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| REVIEW ARTICLE |
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| Year : 2023 | Volume
: 7
| Issue : 1 | Page : 13-17 |
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Impact of cardiac rehabilitation on psychological factors, cardiorespiratory fitness, and survival: A narrative review
Nadia Isabel Abelhad1, Sergey M Kachur2, Alexandra Sanchez1, Carl J Lavie1, Richard V Milani1
1 Department of Cardiology, The University of Queensland School of Medicine, John Ochsner Heart and Vascular Institute, Jefferson, Louisiana, USA
2 Ascension Sacred Heart, Pensacola, Department of Cardiology, University of Central Florida, Orlando, Florida, USA
| Date of Submission | 17-Nov-2022 |
| Date of Acceptance | 16-Jan-2023 |
| Date of Web Publication | 13-Mar-2023 |
Correspondence Address:
Prof. Carl J Lavie
John Ochsner Heart and Vascular Institute, 1514 Jefferson Highway, Jefferson, Louisiana 70121
USA
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/hm.hm_58_22
Cardiac rehabilitation (CR) is a form of prescribed exercise that is a multidisciplinary approach designed to improve cardiac function and quality of life following major adverse cardiovascular events. In this comprehensive overview, we will describe the individual components of exercise training and discuss the preset doses for effective CR based on recent meta-analyses. We will also review the effects of prescribed exercise medicine on outcomes such as psychosocial stress factors, cardiorespiratory fitness, and survival and their individualized impact on special populations.
Keywords: Cardiac rehabilitation, cardiorespiratory fitness, depression, exercise, psychological factors, survival
How to cite this article:
Abelhad NI, Kachur SM, Sanchez A, Lavie CJ, Milani RV. Impact of cardiac rehabilitation on psychological factors, cardiorespiratory fitness, and survival: A narrative review. Heart Mind 2023;7:13-7 |
How to cite this URL:
Abelhad NI, Kachur SM, Sanchez A, Lavie CJ, Milani RV. Impact of cardiac rehabilitation on psychological factors, cardiorespiratory fitness, and survival: A narrative review. Heart Mind [serial online] 2023 [cited 2023 Mar 29];7:13-7. Available from: http://www.heartmindjournal.org/text.asp?2023/7/1/13/371617 |
| Introduction | |  |
The idea of “exercise as medicine≵ has been considered essential to health in cultures dating back to the Indus Valley and Yellow River civilizations.[1] However, industrialization has now created nonlabor-intensive settings consisting of vehicular travel and cognitive tasks leading to a general decline in physical fitness. This has ushered in an era of silent killers, such as obesity, diabetes, atherosclerotic disease, and mental illness. Links between sedentary behaviors and coronary heart disease (CHD) and heart failure (HF) have already been established. The “mind-heart≵ connection has been shown to be a further independent risk factor for cardiovascular disease (CVD) events and accounts for a substantial[2] factor in survival outcomes. Thus, nonmedicinal prescription therapies, such as physical activity (PA) and prescription exercise have been explored.
Cardiac rehabilitation (CR), a form of prescription exercise, is a multidisciplinary approach designed to improve cardiac function, CVD morbidity, and CVD- and all-cause mortality following major adverse CV events, with exercise training at its core. Components of these programs include early mobilization and exercise training, counseling on nutrition and PA, smoking cessation, weight management, and psychosocial stress (PSS) counseling. The beneficial effects of exercise therapy have been linked to reductions in psychological stress factors and overall PSS, improvement in cardiorespiratory fitness (CRF), and mortality benefits in patients with CVD.[3] The aim of this review is to summarize the benefits of CR, describe its individual components and effective dose as well as describe the limitations of delivering exercise medicine and how it relates to special subpopulations.
| Benefits of Cardiac Rehabilitation: Psychological Factors | | |
PSS is one of the most frequent complaints from patients and its deleterious and broad effects on chronic medical conditions have been underrecognized among clinicians.[4],[5],[6],[7] Public attention in this topic has garnered interest as more evidence over the past two decades has shown a link between PSS in the pathogenesis and progression of CVD.[4],[5],[6],[7] Systematic screening for PSS can be performed in clinical health-care settings with validated questionnaires such as the Patient Health Questionnaire-9[8] or General Anxiety Disorder-7[9] or by performing structured interviews. Cardiologists can also increase detection by asking additional questions during the review of systems to include questions about psychosocial risk factors.
