Description of the condition
Heart valve diseases account for one-third of heart diseases, with increasing prevalence due to an ageing population and advances in treatment methods. Previously, heart valve diseases were typically caused by rheumatic heart disease, but now most are degenerative in nature (Nkomo 2006). The overall prevalence of heart valve diseases is widely discussed, as exact estimates do not exist, probably because studies have largely focused on hospitalised patients (Iung 2003), and due to the diagnostic inaccuracy of echocardiography (Nkomo 2006). Prevalence in the USA is 2.5% and is likely to be similar in Europe, although divergent counts exist worldwide, for example, in different countries prevalence for aortic regurgitation ranges from 0% to 39% (Supino 2006).
Heart valve disease is either left-sided (aortic and mitral valve disease), which is more common, right-sided (tricuspid and pulmonary valves), or a combination of the two. Heart valve disease is often asymptomatic initially, but, when they present, symptoms include dyspnoea (difficulty breathing), fatigue, fluid retention and decreased physical capacity. Symptomatic heart valve disease severely impacts quality of life and physical function, and is associated with significant morbidity and mortality (Ben-Dor 2010). Treatment includes medical stabilisation with echocardiographic follow-up (Vahanian 2012). The treatment of choice when severe symptoms present is valve surgery to repair existing valves, or replacement with biological or artificial valves (Nishimura 2008; Vahanian 2012).
The changing disease pattern and expected increase in healthcare burden of people after heart valve surgery seem to require a well-established healthcare system, and an after-care programme to support the patient's post-surgical problems. These include both physical and psychological issues and the challenge of returning to work.
Before valve surgery, inactivity due to dyspnoea and physical incapacity is common. After surgery, people are often immobilised due to hospitalisation, possible post-surgery complications, and restrictions designed to assist healing of the sternum can mean that physical capacity can decrease further. As open heart surgery is an extraordinary, and very stressful, life event (Karlsson 2010), quality of life may be affected (Hansen 2009), with some patients experiencing mental problems including depressive symptoms and anxiety (Fredericks 2012). A Cochrane review (Whalley 2011) showed that people who had undergone surgery for a coronary artery bypass graft might benefit from psychological interventions, though, the bias risk of the study was considered to be high (Whalley 2011). Little is known about the effects of psychological interventions in people after heart valve surgery.
In summary, the possible physical or mental recovery problems experienced after heart valve surgery may include affected quality of life, increased healthcare costs, readmission(s) to hospital, loss of earnings, and increased morbidity and mortality. Exercise-based cardiac rehabilitation might affect all of these problems positively, but evidence for this is lacking.
Description of the intervention
Cardiac rehabilitation is a comprehensive complex intervention including components of exercise training, education, psychosocial management and a behaviour-modification programme designed to improve the physical and emotional conditions of people with heart disease (Piepoli 2010). Cardiac rehabilitation can also include patient assessment, nutritional counselling, and risk factor management for lipids, blood pressure, weight, diabetes mellitus, and smoking cessation (Piepoli 2010).
European guidelines for people after heart valve surgery recommend the importance of rehabilitation that includes exercise training, anticoagulant therapy, and medical and echocardiographic follow-up, but do not recommend psycho-educational interventions as part of the rehabilitation programmes (Butchart 2005). American guidelines do not describe cardiac rehabilitation after heart valve surgery (Vahanian 2012).
No specific information exists about how physical exercise should be performed by people after heart valve surgery. The European Society of Cardiology recommends that physical exercise for people with cardiovascular disease should consist of 150 minutes per week (that is, two-and-a-half hours), while others recommend three to four hours per week (Piepoli 2010). Further recommendations describe that low-risk patients should perform 30 minutes of aerobic exercise daily in order to achieve a weekly expenditure of 1000 kcal, whereas high-risk patients should have the amount of physical activity individually prescribed (Gianuzzi 2003). Preferably, the physical exercise should consist of submaximal endurance training (that is, starting at an intensity of 50% of maximum load), the intensity of which is increased over time, and the programme expanded to also include weight/resistance training. The uncertainty surrounding physical exercise for people after heart valve surgery is reflected in the very different training protocols employed in randomised clinical trials and observational studies that have investigated the effect of physical exercise for this group of people.
