Clinical UM Guideline

This document addresses cardiac rehabilitation services that are provided on an outpatient basis during the immediate post-discharge period and are considered Phase II cardiac rehabilitation programs (see Discussion/General Information section for further information related to the phases of Cardiac Rehabilitation Programs).

Medically Necessary:

Phase II cardiac rehabilitation is considered medically necessary when individually prescribed by a physician and the following criteria are met:

1. Cardiac rehabilitation is initiated within 12 months of ANY of the following:
   1. Acute myocardial infarction (MI); or
   2. Coronary artery bypass grafting (CABG); or
   3. Heart transplantation; or
   4. Percutaneous coronary intervention (that is, atherectomy, angioplasty, stenting); or
   5. Survivor of sudden cardiac death; or
   6. Survivor of sustained ventricular tachycardia or fibrillation; or
   7. Valve replacement or repair; or
   8. New York Heart Association (NYHA) Class II to IV congestive heart failure (CHF) that is interfering with the ability to perform age-related activities of daily living; or
   9. Coronary artery disease (CAD) with chronic stable angina pectoris that has failed to respond to pharmacotherapy and is interfering with the ability to perform age-related activities of daily living;
      and
2. The individual does not have an absolute contraindication to cardiac rehabilitation (examples include: unstable angina, overt cardiac failure, dangerous arrhythmias, dissecting aneurysm, myocarditis, acute pericarditis, severe obstruction of the left ventricular outflow tract, severe hypertension, exertional hypotension or syncope, uncontrolled diabetes mellitus, severe orthopedic limitations, and recent systemic or pulmonary embolus);
   and
3. A formal exercise stress test has been completed following the qualifying cardiac event and prior to initiation of the rehabilitation program or, for individuals at low risk based on current symptoms, clinical features and exercise history, during the first rehabilitation session.

Not Medically Necessary:

The following are considered not medically necessary:

1. When the criteria above are not met;
2. Phase III cardiac rehabilitation programs, or self-directed, self-controlled or monitored exercise programs;
3. Phase IV cardiac rehabilitation programs or maintenance therapy that may be safely carried out without medical supervision;
4. Cardiac rehabilitation when used in a preventive or prophylactic way, such as for angina, hypertension, or diabetes.

Place of Service: Ambulatory, Outpatient Facility

Frequency/Duration:
The frequency and duration of treatment is determined by the following:

• The cardiac risk level; and
• The degree of exercise limitation as demonstrated by a treadmill electrocardiogram (ECG) stress test.

High Risk:
Individuals in the high-risk category may have ANY of the following:

• Exercise test limited to less than or equal to 5 metabolic equivalents (METS). (MET = a multiple of the resting energy expenditure, and is used as a means of estimating cardiac functional capacity. [1 MET = 3.5ml O2/kg body wt/min]); or
• Marked exercise-induced ischemia, as indicated by either anginal pain or 2 mm or more ST segment depression by ECG; or
• Severely depressed left ventricular function (ejection fraction less than 30%); or
• Resting complex ventricular arrhythmias; or
• Ventricular arrhythmias appearing or increasing with exercise or occurring in the recovery phase of stress testing; or
• Decrease in systolic blood pressure of greater than 15 mm Hg with exercise; or
• Recent myocardial infarction (less than 6 months) which was complicated by serious ventricular arrhythmias, cardiogenic shock, or congestive heart failure (CHF); or
• Survivor of sudden cardiac arrest.

Cardiac rehabilitation programs for high-risk individuals may include the following:

• 36 sessions (e.g., 3x/wk x 12 wks) of supervised exercise with continuous telemetry monitoring; and
• Educational program for risk factor/stress reduction; and
• Creation of an individual outpatient exercise program that can be self-monitored and maintained.

Note: If no clinically significant arrhythmia is documented during the first three weeks of the program, the remaining portion may be completed without telemetry monitoring.

Intermediate Risk:
Individuals in the intermediate risk category may have ANY of the following:

• Exercise test limited to 6-9 METS; or
• Ischemic ECG response to exercise of less than 2 mm of ST segment depression; or
• Uncomplicated myocardial infarction, coronary artery bypass surgery, or angioplasty and has a post-cardiac event maximal functional capacity of 8 METS or less on ECG exercise test.

