Higher cardiorespiratory fitness predicts long-term survival in patients with heart failure and preserved ejection fraction: the Henry Ford Exercise Testing (FIT) Project

INTRODUCTION

Higher cardiorespiratory fitness (CRF) is associated with improved exercise capacity and quality of life in heart failure with preserved ejection fraction (HFpEF), but there are no large studies evaluating the association of HFpEF, CRF, and long-term survival. We therefore aimed to determine the association between CRF and all-cause mortality, in patients with HFpEF.

MATERIAL AND METHODS

In the Henry Ford Exercise Testing (FIT) Project, 167 patients had baseline HFpEF, defined as a clinical diagnosis of heart failure with ejection fraction ≥ 50% on echocardiogram. The CRF was estimated from the peak workload (in METs) from a clinician-referred treadmill stress test and categorized as poor (1-4 METs), intermediate (5-6 METs), and moderate-high (≥ 7 METs). Additional analyses assessing the effect of HFpEF and CRF on mortality were also conducted, matching HFpEF patients to non-HFpEF patients using propensity scores.

RESULTS

Mean age was 64 ±13 years, with 55% women, and 46% Black. Over a median follow-up of 9.7 (5.2-18.9) years, there were 103 deaths. In fully adjusted models, moderate-high CRF was associated with 63% lower mortality risk (HR = 0.37, 95% CI: 0.18-0.73) compared to the poor-CRF group. In the propensity-matched cohort, HFpEF was associated with a HR of 2.3 (95% CI: 1.7-3.2) for mortality compared to non-HFpEF patients, which was attenuated to 1.8 (95% CI: 1.3-2.5) after adjusting for CRF.

CONCLUSIONS

Moderate-high CRF in patients with HFpEF is associated with improved survival, and differences in CRF partly explain the intrinsic risk of HFpEF. Randomized trials of interventions aimed at improving CRF in HFpEF are needed.

Exercise Oscillatory Ventilation: Interreviewer Agreement and a Novel Determination

INTRODUCTION

Determination of exercise oscillatory ventilation (EOV) is subjective, and the interreviewer agreement has not been reported. The purposes of this study were, among patients with heart failure (HF), as follows: 1) to determine the interreviewer agreement for EOV and 2) to describe a novel, objective, and quantifiable measure of EOV.

METHODS

This was a secondary analysis of the HEART Camp: Promoting Adherence to Exercise in Patients with Heart Failure study. EOV was determined through a blinded review by six individuals on the basis of their interpretation of the EOV literature. Interreviewer agreement was assessed using Fleiss kappa (κ). Final determination of EOV was based on agreement by four of the six reviewers. A new measure (ventilation dispersion index; VDI) was calculated for each test, and its ability to predict EOV was assessed with the receiver operator characteristics curve.

RESULTS

Among 243 patients with HF (age, 60 ± 12 yr; 45% women), the interreviewer agreement for EOV was fair (κ = 0.303) with 10-s discrete data averages and significantly better, but only moderate (κ = 0.429) with 30-s rolling data averages. Prevalence rates of positive and indeterminate EOVs were 18% and 30% with the 10-s discrete averages and 14% and 13% with the 30-s rolling averages, respectively. VDI was strongly associated with EOV, with areas under the receiver operator characteristics curve of 0.852 to 0.890.

CONCLUSIONS

Interreviewer agreement for EOV in patients with HF is fair to moderate, which can negatively affect risk stratification. VDI has strong predictive validity with EOV; as such, it might be a useful measure of prognosis in patients with HF.

Inverse association of pulse pressure augmentation during exercise with heart failure and death

OBJECTIVE

Resting pulse pressure (PP) is a risk factor for heart failure (HF); however, whether PP augmentation during exercise, a parameter easily obtained from routine treadmill stress testing, is associated with incident HF is unknown. Thus, we aimed to study the relationship between a novel parameter, the pulse pressure stress index (P2SI), and adverse outcomes among adults undergoing clinical exercise stress testing in the Henry Ford Exercise Testing Project.

METHODS

The P2SI was calculated as PP at peak exercise divided by resting PP and was analysed continuously and categorically using quartiles. Cox models examined the association between P2SI and adjusted HR (aHR) of incident HF, myocardial infarction (MI) or death. Receiver operating curve (ROC) analyses tested the optimal prognostic cut-point for P2SI.

