Cardiac rehabilitation: evidence for action

Background

Cardiac rehabilitation programs were first initiated in the ’60s for patients recovering from acute myocardial infarction and then expanded to other cardiac patients - postoperative, myocardiopathies and heart failure patients as well. It is the process by which cardiac patients recover and readapt to reach and maintain optimal physical, sensory, intellectual, psychological and social functional levels through strategies such that they are provided with the tools to resume their ordinary activities as soon as possible after a cardiac event. (1) Aims of cardiac rehabilitation are to attain 1) improved cardio-pulmonary capacity 2) risk factor management to delay or possibly reverse atherothrombosis (secondary and primary prevention) 3) psychological support and 4) insertion into social and employment activities (1). 

I - Benefit

Numerous animal and clinical studies have reported positive cardiovascular effects after a controlled training programme. (2-5). 
1) Risk factors

• Lipid profile: with a controlled training programme, lipid profile improves significantly with a reduction in total cholesterol, LDL and triglyceride levels. Moreover, with intense energetic activities, moderate increases in HDL cholesterol have been documented: available data indicates that 7-12 weeks of physical activity with moderate intensity (75% of maximal exercise capacity) over 30-45 minutes, 3-4 times per week, provide these beneficial effects. (6-7)
• Smoking cessation: cardiac rehabilitation has proven effective in smoking cessation, helping patients reduce their risk for subsequent ischaemic heart disease progression (again, data would be good). Similarly, these programs can be helpful for patients willing to reduce overweight and improve blood pressure control. (6-8)
• Insulin: for diabetic and hypergylcemic patients, cardiac rehabilitation can be useful in achieving better control, and lowering circulating levels of insulin. In addition, cardiac training can modulate platelet function and the fibrinolytic system, increasing plasminogen activity by reducing its inhibitor levels. (7-12)

2) Coronary arteries, myocardium and systolic function and rhythm disorders

• Coronary arteries, myocardial perfusion and coronary vasodilation capacity: clinical and experimental data show that physical training is of benefit. Animal studies have demonstrated an increased capillary development, increased and dilated collaterals and higher diameters of coronary arteries after aerobic training. These changes lead to an increased coronary reserve andmicrovasculature. (13-15)
• Myocardial performance: Supervised training can modify contractile proteins enhancing myocardial shortening, increasing myosin with elevated ATP-ase concentration, possibly mediated by stimulating alpha receptors during exercise. (9) This phenomenon has clinical manifestations: patients under cardiac rehabilitation show improvement in ventricular function, associated with a better prognosis. In addition, myocardial performance is favoured by an increased end-systolic volume and arteriovenous oxygen difference. (9)
• Antiarrhythmic properties: Controlled progressive exercise can reduce ventricular fibrillation, correlated with sympathetic activation that causes sudden cardiac death in ischaemic patients.  
• Heart rate and blood pressure modulation: Cardiac rehabilitation, as betablockers, improve anaerobic and ischaemic threshold. Mechanisms leading to this effect include an increased ischaemic threshold, reduced sensitivity of beta receptors and the reduction of alpha and cholinergic receptors after exercise, as well as a significant reduction in plasmatic norepinephrine release. (7)

3) Symptoms and mortality

• Oxygen consumption: Functional capacity increases markedly after CR, with an maximal oxygen consumption that becomes elevated and myocardial oxygen demand for the same level of exercise reduced. This improvement is achieved both in normal subjects and in cardiac patients, both males and females. Increased maximal oxygen consumption is directly related to intensity and duration of physical training, as well as with previous physical training. Increases up to 10 and 30% are achieved, but in sedentary subjects, it can reach up to 100%. (14-16) This improvement in functional capacity reduces dyspnoea. To this extent, improved respiratory flow and diaphragmatic performance, contribute to reducing the perception of weakness. (14) 
• Peripheral artery disease: cardiac rehabilitation has shown effective for patients complaining of symptomatic peripheral arterial disease: central and peripheral changes lead to an increased achieved walking distance and reduced calf pain. (12) Physical training reduces baseline and submaximal heart rate; although less markedly, it also reduces blood pressure. Those changes are beneficial in patients with chronic angina, achieving a significant increase in anginal threshold. (7)
• Mortality: Numerous clinical studies have shown reduced mortality up to 20% after controlled cardiac rehabilitation programs after myocardial infarction. Similarly, mortality can be reduced for patients in primary prevention at high risk for cardiovascular disease (35% reduction compared to sedentary subjects). (2-5,7,8)

4) Psychological 

• Self-confidence: Physical exercise can significantly improve self-confidence and help patients resume their work. Recent studies show that low intensity exercise can help patients after myocardial infarction, cardiac surgery, cardiac transplant or for heart failure patients. (6, 7) 
• Anxiety: Physical conditioning reduces anxiety and can help prevent depression which are common disorders in coronary patients. Cardiac rehabilitation can help patients feel healthy after coronary events, transforming the idea of a limited cardiac patient into a healthy coronary subject with higher well-being and self-confidence

II - Indications and contraindications

Initially, cardiac rehabilitation was designed to reduce hospitalisations after myocardial infarction. The experience showed a low incidence of complications. Further on, the concept expanded to include patients with several conditions (summary in Table 1). 
Table 1: Indications for Cardiac Rehabilitation (1-5, 7)