Cardiac rehabilitation programs for intermediate risk individuals may include the following:

• Provide exercise training for 24 sessions or less of exercise training without continuous ECG monitoring (Note: Some individuals may require less than 3x/wk x 8 wks); and
• Be geared towards defining an ongoing exercise program that is self-administered.

Low Risk:
Individuals in the low risk category may have ANY of the following:

• Exercise test limited to greater than 9 METS; or
• Asymptomatic at rest.

Cardiac rehabilitation programs for low risk individuals may include the following:

• 6 one-hour sessions involving risk factor reduction education; and
• Supervised exercise to show safety and define a home program (for example 3x/week x 2wks or 2x/week x 3wks).

Additional cardiac rehabilitation services are considered medically necessary based on the above listed criteria in the event the individual has ANY of the following:

• Another documented myocardial infarction or extension of initial infarction; or
• Another cardiovascular surgery or angioplasty; or
• New evidence of ischemia on an exercise test, including thallium scan; or
• New clinically significant coronary lesions documented by cardiac catheterization.

The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services may be Medically Necessary when criteria are met:

When services are Not Medically Necessary:
For the procedure codes listed above when criteria are not met, or when the code describes a procedure or situation designated in the Clinical Indications section as not medically necessary.

Cardiac rehabilitation (CR) is a program of multidisciplinary interventions, designed to assist clinically suitable individuals to attain and maintain their optimal level of functioning. Over the past 20 years, risk factor modification programs for individuals with cardiac conditions, commonly referred to as cardiac rehabilitation or CR, have evolved into a comprehensive management strategy. The American Heart Association (AHA) and the American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) define CR programs as, “Coordinated, multifaceted interventions designed to optimize a cardiac patient’s physical, psychological, and social functioning, in addition to stabilizing, slowing, or even reversing the progression of the underlying atherosclerotic processes, thereby reducing morbidity and mortality” (Leon, 2005). Interventions include, “Baseline patient assessments, nutritional counseling, aggressive risk factor management, (i.e., lipids, hypertension, weight, diabetes, and smoking), psychosocial and vocational counseling, and physical activity counseling and exercise training, in addition to the appropriate use of cardioprotective drugs” (Leon, 2005).

According to a 2007 scientific statement from the AHA and the AACVPR (Balady, 2007), which addresses the core components of cardiac rehabilitation/secondary prevention programs, the following is noted:

Symptom-limited exercise testing is strongly recommended prior to participation in an exercise-based CR program. The evaluation may be repeated as changes in clinical condition warrant. Test parameters should include assessment of heart rate and rhythm, signs, symptoms, ST-segment changes, hemodynamics, perceived exertion, and exercise capacity. On the basis of patient assessment and the exercise test if performed, it is recommended to risk stratify the patient to determine the level of supervision and monitoring required during exercise training.

A multicenter, randomized controlled trial enrolled 2331 medically stable individuals with heart failure (HF) and reduced ejection fraction who were randomized to receive either usual care plus aerobic exercise training (36 supervised sessions followed by home-based training [traditional CR model]) or usual care alone. The study’s primary endpoints included all-cause mortality or hospitalization and prespecified secondary endpoints of all-cause mortality, cardiovascular mortality or hospitalization, and cardiovascular mortality or HF-related hospitalization. In this study sample, 28% of participants were women, and 37% had New York Heart Association (NYHA) class III or IV symptoms. A total of 759 (65%) participants in the exercise-based CR group died or were hospitalized, compared with 796 (68%) in the usual care group (hazard ratio [HR]=0.93; 95% confidence interval [CI], 0.84-1.02; p=0.13). There were nonsignificant reductions in the exercise-based CR group for mortality (189 [16%] in the exercise group vs 198 [17%] in the usual care group; HR=0.96; 95% CI, 0.79-1.17; p=0.70), cardiovascular mortality or cardiovascular hospitalization (632 [55%] in the exercise group vs 677 [58%] in the usual care group; HR=0.92; 95% CI, 0.83-1.03; p=0.14), and cardiovascular mortality or HF hospitalization (344 [30%] in the exercise group vs 393 [34%] in the usual care group; HR=0.87; 95% CI, 0.75-1.00; p=0.06). A prespecified supplementary analyses adjusted for highly prognostic baseline characteristics, the resulting HR for all-cause mortality or hospitalization was 0.89 (95% CI, 0.81-0.99; p=0.03), for cardiovascular mortality or cardiovascular hospitalization the HR was 0.91 (95% CI, 0.82-1.01; p=0.09), and for cardiovascular mortality or HF hospitalization the HR was 0.85 (95% CI, 0.74-0.99; p=0.03). Authors concluded that in the protocol-specified primary analysis, exercise-based CR resulted in nonsignificant reductions in the primary endpoint of all-cause mortality or hospitalization and after adjustment for highly prognostic predictors of the primary endpoint, was associated with modest but significant reductions for both all-cause mortality or hospitalization and cardiovascular mortality or HF hospitalization (O’Connor, 2009).