RESULTS

Among 55 524 participants without prior MI or HF, mean (SD) age was 53 (13) years, 51% were men and 29% black. A total of 2516 HF, 1606 MI and 6224 mortality outcomes occurred. Quartile 3 P2SI (2.0-2.4) was chosen as the reference category based on ROC analyses. There was a graded inverse association of low P2SI with excess HF (aHR of 1.3 (95% CI 1.1 to 1.5) for quartile 2 and 1.5 (95% CI 1.2 to 1.8) for quartile 1, p for trend<0.001) and mortality (aHR of 1.1 (95% CI 1.01 to 1.2) for quartile 2 and 1.3 (95% CI 1.2 to 1.5) for quartile 1, p for trend<0.001). There was no association between P2SI and MI after adjustment. P2SI added significant prognostic information to more established stress testing parameters such as peak systolic blood pressure, per cent maximal predicted heart rate achieved and metabolic equivalents of task achieved.

CONCLUSIONS

Poor augmentation of PP with exercise, specifically a P2SI below 2, is a novel and readily quantifiable exercise-based risk feature for HF and death.

Exercise training workloads in cardiac rehabilitation are associated with clinical outcomes in patients with heart failure

BACKGROUND

In patients with coronary heart disease, the exercise workload (i.e., metabolic equivalents of task, METs) at which patients exercise train upon entry and completion of cardiac rehabilitation (CR) are independently related to prognosis. Unknown is the association between exercise training workloads in CR and clinical outcomes in patients with heart failure (HF).

METHODS

Patients with HF who participated in an early outpatient CR program were used in this retrospective analysis. Exercise workloads upon entry and completion of CR were converted to METs. The primary outcome was all-cause mortality and the secondary outcome was HF hospitalization. Cox regression analysis was used to assess the adjusted risk between MET levels in CR and clinical outcomes.

RESULTS

Among 707 patients, the median exercise training workload at the start and end of CR was 2.5 METs (IQR 2.1 to 3.1 METs) and 3.2 METS (IQR 2.7 to 4.1 METs), respectively, for men and 2.2 METs (IQR 1.9 to 2.6 METs) and 2.9 METS (IQR 2.3 to 3.4 METs), respectively, for women. There were 242 deaths and 266 HF hospitalizations. METs achieved at the end of CR had the strongest independent association with all-cause mortality (adjusted HR, 95% CI: 0.58, 0.48-0.70) and HF hospitalization (adjusted HR, 95% CI: 0.62, 0.52-0.74). Each 1 MET higher work load at the end of CR was associated with a 42% and 38% lower adjusted risk for all-cause mortality and HF hospitalization, respectively.

CONCLUSIONS

In a diverse cohort of patients with chronic HF our data suggests that an easily accessible measure of exercise capacity (i.e., METs) that is collected during CR is independently associated with the adjusted risk for both all-cause mortality and HF-specific hospitalization. Training at MET levels <3.5 METs identifies patients that might benefit from closer clinical surveillance and reinforced adherence to medical and lifestyle preventive strategies.

Exercise Capacity and the Obesity Paradox in Heart Failure: The FIT (Henry Ford Exercise Testing) Project

OBJECTIVES

To assess the influence of exercise capacity and body mass index (BMI) on 10-year mortality in patients with heart failure (HF) and to synthesize these results with those of previous studies.

PATIENTS AND METHODS

This large biracial sample included 774 men and women (mean age, 60±13 years; 372 [48%] black) with a baseline diagnosis of HF from the Henry Ford Exercise Testing (FIT) Project. All patients completed a symptom-limited maximal treadmill stress test from January 1, 1991, through May 31, 2009. Patients were grouped by World Health Organization BMI categories for Kaplan-Meier survival analyses and stratified by exercise capacity (<4 and ≥4 metabolic equivalents [METs] of task). Associations of BMI and exercise capacity with all-cause mortality were assessed using multivariable-adjusted Cox proportional hazards models.

RESULTS

During a mean follow-up of 10.1±4.6 years, 380 patients (49%) died. Kaplan-Meier survival plots revealed a significant positive association between BMI category and survival for exercise capacity less than 4 METs (log-rank, P=.05), but not greater than or equal to 4 METs (P=.76). In the multivariable-adjusted models, exercise capacity (per 1 MET) was inversely associated, but BMI was not associated, with all-cause mortality (hazard ratio, 0.89; 95% CI, 0.85-0.94; P<.001 and hazard ratio, 0.99; 95% CI, 0.97-1.01; P=.16, respectively).

CONCLUSION

Maximal exercise capacity modified the relationship between BMI and long-term survival in patients with HF, upholding the presence of an exercise capacity-obesity paradox dichotomy as observed over the short-term in previous studies.

Prognostic value of exercise capacity among patients with treated depression: The Henry Ford Exercise Testing (FIT) Project

BACKGROUND

Exercise capacity is associated with survival in the general population. Whether this applies to patients with treated depression is not clear.

HYPOTHESIS

High exercise capacity remains associated with lower risk of all-cause mortality (ACM) and nonfatal myocardial infraction (MI) among patients with treated depression.

