High-Intensity Interval Training in Patients With Heart Failure With Reduced Ejection Fraction

Abstract

Background: Small studies have suggested that high-intensity interval training (HIIT) is superior to moderate continuous training (MCT) in reversing cardiac remodeling and increasing aerobic capacity in patients with heart failure with reduced ejection fraction. The present multicenter trial compared 12 weeks of supervised interventions of HIIT, MCT, or a recommendation of regular exercise (RRE).

Methods: Two hundred sixty-one patients with left ventricular ejection fraction ≤35% and New York Heart Association class II to III were randomly assigned to HIIT at 90% to 95% of maximal heart rate, MCT at 60% to 70% of maximal heart rate, or RRE. Thereafter, 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 end point was a between-group comparison of change in left ventricular end-diastolic diameter from baseline to 12 weeks.

Results: Groups did not differ in age (median, 60 years), sex (19% women), ischemic pathogenesis (59%), or medication. Change in left ventricular end-diastolic diameter from baseline to 12 weeks was not different between HIIT and MCT (P=0.45); left ventricular end-diastolic diameter changes compared with RRE were -2.8 mm (-5.2 to -0.4 mm; P=0.02) in HIIT and -1.2 mm (-3.6 to 1.2 mm; P=0.34) in MCT. There was also no difference between HIIT and MCT in peak oxygen uptake (P=0.70), but both were superior to RRE. However, none of these changes was maintained at follow-up after 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 target in MCT.

Conclusions: HIIT was not superior to MCT in changing left ventricular remodeling or aerobic capacity, and its feasibility remains unresolved in patients with heart failure.

Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00917046.

Keywords: exercise; heart failure.

Figure 1.

Study enrollment, randomization, and follow-up. Enrollment was stopped when it was estimated that at least 200 patients would complete the 12-week assessments according to protocol. Two hundred fifteen patients came to follow-up assessments and were included in the intention-to-treat analysis; 207 of these were included in per-protocol analysis. Two hundred two patients came to the 52-week assessments and fulfilled the criterion of having completed either echocardiography or cardiopulmonary exercise testing. LVEF indicates left ventricular ejection fraction; and SAE, serious adverse event.

Figure 2.

Training intensity during the 12-week intervention. A, Heart rate during training. Average heart rate during the 12-week intervention, estimated as weekly mean (SD) during moderate continuous training (MCT) and during the last 2 minutes of high-intensity interval training (HIIT). Constant difference between groups: 16 bpm (10–22 bpm; P<0.001). B, Workload. Average workload estimated as for heart rate. Difference between groups: 33 W (24–42 W; P<0.001). C, Training intensity. Average relative training intensity (percentage of maximal heart rate) estimated as for heart rate: HIIT, 90% (88%–92%); MCT, 77% (74%–82%); difference, 10% (8%–13%; P<0.001). Some of the variability in estimated training intensity probably results from variation in maximal heart rate. Comparing baseline and follow-up assessments in individual patients revealed differences that seemed randomly distributed and independent of intervention group, center, and whether the patients had sinus rhythm or atrial fibrillation (data not shown). Shaded areas mark boundaries of prescribed training intensity: HIIT, 90% to 95%; MCT, 60% to 70%. D, Training intensity on target. Distribution of average training intensity during the 12-week intervention; MCT, left histogram; HIIT, right histogram. Shaded areas mark boundaries for prescribed training intensity. Fifty-one percent of HIIT patients exercised below their prescribed training intensity, and 80% of MCT patients exercised above theirs. Density scales the height of the bars so that the sum of their areas equals 1.00.