We have not identified any international consensus reports (for example from the World Health Organization), or guidelines from developing countries that describe detailed recommendations for physical exercise after heart valve surgery.
How the intervention might work
After heart valve surgery, patients often present with a low tolerance of exercise, and low physical capacity. These people have been inactive prior to surgery, then endured a period of bedrest and hospitalisation. At present the effect of cardiac rehabilitation with physical exercise on total mortality, morbidity, and quality of life after heart valve surgery remains uncertain. The existing evidence from both randomised clinical trials and observational studies indicates that exercise-based interventions for people after heart valve surgery have a positive effect on physical recovery, blood pressure (decreases), New York Heart Association class (decreases) and left ventricular ejection fraction (increases) (Gohlke-Bärwolf 1992; Landry 1984; Meurin 2005; Newell 1980; Sire 1987).
Exercise training for all cardiac patients - as well as after heart valve surgery - might have direct benefits on the heart and coronary vasculature, including myocardial oxygen demand, endothelial function, autonomic tone, coagulation and clotting factors, inflammatory markers, and the development of coronary collateral vessels (Clausen 1976; Hambrecht 2000). A study that included heart valve surgery patients as well as other cardiac patients, found that physical exercise had positive effects on exercise duration time, the intensity of exercise performed (measured by heart rate), and relative increase in oxygen uptake (Vanhees 2004).
As the evidence is sparse, we might expect to see the same type of effects for exercise after heart valve surgery as are seen in people with heart failure (HF) and ischaemic heart disease (IHD). Two Cochrane reviews have shown that exercise-based cardiac rehabilitation has a number of positive effects (Davies 2010; Heran 2011). The Heran 2011 review investigated exercise-based rehabilitation in people with IHD and indicated an overall reduction in all-cause and cardiovascular mortality and hospital admissions in the shorter term (< 12 months follow-up) compared with usual care. However, the risk of bias was high, as the reporting of the methodology and outcomes in many of the included trials was categorised as poor. Furthermore, the review found that cardiac rehabilitation did not reduce the risk of total myocardial infarction, coronary artery bypass graft or percutaneous transluminal coronary angiography. Meta-analysis of seven out of the ten trials included in this Cochrane review showed that health-related quality of life level significantly improved with exercise-based cardiac rehabilitation compared to usual care that did not include an exercise-based intervention (Heran 2011). Again, the risk of bias was high, as the reporting of the methodology and outcomes in many of the included trials was categorised as poor. Moreover, there are always risks of random errors that have not been accounted for in cumulative meta-analyses (Thorlund 2011; Wetterslev 2008).
The other Cochrane review investigated people with heart failure (Davies 2010), and reported that exercise-based cardiac rehabilitation seemed to be effective at reducing total and cardiovascular mortality in long-term studies and hospital admissions in shorter-term studies, but does not affect total myocardial infarction or revascularisation. The risk of bias in this review was judged to be high, as the overall quality of trials was reported to be poor. Furthermore, the risks of random errors were ignored (Thorlund 2009; Thorlund 2011; Wetterslev 2008).
Apart from the effects mentioned in the Cochrane reviews for people with IHD and HF that might be expected to apply to people after heart valve surgery, exercise-based rehabilitation might also reduce the symptom burden, improve symptom and disease management, and decrease rates of anxiety and depression.
Possible harmful effects of physical exercise in people after heart valve surgery have not been investigated in randomised clinical trials as far as we know. We can expect valve surgery-specific adverse events (e.g. arrhythmias, pericardial exudate, arterial embolism, death), as well as adverse events associated with valve disease (e.g. any arrhythmias, heart failure, death). A French prospective study of rehabilitation after cardiac surgery, that included coronary artery bypass grafting and valvular surgery, found a severe cardiac event rate of 1/49,565 patient-hours of training, which the authors considered to be low (Pavy 2006).
Why it is important to do this review
National and international guidelines recommend physical rehabilitation after heart valve surgery (Butchart 2005; Vahanian 2012). Whilst randomised clinical trials (Landry 1984; Newell 1980; Sire 1987), and a narrative review of exercise-based rehabilitation programmes for heart valve surgery patients have been conducted (Kiel 2011), we have not been able to identify any systematic reviews or meta-analysis of these trials. Therefore, the benefits and harms of exercise-based rehabilitation programmes for adults after heart valve surgery are unclear.