METHODS

We included 5128 patients on antidepressant medications who completed a clinically indicated exercise stress test between 1991 and 2009. Patients were followed for a median duration of 9.4 years for ACM and 4.5 years for MI. Exercise capacity was estimated in metabolic equivalents of tasks (METs). Cox proportional hazards regression models were used.

RESULTS

Patients with treated depression who achieved ≥12 METs (vs those achieving <6 METs) were younger (age 46 ± 9 vs 61 ± 12 years), more often male (60% vs 23%), less often black (10% vs 27%), and less likely to be hypertensive (51% vs 86%), have DM (9% vs 38%), or be obese (11% vs 36%) or dyslipidemic (45% vs 54%). In the fully adjusted Cox proportional hazard regression model, exercise capacity was associated with a lower ACM (HR per 1-MET increase in exercise capacity: 0.82, 95% CI: 0.79-0.85, P < 0.001) and nonfatal MI (HR: 0.92, 95% CI: 0.87-0.97, P = 0.004).

CONCLUSIONS

Exercise capacity had an inverse association with both ACM and nonfatal MI in patients with treated depression, independent of cardiovascular risk factors. These results highlight the potential impact of assessing exercise capacity to identify risk, as well as promoting an active lifestyle among treated depression patients.

Cardiopulmonary Exercise Measures of Men and Women with HFrEF Differ in Their Relationship to Prognosis: The Henry Ford Hospital Cardiopulmonary Exercise Testing (FIT-CPX) Project

BACKGROUND

This study evaluated if different prognostic characteristics exist for peak oxygen consumption (VO₂), percent predicted peak VO₂ (ppVO₂), and the slope of the change in minute ventilation to volume of carbon dioxide produced (V_E-VCO₂) slope between men and women with heart failure and reduced ejection fraction (HFrEF).

METHODS

Analysis of the Henry Ford Hospital Cardiopulmonary Exercise Testing database (n = 1085; 33% women, 55% black) of individuals with HFrEF who completed a physician-referred cardiopulmonary exercise testing (CPX) between 1997 and 2010. Primary outcome was a composite of all-cause death, left ventricular assist device placement, and orthotopic heart transplant . Logistic and Cox regressions were performed and Kaplan-Meier survival curves were developed to describe relationships of the CPX variables and the composite outcome within and between men and women.

RESULTS

All patients were followed-up for a minimum of 5 years, during which there were 643 combined events (62%; 499 deaths, 64 left ventricular assist device implants, 80 orthotopic heart transplant). Each CPX variable was significantly related to event-free survival among both men and women. Log-rank assessment of Kaplan-Meier curves noted survival differences for peak VO₂ and V_E-VCO₂ slope (p ≤ .002), but not ppVO₂ (P = .32), between men and women.

CONCLUSIONS

Prognostic values for peak VO₂ and the V_E-VCO₂ slope might be considered separately for men and women, whereas the ppVO₂ value corresponding to 1- and 3-year survival rates may not be different between the sexes.

Using Machine Learning to Define the Association between Cardiorespiratory Fitness and All-Cause Mortality (from the Henry Ford Exercise Testing Project)

Previous studies have demonstrated that cardiorespiratory fitness is a strong marker of cardiovascular health. Machine learning (ML) can enhance the prediction of outcomes through classification techniques that classify the data into predetermined categories. The aim of the analysis is to compare the prediction of 10 years of all-cause mortality (ACM) using statistical logistic regression (LR) and ML approaches in a cohort of patients who underwent exercise stress testing. We included 34,212 patients (55% males, mean age 54 ± 13 years) free of coronary artery disease or heart failure who underwent exercise treadmill stress testing between 1991 and 2009 and had complete 10-year follow-up. The primary outcome of this analysis was ACM at 10 years. The probability of 10-years ACM was calculated using statistical LR and ML, and the accuracy of these methods was calculated and compared. A total of 3,921 patients died at 10 years. Using statistical LR, the sensitivity to predict ACM was 44.9% (95% confidence interval [CI] 43.3% to 46.5%), whereas the specificity was 93.4% (95% CI 93.1% to 93.7%). The sensitivity of ML to predict ACM was 87.4% (95% CI 86.3% to 88.4%), whereas the specificity was 97.2% (95% CI 97.0% to 97.4%). The ML approach was associated with improved model discrimination (area under the curve for ML [0.923 (95% CI 0.917 to 0.928)]) compared with statistical LR (0.836 [95% CI 0.829 to 0.846], p<0.0001). In conclusion, our analysis demonstrates that ML provides better accuracy and discrimination of the prediction of ACM among patients undergoing stress testing.

