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Exercise-Based Cardiac Rehabilitation and Improvements in Cardiorespiratory Fitness: Implications Regarding Patient Benefit

  • Barry A. Franklin
    Correspondence
    Correspondence: Address to Barry A. Franklin, PhD, Preventive Cardiology and Cardiac Rehabilitation, Beaumont Health Center, Area C, 4949 Coolidge Hwy, Royal Oak, MI 48073.
    Affiliations
    Department of Cardiovascular Diseases, William Beaumont Hospital, Royal Oak, MI
    Oakland University William Beaumont School of Medicine, Rochester, MI
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  • Carl J. Lavie
    Affiliations
    Department of Cardiovascular Diseases, John Ochsner Heart and Vascular Institute, Ochsner Clinical School, The University of Queensland School of Medicine, New Orleans, LA
    Department of Preventive Medicine, Pennington Biomedical Research Center, Louisiana State University Health Systems, Baton Rouge, LA
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  • Ray W. Squires
    Affiliations
    Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester, MN
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  • Richard V. Milani
    Affiliations
    Department of Cardiovascular Diseases, John Ochsner Heart and Vascular Institute, Ochsner Clinical School, The University of Queensland School of Medicine, New Orleans, LA
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      Abbreviations and Acronyms:

      CHD (coronary heart disease), CR (cardiac rehabilitation), CRF (cardiorespiratory fitness), CVD (cardiovascular disease), ET (exercise training), MET (metabolic equivalent), MI (myocardial infarction), V˙o2 (oxygen uptake)
      The cost of cardiovascular disease (CVD) is expected to triple in the next 20 years,
      • Weintraub W.S.
      • Daniels S.R.
      • Burke L.E.
      • et al.
      Value of primordial and primary prevention for cardiovascular disease: a policy statement from the American Heart Association.
      highlighting the need for low-cost preventive therapies to achieve improved cardiovascular health outcomes and patient value.
      • Porter M.E.
      What is the value of health care?.
      For literally millions of previously affected adults in the United States, interventions that have been shown to reduce the risk of recurrent cardiovascular events, collectively referred to as secondary prevention (Figure 1),
      • Franklin B.A.
      • Cushman M.
      Recent advances in preventive cardiology and lifestyle medicine.
      may include exercise training (ET)–based cardiac rehabilitation (CR) programs.
      Figure thumbnail gr1
      Figure 1Risk factor framework and the progression of cardiovascular disease, with types of prevention interventions: primordial (prevention of risk factors), primary (treatment of risk factors), and secondary (prevention of recurrent cardiovascular events). Environmental and cardiovascular health modulators include dietary and physical activity practices, cigarette smoking, pharmacotherapies (eg, aspirin, β-adrenergic blockers, statins, and angiotensin-converting enzyme inhibitors) when indicated, and coronary revascularization when appropriate. CHF = congestive heart failure; MI = myocardial infarction; PAD = peripheral arterial disease.
      From Circulation,
      • Franklin B.A.
      • Cushman M.
      Recent advances in preventive cardiology and lifestyle medicine.
      with permission.
      Numerous epidemiologic studies in men and women with and without known coronary heart disease (CHD) and varied comorbid conditions (eg, overweight/obesity, hypertension, metabolic syndrome, and type 2 diabetes mellitus) have now identified a low level of cardiorespiratory fitness (CRF), expressed as peak or maximal metabolic equivalents (METs; 1 MET equals a whole-body resting oxygen consumption of 3.5 mL/kg per min), as an independent risk factor for all-cause and cardiovascular mortality. Individuals with low CRF were approximately 2 to 5 times more likely to die during follow-up compared with their higher CRF counterparts.
      • Franklin B.A.
      • McCullough P.A.
      Cardiorespiratory fitness: an independent and additive marker of risk stratification and health outcomes.
      The study by Martin et al,
      • Martin B.J.
      • Arena R.
      • Haykowsky M.
      • et al.
      Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
      published in the current issue of Mayo Clinic Proceedings, extends these analyses to a cohort of middle-aged and older men and women with documented CHD who participated in a 12-week ET-based CR program in Calgary, Alberta, Canada, examining the association between improvements in peak METs achieved through CR and subsequent mortality, with specific reference to patients in the low CRF cohort at baseline.
      To assess the association among baseline, immediate postexercise-based CR (ie, after 12 weeks), and 1-year follow-up measures of peak METs on the risk of mortality in men and women with known CHD, Martin et al
      • Martin B.J.
      • Arena R.
      • Haykowsky M.
      • et al.
      Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
      conducted a retrospective analysis of data from the Cardiac Wellness Institute of Calgary, including 5641 patients (4282 men [76%] and 1359 women [24%]; mean ± SD age, 60.0±10.3 years) who participated in CR between July 1, 1996, and February 28, 2009. The CRF was estimated from the attained speed, grade, and duration of graded treadmill exercise testing to volitional exhaustion or adverse signs and symptoms. Patients were categorized into low (<5 METs), moderate (5-8 METs), and high (>8 METs) CRF groups. Following the baseline exercise test, patients engaged in a 12-week supervised ET regimen, 2 times per week, and were encouraged to participate in an additional 2 to 3 ET sessions on their own, using a prescribed target heart rate, MET level, and perceived exertion (“somewhat hard”) as adjunctive intensity modulators. After completing the 12-week CR program, participants were educated regarding continued home-based lifestyle modification, including ET and dietary practices. A subset of the original population (3514 of 5641 [62.3%]) additionally underwent a repeated assessment at 1 year. All patients had a minimum 1-year follow-up; however, deaths in the entire study population during the full follow-up period program (approximately 13 years) were considered.
      During the 12-week CR program, all subgroups demonstrated significant increases in their level of CRF (P<.001); however, improvements were greatest in those patients who had the lowest baseline CRF. Specifically, improvements were 1.41 METs (39% improvement), 1.01 METs (15% improvement), and 0.80 MET (8.6% improvement) for the low, moderate, and high CRF patients (at baseline), respectively. Restated, the greatest improvements occurred in those patients who were most likely to benefit most from an ET intervention, that is, those in the lowest CRF, high-risk cohort. Baseline CRF was inversely related to long-term mortality, even after adjusting for potential confounders, including age, sex, comorbid conditions, and disease severity. Improvement in CRF at 12 weeks was associated with decreased overall mortality, with the greatest reduction in mortality per MET increase (30%) among those patients with the lowest baseline CRF levels (<5 METs). At 1 year, each 1-MET increase in CRF was associated with a 22% reduction in overall mortality for the entire cohort (P<.001). In view of the very modest changes in conventional risk factors (eg, cholesterol level, triglyceride value, and body mass index), even at 1 year, the investigators concluded that a significant mortality benefit of CR is due to the ET component of the program, whether it is medically supervised, home based, or both. This study may be somewhat limited by the lack of information regarding the ET habits after completing the CR program and underrepresentation of women, common problems in many such studies.