Indeed, depression, anxiety, hostility, isolation, strong adverse emotions, time urgency, and total PSS have a significant impact on CVD and have been comparable to traditional modifiable risk factors, such as hypertension, smoking, and low PA[6],[7] [Figure 1]. The landmark multicenter INTERHEART study evaluated 11,119 age- and sex-matched participants and demonstrated that PSS ranked third among modifiable risk factors, only behind lipids (mostly low-density lipoprotein cholesterol), and smoking and accounted for nearly one-third of total attributable risks of acute myocardial infarction (MI). Possible hypotheses for these findings include higher sympathetic tone leading to pro-arrhythmias, blunted exercise response, and endothelial dysfunction favoring a pro-thrombotic state [Figure 2].[3] In addition, PSS may further hinder recovery from major CVD events[11] due to imbalances in cardiometabolic function, such as increased inflammation, insulin resistance, hyperglycemia, and hypertension.[5] This can lead to a harmful cycle that can then propagate maladaptive behaviors, such as medication nonadherence, substance abuse, worsening socioeconomic status, and poor lifestyle habits. | Figure 1: The impact of PSS on CVD. Several reasons for interest by medical practices in the evaluation and treatment of PSS. PSS=Psychosocial stress, CVD=Cardiovascular disease
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 | Figure 2: The complex interactions among stress, CVD, and exercise. CVD=Cardiovascular disease, ANS=Autonomic nervous system, HPA=Hypothalamus–pituitary–adrenal, SNS=Sympathetic nervous system, SSRI=Selective serotonin reuptake inhibitor
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Among the various psychological stressors, depression and its link to CVD have the strongest evidence. In a meta-analysis of 20 prospective studies of patients with CHD, depressive symptoms were associated with an odds ratio of 2.24 for mortality.[12] Furthermore, depression has been shown to have a correlation between an increased risk of future CHD/CVD events[7],[13] and a 2-fold risk in patients undergoing bypass surgery.[14] Grace et al. demonstrated that the presence of depression at the time of the index hospitalization worsens subsequent mortality.[15] Furthermore, there is a high prevalence of depression in the most at-risk populations with CHD, such as women and diabetic patients.[16] Although less established, anxiety and hostility have also been linked to increased risk of CHD/CVD events.[17]
The role of CR in the reduction of depressive symptoms has been previously cited.[18],[19],[20],[21],[22],[23],[24] Lavie and Milani demonstrated a 50% reduction in depression after formal completion of CR.[19] In another study, the prevalence of depressive symptoms fell from 17% to 6% (P < 0.001) among patients with improvements in peak oxygen consumption (VO2). Moreover, CR patients with depression had almost 4-fold higher mortality over a 3-year follow-up in comparison to nondepressed patients. Depressed patients who did not attend CR had a 3-fold higher mortality during a 3-year follow-up compared to those attending and completing formal CR.[22] Although comorbid depression (depression combined with anxiety and/or hostility) was associated with worse prognosis than depression alone, most of the increased mortality risks were due to depression.[20],[21] Furthermore, a survival benefit has been demonstrated in depressed HF patients after CR after significant increases in peak VO2 (18% vs. 44%, P < 0.005).[24] In patients with CHD who have multiple PSS risk factors, such as anxiety, hostility, and/or depression, CR may lower mortality. In a study of 522 patients with high PSS scores (based on cumulative Kellner scores for each stressor), a mortality benefit was seen at 3 years if peak VO2 improved by 10% or more.[21] When compared to patients who completed CR without depression, depressed patients obtained similar peak VO2 (16.8 mL/kg/min vs. 16 mL/kg/min, P < 0.05),[22] respectively.
