John R. Schairer

Peak aerobic capacity predicts prognosis in patients with coronary heart disease

BACKGROUND It is unknown if contemporary preventive treatments such as statins or primary percutaneous coronary intervention in patients with coronary heart disease (CHD) have rendered obsolete the use of measured exercise capacity for assessment of future risk and prognosis. Using a sample of patients from 2 clinical sites, most of whom were taking beta-blockade, antiplatelet, and statin therapy, we hypothesized that peak oxygen consumption (Vo(2)) would remain a strong and independent predictor of all-cause and cardiovascular-specific mortality in men and women with CHD. METHODS We studied 2,812 patients with CHD between 1996 and 2004. All-cause and cardiovascular disease-specific mortality served as end points. RESULTS In all men and women and in a subgroup of patients following evidence-based care, peak Vo(2) remained a strong predictor of all-cause death, with every 1 mL x kg(-1) x min(-1) increase in peak Vo(2) associated with an approximate 15% decrease in risk of death. Among men, a peak Vo(2) (mL x kg(-1) x min(-1)) below approximately 15 was associated with the highest risk, whereas a peak Vo(2) above approximately 19 was associated with a low rate and risk for annual all-cause mortality. Among women, a peak Vo(2) below approximately 12 was associated with the highest risk, whereas a peak Vo(2) above approximately 16.5 was associated with the lowest rate and risk for annual all-cause mortality. CONCLUSIONS In men and women with CHD, peak Vo(2) remains an independent predictor of all-cause and cardiovascular-specific mortality.

Effects of exercise training on chronotropic incompetence in patients with heart failure.

OBJECTIVE To describe the effects of exercise training on chronotropic incompetence in patients with stable heart failure, as measured by their inability to achieve a peak exercise heart rate greater than 85% of maximum. BACKGROUND Exercise intolerance and chronotropic incompetence are characteristic of patients with heart failure. Exercise training improves exercise capacity in these patients; however, to what extent reversal of chronotropic incompetence contributes to such a response remains uncertain. METHODS Fifty-one patients undergoing standard medical therapy were randomly assigned to a 24-week exercise training program or a no exercise control group. Twenty-one of 26 patients assigned to the exercise group and 22 of 25 control patients completed the study. Peak oxygen consumption, resting and exercise plasma norepinephrine level, and quality of life (Living With Heart Failure Questionnaire) were assessed. RESULTS A significant (P <.05) increase in peak heart rate was observed in the exercise group (9 +/- 3 beats/min) when compared with the control group (1 +/- 3 beats/min). Among exercise-trained patients with chronotropic incompetence at baseline (n = 14), the increase in peak heart rate at week 24 was 12 +/- 3 beats/min. Peak oxygen consumption was significantly (P <.05) increased in the exercise group (204 +/- 57 mL/min) versus the control group (72 +/- 33 mL/min). Health-related quality of life was not significantly changed with exercise training. Twenty-four weeks of exercise training induced a greater (P <.05) reduction in plasma norepinephrine at rest and during exercise in patients with a nonischemic cardiomyopathy versus those with ischemic cardiomyopathy. CONCLUSIONS Exercise training results in an increase in peak heart rate and partial reversal of chronotropic incompetence among patients with stable heart failure. These responses contribute, in part, to the exercise training-induced increase in exercise capacity that occurs in these patients.

An Early Appointment to Outpatient Cardiac Rehabilitation at Hospital Discharge Improves Attendance at Orientation A Randomized, Single-Blind, Controlled Trial