      Fitness or Exercise Tolerance and Mortality in Secondary Prevention

      Vanhees et al
      • Vanhees L.
      • Fagard R.
      • Thijs L.
      • Staessen J.
      • Amery A.
      Prognostic significance of peak exercise capacity in patients with coronary artery disease.
      reported the prognostic significance of peak oxygen uptake (V˙o2) in 527 men with CVD who were referred to an outpatient CR program. Peak V˙o2 on a cycle ergometer was directly measured by open-circuit spirometry a mean ± SD of 12.9±2.7 weeks after acute myocardial infarction (MI; n=312) or coronary artery bypass surgery (n=215). All tests were terminated at a comparable end point, that is, volitional fatigue (exhaustion). During a mean follow-up of 6.1 years, 33 and 20 patients died of cardiovascular and noncardiovascular causes, respectively. Those with the highest cardiovascular and all-cause mortality averaged 4.4 METs or less. In contrast, no deaths occurred among patients who averaged 9.2 METs or more. Similarly, long-term findings from the National Exercise and Heart Disease Project among post-MI patients demonstrated that every 1-MET increase in CRF after a training period was associated with a reduction in mortality from any cause that ranged from 8% to 14% during a 19-year follow-up.
      • Dorn J.
      • Naughton J.
      • Imamura D.
      • Trevisan M.
      Results of a multicenter randomized clinical trial of exercise and long-term survival in myocardial infarction patients: the National Exercise and Heart Disease Project (NEHDP).
      Kavanagh et al
      • Kavanagh T.
      • Mertens D.J.
      • Hamm L.F.
      • et al.
      Prediction of long-term prognosis in 12 169 men referred for cardiac rehabilitation.
      • Kavanagh T.
      • Mertens D.J.
      • Hamm L.F.
      • et al.
      Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation.
      evaluated the predictive value of cardiopulmonary exercise testing in 12,169 men (55.0±9.6 years old) and 2380 women (59.7±9.5 years old) with known CHD who were followed up for a mean of 7.9 and 6.1 years, respectively. Directly measured peak V˙o2 on a cycle ergometer at program entry proved to be a powerful predictor of cardiovascular and all-cause mortality. The cutoff point, above which there was a marked benefit in prognosis, was 13 mL/kg per minute (3.7 METs) in women and 15 mL/kg per minute (4.3 METs) in men. For each 1-mL/kg per minute increase in peak V˙o2, there was a 10% reduction of cardiovascular mortality in women vs 9% in men. The investigators concluded that men and women referred to CR who achieve only modest gains in CRF could nevertheless obtain significant prognostic and functional benefits.
      In 2008, Kavanagh et al
      • Kavanagh T.
      • Hamm L.F.
      • Beyene J.
      • et al.
      Usefulness of improvement in walking distance versus peak oxygen uptake in predicting prognosis after myocardial infarction and/or coronary artery bypass grafting in men.
      compared changes in CRF, as measured by peak V˙o2, vs improvement in walking distance in predicting prognosis after acute MI and/or coronary artery bypass surgery in 6956 men who completed a 12-month walking-based CR program. After a median 9-year follow-up, improvement in walking distance was a strong independent predictor and a more accurate guide to prognosis than gains in peak METs. Each 1-mile increase in walking distance conferred a 20% reduction in cardiovascular mortality in this cohort of men with CHD. More recently, others have reported that distance walked on a 6-minute walk test predicted subsequent cardiovascular events during an 8-year follow-up in patients with stable CHD.
      • Beatty A.L.
      • Schiller N.B.
      • Whooley M.A.
      Six-minute walk test as a prognostic tool in stable coronary heart disease: data from the Heart and Soul Study.
      The Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training randomized controlled trial in patients with chronic heart failure with reduced left ventricular ejection fraction (≤35%) found that ET was associated with a decreased incidence (11%) of combined all-cause mortality or hospitalization after adjusting for baseline prognostic variables.
      • O’Connor C.M.
      • Whellan D.J.
      • Lee K.L.
      • et al.
      Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial.
      Interestingly, the mean postconditioning improvement in directly measured peak V˙o2 was only 0.7 mL/kg per minute. In another investigation of 600 patients with CVD who were referred to a 12-week CR program, participants performed both entry-level and exit-level submaximal treadmill workloads, using fixed target heart rate ranges and perceived exertion ratings. After adjusting for age, each 1-MET increase in exit training level was associated with a 28% decrease in all-cause mortality.