Relation of Exercise Capacity to Risk of Development of Diabetes in Patients on Statin Therapy (the Henry Ford Exercise Testing Project)

High exercise capacity (EC) has been associated with a lower risk of incident diabetes, whereas statin therapy has been associated with a higher risk. We sought to investigate whether the association between EC and diabetes risk is modified by statin therapy. This retrospective cohort study included 47,337 patients without diabetes or coronary artery disease at baseline (age 53 ± 13 years, 48% women, 66% white) who underwent clinical treadmill stress testing within the Henry Ford Health System from January 1, 1991, to May 31, 2009. The patients were stratified by baseline statin use and estimated peak METs achieved during exercise testing. Hazard ratios for incident diabetes were calculated using Cox proportional hazards models adjusted for demographic characteristics, co-morbidities, pertinent medications, and stress test indication. We observed 6,921 new diabetes cases (14.6%) over a median follow-up period of 5.1 years (interquartile interval of 2.6 to 8.2 years). Compared with the statin group, the no-statin group achieved higher mean METs (8.9 ± 2.7 vs 9.6 ± 3.0, respectively; p <0.001). After adjustment for covariates, a higher EC was associated with a lower risk of incident diabetes, irrespective of statin use (p-interaction = 0.15). Each 1-MET increment was associated with an 8%, 8%, and 6% relative risk reduction in the total cohort, the no-statin, and the statin groups, respectively (95% confidence interval, 0.91 to 0.93, 0.91 to 0.93, and 0.91 to 0.96, respectively; p <0.001 for all). We conclude that a higher EC is associated with a lower risk of incident diabetes regardless of statin use.

Prognostic value of exercise capacity among men undergoing pharmacologic treatment for erectile dysfunction: The FIT Project

BACKGROUND

Vascular erectile dysfunction (ED) has been identified as a potentially useful risk factor for predicting future cardiovascular events, particularly in younger men. Because these men typically score more favorably on traditional cardiovascular disease risk assessment tools, there exists a gap in knowledge for how to most appropriately identify those men who would benefit from more aggressive treatments. To date, no studies have examined the impact of fitness on cardiovascular outcomes in men with ED. This study sought to examine the prognostic impact of maximal exercise capacity on cardiovascular-related outcomes in men ages 40 to 60 years being treated for ED.

HYPOTHESIS

We hypothesized that there would be an independent association between higher baseline fitness level and lower cardiovascular events.

METHODS

We analyzed 1152 men with pharmacy claims file-confirmed active pharmacologic treatment for ED from the Henry Ford Exercise Testing (FIT) Project (1991-2009). All patients were free of coronary heart disease and heart failure, and underwent clinician-referred exercise stress testing, with fitness measured in metabolic equivalents of task (METs). Multivariable Cox proportional hazard models adjusted for traditional cardiovascular risk factors were used to study the association between fitness and all-cause mortality, major adverse cardiovascular events (MACE) (defined as myocardial infarction or revascularization), and incident type 2 diabetes mellitus.

RESULTS

The mean age of the population was 53 years, with 39% African Americans. In multivariable analysis, each 1 MET of fitness was associated with a 16% lower risk of death (hazard ratio [HR]: 0.84, 95% confidence interval [CI]: 0.76-0.94, P = 0.002), and a nonsignificant reduction in MACE (HR: 0.89, 95% CI: 0.79-1.003, P = 0.048), and incident diabetes (HR: 0.92, 95% CI: 0.85-1.01, P = 0.129).

CONCLUSIONS

Higher baseline fitness is associated with improved cardiovascular prognosis in a population of middle-aged men treated for ED.

Cardiorespiratory fitness and incident heart failure: The Henry Ford ExercIse Testing (FIT) Project

BACKGROUND

Prior studies have demonstrated cardiorespiratory fitness (CRF) to be a strong marker of cardiovascular health. However, there are limited data investigating the association between CRF and risk of progression to heart failure (HF). The purpose of this study was to determine the relationship between CRF and incident HF.

METHODS

We included 66,329 patients (53.8% men, mean age 55 years) free of HF who underwent exercise treadmill stress testing at Henry Ford Health Systems between 1991 and 2009. Incident HF was determined using International Classification of Diseases, Ninth Revision codes from electronic medical records or administrative claim files. Cox proportional hazards models were performed to determine the association between CRF and incident HF.

RESULTS

A total of 4,652 patients developed HF after a median follow-up duration of 6.8 (±3) years. Patients with incident HF were older (63 vs 54 years, P<.001) and had higher prevalence of known coronary artery disease (42.3% vs 11%, P<.001). Peak metabolic equivalents (METs) of task were 6.3 (±2.9) and 9.1 (±3) in the HF and non-HF groups, respectively. After adjustment for potential confounders, patients able to achieve ≥12 METs had an 81% lower risk of incident HF compared with those achieving <6 METs (hazard ratio 0.19 [95% CI 0.14-0.29], P for trend < .001). Each 1 MET achieved was associated with a 16% lower risk (hazard ratio 0.84 [95% CI 0.82-0.86], P<.001) of incident HF.