Thus, indications are not restricted to post-acute myocardial infarction patients:

1. Cardiac surgery and coronary interventions: cardiac rehabilitation programs combined with technical advances have increased the number of patients returning to work. 
2. Symptomatic angina: In patients who cannot be operated or revascularised percutaneously, cardiac rehabilitation together with optimal medical therapy will increase anginal threshold. (13) 
3. Cardiac surgery for valvular disease or congenital heart disease: after careful evaluation
4. Heart transplant and heart failure patients are also potential candidates
5. Subjects at high cardiovascular risk, namely hypertensive patients and/or diabetics, can complete CR that will supervise physical training and establish primary prevention recommendations aiming to achieve a normal functional capacity (11, 16).

A better understanding of the results and potential risks of physical training has increased the indications for cardiac rehabilitation and limited contraindications, provided it is performed progressively and under surveillance. Nevertheless, there are absolute contraindications to cardiac rehabilitation (See Table 2 for summary). They include all scenarios where physical exercise has a potential risk such as unstable angina, severe hypertension, aortic aneurysm and dissection, recent pulmonary embolism, severe aortic stenosis and documented inappropriate response of blood pressure to exercise together with symptoms suggesting severe left ventricular dysfunction. Additionally, several conditions can be considered temporary contraindications, such as decompensated heart failure and supraventricular arrhythmias. Others are febrile illnesses or severe systemic diseases.
Table 2: Contraindications for Cardiac Rehabilitation (2-5)

III - Risks and complications

Most complications are the result of incorrect indication or inappropriate surveillance - especially regarding exercise levels.

• Ventricular fibrillation, myocardial infarction and sudden death: the most feared complications of cardiac rehabilitation are ventricular fibrillation, myocardial infarction and sudden death. Should they occur, they would likely occur during or after exercise: potential risk for complications increases significantly when 80% of maximal aerobic functional capacity or 85% of maximal heart rate is exceeded. Thus, surveillance is recommended during resting periods and 15 minutes after physical training.

However incidence of complications during cardiac rehabilitation programs is lower than the one described for the standard treadmill exercise test. Ventricular fibrillation incidence can vary from 1/9000 to 1/32000 per patient or per hour. Other authors have reported one episode after 113,583 hours of cardiac rehabilitation. In a hospital facility, this complication can be treated immediately and death for this cause is rare. Accidents can be divided into moderate or severe, as Table 3 summarises. Moderate accidents might force to quit cardiac rehabilitation temporarily.
Table 3: Accidents during Cardiac Rehabilitation (1, 2-5)

IV - Larger context

Although the value of cardiac rehabilitation is not generally disputed, obstacles to cardiac rehabilitation are many (17).

• Physician referral: lack of knowledge of content or value benefits of cardiac rehabilitation or centers that offer it. In Europe, the EuroAspire survey, which analysed medical records and interviews of 9,000 patients with coronary heart disease in 22 countries of Europe, showed that inappropriately one third only of coronary artery disease patients receive any form of cardiac rehabilitation, with considerable variation between regions (18). Oftentimes also, patients are adequately referred but patients do not get actually enrolled. 
• Reimbursement: Large variations across countries in Europe exist, and in some countries reimbursement of cardiac rehabilitation is altogether under threat.

However the increased number of men and women who now survive acute events leave society with a heavier burden of chronic conditions and clinical need, which rehabilitation can help to reduce. The European Association of Cardiovascular Prevention and Rehabilitation EACPR has issued the following documents:

• Policy Statement: A recent policy statement from the cardiac rehabilitation section states that the development of a systematic and full comprehensive preventive programme is needed, and that it should be integrated in the organisation of national health systems. It also makes the case that systematic monitoring of the process of delivery and outcomes is necessary (19). 
• Position Paper: It follows a "call-for-action" position paper published by the Cardiac Rehabilitation Section Committee for Science Guidelines that presents the key components of a cardiac rehabilitation programme (20), which itself was initially presented in 2008 (21) and prompted by the publication of the European Commission's European Heart Health Charter in 2008, which recognised that cardiac rehabilitation was a means to effectively diminish the overall burden of cardiovascular disease. 

Conclusions

We hope that if they are given the evidence, physicians will believe in the indications and benefits of cardiac rehabilitation, and this will help overcome the lack of referrals and to also identify and motivate the patients who need cardiac rehabilitation. Indeed, a well controlled training programme aims to improve cardiopulmonary capacity of coronary heart disease: it will have a positive effect on lipid levels, smoking status, and insulin profiles, coronary arteries, myocardial and systolic function, heart rhythm, myocardial perfusion and coronary vasodilation capacity, myocardial performance, heart rate and blood pressure, oxygen consumption, peripheral artery disease, psychological state, productivity and mortality.
Contra-indications include scenarios where physical exercise has a potential risk and complications derive mainly from inappropriate surveillance during exercise - special care for example is needed during resting periods and 15 minutes after physical training and it is also important to know that risk also increases when 80% of maximal aerobic functional capacity or 85% of maximal heart rate is exceeded. 
For a detailed view on whether and how to establish an exercise plan in cardiac patients, see previous article by French sports cardiologist, François Carré.