      • Feuerstadt P.
      • Chai A.
      • Kligfield P.
      Submaximal effort tolerance as a predictor of all-cause mortality in patients undergoing cardiac rehabilitation.
      Collectively, the aforementioned referenced studies (Table 1) and other recent reports
      • Myers J.
      • Herbert W.
      • Ribisl P.
      • Franklin B.
      Is new science driving practice improvements and better patient outcomes? applications for cardiac rehabilitation.
      support the hypothesis that CRF provides a strong, graded inverse association with cardiovascular and all-cause mortality in patients with and without CHD, irrespective of sex, body mass index, major risk factors, heart failure, and other comorbid conditions. An exercise capacity of less than 5 METs correlates with a higher mortality group, whereas 9 to 10 METs or more generally identifies a cohort with an excellent long-term prognosis, regardless of the underlying extent of CHD. These data and the results of other investigations
      • Kokkinos P.
      • Myers J.
      Exercise and physical activity: clinical outcomes and applications.
      also suggest an “asymptote of gain” beyond which further improvements in CRF (ie, beyond 9-10 METs) convey little or no additional survival benefit. The findings of Martin et al
      • Martin B.J.
      • Arena R.
      • Haykowsky M.
      • et al.
      Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
      reinforce the notion of small gains yielding big results and suggest that CHD patients with low CRF should be particularly targeted in CR programs to increase their functional capacity in an effort to reduce their heightened mortality.
      Table 1Relation of Fitness or Exercise Tolerance to All-Cause or Cardiovascular Mortality in Secondary Prevention
      CABG = coronary artery bypass graft surgery; CHD = coronary heart disease; CR = cardiac rehabilitation; CVD = cardiovascular disease; EF = ejection fraction; MET = metabolic equivalent (where 1 MET equals 3.5 mL/kg/min); MI = myocardial infarction; 6MWT = 6-minute walk test; V˙o2 = oxygen consumption.
      ReferencePopulation/follow-up periodFitness measurementAll-cause or cardiovascular mortality
      Vanhees et al,
      • Vanhees L.
      • Fagard R.
      • Thijs L.
      • Staessen J.
      • Amery A.
      Prognostic significance of peak exercise capacity in patients with coronary artery disease.
      1994
      Male patients ≥4 wk after MI (n=312) or CABG (n=215) for 6.1 yPeak V˙o271% Decrease per 1-L/min increase
      Dorn et al,
      • Dorn J.
      • Naughton J.
      • Imamura D.
      • Trevisan M.
      Results of a multicenter randomized clinical trial of exercise and long-term survival in myocardial infarction patients: the National Exercise and Heart Disease Project (NEHDP).
      1999
      315 Post-MI men randomized to a 6-mo exercise program; patients were followed up for 19 yPeak METs8%-14% Decrease per 1-MET increase
      Kavanagh et al,
      • Kavanagh T.
      • Mertens D.J.
      • Hamm L.F.
      • et al.
      Prediction of long-term prognosis in 12 169 men referred for cardiac rehabilitation.
      2002
      12,169 Men with CVD referred for exercise-based CR; median follow-up was 7.9 yPeak V˙o29% Decrease per 1-mL/kg/min increase
      Kavanagh et al,
      • Kavanagh T.
      • Mertens D.J.
      • Hamm L.F.
      • et al.
      Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation.
      2003
      2380 Women with CVD referred for exercise-based CR; mean follow-up was 6.1 yPeak V˙o210% Decrease per 1-mL/kg/min increase
      Kavanagh et al,
      • Kavanagh T.
      • Hamm L.F.
      • Beyene J.
      • et al.
      Usefulness of improvement in walking distance versus peak oxygen uptake in predicting prognosis after myocardial infarction and/or coronary artery bypass grafting in men.
      2008
      6956 Men with CVD completing a 12-mo walking-based training regimen; median follow-up was 9.0 yWalking distance20% Decrease per 1-mile improvement
      O’Connor et al,
      • O’Connor C.M.
      • Whellan D.J.
      • Lee K.L.
      • et al.
      Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial.
      2009
      2331 Medically stable outpatients with heart failure and reduced EF (≤35%), randomized to exercise training or usual care; median follow-up was 30 moPeak V˙o211% Decrease per 0.7-mL/kg/min increase
      Feuerstadt et al,
      • Feuerstadt P.
      • Chai A.
      • Kligfield P.
      Submaximal effort tolerance as a predictor of all-cause mortality in patients undergoing cardiac rehabilitation.
      2007
      600 Men and women with CVD who were referred to a 12-wk exercise-based CR program; mean follow-up was 4.4 yExit training MET level34% Decrease per 1-MET increase;