CONCLUSIONS

Our analysis demonstrates that higher level of fitness is associated with a lower incidence of HF independent of HF risk factors.

Higher Fitness Is Strongly Protective in Patients with Family History of Heart Disease: The FIT Project

BACKGROUND

Cardiorespiratory fitness protects against mortality; however, little is known about the benefits of improved fitness in individuals with a family history of coronary heart disease. We studied the association between cardiorespiratory fitness and risk of incident coronary heart disease and all-cause mortality, hypothesizing an inverse relationship similar to individuals without a family history of coronary heart disease.

METHODS

We included 57,999 patients (aged 53 ± 13 years; 49% were female; 29% were black) from the Henry Ford Exercise Testing (FIT) Project. Cardiorespiratory fitness was expressed in metabolic equivalents of task based on exercise stress testing. Family history was determined as self-reported coronary heart disease in a first-degree relative at any age. We used Cox proportional hazards models adjusted for demographics and cardiovascular disease risk factors to examine the association between cardiorespiratory fitness and risk of incident coronary heart disease and mortality over a median (interquartile range) follow-up of 5.5 (5.6) and 10.4 (6.8) years, respectively.

RESULTS

Overall, 51% reported a positive family history. Each 1-unit metabolic equivalent increase was associated with lower incident coronary heart disease and mortality risk regardless of family history status. The hazard ratio and 95% confidence interval for a negative family history and a positive family history were 0.87 (0.84-0.89) and 0.87 (0.85-0.89) for incident coronary heart disease and 0.83 (0.82-0.84) and 0.83 (0.82-0.85) for mortality, respectively. There was no significant interaction between family history and categoric cardiorespiratory fitness, sex, or age (P >.05 for all).

CONCLUSIONS

Higher cardiorespiratory fitness is strongly protective in all patients regardless of family history status, supporting recommendations for regular exercise in those with a family history.

Change in Maximal Exercise Capacity Is Associated With Survival in Men and Women

OBJECTIVE

To describe the relationship between change in maximal exercise capacity (MEC) over time and risk of all-cause mortality separately in men and women.

PATIENTS AND METHODS

Consecutive patients (n=10,854; mean ± SD age, 54±11 years; 43% women; 30% nonwhite) who completed 2 physician-referred exercise tests between January 2, 1991, and May 28, 2009, were identified from the Henry Ford Exercise Testing (FIT) Project. The MEC was quantified in metabolic equivalents of task (METs) calculated from peak workload on a treadmill and adjusted to the equivalent for a 50-year-old man. Multivariable Cox proportional hazards regression was performed to assess risk of all-cause mortality associated with change in MEC based on (1) change from age-/sex-adjusted low fitness (<8 METs) to intermediate or high fitness and (2) an absolute change in METs.

RESULTS

Relative to patients with low fitness at both tests, increasing from low to intermediate or high fitness was associated with lower risk of all-cause mortality (adjusted hazard ratio [aHR] = 0.63 [95% CI, 0.45-0.87] in men and 0.56 [95% CI, 0.34-0.91] in women). Each 1-MET increase in age-/sex-adjusted MEC between baseline and follow-up was associated with an aHR of 0.87 (95% CI, 0.84-0.91) in men and 0.84 (95% CI, 0.79-0.89) in women, with no significant interaction by sex (P=.995). Similar aHRs were observed in a subgroup with intermediate fitness at baseline.

CONCLUSION

In men and women referred for an exercise stress test, change in MEC over time is inversely related to risk of all-cause mortality.

Chronotropic Incompetence and Risk of Atrial Fibrillation: The Henry Ford ExercIse Testing (FIT) Project

OBJECTIVES

To examine the association between chronotropic incompetence and incident atrial fibrillation (AF).

BACKGROUND

Patients with inadequate heart rate response during exercise may have abnormalities in sinus node function or autonomic tone that predispose to the development of AF.

METHODS

We examined the association between heart rate response and incident AF in 57,402 (mean age=54±13 years, 47% female, 64% white) patients free of baseline AF who underwent exercise-treadmill stress testing from the Henry Ford ExercIse Testing (FIT) Project. Age-predicted maximum heart rate (pMHR) values <85% and chronotropic index values <80% were used to define chronotropic incompetence. Cox regression, adjusting for demographics, cardiovascular risk factors, medications, coronary heart disease, heart failure, and metabolic equivalent of task achieved, was used to compute hazard ratios (HR) and 95% confidence intervals (CI) for the association between chronotropic incompetence and incident AF.

RESULTS

Over a median follow-up of 5.0 years (25^th-75^th percentiles=2.6, 7.8), a total of 3,395 (5.9%) participants developed AF. pMHR values <85% were associated with an increased risk for AF development (HR=1.33, 95%CI=1.22, 1.44). Chronotropic index values <80% also were associated with an increased risk of AF (HR=1.28, 95%CI=1.19, 1.38). The associations of pMHR and chronotropic index with AF remained significant with varying cut-off points to define chronotropic incompetence.