Background— Outpatient cardiac rehabilitation (CR) decreases mortality rates but is underutilized. Current median time from hospital discharge to enrollment is 35 days. We hypothesized that an appointment within 10 days would improve attendance at CR orientation. Methods and Results— At hospital discharge, 148 patients with a nonsurgical qualifying diagnosis for CR were randomized to receive a CR orientation appointment either within 10 days (early) or at 35 days (standard). The primary end point was attendance at CR orientation. Secondary outcome measures were attendance at ≥1 exercise session, the total number of exercise sessions attended, completion of CR, and change in exercise training workload while in CR. Average age was 60±12 years; 56% of participants were male and 49% were black, with balanced baseline characteristics between groups. Median time (95% confidence interval) to orientation was 8.5 (7–13) versus 42 (35 to NA [not applicable]) days for the early and standard appointment groups, respectively (P<0.001). Attendance rates at the orientation session were 77% (57/74) versus 59% (44/74) in the early and standard appointment groups, respectively, which demonstrates a significant 18% absolute and 56% relative improvement (relative risk, 1.56; 95% confidence interval, 1.03–2.37; P=0.022). The number needed to treat was 5.7. There was no difference (P>0.05) in any of the secondary outcome measures, but statistical power for these end points was low. Safety analysis demonstrated no difference between groups in CR-related adverse events. Conclusions— Early appointments for CR significantly improve attendance at orientation. This simple technique could potentially increase initial CR participation nationwide. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01596036.

Caloric expenditure during cardiac rehabilitation.

PURPOSE The purpose of this study was to describe estimated caloric expenditure among patients in a maintenance cardiac rehabilitation program relative to a stated goal of approximately 300 kcal/session or 1,000 kcal/week. Additionally, we assessed the validity of several different methods for estimating caloric expenditure. METHODS The caloric expenditure for an exercise session was evaluated in 30 of 65 patients exercising in a maintenance cardiac rehabilitation program. Patients exercised using a treadmill, dual-action ergometer, upright stepper, or reclining stepper. The kilocalorie expenditure was assessed by three different techniques. The first used liquid crystal display (LCD) readings from the equipment (LCD method), the second combined both the American College of Sports Medicine metabolic equations for treadmill walking and the LCD values from the other equipment (Combined method), and the third measured oxygen consumption (VO2 method). RESULTS The caloric expenditure for the LCD, Combined, and VO2 methods were 247 +/- 83, 245 +/- 80, and 230 +/- 88 kcal, respectively. Agreement between methods using intraclass correlation analysis was r = 0.84 (0.68 to 0.92, 95% confidence intervals) for LCD versus VO2 and r = 0.88 (0.77 to 0.94, 95% confidence intervals) for Combined versus VO2 method. CONCLUSIONS Most patients (83%) in a maintenance cardiac rehabilitation program exercise below 300 kcal per session, a level believed to be necessary to illicit favorable changes in cardiovascular health. Additionally, the Combined method provides a reasonable estimate of kilocalorie expenditure. Use of kilocalorie expenditure should be considered in the cardiac rehabilitation setting as a fourth component in the exercise prescription.

Greater improvement in cardiorespiratory fitness using higher-intensity interval training in the standard cardiac rehabilitation setting.

PURPOSE: We tested the hypothesis that higher-intensity interval training (HIIT) could be deployed into a standard cardiac rehabilitation (CR) setting and would result in a greater increase in cardiorespiratory fitness (ie, peak oxygen uptake, ) versus moderate-intensity continuous training (MCT). METHODS: Thirty-nine patients participating in a standard phase 2 CR program were randomized to HIIT or MCT; 15 patients and 13 patients in the HIIT and MCT groups, respectively, completed CR and baseline and followup cardiopulmonary exercise testing. RESULTS: No patients in either study group experienced an event that required hospitalization during or within 3 hours after exercise. The changes in resting heart rate and blood pressure at followup testing were similar for both HIIT and MCT. at ventilatory-derived anaerobic threshold increased more (P < .05) with HIIT (3.0 ± 2.8 mL·kg·−1min−1) versus MCT (0.7 ± 2.2 mL·kg·−1min−1). During followup testing, submaximal heart rate at the end of stage 2 of the exercise test was significantly lower within both the HIIT and MCT groups, with no difference noted between groups. Peak V˙o2 improved more after CR in patients in HIIT versus MCT (3.6 ± 3.1 mL·kg.−1·min−1 vs 1.7 ± 1.7 mL·kg.−1·min−1; P < .05). CONCLUSIONS: Among patients with stable coronary heart disease on evidence-based therapy, HIIT was successfully integrated into a standard CR setting and, when compared to MCT, resulted in greater improvement in peak exercise capacity and submaximal endurance.

