Effects of high intensity interval training on cardiac function at rest and during exercise.

Rationale:

Physical training has beneficial effects on exercise capacity, cardiac function, quality of life and mortality in patients with chronic heart failure (CHF). However, the optimal training mode and intensity are not yet established.

In a recent small trial in elderly CHF patients, high intensity interval training (HIT) was shown to be superior to moderate intensity exercise training. Whereas both training modalities resulted in improved skeletal muscle metabolism and perfusion, HIT also induced improvements in cardiac function and size. However, as cardiac function was assessed at rest only, and measurements were performed by 2D echocardiography, which has limited accuracy for this purpose in patients with remodeled hearts, definitive conclusions cannot be drawn from this study.



Objective:

The main objectives of this study are to evaluate the effects of HIT in CHF patients on cardiac output at rest assessed with cardiac magnetic resonance imaging(cMRI), and to investigate the relation between changes in resting cardiac output and changes in cardiac output during maximal exercise (assessed by LiDCO). Secondary objectives are to investigate the relation between training-induced changes in central haemodynamics and changes in the following variables: cardiac size at rest, cardiac output kinetics during and after submaximal exercise, local oxygen delivery in skeletal muscles and quality of life.



Study design:

Prospective randomised controlled intervention trial.



Study population:

Stable CHF patients (left ventricular ejection fraction ≤40%), NYHA class II or III, on optimal medical treatment, who are able and motivated to perform an exercise training program.



Intervention:

HIT is performed 3 times a week during 12 weeks and consists of 4 intervals of 4 minutes cycling on a ergometer at 85-95% of the peak aerobic capacity (peak Vo2) separated by 3 minute active pauses. The entire program is performed in the hospital under direct supervision of trained physiotherapists.



Main study parameters/endpoints:

Primary endpoints:

1. Training induced changes in resting cardiac output as determined by cMRI;

2. Correlation between training induced changes in resting cardiac output and cardiac output during maximal exercise (LiDCO).

Secondary endpoints:

Correlation between training induced changes in resting c.q. exercizing cardiac output and changes in the following variables:

1. Cardiac size at rest (cMRI);

2. Cardiac output onset and recovery kinetics at submaximal exercise (LiDCO);

3. Recovery kinetics of muscle tissue oxygenation after submaximal exercise (Near Infrared Spectroscopy);

4. Quality of life (Minnesota Living With Heart Failure Questionnaire).



Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

Exercise training performed by patients with chronic heart failure patients is considered to be safe and has a class Ia recommendation for treatment of CHF patients.

The HIT program that will be used in this study has been evaluated in a similar population of elderly CHF patients and also in patients with coronary artery disease without any documented harmful effects. In order to reduce potential risks of exercise training all patients perform a maximal cardiopulmonary exercise test at baseline, excluding patients with myocardial ischaemia and ventricular arrhythmias during exercise. Training sessions will be under supervision of trained physiotherapist in a clinical setting. Regarding the study procedures:

Cardiac output during exercise is evaluated by using a method (LIDCO) requiring radial artery cannulation. Radial artery canulation is considered to be relatively safe with complication rate of 0.09% for permanent ischemia of the hand. To ensure collateral circulation a normal Allen test must be present. Puncture will be under local anaesthesia to minimize patients burden. In patients who take oral anticoagulation , dosage will be temporarily adjusted (INR <1,5) for the safety of the procedure. All other study procedures are non-invasive and considered to be safe in the selected patient population.

Physical training has beneficial effects on exercise capacity, cardiac function, quality of life and mortality in patients with chronic heart failure (CHF). However, the optimal training mode and intensity are not yet established.

In a recent small trial in elderly CHF patients, high intensity interval training (HIT) was shown to be superior to moderate intensity exercise training. Whereas both training modalities resulted in improved skeletal muscle metabolism and perfusion, HIT also induced improvements in cardiac function and size. However, as cardiac function was assessed at rest only, and measurements were performed by 2D echocardiography, which has limited has limited accuracy for this purpose in patients with remodeled hearts, definitive conclusions cannot be drawn from this study.

1. Baseline assesment;

2. Intervention 3 months fysiotherapy;

3. Final assesment.

HIT is performed 3 times a week during 12 weeks and consists of 4 intervals of 4 minutes cycling on a ergometer at 85-95% of the peak aerobic capacity (peak Vo2) separated by 3 minute active pauses. The entire program is performed in the hospital under direct supervision of trained physiotherapists.



The control group receives global exercise advice, but no training by a physiotherapist. Controls can receive training once the trial has been finished.