CONCLUSIONS

Our analysis suggests that patients with inadequate heart rate response during exercise have an increased risk for developing AF.

Variables Measured During Cardiopulmonary Exercise Testing as Predictors of Mortality in Chronic Systolic Heart Failure

BACKGROUND

Data from a cardiopulmonary exercise (CPX) test are used to determine prognosis in patients with chronic heart failure (HF). However, few published studies have simultaneously compared the relative prognostic strength of multiple CPX variables.

OBJECTIVES

The study sought to describe the strength of the association among variables measured during a CPX test and all-cause mortality in patients with HF with reduced ejection fraction (HFrEF), including the influence of sex and patient effort, as measured by respiratory exchange ratio (RER).

METHODS

Among patients (n = 2,100, 29% women) enrolled in the HF-ACTION (HF-A Controlled Trial Investigating Outcomes of exercise traiNing) trial, 10 CPX test variables measured at baseline (e.g., peak oxygen uptake [Vo2], exercise duration, percent predicted peak Vo2 [%ppVo2], ventilatory efficiency) were examined.

RESULTS

Over a median follow-up of 32 months, there were 357 deaths. All CPX variables, except RER, were related to all-cause mortality (all p < 0.0001). Both %ppVo2 and exercise duration were equally able to predict (Wald chi-square: ∼141) and discriminate (c-index: 0.69) mortality. Peak Vo2 (ml·kg(-1)·min(-1)) was the strongest predictor of mortality among men (Wald chi-square: 129) and exercise duration among women (Wald chi-square: 41). Multivariable analyses showed that %ppVo2, exercise duration, and peak Vo2 (ml·kg(-1)·min(-1)) were similarly able to predict and discriminate mortality. In men, a 10% 1-year mortality rate corresponded to a peak Vo2 of 10.9 ml·kg(-1)·min(-1) versus 5.3 ml·kg(-1)·min(-1) in women.

CONCLUSIONS

Peak Vo2, exercise duration, and % ppVo2 carried the strongest ability to predict and discriminate the likelihood of death in patients with HFrEF. The prognosis associated with a given peak Vo2 differed by sex. (Exercise Training Program to Improve Clinical Outcomes in Individuals With Congestive Heart Failure; NCT00047437).

Sex Differences in Cardiorespiratory Fitness and All-Cause Mortality: The Henry Ford ExercIse Testing (FIT) Project

OBJECTIVE

To determine whether sex modifies the relationship between fitness and mortality.

PATIENTS AND METHODS

We included 57,284 patients without coronary artery disease or heart failure who completed a routine treadmill exercise test between 1991 and 2009. We determined metabolic equivalent tasks (METs) and linked patient records with mortality data via the Social Security Death Index. Multivariable Cox regression was used to determine the association between sex, fitness, and all-cause mortality.

RESULTS

There were 29,470 men (51.4%) and 27,814 women (48.6%) with mean ages of 53 and 54 years, respectively. Overall, men achieved 1.7 METs higher than women (P<.001). During median follow-up of 10 years, there were 6402 deaths. The mortality rate for men in each MET group was similar to that for women, who achieved an average of 2.6 METs lower (P=.004). Fitness was inversely associated with mortality in both men (hazard ratio [HR], 0.84 per 1 MET; 95% CI, 0.83-0.85) and women (HR, 0.83 per 1 MET; 95% CI, 0.81-0.84). This relationship did not plateau at high or low MET values.

CONCLUSION

Although men demonstrated 1.7 METs higher than women, their survival was equivalent to that of women demonstrating 2.6 METs lower. Furthermore, higher MET values were associated with lower mortality for both men and women across the range of MET values. These findings are useful for tailoring prognostic information and lifestyle guidance to men and women undergoing stress testing.

Relationship Between Exercise Workload During Cardiac Rehabilitation and Outcomes in Patients With Coronary Heart Disease