Physical Fitness and Hypertension in a Population at Risk for Cardiovascular Disease: The Henry Ford ExercIse Testing (FIT) Project

Background Increased physical fitness is protective against cardiovascular disease. We hypothesized that increased fitness would be inversely associated with hypertension. Methods and Results We examined the association of fitness with prevalent and incident hypertension in 57 284 participants from The Henry Ford ExercIse Testing (FIT) Project (1991–2009). Fitness was measured during a clinician‐referred treadmill stress test. Incident hypertension was defined as a new diagnosis of hypertension on 3 separate consecutive encounters derived from electronic medical records or administrative claims files. Analyses were performed with logistic regression or Cox proportional hazards models and were adjusted for hypertension risk factors. The mean age overall was 53 years, with 49% women and 29% black. Mean peak metabolic equivalents (METs) achieved was 9.2 (SD, 3.0). Fitness was inversely associated with prevalent hypertension even after adjustment (≥12 METs versus <6 METs; OR: 0.73; 95% CI: 0.67, 0.80). During a median follow‐up period of 4.4 years (interquartile range: 2.2 to 7.7 years), there were 8053 new cases of hypertension (36.4% of 22 109 participants without baseline hypertension). The unadjusted 5‐year cumulative incidences across categories of METs (<6, 6 to 9, 10 to 11, and ≥12) were 49%, 41%, 30%, and 21%. After adjustment, participants achieving ≥12 METs had a 20% lower risk of incident hypertension compared to participants achieving <6 METs (HR: 0.80; 95% CI: 0.72, 0.89). This relationship was preserved across strata of age, sex, race, obesity, resting blood pressure, and diabetes. Conclusions Higher fitness is associated with a lower probability of prevalent and incident hypertension independent of baseline risk factors.

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.

Left ventricular response to submaximal exercise in endurance-trained athletes and sedentary adults

This investigation examines the hypothesis that athletes increase stroke volume with submaximal exercise through an augmentation of left ventricular (LV) end-diastolic volume and a reduction of LV end-systolic volume, whereas sedentary adults only increase stroke volume modestly, because LV end-diastolic volume does not increase. Upright bicycle exercise was performed by 17 endurance-trained male athletes and 15 sedentary men. M-mode echocardiograms were obtained during submaximal exercise at predetermined heart rates. Athletes, at a heart rate of 130 beats/min, increased their stroke volume 67% from 72 +/- 18 ml to 120 +/- 26 ml (p less than 0.001). This resulted from an increase of LV end-diastolic volume from 119 +/- 23 to 152 +/- 28 ml (p less than 0.001) and a reduction in LV end-systolic volume from 46 +/- 14 to 31 +/- 9 ml (p less than 0.001). Sedentary men at the same heart rate increased stroke volume 22% from 63 +/- 15 to 77 +/- 21 ml (p less than 0.05). LV end-diastolic volume did not change (96 +/- 20 vs 97 +/- 28 ml) (p = not significant), but LV end-systolic volume decreased (33 +/- 11 vs 20 +/- 9 ml) (p less than 0.001). In conclusion, athletes increased cardiac output through a more prominent augmentation of stroke volume than sedentary subjects at submaximal exercise. This was accomplished through an augmentation of LV end-diastolic volume. This may have a conserving effect on myocardial oxygen consumption at these levels of exercise.

Prognostic value of exercise capacity in patients with coronary artery disease: the FIT (Henry Ford ExercIse Testing) project.

