-term outcomes in patients with heart failure receiving β-blocker therapy: data from the HF-ACTION trial

AIMS

The aim of this study was to assess the association between resting heart rate (HR), chronotropic index (CI), and clinical outcomes in optimally treated chronic heart failure (HF) patients on β-blocker therapy.

METHODS AND RESULTS

We performed a sub-study in 1118 patients with HF and reduced ejection fraction (EF < 35%) included in the HF-ACTION trial. Patients in sinus rhythm who received a β-blocker and who performed with maximal effort on the exercise test were included. Chronotropic index was calculated as an index of HR reserve achieved, by using the equation (220-age) for estimating maximum HR. A sensitivity analysis using an equation developed for HF patients on β-blockers was also performed. Cox proportional hazards models were fit to assess the association between CI and clinical outcomes. Median (25th, 75th percentiles) follow-up was 32 (21, 44) months. In a multivariable model including resting HR and CI as continuous variables, neither was associated with the primary outcome of all-cause mortality or hospitalization. However, each 0.1 unit decrease in CI <0.6 was associated with 17% increased risk of all-cause mortality (hazard ratio 1.17, 95% confidence interval 1.01-1.36; P = 0.036), and 13% increased risk of cardiovascular mortality or HF hospitalization (hazard ratio 1.13, 1.02-1.26; P = 0.025). Overall, 666 of 1118 (60%) patients had a CI <0.6. Chronotropic index did not retain statistical significance when dichotomized at a value of ≤ 0.62.

CONCLUSION

In HF patients receiving optimal medical therapy, a decrease in CI <0.6 was associated with adverse clinical outcomes. Obtaining an optimal HR response to exercise, even in patients receiving optimal β-blocker therapy, may be a therapeutic target in the HF population.