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Exercise Training in Systolic Heart Failure Patients
Study Questions:
Is high intensity interval training (HIIT) superior to moderate continuous training (MCT) in reversing cardiac remodeling and increasing aerobic capacity in systolic heart failure (HF) patients?
Methods:
The study cohort was comprised of 261 patients with left ventricular ejection fraction (LVEF) <35% and New York Heart Association (NYHA) class II-III. These HF patients were randomly assigned 1:1:1 to a 12-week program of HIIT at 90-95% of maximal heart rate (HRmax), MCT at 60-70% of HRmax, or a recommendation of regular exercise (RRE). HIIT and MCT had three supervised sessions per week on treadmill or bicycle. HIIT performed four 4-minute intervals aiming at 90-95% of maximal heart rate (HRmax) separated by 3-minute active recovery periods of moderate intensity. HIIT sessions lasted 38 minutes including warm-up and cool-down at moderate intensity. MCT sessions aimed at 60-70% of HRmax and lasted 47 minutes. Patients randomized to RRE were advised to exercise at home according to current recommendations and attended a session of moderate intensity training at 50-70% of maximal heart rate every 3 weeks. Thereafter, these HF patients were encouraged to continue exercising on their own. Clinical assessments were performed at baseline, after the intervention, and at follow-up after 52 weeks. Primary endpoint was between-group comparison of change in left ventricular end-diastolic diameter (LVEDD) from baseline to 12 weeks. Key secondary endpoints were change in LVEF and peak VO2; the latter was also considered a measure of training effect.
Results:
After initial exclusions and withdrawals, 231 patients were included in HIIT, MCT, or RRE. Nine dropped out due to serious adverse events and seven withdrew or were lost to follow-up; 215 patients were assessed after 12 weeks and were included in the intention-to-treat analysis. Baseline characteristics were similar in all groups, although more RRE patients had a history of hypertension. The study investigators found that groups did not differ for age (median 60 years), gender (19% women), ischemic etiology (59%), or medication. Change in LVEDD from baseline to 12 weeks was not different between HIIT and MCT, p = 0.45; respective changes versus RRE were -2.8 mm (-5.2, -0.4; p = 0.02) in HIIT and -1.2 mm (-3.6, 1.2; p = 0.34) in MCT. They also found that there was no difference between HIIT and MCT in peak oxygen uptake, p = 0.70, but both were superior to RRE. However, none of these changes were maintained at follow-up after 52 weeks. There were no within-group or between-group differences in the quality-of-life measures at baseline, 12 weeks, or 52 weeks. Serious adverse events were not statistically different during supervised intervention or at follow-up at 52 weeks (HIIT 39%, MCT 25%, RRE 34%, p = 0.16). Training records showed that 51% of patients exercised below prescribed target during supervised HIIT and 80% above in MCT.
Conclusions:
The study authors concluded that HIIT was not superior to MCT in changing LV remodeling or aerobic capacity, and its feasibility remains unresolved in HF patients.
Perspective:
As the authors point out, limitations of the study include possibly short duration of the study and the fact that target intensity was not achieved by a substantial number of participants of the study cohort. In the HF-ACTION study, exercise training resulted in nonsignificant reductions in the primary endpoint of all-cause mortality or hospitalization. Until we have more data, given these findings of the HF-ACTION study, patients with systolic HF should be encouraged to exercise regularly.
Keywords: Bicycling, Exercise, Exercise Test, Exercise Tolerance, Heart Failure, Heart Failure, Systolic, Hypertension, Quality of Life, Stroke Volume
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