Rehabilitation after cardiac surgery

One of the authors of this editorial comment is old enough to remember when a patient who had had a myocardial infarction or underwent cardiac surgery was kept in bed for weeks, often for one or two months. This is true to such an extent that in our city (one of the most advanced in the world for health services) the rooms of the coronary and intensive care units, different to those of all other wards, were in those years, lacking in toilets as they were considered useless since the patients were forbidden to get up from bed until discharge. Now it is known that the consequences of sedation and muscle weakness, which are typical of reduction in mobility in intensive care units, trigger a process decreasing protein synthesis, increasing proteolysis and compromising functional capacity, potentially lasting for months.1 Muscle atrophy and prolonged inactivity are responsible for the sensation of fatigue and reduced functional capacity in the postoperative period in patients who undergo invasive cardiac procedures,1 a reason why cardiac rehabilitation is now ‘highly recommended’ and ‘contributes to improvement in functional capacity and quality of life’.1 To our knowledge, nobody knows who decided first to shorten the bed-rest time after cardiac surgery. It is plausible that this practice has simply been suggested by the progressive need to reduce hospital stays based on costs considerations. What is certain is that prognostic improvement and greater well-being were observed, so that this approach progressively became routine for coronary patients and for those who underwent cardiac surgery.2 It was demonstrated that, even in the elderly and in the very old, early extubation rapidly followed by an exercise-based rehabilitation programme was associated with an improvement in physical performance, namely in exercise capacity, muscular strength, physical function, activities of daily living, health-related quality of life and exercise tolerance,3,4 and with a lower rate of one-year readmission,5 the only question being how early the rehabilitation had to be. Actually, the literature is very poor as far as the outcome of patients starting aerobic exercise ‘early after cardiac surgery’ is concerned. The post-sternotomy cardiac rehabilitation exercise training (SCAR) study, the protocol of which was published in September 2018, is dealing with this problem in the form of a controlled clinical trial.6 In the meantime, the article ‘Safety and efficacy of aerobic exercise commenced early after cardiac surgery: a systematic review and meta-analysis’, based on the electronic databases Medline, ProQuest, Web of Science, ScienceDirect and Cochrane Central Register of Controlled Trials and published by Doyle et al.,7 emphasises the opportunity to start aerobic exercise as soon as possible (plausibly after one week from cardiac surgery, if allowed by clinical conditions), as an ‘aerobic exercise commenced in the immediate postoperative period and completed at hospital discharge’ is followed in average by a better outcome and entails a lower risk than that started weeks after discharge.7 The reasons for the beneficial effect of early rehabilitation are unclear, although the consequences of aerobic exercise have been widely studied, at least from a cardiological point of view. Isotonic work, not only regularly repeated in the form of so-called ‘endurance exercise training’ but also acutely performed, is followed in the recovery phase and in the medium to long term by a reduction in systolic and sometimes diastolic blood pressure.8,9 The pressor drop has been attributed time to time to a decrease in peripheral resistance (vasodilation), to modifications in cardiopulmonary baroreflex, and to a reduction of sympathetic discharge.8 For the reader who is also a cardiologist, it is worthwhile to stress that in the meta-analysis of Doyle et al.7 aerobic exercise was defined as physical activity that induces a steady and sustainable increase in aerobic metabolism when performed at an intensity below the anaerobic threshold (when isolated walking programmes were included, they had to exceed in intensity simple ambulation).7 We have a certain experience in the field of aerobic exercise. Using simultaneous strain-gauge plethysmography in volunteers, echocardiography and intra-arterial blood pressure monitoring in a human physiology laboratory, we previously repeatedly found a significant reduction in arteriolar resistance after bicycle ergometric exercise, mirrored by a significant increase in peripheral flow and cardiac output after a bout of aerobic exercise (Figure 1).8,9 Interestingly, heart contractility was not depressed: on the contrary, the left ventricular ejection fraction was increased.8,9 Haemodynamic parameters during 10 minutes of recovery after a bout of bicycle ergometry in a laboratory of human physiology, in comparison to baseline rest on peripheral resistance at the forearm (FPR, in UR = mmHg × ml–1 dltissue × min) calculated from mean blood pressure and arterial flow, echocardiographic cardiac output (CO, in l × min–1), strain-gauge plethysmographic peripheral arterial flow at the forearm (FPF, in ml × min–1 × dltissue–1), electrocardiographic heart rate (HR, in beats × min–1) and intra-arterial systolic blood pressure (SBP, in mmHg) in eight normal volunteers.8,9 All recovery values: P < 0.05 versus baseline. All these variations are obviously favourable in terms of heart load and work and – from a prognostic point of view – in terms of outcome. It is plausible that reiterating the above-mentioned pressor and haemodynamic effects in a systematic controlled setting leads to a reduction of work load and oxygen consumption, so improving the convalescence and reducing the risk. It is important to insist on the term ‘controlled’, as aerobic exercise is per se a stress condition not exempt from risk. Aerobic exercise is a form of rehabilitation, but also a provocative test: even if followed by a persistent pressor decrease in the recovery time, there is a temporary rise in arterial blood pressure – particularly systolic – just during the bout of exercise, and the mentioned increase of cardiac output is obtained at the price of a rise in heart rate and in ventricular contractility. These modifications have an energetic cost and provoke myocyte sacrifice, as demonstrated for instance by a rise in myocardial enzymes paralleling the increase in peripheral flow.10 In the meta-analysis by Doyle et al.,7 patients recovering from cardiac surgery, obviously well controlled from a cardiological point of view, a small but not null number of major events including death was recorded. Early cardiac rehabilitation must therefore be reserved to an expert cardiologist, to a trained staff, and to health structures used to perform a number of rehabilitation bouts per year sufficient to qualify the centres as expert. Even so, potentially severe adverse effects are probably unavoidable, an occurrence the patient must made aware of: early rehabilitation – like aerobic exercise in general, but even more – is followed by a short, medium and long-term benefit, provided that the patient survives to each single bout of exercise. In conclusion, the meta-analysis by Doyle et al.,7 limited to the best studies available in the literature, gives provisional substance to the general belief that aerobic exercise commenced early after cardiac surgery (as early as the first postoperative week) significantly improves functional and aerobic capacity with a rate of adverse effects that is relatively low and not different in comparison to usual rehabilitation.7 Nevertheless, the authors correctly observe that further studies are mandatory to assess the safety outcomes of this practice, particularly in high-risk cohorts. It is also desirable that categories neglected until now, such as women and fragile elderly, should be included in controlled trials on the effectiveness of rehabilitation and the best time to start it, topics which are currently still lacking. Another open question is whether cardiac rehabilitation after surgical11 or transcatheter12 valve treatment may benefit from early commencement, a topic that should be dealt with as soon as possible, particularly as the frail elderly are considered. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.