Goel and colleagues (2011) conducted a retrospective review which looked at 2395 individuals over a 14 year period that underwent percutaneous coronary intervention. Of the 2395 individuals who underwent percutaneous coronary intervention, 964 of them enrolled in CR following the intervention. Mean follow-up was 6.3 years. During that time, there were 503 deaths, of which 199 were due to cardiovascular disease. Revascularization was required in 755 individuals and 394 individuals had subsequent myocardial infarction. The authors reported a 45% to 47% decrease in mortality of those individuals who participated in CR after percutaneous intervention compared with those individuals who did not participate in CR.

A study by Lee and colleagues (2014) reported on 576 individuals who were post drug-eluting stent implantation for coronary artery disease who were then referred for CR. A total of 288 participants successfully completed the CR program. The primary endpoint was in-stent luminal loss at a 9-month angiographic follow-up. Those who completed the CR program had a 35% less in-stent luminal loss when compared to those who didn’t complete the CR. Those in the CR group also showed an improvement in overall risk factors including current smoking, biochemical profiles, depression, obesity and exercise capacity.

A Cochrane review investigating the effect of exercise-based CR on individuals with HF included 44 studies which were comprised of 5783 participants. All studies included a ‘no formal exercise’ training intervention comparator, although a wide range of comparators were seen across studies (such as, education, psychological intervention or usual medical care alone). The review concluded that there were probable benefits of exercise-based CR, including a reduction in the risk of overall hospital admissions in the short term, as well as a potential reduction in HF-related admissions. The effect of exercise-based rehabilitation on health-related quality of life (QoL) for individuals with HF remains uncertain due to ‘very low-quality evidence’ as rated by the GRADE method. Authors conclude that exercise-based rehabilitation may make little or no difference in all-cause mortality in the short-term (less than 12 months; risk ratio [RR]=0.89, 95% CI, 0.66-1.2) but may impact all-cause mortality in the longer-term (RR 0.88, 95% CI, 0.75 to 1.02; high-quality evidence) and that further evidence is needed to better elucidate the effects of exercise-based CR on individuals with HF in both the long and short-term (Long, 2019b).

Another Cochrane review investigating the effect of exercise-based CR on individuals with implantable ventricular assist devices (VADs) included two studies which combined were comprised of just 40 participants. In the studies, exercise-based CR consisted of aerobic training, resistance training, or both three times per week for 6 to 8 weeks. Exercise intensity was measured as 50% of oxygen consumption (VO2) reserve, or 60% to 80% of heart rate reserve. A large difference in quality of life was observed between groups at the end of follow-up (standardized mean difference 0.88, 95% CI, 0.12-1.88). The effectiveness of exercise-based CR was not realized due to the age of participants (relatively young), high risk of performance bias and small sample size, which resulted in very low-quality evidence (using GRADE method). Ideally, well-designed clinical trials would also measure the effect of exercise-based CR on mortality, rehospitalization or heart transplantation, but these outcomes were not reported in either study. Cochrane authors concluded that, “evidence is currently inadequate to assess the safety and efficacy of exercise-based CR for people with implantable VADs compared with usual care” (Yamamoto, 2018).