CR also plays a role in the secondary prevention of CVD events that can be enhanced when combined with stress management therapy. Blumenthal et al. randomized 151 patients with CHD to standard CR or CR plus stress management therapy (1.5-h group therapy sessions delivered over 12 weeks).[23] The combined therapy arm exhibited lower composite clinical event rates (18% vs. 33%; hazard ratio [HR]: 0.49, confidence interval [CI]: 0.25–0.95; P < 0.04) and overall lower PSS levels when compared to CR alone. This effect was primarily driven by reductions in anxiety, distress, and perceived stress. Thus, the combination of exercise therapy and cognitive behavioral therapy may be synergistic.
Although the mechanisms of PSS improvement in CR are not fully understood, plausible explanations include the promotion of socialization and bonding among other patients in CR, increased understanding of their disease processes in phase II leading to feelings of empowerment, improving access to assistance educational and assistance resources, as well as possible changes in brain plasticity and cognition.[24]
| Benefits of Cardiac Rehabilitation: Cardiorespiratory Fitness | | |
CRF can be quantified by measuring maximal oxygen consumption (VO2 max) or can be from the peak work achieved on a treadmill defined as metabolic equivalent of task (MET) (estimated METs). It reflects the ability to transport ambient oxygen to the electron transport chain within the mitochondria and reflects the health of numerous physiological systems. This includes pulmonary ventilation and diffusion, right and left ventricular function, ventricular-arterial coupling as well as the transportation and deliverance of oxygen to respective muscle cells. Thus, CRF can be considered a reflection of an individual's global health. Levels of CRF have been associated with high-risk CVD and all-cause mortality.[25] When combined with traditional risk factors (i.e., hypertension, smoking, and dyslipidemia), CRF can aid in the improved estimation of health risk. Importantly, improvements in CRF have been associated with reduced mortality.[26] In a meta-analysis by Kodoma et al., every 1-MET increase was associated with an 8%–35% (median: 16%) reduction in mortality in patients with stable CHD.[27] Similarly in HF patients, a 1-MET increase in CRF was associated with a 16% risk reduction of HF.[28]
Recently, there have been several publications in the standardization and delivery of exercise regimens in CR for various population subsets.[29],[30] Moderate-intensity continuous training is targeted and is defined as achieving an intensity of 50%–65% of peak VO2 or heart rate with a duration of a minimum of 36 sessions.[31] After successful completion of CR, VO2 max can increase up to 2.5 mL/kg/min (95% CI: 2.65–1.19, P=0.004).
Most of the benefits of CR can be explained by the improvements in CRF, either measured by gas exchange or estimated by estimated METs or other measures of CRF, such as 6-min walk tests and shuttle tests.[26],[32],[33],[34],[35] In addition, in patients with HF, moderate-intensity continuous training was associated with reductions in depressive symptoms which was not influenced by age, duration of the exercise intervention, or exercise setting.[36]
| Survival | | |
When analyzing the prognosis and characteristics of patients enrolled in CR, it is important to stratify based on their level of improvement in CRF after optimization of medical and/or revascularization therapies. Patients who are nonresponders with respect to peak VO2 have poorer outcomes, while high responders demonstrate the best overall survival.[32] De Schutter et al. studied long-term mortality risk in a large cohort of patients with CHD along with factors that predicted the nonresponders' phenotype after CR and subsequently found that mortality predictors included a protective effect from higher body mass index with HR: 0.58, 95% CI: 0.48–0.80, younger age (HR: 1.03, 95% CI: 1.01–1.05), male gender (HR: 1.64, 95% CI: 1.13–2.37), and higher baseline VO2 (HR: 0.84, 95% CI: 0.80–0.88).[32]