      28% decrease per 1-MET increase
      After adjustment for age.
      Beatty et al,
      • Beatty A.L.
      • Schiller N.B.
      • Whooley M.A.
      Six-minute walk test as a prognostic tool in stable coronary heart disease: data from the Heart and Soul Study.
      2012
      556 Outpatients with stable CHD; median follow-up was 8.0 y for cardiovascular events (heart failure, MI, and death)6MWTEach SD decrease in 6MWT distance (104 m) was associated with a 30%
      Adjusted for potential confounders.
      to 55%
      Unadjusted.
      higher rate of cardiovascular events
      Martin et al,
      • Martin B.J.
      • Arena R.
      • Haykowsky M.
      • et al.
      Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
      2013
      5641 Patients with CHD who participated in a 12-wk exercise-based CR program; ≥1 y follow-up for all patientsPeak METs22% Decrease per MET increase (entire cohort) and a 30% decrease per MET increase in those with low baseline fitness (<5 METs)
      a CABG = coronary artery bypass graft surgery; CHD = coronary heart disease; CR = cardiac rehabilitation; CVD = cardiovascular disease; EF = ejection fraction; MET = metabolic equivalent (where 1 MET equals 3.5 mL/kg/min); MI = myocardial infarction; 6MWT = 6-minute walk test; V˙o2 = oxygen consumption.
      b After adjustment for age.
      c Adjusted for potential confounders.
      d Unadjusted.