A systematic review was conducted to summarize and characterize the current state of evidence related to the effects of exercise-based CR on the health-status of individuals diagnosed with stable angina. A total of 7 studies, which included 581study participants in total met the criteria for analysis. The effect of exercise-based CR on all-cause mortality (RR=1.01, 95% CI, 0.18-5.67), acute myocardial infarction (RR=0.33, 95% CI, 0.07-1.63) and cardiovascular-related hospital admissions (RR=0.14, 95% CI, 0.02 to 1.1) relative to control were not determined to be statistically significant. Exercise-based CR was determined to have a moderately positive impact on exercise capacity (standard mean difference 0.45, 95% CI, 0.20 to 0.70), though this was based on low-quality evidence (GRADE method). There was limited and very low-quality evidence on the effect of exercise-based CR on health related QoL measures. Authors concluded that exercise-based CR may improve short-term exercise capacity in individuals with stable angina but well-designed, randomized controlled clinical trials are needed to definitely determine the impact on outcomes including mortality, morbidity and QoL (Long, 2019a).

Exercise training is the principal component of CR, since it results in increased peak exercise capacity, which is usually expressed in METs (metabolic equivalents). This is the total oxygen requirement of the body, with 1 MET equal to 3.5 mL of oxygen consumed per kilogram of body weight per minute. Exercise training improves MET capacity by 10% to 50%, resulting in improved oxygen delivery and extraction by exercising skeletal muscles, thereby decreasing the cardiovascular requirements of exercise and increasing the amount of work that can be done before ischemia occurs. Although dynamic aerobic exercise is necessary to improve cardiovascular endurance, resistance exercise is becoming a useful adjunctive component of the exercise regimen as well. Resistance training should be included in the exercise program to minimize loss of muscle mass.

A few small studies suggest virtual reality-enhanced cardiac rehabilitation may provide improvements in the outcomes, adherence, and satisfaction.

Garcia-Bravo and colleagues (2020) conducted a randomized pilot clinical trial to determine the effects of virtual reality program as a complementary tool to stage II cardiac rehabilitation. The study recruited 26 participants but 6 did not complete the program. The control group (n=10) received conventional cardiac rehabilitation and the experimental group (n=10) received conventional cardiac rehabilitation along with physical exercise through virtual reality and video games. No significant differences were observed between the two groups when reviewing outcomes. The Client Satisfaction Survey showed an average score of 31.60 (±0.96) for the experimental group and 30.70 (±2.86) for the control group. The study noted that virtual reality protocol could be an alternative and that focus of future studies should be on compliance to physical exercise in stage III of cardiac rehabilitation with virtual reality by follow-up evaluations.

Gulick and colleagues (2021) completed a randomized controlled trial to evaluate if virtual reality program incorporated with cardiac rehabilitation program could increase patient’s motivation, understanding and adherence. The study contained 72 individuals, 31 in the control group and 41 in the intervention group. The control group received standard cardiac rehabilitation care. While the intervention group received standard cardiac rehabilitation care, except the treadmill component used the Bionautica Trails system, a virtual reality platform. Results showed the control group had higher completion rates (P=.02; 95% CI 0.04-0.53). There were no significant differences in the 6-minute walk test (6MWT), the control group improved by an average of 298 feet and the intervention group by 340 feet. Author concluded that to determine if virtual walking trails are worth implementing in stage II cardiac rehabilitation, additional studies are required.

CR programs are generally divided into four phases: phase I, inpatient or recovery phase; phase II, outpatient or intermediate phase; phase III, community-based or home long-term phase; phase IV, maintenance (Thompson, 2007).

Phases of Cardiac Rehabilitation

Duke Treadmill Score (DTS): A quantitative means of expressing cardiac risk derived entirely from the exercise ECG. It incorporates ST segment deviation (depression or elevation), treadmill time (METS) and exercise-induced angina. The angina index has a value of 0 if there is no angina during exercise, 1 if the individual had non-limiting angina and 2 if angina was the reason the individual stopped exercising. The typical observed range for the DTS is highest risk of –25 to lowest risk of +15.

