HEART DISEASE Part 3
Exercise in the treatment of CHD
The use of exercise for treating coronary disease preceded its use for treating any other medical problem. Back in the 18th century Dr William Heberden recognised angina and in 1768 he described one of his patients, who had been cured by sawing wood for half an hour a day!
Coronary heart disease (CHD) however, was infrequently diagnosed over the next 150 years and by the time it became accepted as a serious health problem, early in the 20th century, this lesson had been forgotten.
When a heart attack was diagnosed, prolonged bed rest was thought to be essential if the patient’s life were to be saved –it was believed that exertion too soon after the attack risked rupturing the damaged heart. Doctors and nurses went to amazing lengths to keep the patient at complete ‘rest’ for several weeks, spoon-feeding them and insisting on the use of that most exercise-intensive utensil, the bedpan! When the patient was eventually released from hospital, the advice was for exercise to be restricted in favour of a peaceful, sedentary life.
Cardiac rehabilitation (CR)
By the 1950s some of the undesirable consequences of bed-rest were being appreciated – deconditioning, boredom, depression, venous thrombosis and chest infection to mention just a few. The idea of early mobilisation was came on the scene. In Cleveland, Ohio, a farseeing cardiologist called Herman Hellerstein and his colleagues developed a comprehensive rehabilitation programme with graduated exercise training as its centrepiece. The idea was to ‘add life to years and perhaps years to life’ for ‘habitually sedentary, lazy, hypokinetic, sloppy, endo-mesomorphic overweight males’ through a programme of enhanced physical activity. Dr Hellerstein appears to have held his coronary patients in high regard!
The early cardiac rehabilitation programmes also included improvement in nutrition, giving up smoking and continuation of gainful employment and normal social life. The results showed that patients who had recovered from a heart attack could have their physical fitness improved, ECG changes recorded during and after exertion reduced and psychological status raised.
The effects of CR on mortality
The early randomised controlled trials were too small to show a reduction in mortality from CR. However by the 1980s it was possible to combine the results of a number of RCTs (this is called meta-analysis) to give results for larger numbers. Several meta-analyses found that CR can reduce the mortality rate of treated groups by about 25% over the following three years.
Interestingly, when exercise-only programmes have been compared with more comprehensive programmes, the exercise-only treatments fare as well as those offering in addition counselling, education and risk-factor advice. It is my belief that it is extremely difficult to change the behaviour of the middle-aged and the only advice that has much chance of making an impact is that concerning exercise – particularly when it is incorporated into patient management.
Long term effects of exercise
In patients with established CHD, exercise capacity remains a powerful predictor of prognosis. For every 1 MET reduction in fitness there is an increased risk of death of 13 per cent. One study has shown that mortality in CHD patients with a VO2max of less than 15 is more than double that of those with a VO2max of more than 22 in those followed up for an average of 8 years. Indeed, physical fitness in CHD patients is a better predictor of future mortality than any other measure. This effect is partly because low fitness reflects greater heart damage; even so, increasing fitness with exercise training reduces mortality risk to the level of untrained subjects with an equivalent fitness level.
CR in practice
The RCTs which showed the mortality benefits of CR were based on exercise sessions three times per week for at least three months. Unfortunately the CR programmes provided by the NHS today use much lower levels of exercise and are much shorter in duration – typically once or twice weekly for six to eight weeks. This is probably too little to be effective. One recent study showed that, in a sample of 70 coronary patients receiving the usual twice-weekly exercise course for eight weeks, there was no increase in fitness level and no reduction in five-year mortality. A further failure of our care of heart patients was shown by a study of 4,000 people recovering from a coronary event from the previous two years: 45 per cent were still smoking, 36 per cent were obese, 53 per cent had central obesity and 52 per cent were classified as inactive.
Exercise in the treatment of heart failure
I mentioned in a previous blog about CHD that one important consequence of cardiac damage from coronary disease is heart failure. In this condition the ability of the heart to pump out enough blood for daily living is impaired, with resulting tiredness, breathlessness and restriction of activities. There are about 900,000 people living with heart failure in the UK.
The more the heart is damaged, the less effect any physical training has on its function. However with heart failure it is still possible to increase physical fitness, but this is through peripheral training effects – improved muscular efficiency and blood-flow distribution. The exercise training of patients with heart failure is further restricted by the limited exercise intensity and dose that they can sustain. Exercise training of heart-failure patients can be helpful but must be increased slowly and carefully. The resulting benefits are modest.
A meta-analysis of RCTs of exercise training for 4,400 heart-failure patients found an increase in timed walking distance of about 6 per cent, which is enough to be helpful. Quality of life scores increased slightly but there was no increase in either hospital admission or mortality.
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