As mentioned previously, CR benefits are mediated by improvements in CRF.[25],[26],[33] Measuring peak VO2 at the beginning and at the end of CR is critical when predicting long-term survival.[34] Prior studies have shown that greater changes in CRF during CR (i.e., responders) would present a more favorable long-term prognosis.[32],[34],[35] Carbone et al. found that achieving an END-peak VO2 ≥17.6 mL/kg/min at the end of CR predicts favorable long-term survival compared to those who achieve a lower END-peak VO2.[35] As a continuous variable, a 1 mL/kg/min or higher improvement in VO2 was associated with a reduction in all-cause mortality by 10%.[37] These findings suggest that individuals who achieve suboptimal levels of CRF (i.e., END-peak VO2) would benefit from additional therapies that target improvement in CRF, let it be longer duration CR programs or higher intensity programs.[35]
While nonresponders lacked a significant improvement in CRF according to De Schutter et al., they did have some benefits from CR including anthropomorphic (mean body fat loss: 0.8%), metabolic (mean high-density lipoprotein cholesterol [HDL-C] gain: 1.6 mg/dL), and psychosocial metrics (mean improvement in PSS: 11.5 out of 40.0).[32] High responders, on the other hand, showed higher absolute improvements with a lower all-cause mortality, greater improvements in HDL-C, and greater weight and body fat loss, supporting prior conclusions that exercise training is associated with increased insulin sensitivity and HDL-C.[38],[39] This is thought to be due to closer adherence to an exercise training regimen and other preventative therapies such as diet and medication compliance. As patients notice greater weight/fat loss and reduction in stress levels, they may be more inclined to put more effort into enrollment, participation, and competition of cardiac rehabilitation.
Overall, low- and non-responders have higher mortality rates when compared to high responders when outcomes are stratified by measures of CRF. The benefits of exercise training not only improve health but contribute to a reduction in mortality among patients with CHD[12],[18],[28],[29],[40],[41],[42],[43],[44] [Table 1], especially those patients exhibiting high PSS. We find that PSS plays a role as an independent risk factor for mortality in patients with CHD, leading to a 4-fold increase in mortality.[19] While these PSS factors remain underappreciated as contemporary CHD risk factors, studies show that they can increase the odds of first MI by approximately 3-fold and significantly elevate the risk of subsequent MI and death in patients with known CHD.[19] Studies have shown that among patients referred for CR, those with high PSS had a 2.5-fold increased risk of rehospitalization, a 5-fold increased risk of major CVD events, and a 4-fold increase in medical costs compared with those who had low levels of psychologic stress.[45] This further confirms exercise training using CR is an effective tool in enhancing survival in patients with CHD-likely from improved levels of CRF and reduced PSS.
| Limitations and Special Populations | | |
A limitation in delivering effective CR is patient compliance in subsets with HF and reduced ejection fraction (ejection fraction ≤40%).[46] In the CR Outcome Study in HF meta-analysis, there was no reduction in mortality or reduction of hospitalizations in this patient population. Upon closer inspection, the majority of patients (60%) were not adherent with the prescribed training. Subsequent meta-analysis has shown a dose-response relationship between intensity of training (3–7 MET-h/week) and improvement of mortality and rehospitalization.[47]
| Conclusions | | |
CRF has significant CV protective effects and may be the single most important predictor in overall health, including psychosocial. Ideally, everyone would remain lean and fit throughout their lifetime; however, modern-day economics favor sedentary professions and an abundance of dietary calories. Greater efforts are needed to focus on methods that will improve the delivery of therapy by focusing on patients who have adverse effects to exercise training or those who are nonresponders in CR. Such efforts would go a long way in preventing CVD and improving the prognosis in those with established CVD.
Ethical statement
The ethical statement is not applicable for this article.
Financial support and sponsorship
Nil.
Conflicts of interest
Dr. Carl J. Lavie is an Associate Editor-in-Chief of Heart and Mind. The article was subject to the journal's standard procedures, with peer review handled independently of Dr. Carl J. Lavie and the research groups. There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1]
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