New York Heart Association (NYHA) Classes of Heart Failure:

Peer Reviewed Publications:

1. Dunlay SM, Pack QR, Thomas RJ, et al. Participation in cardiac rehabilitation, readmissions, and death after acute myocardial infarction. Am J Med. 2014; 127(6):538-546.
2. García-Bravo S, Cano-de-la-Cuerda R, Domínguez-Paniagua J, et al. Effects of virtual reality on cardiac rehabilitation programs for ischemic heart disease: a randomized pilot clinical trial. Int J Environ Res Public Health. 2020 Nov 16;17(22):8472.
3. Goel K, Lennon RJ, Tilbury RT, et al. Impact of cardiac rehabilitation on mortality and cardiovascular events after percutaneous coronary intervention in the community. Circulation. 2011; 123(21):2344-2352.
4. Gulick V, Graves D, Ames S, et al. Effect of a virtual reality-enhanced exercise and education intervention on patient engagement and learning in cardiac rehabilitation: Randomized Controlled Trial. J Med Internet Res. 2021 Apr 15;23(4):e23882.
5. Johnson DA, Sacrinty MT, Gomadam PS, et al. Effect of early enrollment on outcomes in cardiac rehabilitation. Am J Cardiol. 2014; 114(12):1908-1911.
6. Kobashigawa JA, Leaf DA, Lee N, et al. A controlled trial of exercise rehabilitation after heart transplantation. N Engl J Med. 1999; 340(4):272-277.
7. Lee JY, Yun SC, Ahn JM, et al. Impact of cardiac rehabilitation on angiographic outcomes after drug-eluting stents in patients with de novo long coronary artery lesions. Am J Cardiol. 2014; 113(12):1977-1985.
8. Long L, Anderson L, He J, et al. Exercise-based cardiac rehabilitation for stable angina: systematic review and meta-analysis. Open Heart. 2019a. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6560669/. Accessed on October 6, 2023.
9. O'Connor CM, Whellan DJ, Lee KL, et a. Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial. JAMA. 2009; 301(14):1439-1350.
10. Pack QR, Dudycha KJ, Roschen KP, et al. Safety of early enrollment into outpatient cardiac rehabilitation after open heart surgery. Am J Cardiol. 2015; 115(4):548-552.
11. Risom SS, Zwisler AD, Rasmussen TB, et al. Cardiac rehabilitation versus usual care for patients treated with catheter ablation for atrial fibrillation: Results of the randomized CopenHeartRFA trial. Am Heart J. 2016; 181:120-129.
12. Sibilitz KL, Berg SK, Rasmussen TB, et al. Cardiac rehabilitation increases physical capacity but not mental health after heart valve surgery: a randomised clinical trial. Heart. 2016; 102(24):1995-2003.
13. Sibilitz KL, Tang LH, Berg SK, et al. Long-term effects of cardiac rehabilitation after heart valve surgery - results from the randomised CopenHeartVR trial. Scand Cardiovasc J. 2022 Dec;56(1):247-255.
14. Tarro Genta F, Tidu M, Bouslenko Z, et al. Cardiac rehabilitation after transcatheter aortic valve implantation compared to patients after valve replacement. J Cardiovasc Med (Hagerstown). 2017; 18(2):114-120.
15. Taylor RS, Brown A, Ebrahim S, et al. Exercise-based rehabilitation for patients with coronary heart disease: systematic review and meta-analysis of randomized controlled trials. Am J Med. 2004; 116(10):682-692.
16. Wilson JR, Groves J, Rayos G. Congestive heart failure/heart transplantation/pulmonary circulation: Circulatory status and response to cardiac rehabilitation in patients with heart failure. Circulation 1996; 94(7):1567-1572.

Government Agency, Medical Society, and Other Authoritative Publications:

