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Effect of Endurance Training on the Determinants of Peak Exercise Oxygen Consumption in Elderly Patients With Stable Compensated Heart Failure and Preserved Ejection Fraction
Study Questions:
How effective are the mechanisms for improved exercise capacity after endurance exercise training (ET) in elderly patients with heart failure and preserved ejection fraction (HFPEF)?
Methods:
Forty stable, compensated HFPEF outpatients were examined at baseline and after 4 months of ET (n = 22) or attention control (n = 18). The VO2 and its determinants were assessed during rest and peak upright cycle exercise. The initial power output was set at 12.5 W for 2 minutes, increased to 25 W for 3 minutes, followed thereafter by 25 W increments every 3 minutes until volitional exhaustion. Eligibility included adequate acoustical windows for resting and exercise echocardiograms performed using ultrasound imaging in the parasternal long- and short-axis views and apical four- and two-chamber views. Endurance exercise training was performed 3 days a week for 4 months by walking and cycling, with exercise intensity progressively increased from 40% to 70% heart rate reserve. Subjects completed a minimum of 40 of 48 training sessions.
Results:
Mean age was 69 ± 6 years and >80% were women. About 65% were New York Heart Association class II and 35% class III. After ET, peak VO2 in those patients was higher than in control patients (16.± 2.6 ml/kg/min vs. 13.1 ± 3.4 ml/kg/min; p = 0.002). That was associated with higher peak heart rate (139 ± 16 bpm vs. 131 ± 20 bpm; p = 0.03), but no difference in peak end-diastolic volume (77 ± 18 ml vs. 77 ± 17 ml; p = 0.51), stroke volume (48 ± 9 ml vs. 46 ± 9 ml; p = 0.83), or cardiac output (6.6 ± 1.3 L/min vs. 5.9 ± 1.5 L/min; p = 0.32). However, estimated peak arterial-venous oxygen difference was significantly higher in ET patients (19.8 ± 4.0 ml/dl vs. 17.3 ± 3.7 ml/dl; p = 0.03). The effect of ET on cardiac output was responsible for <15% of the improvement in peak VO2.
Conclusions:
In elderly stable compensated HFPEF patients, peak arterial-venous oxygen difference was higher after ET and was the primary contributor to improved peak VO2. This finding suggests that peripheral mechanisms (improved microvascular and/or skeletal muscle function) contribute to the improved exercise capacity after ET in HFPEF.
Perspective:
HFPEF is the most common form of HF in the elderly. As with HF with reduced EF, the improved exercise capacity as measured by peak VO2 with endurance training is primarily related to improved peripheral oxygen utilization and improved heart rate reserve. Improved cardiac performance (increase in left ventricular [LV] end-diastolic volume and stroke volume) as seen with ET in healthy persons does not occur in HF with or without preserved LVEF.
Keywords: Physical Endurance, Cardiac Output, New York, Heart Rate, Heart Diseases, Walking, Oxygen Consumption, Exercise Therapy, Cardiology, Heart Failure, Stroke Volume, Channelopathies, Muscles
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