      Cardioprotective Effects of Regular ET and/or Improved CRF

      Numerous mechanisms may be responsible for the decreased mortality associated with ET-based CR, including antiatherosclerotic, anti-ischemic, antiarrhythmic, antithrombotic, and psychologic effects (Table 2).
      • Franklin B.A.
      • McCullough P.A.
      Cardiorespiratory fitness: an independent and additive marker of risk stratification and health outcomes.
      Because more than 40% of the risk reduction associated with ET cannot be accounted for by changes in traditional risk factors, Green et al
      • Green D.J.
      • O’Driscoll G.
      • Joyner M.J.
      • Cable N.T.
      Exercise and cardiovascular risk reduction: time to update the rationale for exercise?.
      proposed a cardioprotective “vascular conditioning” effect, including enhanced nitric oxide vasodilator function, improved vascular reactivity, altered vascular structure, or combinations thereof. This adaptation may explain, at least in part, the significantly higher event-free survival in a cohort of patients (n=101) with obstructive CHD who were randomized to 12 months of ET or percutaneous coronary intervention with stenting (88% vs 70% in the percutaneous coronary intervention group; P=.02).
      • Hambrecht R.
      • Walther C.
      • Möbius-Winkler S.
      • Gielen S.
      • et al.
      Percutaneous coronary angioplasty compared with exercise training in patients with stable coronary artery disease: a randomized trial.
      Whereas percutaneous coronary intervention treats a very short segment of the diseased coronary tree, it was suggested that ET exerts beneficial effects on endothelial function and disease progression in the entire arterial bed.
      • Green D.J.
      • O’Driscoll G.
      • Joyner M.J.
      • Cable N.T.
      Exercise and cardiovascular risk reduction: time to update the rationale for exercise?.
      • Hambrecht R.
      • Walther C.
      • Möbius-Winkler S.
      • Gielen S.
      • et al.
      Percutaneous coronary angioplasty compared with exercise training in patients with stable coronary artery disease: a randomized trial.
      Decreased vulnerability to arrhythmias and increased resistance to threatening ventricular arrhythmias have also been postulated to reflect exercise-related autonomic adaptations (eg, increased vagal tone and decreased adrenergic activity).
      • Swain D.P.
      • Franklin B.A.
      Comparison of cardioprotective benefits of vigorous versus moderate intensity aerobic exercise.
      Table 2Potential Cardioprotective Effects of Regular Physical Activity
      AntiatheroscleroticPsychologicalAntithromboticAnti-ischemicAntiarrhythmic
      Increase in HDL-C and insulin sensitivitySocial supportFibrinolysisCoronary flow, EPCs, CACs, and nitric oxideVagal tone and heart rate variability
      Decrease in total cholesterol, LDL-C, blood pressure, and inflammationDepression and stressPlatelet adhesiveness, fibrinogen, and blood viscosityMyocardial oxygen demand, endothelial dysfunctionAdrenergic activity
      CAC = cultured/circulating angiogenic cells; EPC = endothelial progenitor cells; HDL-C = high-density lipoprotein cholesterol; LDL-C = low-density lipoprotein cholesterol.
      Another benefit of ET-based CR includes improvements in psychological dysfunction, which is common in patients with CHD.
      • Lavie C.J.
      • Milani R.V.
      • O’Keefe J.H.
      • Lavie T.J.
      Impact of exercise training on psychological risk factors.
      • Lavie C.J.
      • Milani R.V.
      Adverse psychological and coronary risk profiles in young patients with coronary artery disease and benefits of formal cardiac rehabilitation.
      Studies have reported nearly 50% reductions in adverse behavioral scores and the prevalence of psychological disorders, including depression, anxiety, hostility, and overall stress, after formal CR.
      • Lavie C.J.
      • Milani R.V.
      • O’Keefe J.H.
      • Lavie T.J.
      Impact of exercise training on psychological risk factors.
      • Lavie C.J.
      • Milani R.V.
      Adverse psychological and coronary risk profiles in young patients with coronary artery disease and benefits of formal cardiac rehabilitation.
      Moreover, CHD patients with depression and/or psychological distress seem to derive the greatest mortality benefits from CR, especially in those who achieve only modest improvements in CRF (<10%). Such patients commonly demonstrate significant reductions in the prevalence of depression and depression-related mortality, similar to that achieved with more marked improvements in peak METs.
      • Milani R.V.
      • Lavie C.J.
      Impact of cardiac rehabilitation on depression and its associated mortality.
      Even greater reductions in depression-related mortality were noted in very high-risk heart failure patients after CR.
      • Milani R.V.
      • Lavie C.J.
      • Mehra M.R.
      • Ventura H.O.
      Impact of exercise training and depression on survival in heart failure due to coronary heart disease.
      Thus, major benefits of CR programs may be related to improving levels of CRF in patients with abnormal psychological profiles.
      • Milani R.V.
      • Lavie C.J.
      Reducing psychosocial stress: a novel mechanism of improving survival from exercise training.