1. American Association of Cardiovascular and Pulmonary Rehabilitation. Guidelines for Cardiac Rehabilitation Programs. Human Kinetics Publishers, 2020. [VitalSource Bookshelf].
2. Anderson L, Sharp GA, Norton RJ, et al. RS. Home-based versus centre-based cardiac rehabilitation. Cochrane Database Syst Rev. 2017;6:CD007130.
3. Anderson L, Taylor RS. Cardiac rehabilitation for people with heart disease: an overview of Cochrane systematic reviews. Cochrane Database Syst Rev. 2014;(12):CD011273.
4. Anderson L, Thompson D, Oldridge N, et al. Exercise-based cardiac rehabilitation for coronary artery disease. Cochrane Database Syst Rev. 2016;(67):CD001800.
5. Balady GJ, Williams MA, Ades PA, et al. Core components of cardiac rehabilitation/secondary prevention programs: 2007 update: a scientific statement from the American Heart Association Exercise, Cardiac Rehabilitation, and Prevention Committee, the Council on Clinical Cardiology; the Councils on Cardiovascular Nursing, Epidemiology and Prevention, and Nutrition, Physical Activity, and Metabolism; and the American Association of Cardiovascular and Pulmonary Rehabilitation. Circulation. 2007; 115(20):2675-2682.
6. Dibben G, Faulkner J, Oldridge N, et al. Exercise-based cardiac rehabilitation for coronary heart disease. Cochrane Database Syst Rev. 2021 Nov 6;11(11):CD001800.
7. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022 May 3;145(18):e895-e1032.
8. King M, Bittner V, Josephson R, et al. AACVPR/AHA Scientific Statement medical director responsibilities for outpatient cardiac rehabilitation/secondary prevention programs: 2012 update a statement for health care professionals from the American Association of Cardiovascular and Pulmonary Rehabilitation and the American Heart Association. Circulation. 2012; 126(21): 2535-2543.
9. Lawton JS, Tamis-Holland JE, Bangalore S, et al. 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022 Jan 18;145(3):e18-e114
10. Leon AS, Franklin BA, Costa F, et al. Cardiac rehabilitation and secondary prevention of coronary heart disease: an American Heart Association scientific statement from the Council on Clinical Cardiology (Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention) and the Council on Nutrition, Physical Activity, and Metabolism (Subcommittee on Physical Activity), in collaboration with the American Association of Cardiovascular and Pulmonary Rehabilitation. Circulation. 2005; 111(3):369-376.
11. Long L, Mordi IR, Bridges C, et al. Exercise-based cardiac rehabilitation for adults with heart failure. Cochrane Database Syst Rev. 2019b;1:CD003331.
12. Mosca L, Benjamin EJ, Berra K, et al. Effectiveness-based guidelines for the prevention of cardiovascular disease in women – 2011 update: a guideline from the American Heart Association. J Am Coll Cardiol, 2011; 57(12):1404-1423.
13. Pio CSA, Chaves G, Davies P, et al. Interventions to promote patient utilisation of cardiac rehabilitation. Cochrane Database Syst Rev. 2019;(2):CD007131.
14. Thomas RJ, King M, Lui K, et al. AACVPR/ACCF/AHA 2010 update: performance measures on cardiac rehabilitation for referral to cardiac rehabilitation/secondary prevention services: a report of the American Association of Cardiovascular and Pulmonary Rehabilitation and the American College of Cardiology Foundation/American Heart Association Task Force on Performance Measures (Writing Committee to Develop Clinical Performance Measures for Cardiac Rehabilitation). J Cardiopulm Rehabil Prev. 2010; 30(5):279-288.
15. Thompson PD. Chapter 46: Comprehensive rehabilitation of patients with cardiovascular disease. In: Zipes DP, Libby P, Bonow RO, Braunwald E, editors. Braunwald’s heart disease. A textbook of cardiovascular disease. 8th ed. Philadelphia: Saunders. 2007.
16. Yamamoto S, Hotta K, Ota E, et al. Exercise-based cardiac rehabilitation for people with implantable ventricular assist devices. Cochrane Database Syst Rev. 2018; 9:CD012222.
17. Yancy CW, Drazner MH, Coffin ST, et al. 2020 ACC/HFSA/ISHLT Lifelong Learning Statement for Advanced Heart Failure and Transplant Cardiology Specialists: A Report of the ACC Competency Management Committee. J Am Coll Cardiol. 2020 Mar 17;75(10):1212-1230.

1. American Heart Association (AHA). What is cardiac rehabilitation? Available at: https://www.goredforwomen.org/en/health-topics/cardiac-rehab/what-is-cardiac-rehabilitation. Accessed on October 6, 2023.
2. New York Heart Association (NYHA) Classes of Heart Failure. Available at: https://www.heart.org/en/health-topics/heart-failure/what-is-heart-failure/classes-of-heart-failure. Accessed on October 6, 2023.