The purpose of this retrospective, observational study was to describe the relation between exercise workload during cardiac rehabilitation (CR), expressed as metabolic equivalents of task (METs), and prognosis among patients with coronary heart disease. We included patients with coronary heart disease who participated in CR between January 1998 and June 2007. METs were calculated from treadmill workload. Cox regression analysis was used to describe the relationship between METs and time to a composite outcome of all-cause mortality, nonfatal myocardial infarction, or heart failure hospitalization. Among 1,726 patients (36% women; median age 59 years [interquartile range, 52 to 66]), there were 467 events (27%) during a median follow-up of 5.8 years (interquartile range, 2.6 to 8.7). In analyses adjusted for age, sex, Charlson co-morbidity index, hypertension, diabetes, and CR referral diagnosis, METs were independently related to the composite outcome at CR start (Wald chi-square 43, hazard ratio 0.59 [95% confidence interval 0.51 to 0.70]) and CR end (Wald chi-square 47, hazard ratio 0.68 [95% confidence interval 0.61 to 0.76]). Patients exercising below 3.5 METs on exit from CR represent a high-risk group with 1- and 3-year event rates ≥7% and ≥18%, respectively. In conclusion, METs during CR is available at no additional cost and can be used to identify patients at increased risk for an event who may benefit from closer follow-up, extended length of stay in CR, and/or participation in other strategies aimed at maximizing adherence to secondary preventive behaviors and improving exercise capacity.

Prognostic value of cardiopulmonary exercise testing in heart failure with preserved ejection fraction. The Henry Ford HospITal CardioPulmonary EXercise Testing (FIT-CPX) project

BACKGROUND

Although cardiopulmonary exercise (CPX) testing in patients with heart failure and reduced ejection fraction is well established, there are limited data on the value of CPX variables in patients with HF and preserved ejection fraction (HFpEF). We sought to determine the prognostic value of select CPX measures in patients with HFpEF.

METHODS

This was a retrospective analysis of patients with HFpEF (ejection fraction ≥ 50%) who performed a CPX test between 1997 and 2010. Selected CPX variables included peak oxygen uptake (VO2), percent predicted maximum oxygen uptake (ppMVO2), minute ventilation to carbon dioxide production slope (VE/VCO2 slope) and exercise oscillatory ventilation (EOV). Separate Cox regression analyses were performed to assess the relationship between each CPX variable and a composite outcome of all-cause mortality or cardiac transplant.

RESULTS

We identified 173 HFpEF patients (45% women, 58% non-white, age 54 ± 14 years) with complete CPX data. During a median follow-up of 5.2 years, there were 42 deaths and 5 cardiac transplants. The 1-, 3-, and 5-year cumulative event-free survival was 96%, 90%, and 82%, respectively. Based on the Wald statistic from the Cox regression analyses adjusted for age, sex, and β-blockade therapy, ppMVO2 was the strongest predictor of the end point (Wald χ(2) = 15.0, hazard ratio per 10%, P < .001), followed by peak VO2 (Wald χ(2) = 11.8, P = .001). VE/VCO2 slope (Wald χ(2)= 0.4, P = .54) and EOV (Wald χ(2) = 0.15, P = .70) had no significant association to the composite outcome.

CONCLUSION

These data support the prognostic utility of peak VO2 and ppMVO2 in patients with HFpEF. Additional studies are needed to define optimal cut points to identify low- and high-risk patients.

Exercise Parameters and Risk of Coronary Artery Disease and Mortality Among Patients Who Use Pulmonary Medications: The FIT Project

BACKGROUND

In the general population, the exercise treadmill testing variables of lower resting heart rate, higher peak heart rate, and greater fitness have favorable prognosis for mortality. Patients with obstructive lung disease have increased mortality risk. Furthermore, some pulmonary medications (ie, beta2-agonists) can influence heart rate. We determined whether exercise treadmill test parameters carry the same prognostic value in patients who are using versus not using pulmonary medications.

METHODS

We analyzed data on 69,855 patients (mean age, 55 years) who completed a clinically indicated exercise treadmill test. Patients were defined as having "lung disease" if they were taking medications routinely used to treat obstructive lung disease (n = 6145, 9%). International Classification of Diseases, 9th Revision codes regarding the type of lung disease were not available. Multivariate-adjusted Cox models were used to determine the risk of mortality, major adverse cardiac events, and myocardial infarction over a mean of 11 years follow-up.

RESULTS

Higher resting heart rate was associated with increased mortality risk, and higher peak heart rate and fitness were associated with decreased risk. No significant interaction for lung disease status was seen for the heart rate variables, but a slightly stronger protective effect was observed for higher fitness among patients with lung disease (P interaction = .032). The results were similar for major adverse cardiac events and myocardial infarction.

CONCLUSIONS

Heart rate parameters achieved on exercise treadmill tests are equally prognostic among patients using versus not using pulmonary medications. Higher fitness was associated with improved clinical outcomes for both; however, the relative benefit of fitness on survival was even greater in patients using pulmonary medications compared with those not using them.

High Exercise Capacity Attenuates the Risk of Early Mortality After a First Myocardial Infarction: The Henry Ford Exercise Testing (FIT) Project

OBJECTIVE

To examine the effect of objectively measured exercise capacity (EC) on early mortality (EM) after a first myocardial infarction (MI).