      Exercise Recommendations for Patients With CHD

      Patients with CHD should be counseled to participate in 30 to 60 minutes of moderate-intensity aerobic physical activity, such as brisk walking, at least 5 days and preferably 7 days per week, complemented by resistance training 2 or more days per week and an increase in daily lifestyle activities (eg, walking breaks at work, gardening, and household work).
      • Smith Jr., S.C.
      • Benjamin E.J.
      • Bonow R.O.
      • et al.
      AHA/ACCF secondary prevention and risk reduction therapy for patients with coronary and other atherosclerotic vascular disease: 2011 update: a guideline from the American Heart Association and American College of Cardiology Foundation.
      • Quell K.J.
      • Porcari J.P.
      • Franklin B.A.
      • Foster C.
      • Andreuzzi R.A.
      • Anthony R.M.
      Is brisk walking an adequate aerobic training stimulus for cardiac patients?.
      A major goal is to improve CRF and move patients out of the lowest CRF, least active, high-risk cohort.
      • Smith Jr., S.C.
      • Benjamin E.J.
      • Bonow R.O.
      • et al.
      AHA/ACCF secondary prevention and risk reduction therapy for patients with coronary and other atherosclerotic vascular disease: 2011 update: a guideline from the American Heart Association and American College of Cardiology Foundation.
      The threshold intensity for training to improve CRF in exercise-based CR has been suggested to approximate 45% of the oxygen uptake reserve,
      • Swain D.P.
      • Franklin B.A.
      Is there a threshold intensity for aerobic training in cardiac patients?.
      which is the difference between resting and peak METs, using a level of metabolism that starts at a resting level (ie, 1 MET) rather than at zero. To illustrate, if a patient has an aerobic capacity of 5 METs, the minimum intensity for training would be calculated as 45% of the range between rest and his/her functional capacity, that is, ([5 − 1] × 0.45) + 1 = 2.8 METs. In the absence of a baseline peak or symptom-limited exercise test, the threshold intensity for training in CR can be approximated by the patient’s standing resting heart rate plus 20 to 30 beats/min,
      • Dressendorfer R.H.
      • Franklin B.A.
      • Smith J.L.
      • et al.
      Early cardiac rehabilitation training heart rate based on low-level treadmill testing after myocardial infarction and before hospital discharge.
      • Joo K.C.
      • Brubaker P.H.
      • MacDougall A.
      • Saikin A.M.
      • Ross J.H.
      • Whaley M.H.
      Exercise prescription using resting heart rate plus 20 or perceived exertion in cardiac rehabilitation.
      using perceived exertion (fairly light to somewhat hard) as an adjunctive intensity modulator.
      Although numerous studies have reported modest improvements in CRF and selected CHD risk factors with standard exercise-based CR, other investigations have sought to determine the amount of physical activity (kilocalories per week) needed to attenuate the progression of coronary atherosclerotic lesions and/or promote greater weight losses and even more favorable cardiometabolic risk profiles (Figure 2).
      • Hambrecht R.
      • Niebauer J.
      • Marburger C.
      • et al.
      Various intensities of leisure time physical activity in patients with coronary artery disease: effects on cardiorespiratory fitness and progression of coronary atherosclerotic lesions.
      • Ades P.A.
      • Savage P.D.
      • Toth M.J.
      • et al.
      High-calorie-expenditure exercise: a new approach to cardiac rehabilitation for overweight coronary patients.
      Comparing coronary angiographic findings at baseline and after 12 months of an exercise intervention, Hambrecht et al
      • Hambrecht R.
      • Niebauer J.
      • Marburger C.
      • et al.
      Various intensities of leisure time physical activity in patients with coronary artery disease: effects on cardiorespiratory fitness and progression of coronary atherosclerotic lesions.
      reported that CHD patients with moderate (1533±122 kcal/wk) and high levels (2204±237 kcal/wk) of leisure-time physical activity showed no change and regression of coronary atherosclerotic lesions, respectively, whereas those with the lowest level of leisure-time physical activity (1022±142 kcal/wk) demonstrated progression of disease (P<.005). Similarly, Ades et al
      • Ades P.A.
      • Savage P.D.
      • Toth M.J.
      • et al.
      High-calorie-expenditure exercise: a new approach to cardiac rehabilitation for overweight coronary patients.
      noted profound reductions in body weight and fat stores and marked improvements in cardiometabolic risk factors in overweight CHD patients who underwent a high-calorie energy expenditure (3000 to 3500 kcal/wk) CR program compared with a standard CR control group. These data suggest that CHD patients who are able to adopt a more aggressive training regimen (ie, approximating 5-6 hours per week of vigorous ET) are likely to derive even greater benefits.
      Figure thumbnail gr2
      Figure 2Impact of the amount of physical activity (kilocalories per week) on angiographic, risk factor, and weight loss outcomes associated with exercise-based cardiac rehabilitation.

      Implications for Health Care Professionals

      Although the inverse association between aerobic capacity and cardiovascular and all-cause mortality has been widely promulgated among physiologists and epidemiologists, the medical community has been less sanguine in embracing CRF as one of the strongest and most consistent prognostic markers in patients with and without CHD. For patients with stable CHD, each 1-MET increase in CRF is associated with an 8% to 35% (median, 16%) reduction in mortality, which compares favorably with the survival benefit conferred by the most commonly prescribed cardioprotective medications.
      • Boden W.E.
      • Franklin B.A.
      • Wenger N.K.
      Physical activity and structured exercise for patients with stable ischemic heart disease.
      Because CRF is such a powerful prognostic indicator, measurement of peak METs should be considered to be a standard assessment for patients with CVD or high CVD risk. The findings of Martin et al
      • Martin B.J.
      • Arena R.
      • Haykowsky M.
      • et al.
      Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
      clearly demonstrate that CHD patients with low CRF can especially benefit from prescribed CR to improve functional capacity and survival. Unfortunately, for too many patients with CHD, the ET prescription remains underfilled.
      • Boden W.E.
      • Franklin B.A.
      • Wenger N.K.
      Physical activity and structured exercise for patients with stable ischemic heart disease.
      • Suaya J.A.
      • Shepard D.S.
      • Normand S.L.
      • Ades P.A.
      • Prottas J.
      • Stason W.B.
      Use of cardiac rehabilitation by Medicare beneficiaries after myocardial infarction or coronary bypass surgery.
      • Thomas R.J.
      Cardiac rehabilitation/secondary prevention programs: a raft for the rapids: why have we missed the boat?.
      • Swift D.L.
      • Lavie C.J.
      • Johannsen N.M.
      • et al.
      Physical activity, cardiorespiratory fitness, and exercise training in primary and secondary coronary prevention.

