The recent recommendations by the European Society of Cardiology’s Working Groups on Heart Failure and Cardiac Rehabilitation and Exercise Physiology are the reference text in this regard.
Any recommendation for exercise training in heart failure should be based on the patient’s particular pathology, response to exercise (heart rate, blood pressure, symptoms, and perceived exertion), and cardiopulmonary exercise test data. Other considerations include current medication, risk factor profile, behavioral characteristics, personal goals, and exercise preferences. Given the central, peripheral, and metabolic changes in heart failure, the premise of rehabilitation is to apply both aerobic and strength training, with sufficient exercise stimuli to skeletal muscles, without significantly loading the cardiovascular system.
Aerobic exercise Exercise modalities
Past options have included walking, jogging, cycling, swimming, rowing, and calisthenics. However, exercise tolerance in heart failure permits few such activities.
Cycle ergometer training allows exercise at very low, exactly reproducible workloads, with continuous monitoring of heart rate, rhythm, and blood pressure. It is also ideal for interval training (see below). It is therefore the best type of aerobic exercise for heart failure patients in general, and more especially those with severe exercise intolerance, a history of serious arrhythmia, frequent changes in diuretic regimen,
obesity, and limitations whether orthopedic, neurologic or age-related with respect to other types of exercise.
A workload tolerated on the cycle ergometer cannot be applied to outdoor cycling owing to environmental factors influencing cardiovascular stress (head wind, incline). Even outdoor cycling on a level track at very slow speed (12 kph) requires almost 1000 mL/min VO2, equivalent to 50 W to 60 W. Thus, even with minimal environmental stress factors it can be recommended only for a small population of heart failure patients, essentially those with long-term stable disease and high exercise capacity tolerance.
Jogging at 80 m/min is the lowest speed at which movement is comfortable. But as even this requires an oxygen consumption of 1200 mL/min or an exercise tolerance >1 W/kg body weight, it is not advised for heart failure patients. Walking, on the other hand, offers a wide range of workloads: low speeds of < 50 m/min equivalent to 650 mL/min V02 require a low exercise tolerance of 0.3 W/kg body weight, while faster speeds of 100 m/min, equivalent to 900 to 1000 mL/min V02 require an exercise tolerance of 0.8 to 0.9 W/kg.
During head-up immersion, the hydrostatically induced volume shift increases volume loading of the left ventricle, with increases in heart volume and pulmonary capillary wedge pressure. Slow swimming (20 to 25 m/min) produces heart rate, blood lactate, and plasma catecholamine responses similar to those measured during cycle ergometry at workloads of 100 to 150 W. Heart failure patients with diastolic and systolic dysfunction should refrain from swimming for these reasons.
Interval versus steady-state exercise
The rationale behind interval training is to intensify peripheral muscle exercise stimuli compared with steady-state training without increasing cardiovascular stress. Short bouts of work are followed by short recovery phases. In coronary patients with low exercise capacity, interval aerobic training is more effective than steady-state training in improving exercise capacity. Patients with very low baseline aerobic capacities show an improved ventilatory threshold (+ 24%) and peak V02 (+ 20%) after only 3 weeks of interval cycle ergometer training. This result is similar to that achieved after much longer training periods (8 to 24 weeks) using steady-state training.
A useful regimen splits work phases of 30 s with recovery phases of 60 s. The work phases are set at 50% of maximum short-term exercise capacity (MSEC). During the recovery phase, patients may pedal at 10 W. Other combinations are tolerable: 15 s/60 s at 70% MSEC, and 10 s/60 s at 80% MSEC. In the first three work phases, the work rate should be successively increased to reach a maximum in the fourth phase. Depending on the work/recovery interval, 10 to 12 work phases are performed per 15-minute training session.
Although the work rate during interval training is markedly higher than in steady-state training, the left ventricular ejection fraction increases significantly, and by the same magnitude, during the course of 15-min interval training as during steady-state exercise performed at the same average power output. Mean blood pressure and heart rate are also similar, while blood lactate is significantly higher, indicating a greater peripheral training stimulus during interval exercise. Thus, interval exercise achieves greater peripheral muscle stimulation at no extra cost in terms of left ventricular stress than when using a steady state training method. It is therefore the preferred aerobic training modality in patients with significant baseline limitations due to heart failure.
Although the cycle ergometer is ideally suited to interval training, the treadmill can also be used, preferably with work and recovery phases of 60 s each. During the work phases, walking speed is adjusted to the heart rate tolerated by the patient during interval cycle ergometer training. During recovery phases, walking speed should be as slow as possible.
Determination of the work rate for interval work phases
The work rate for interval work phases is based on the MSEC determined using a steep ramp test. Patients start with 3 min unloaded pedaling, after which the work rate is increased by 25 W every 10 s. Because of the rapid increase in work rate, many patients can duplicate the maximum work rate from an ordinary ramp test (10 W/min increments), ie, they can perform at 150 to 200 W over exercise periods of 60 to 90 s without complications.