PATIENTS AND METHODS

This retrospective cohort study included 2061 patients without a history of MI (mean age, 62±12 years; 38% [n=790] women; 56% [n=1153] white) who underwent clinical treadmill stress testing in the Henry Ford Health System from January 1, 1991, through May 31, 2009, and suffered MI during follow-up (MI event proportion, 3.4%; mean time from the exercise test to MI, 6.1±4.3 years). Exercise capacity was categorized on the basis of peak metabolic equivalents (METs) achieved: less than 6, 6 to 9, 10 to 11, and 12 or more METs. Early mortality was defined as all-cause mortality within 28, 90, or 365 days of MI. Multivariable logistic regression models were used to assess the effect of EC on the risk of mortality at each time point post-MI adjusting for baseline demographic characteristics, cardiovascular risk factors, medication use, indication for stress testing, and year of MI.

RESULTS

The 28-day EM rate was 10.6% overall, and 13.9%, 10.7%, 6.9%, and 6.0% in the less than 6, 6 to 9, 10 to 11, and 12 or more METs categories, respectively (P<.001). Patients who died were more likely to be older, be less fit, be nonobese, have treated hypertension, and have a longer duration from baseline to incident MI (P<.05). Adjusted regression analyses revealed a decreased risk of EM with increasing EC categories. A 1-MET higher EC was associated with an 8% to 10% lower risk of mortality across all time points (28 days: odds ratio [OR], 0.92; 95% CI, 0.87-0.98; P=.006; 90 days: OR, 0.90; 95% CI, 0.86-0.95; P<.001; 365 days: OR, 0.91; 95% CI, 0.87-0.94; P<.001).

CONCLUSION

Higher baseline EC was independently associated with a lower risk of early death after a first MI.

Relation of Risk of Atrial Fibrillation With Systolic Blood Pressure Response During Exercise Stress Testing (from the Henry Ford ExercIse Testing Project)

Decreases in systolic blood pressure during exercise may predispose to arrhythmias such as atrial fibrillation (AF) because of underlying abnormal autonomic tone. We examined the association between systolic blood pressure response and incident AF in 57,442 (mean age 54 ± 13 years, 47% women, and 29% black) patients free of baseline AF who underwent exercise treadmill stress testing from the Henry Ford ExercIse Testing project. Exercise systolic blood pressure response was examined as a categorical variable across clinically relevant categories (>20 mm Hg: referent; 1 to 20 mm Hg, and ≤0 mm Hg) and per 1-SD decrease. Cox regression, adjusting for demographics, cardiovascular risk factors, medications, history of coronary heart disease, history of heart failure, and metabolic equivalent of task achieved, was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between systolic blood pressure response and incident AF. Over a median follow-up of 5.0 years, a total of 3,381 cases (5.9%) of AF were identified. An increased risk of AF was observed with decreasing systolic blood pressure response (>20 mm Hg: HR 1.0, referent; 1 to 20 mm Hg: HR 1.09, 95% CI 0.99, 1.20; ≤0 mm Hg: HR 1.22, 95% CI 1.06 to 1.40). Similar results were obtained per 1-SD decrease in systolic blood pressure response (HR 1.08, 95% CI 1.04 to 1.12). The results were consistent when stratified by age, sex, race, hypertension, and coronary heart disease. In conclusion, our results suggest that a decreased systolic blood pressure response during exercise may identify subjects who are at risk for developing AF.

Cardiorespiratory fitness and incident diabetes: the FIT (Henry Ford ExercIse Testing) project

OBJECTIVE

Prior evidence has linked higher cardiorespiratory fitness with a lower risk of diabetes in ambulatory populations. Using a demographically diverse study sample, we examined the association of fitness with incident diabetes in 46,979 patients from The Henry Ford ExercIse Testing (FIT) Project without diabetes at baseline.

RESEARCH DESIGN AND METHODS

Fitness was measured during a clinician-referred treadmill stress test performed between 1991 and 2009. Incident diabetes was defined as a new diagnosis of diabetes on three separate consecutive encounters derived from electronic medical records or administrative claims files. Analyses were performed with Cox proportional hazards models and were adjusted for diabetes risk factors.

RESULTS

The mean age was 53 years with 48% women and 27% black patients. Mean metabolic equivalents (METs) achieved was 9.5 (SD 3.0). During a median follow-up period of 5.2 years (interquartile range 2.6-8.3 years), there were 6,851 new diabetes cases (14.6%). After adjustment, patients achieving ≥12 METs had a 54% lower risk of incident diabetes compared with patients achieving <6 METs (hazard ratio 0.46 [95% CI 0.41, 0.51]; P-trend < 0.001). This relationship was preserved across strata of age, sex, race, obesity, hypertension, and hyperlipidemia.

CONCLUSIONS

These data demonstrate that higher fitness is associated with a lower risk of incident diabetes regardless of demographic characteristics and baseline risk factors. Future studies should examine the association between change in fitness over time and incident diabetes.