      Areas of Continued Research

      First, viable systems to assist patients in continuing their secondary prevention efforts, including ET, need to be developed. A disease management system, similar to one developed at the Mayo Clinic, has been demonstrated to be effective.
      • Squires R.W.
      • Montero-Gomez A.
      • Allison T.G.
      • Thomas R.J.
      Long-term disease management of patients with coronary disease by cardiac rehabilitation staff.
      Second, new techniques of ET, including high-intensity interval ET, which may provide greater improvements in CRF and endothelial function than does moderate-intensity ET, should be further evaluated in larger numbers of patients with CVD, including CHD.
      • Arena R.
      • Myers J.
      • Forman D.E.
      • Lavie C.J.
      • Guazzi M.
      Should high-intensity-aerobic interval training become the clinical standard in heart failure?.
      Finally, enhancing the referral, enrollment, and completion of formal CR for all patients, especially women, elderly populations, and those from rural areas, is urgently needed.
      • Daniels K.M.
      • Arena R.
      • Lavie C.J.
      • Forman D.E.
      Cardiac rehabilitation for women across the lifespan.
      • Arena R.
      • Williams M.
      • Forman D.E.
      • et al.
      Increasing referral and participation rates of outpatient cardiac rehabilitation: the valuable role of healthcare professionals in the inpatient and home health settings: a scientific advisory from the American Heart Association.