OBJECTIVE To examine the prognostic value of exercise capacity in patients with nonrevascularized and revascularized coronary artery disease (CAD) seen in routine clinical practice. PATIENTS AND METHODS We analyzed 9852 adults with known CAD (mean ± SD age, 61±12 years; 69% men [n=6836], 31% black race [n=3005]) from The Henry Ford ExercIse Testing (FIT) Project, a retrospective cohort study of patients who underwent physician-referred stress testing at a single health care system between January 1, 1991, and May 31, 2009. Patients were categorized by revascularization status (nonrevascularized, percutaneous coronary intervention [PCI], or coronary artery bypass graft [CABG] surgery) and by metabolic equivalents (METs) achieved on stress testing. Using Cox regression models, hazard ratios for mortality, myocardial infarction (MI), and downstream revascularizations were calculated after adjusting for potential confounders, including cardiac risk factors, pertinent medications, and stress testing indication. RESULTS There were 3824 all-cause deaths during median follow-up of 11.5 years. In addition, 1880 MIs, and 1930 revascularizations were ascertained. Each 1-MET increment in exercise capacity was associated with a hazard ratio (95% CI) of 0.87 (0.85-0.89), 0.87 (0.85-0.90), and 0.86 (0.84-0.89) for mortality; 0.98 (0.96-1.01), 0.88 (0.84-0.92), and 0.93 (0.90-0.97) for MI; and 0.94 (0.92-0.96), 0.91 (0.88-0.95), and 0.96 (0.92-0.99) for downstream revascularizations in the nonrevascularized, PCI, and CABG groups, respectively. In each MET category, the nonrevascularized group had similar mortality risk as and higher MI and downstream revascularization risk than the PCI and CABG surgery groups (P<.05). CONCLUSION Exercise capacity was a strong predictor of mortality, MI, and downstream revascularizations in this cohort. Furthermore, patients with similar exercise capacities had an equivalent mortality risk, irrespective of baseline revascularization status.

Leisure time physical activity of patients in maintenance cardiac rehabilitation

PURPOSE Increasing caloric expenditure through physical activity is associated with reduced mortality. On the basis of observational studies, previous authors have suggested that at least 1000 kcal per week and possibly 1500 kcal per week of physical activity is necessary for health benefits. The authors have previously reported that patients in maintenance cardiac rehabilitation accumulate approximately 230 kcal per exercise session, suggesting that additional activity outside of cardiac rehabilitation is needed to achieve the goal of 1500 kcal per week. The authors estimated the amount of energy expenditure performed each week by patients in cardiac rehabilitation during both program participation and leisure time. METHODS For this study, 104 patients enrolled in a supervised maintenance cardiac rehabilitation program at both tertiary care and community settings for at least 6 months completed a self-administered physical activity questionnaire. Energy expenditure in cardiac rehabilitation and leisure time activity was measured in kilocalories. Total caloric expenditure was determined by adding up the number of kilocalories expended by the patients each week climbing stairs, walking, participating in cardiac rehabilitation, and engaging in sports. RESULTS Patients in cardiac rehabilitation expended weekly, on the average, 1504 +/- 830 kcal in physical activity, 830 +/- 428 kcal in cardiac rehabilitation, and 675 +/- 659 kcal in leisure time activity. There was a significant difference in caloric expenditure between men and women, between those with a body mass index (BMI) less than 30 and those with a BMI of 30 or more, and between those younger than 70 years and those 70 years or older. There was no difference between races. Whereas 43% of the patients accumulated 1500 kcal, 57% did not. CONCLUSIONS The findings showed that 72% of the patients in cardiac rehabilitation accumulated at least 1000 kcal of energy expenditure per week and met public health guidelines. Also, 43% of the patients in cardiac rehabilitation accumulated more than 1500 kcal of energy expenditure per week, a level identified as necessary to reduce all-cause mortality. Women of either race, patients with a BMI of 30 or more, and patients age 70 years or older are the groups least likely to achieve 1500 kcal of energy expenditure per week. The authors recommend incorporating weekly kilocalories of energy expenditure in the exercise prescription of patients to ensure achievement of maximum health benefits.