High Intensity Interval Training vs Moderate Intensity and Continuous Training in Chronic Heart Failure

Efficacy of High Intensity Interval Training vs Moderate Intensity and Continuous Training on Autonomic Nervous System Modulations in Chronic Heart Failure

Purpose: Exaggerated sympathetic nervous system (SNS) activity associated with low heart rate variability (HRV) is considered as a trigger of cardiac arrhythmias and sudden death. Regular exercise training is efficient to improve autonomic balance. In 2013, the investigators published that a single session of an optimized short-high intensity interval exercise with passive recovery (HIIT) protocol was efficient in chronic heart failure (CHF) patients for enhancing vagal tone and to decrease arrhythmias in the 24-h post exercise period when compared to a single session of moderate intensity continuous exercise (MICT). Nevertheless the effects of HIIT training performed on several weeks have never yet been studied on the parameters described by Coumel's triangle (the arrhythmogenic substrate, the trigger factor as premature ventricular contraction and the modulation factors of which the most common is the autonomic nervous system). The aim of this study was to verify the superiority of HIIT to enhance parasympathetic activity, cardiorespiratory fitness and cardiac function when compared to MICT in a short and intense cardiac rehabilitation program.

Before and after the Rehabilitation Program (RP), all patients underwent a 24-hour ECG recording, an echocardiography, a cardiopulmonary exercise test.

The RP consisted of 2 types of exercise training according to the randomization:

1. a short-high intensity interval exercise with passive recovery
2. a classical moderate and continuous exercise training at 60% of peak power output

The RP lasted 4 weeks.

Inclusion Criteria:

• stable chronic heart failure with NYHA functional class from I to III
• stable left ventricular ejection fraction (LVEF) < 45% over at least 6 months
• stable optimal medical therapy including a beta-blocker and an angiotensin-converting enzyme inhibitor or angiotensin receptor blockers for at least 6 weeks
• ability to perform a maximal cardiopulmonary exercise test
• admitted to the Rehabilitation Centre for a comprehensive Cardiovascular Rehabilitation Program

Exclusion Criteria:

• any relative or absolute contraindications to exercise training according to current recommendations
• fixed-rate pacemaker with heart rate limits set lower than exercise training target
• major cardiovascular event or procedure within the 3 months preceding enrolment
• chronic atrial fibrillation
• heart failure secondary to significant uncorrected primary valve disease (except for mitral regurgitation secondary to left ventricular dysfunction)
• heart failure secondary to congenital heart disease or obstructive cardiomyopathy.