      References

        • Weintraub W.S.
        • Daniels S.R.
        • Burke L.E.
        • et al.
        Value of primordial and primary prevention for cardiovascular disease: a policy statement from the American Heart Association.
        Circulation. 2011; 124: 967-990
        • Porter M.E.
        What is the value of health care?.
        N Engl J Med. 2010; 363: 2477-2481
        • Franklin B.A.
        • Cushman M.
        Recent advances in preventive cardiology and lifestyle medicine.
        Circulation. 2011; 123: 2274-2283
        • Franklin B.A.
        • McCullough P.A.
        Cardiorespiratory fitness: an independent and additive marker of risk stratification and health outcomes.
        Mayo Clin Proc. 2009; 84: 776-779
        • Martin B.J.
        • Arena R.
        • Haykowsky M.
        • et al.
        Cardiovascular fitness and mortality after contemporary cardiac rehabilitation.
        Mayo Clin Proc. 2013; 88: 455-463
        • Vanhees L.
        • Fagard R.
        • Thijs L.
        • Staessen J.
        • Amery A.
        Prognostic significance of peak exercise capacity in patients with coronary artery disease.
        J Am Coll Cardiol. 1994; 23: 358-363
        • Dorn J.
        • Naughton J.
        • Imamura D.
        • Trevisan M.
        Results of a multicenter randomized clinical trial of exercise and long-term survival in myocardial infarction patients: the National Exercise and Heart Disease Project (NEHDP).
        Circulation. 1999; 100: 1764-1769
        • Kavanagh T.
        • Mertens D.J.
        • Hamm L.F.
        • et al.
        Prediction of long-term prognosis in 12 169 men referred for cardiac rehabilitation.
        Circulation. 2002; 106: 666-671
        • Kavanagh T.
        • Mertens D.J.
        • Hamm L.F.
        • et al.
        Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation.
        J Am Coll Cardiol. 2003; 42: 2139-2143
        • Kavanagh T.
        • Hamm L.F.
        • Beyene J.
        • et al.
        Usefulness of improvement in walking distance versus peak oxygen uptake in predicting prognosis after myocardial infarction and/or coronary artery bypass grafting in men.
        Am J Cardiol. 2008; 101: 1423-1427
        • Beatty A.L.
        • Schiller N.B.
        • Whooley M.A.
        Six-minute walk test as a prognostic tool in stable coronary heart disease: data from the Heart and Soul Study.
        Arch Intern Med. 2012; 172: 1096-1102
        • O’Connor C.M.
        • Whellan D.J.
        • Lee K.L.
        • et al.
        Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial.
        JAMA. 2009; 301: 1439-1450
        • Feuerstadt P.
        • Chai A.
        • Kligfield P.
        Submaximal effort tolerance as a predictor of all-cause mortality in patients undergoing cardiac rehabilitation.
        Clin Cardiol. 2007; 30: 234-238
        • Myers J.
        • Herbert W.
        • Ribisl P.
        • Franklin B.
        Is new science driving practice improvements and better patient outcomes? applications for cardiac rehabilitation.
        Clin Invest Med. 2008; 31: E400-E407
        • Kokkinos P.
        • Myers J.
        Exercise and physical activity: clinical outcomes and applications.
        Circulation. 2010; 122: 1637-1648
        • Green D.J.
        • O’Driscoll G.
        • Joyner M.J.
        • Cable N.T.
        Exercise and cardiovascular risk reduction: time to update the rationale for exercise?.
        J Appl Physiol. 2008; 105: 766-768
        • Hambrecht R.
        • Walther C.
        • Möbius-Winkler S.
        • Gielen S.
        • et al.
        Percutaneous coronary angioplasty compared with exercise training in patients with stable coronary artery disease: a randomized trial.
        Circulation. 2004; 109: 1371-1378
        • Swain D.P.
        • Franklin B.A.
        Comparison of cardioprotective benefits of vigorous versus moderate intensity aerobic exercise.
        Am J Cardiol. 2006; 97: 141-147
        • Lavie C.J.
        • Milani R.V.
        • O’Keefe J.H.
        • Lavie T.J.
        Impact of exercise training on psychological risk factors.
        Prog Cardiovasc Dis. 2011; 53: 464-470
        • Lavie C.J.
        • Milani R.V.
        Adverse psychological and coronary risk profiles in young patients with coronary artery disease and benefits of formal cardiac rehabilitation.
        Arch Intern Med. 2006; 166: 1878-1883
        • Milani R.V.
        • Lavie C.J.
        Impact of cardiac rehabilitation on depression and its associated mortality.
        Am J Med. 2007; 120: 799-806
        • Milani R.V.
        • Lavie C.J.
        • Mehra M.R.
        • Ventura H.O.
        Impact of exercise training and depression on survival in heart failure due to coronary heart disease.
        Am J Cardiol. 2011; 107: 64-68
        • Milani R.V.
        • Lavie C.J.
        Reducing psychosocial stress: a novel mechanism of improving survival from exercise training.
        Am J Med. 2009; 122: 931-938
        • Smith Jr., S.C.
        • Benjamin E.J.
        • Bonow R.O.
        • et al.
        AHA/ACCF secondary prevention and risk reduction therapy for patients with coronary and other atherosclerotic vascular disease: 2011 update: a guideline from the American Heart Association and American College of Cardiology Foundation.
        Circulation. 2011; 124: 2458-2473
        • Quell K.J.
        • Porcari J.P.
        • Franklin B.A.
        • Foster C.
        • Andreuzzi R.A.
        • Anthony R.M.
        Is brisk walking an adequate aerobic training stimulus for cardiac patients?.
        Chest. 2002; 122: 1852-1856
        • Swain D.P.
        • Franklin B.A.
        Is there a threshold intensity for aerobic training in cardiac patients?.
        Med Sci Sports Exerc. 2002; 34: 1071-1075
        • Dressendorfer R.H.
        • Franklin B.A.
        • Smith J.L.
        • et al.
        Early cardiac rehabilitation training heart rate based on low-level treadmill testing after myocardial infarction and before hospital discharge.
        J Cardiopulm Rehab. 1993; 13: 194-200
        • Joo K.C.
        • Brubaker P.H.
        • MacDougall A.
        • Saikin A.M.
        • Ross J.H.
        • Whaley M.H.
        Exercise prescription using resting heart rate plus 20 or perceived exertion in cardiac rehabilitation.
        J Cardiopulm Rehab. 2004; 24: 178-186
        • Hambrecht R.
        • Niebauer J.
        • Marburger C.
        • et al.
        Various intensities of leisure time physical activity in patients with coronary artery disease: effects on cardiorespiratory fitness and progression of coronary atherosclerotic lesions.
        J Am Coll Cardiol. 1993; 22: 468-477
        • Ades P.A.
        • Savage P.D.
        • Toth M.J.
        • et al.
        High-calorie-expenditure exercise: a new approach to cardiac rehabilitation for overweight coronary patients.
        Circulation. 2009; 119: 2671-2678
        • Boden W.E.
        • Franklin B.A.
        • Wenger N.K.
        Physical activity and structured exercise for patients with stable ischemic heart disease.
        JAMA. 2013; 309: 143-144
        • Suaya J.A.
        • Shepard D.S.
        • Normand S.L.
        • Ades P.A.
        • Prottas J.
        • Stason W.B.
        Use of cardiac rehabilitation by Medicare beneficiaries after myocardial infarction or coronary bypass surgery.
        Circulation. 2007; 116: 1653-1662
        • Thomas R.J.
        Cardiac rehabilitation/secondary prevention programs: a raft for the rapids: why have we missed the boat?.
        Circulation. 2007; 116: 1644-1646
        • Swift D.L.
        • Lavie C.J.
        • Johannsen N.M.
        • et al.
        Physical activity, cardiorespiratory fitness, and exercise training in primary and secondary coronary prevention.
        Circ J. 2013; 77: 281-292
        • Squires R.W.
        • Montero-Gomez A.
        • Allison T.G.
        • Thomas R.J.
        Long-term disease management of patients with coronary disease by cardiac rehabilitation staff.
        J Cardiopulm Rehabil Prev. 2008; 28: 180-186
        • Arena R.
        • Myers J.
        • Forman D.E.
        • Lavie C.J.
        • Guazzi M.
        Should high-intensity-aerobic interval training become the clinical standard in heart failure?.
        Heart Fail Rev. 2013; 18: 95-105
        • Daniels K.M.
        • Arena R.
        • Lavie C.J.
        • Forman D.E.
        Cardiac rehabilitation for women across the lifespan.
        Am J Med. 2012; 125: 937.e1-937.e7
        • Arena R.
        • Williams M.
        • Forman D.E.
        • et al.
        Increasing referral and participation rates of outpatient cardiac rehabilitation: the valuable role of healthcare professionals in the inpatient and home health settings: a scientific advisory from the American Heart Association.
        Circulation. 2012; 125: 1321-1329