Moderate Exercise Still Standard vs High-intensity Routine in Chronic HF


SMARTEX HF is first multicenter RCT to evaluate high intensity interval training in patients with HFrEF

Twelve weeks of high intensity interval training (HIIT) is no better than moderate exercise for changing left ventricular remodeling and improving aerobic capacity in patients with chronic heart failure and reduced ejection fraction (HFrEF), according to a study published online on December 6, 2016 in Circulation.1

The study, called the SMARTEX Heart Failure study, is the first randomized controlled multicenter trial to evaluate HIIT in patients with HFrEF.

 “Given that HIIT was not superior to MCT [moderate continuous training] in reversing remodeling or improving secondary endpoints, and considering that adherence to the prescribed exercise intensity based on heart rate may be difficult to achieve, even when supervised and performed in centers experienced in cardiac rehabilitation, MCT remains the standard exercise modality for patients with chronic heart failure,” wrote first author Øyvind Ellingsen, MD, PhD, of Norwegian University of Science and Technology (Trondheim, Norway), and colleagues with the SMARTEX Heart Failure Study Group.

The European Society of Cardiology recommends exercise training in heart failure patients. However, because no agreement exists about what type of exercise is best, an individualized approach is generally advised.2

Moderate continuous exercise has most support for its efficacy and safety in chronic heart failure, though evidence comes mainly from the HF-ACTION study. Results from that study showed that patients with HFrEF who were randomized to moderate continuous exercise had modest reductions in mortality and hospitalization.3

Recently, however, one small study suggested that HIIT may be better than moderate continuous exercise for reversing cardiac remodeling and increasing aerobic capacity in HFrEF.4 That has raised questions about whether HIIT should be part of standard care for heart failure patients.

The SMARTEX Heart Failure study was designed to address this question in a larger group of patients. The study took place in nine European centers between June 2009 and July 2014. It included patients with HFrEF and symptomatic, stable heart failure. Participants were randomized to 12 weeks of HIIT, moderate continuous exercise, or regular exercise at home.

► HIIT and moderate continuous exercise groups: 3 supervised training sessions/wk on treadmill or bicycle.
    -- HIIT: exercised at targeted maximal heart rate of 90-95% for 38 minutes total, in four minute intervals separated by a three minute active recovery period.
    -- Moderate continuous: exercised for 47 minutes total and trained to 60-70% of maximal heart rate.

► Regular exercise group: exercised at home, attended a moderate exercise session every three weeks; trained to 50-70% of maximal heart rate.

After twelve weeks, researchers encouraged participants to continue exercising on their own.

Researchers did clinical assessments at baseline, after training sessions, and at 52 week follow-up.

The primary endpoint was change in left ventricular end diastolic diameter from baseline to 12 weeks. The analysis included 215 participants.

Key Results>>


Results: SMARTEX Heart Failure Study

► Primary outcome: no significant difference between HIIT and moderate continuous exercise (p=0.45)

► Peak oxygen uptake:
   -- No significant difference between HIIT and moderate continuous exercise (p=0.70)
   -- Both were better than regular exercise

► After 12 weeks both HIIT and moderate continuous exercise showed improvements in the primary outcome and in peak oxygen uptake, but these changes were not maintained at 52 weeks

► No significant difference in serious adverse events during the intervention (p=0.33) or at 52 weeks (p=0.16)
    -- During intervention: Numerically higher adverse events in HIIT, followed by moderate continuous exercise, then regular exercise
    -- At 52 weeks: Nonsignificant trend toward more hospital admissions for CV events with HIIT (n=19) and regular exercise (n=17) vs moderate exercise (n=8) (p=0.10)

► 51% of the HIIT group exercised below heart rate targets

► 80% of the moderate continuous exercise group trained above heart rate targets

The authors pointed out that, while none of the interventions were linked to deterioration in cardiac function, readmissions for worsening heart failure were higher with HIIT. That may suggest that moderate continuous exercise may be more favorable than HIIT or regular exercise, though the study was not large enough to look at this issue.

They concluded: “The present multicenter trial did not confirm the hypothesis that twelve weeks program of supervised high intensity interval training (HIIT) was superior to moderate continuous exercise in reducing left ventricular remodeling in stable heart failure patients…  Further studies are needed to define the role of HIIT as an alternative exercise modality in heart failure patients with reduced ejection fraction.”

Limitations include partial overlap in training intensity between HIIT and moderate continuous exercise. Also, only 19% of the study population were women.The authors suggested that future studies should include more women, and adjust exercise intensities according to improved exercise capacity, worsening of symptoms or medication changes.

Take-home Points

  • After twelve weeks, HIIT was no better than moderate continuous training for improving left ventricular remodeling and peak oxygen uptake in HFrEF

  • Improvements in left ventricular remodeling and peak oxygen uptake with 12 weeks of HIIT and moderate continuous training were not maintained at 52 weeks

  • Though serious adverse events did not differ significantly bewteen HIIT and continuous exercise training, HIIT showed a trend toward increased hospitalization for CV events at 52 weeks

  • More studies are needed to define the role of HIIT in HFrEF

One or more authors report grants, advisory board membership, and/or personal fees from one or more of the following: Else-Kröner-Fresenius Foundation, Novartis, Sanofi-Aventis, MSD, Medtronic, Claret Medical, Edwards, SJM, Bard, and/or Symetis.



Ellingsen Ø, Halle M, Conraads VM, et al. High Intensity Interval Training in Heart Failure Patients with Reduced Ejection Fraction. Circulation. 2017 Jan 12. pii: CIRCULATIONAHA.116.022924. doi: 10.1161/CIRCULATIONAHA.116.022924.

Ponikowski P, Voors AA, Anker SD, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: The Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC)Developed with the special contribution of the Heart Failure Association (HFA) of the ESC. Eur Heart J. 2016;37:2129-2200.

O'Connor CM, Whellan DJ, Lee KL, et al. Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial. JAMA. 2009;301:1439-50. doi: 10.1001/jama.2009.454.

Wisloff U, Stoylen A, Loennechen JP, et al. Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients: a randomized study. Circulation. 2007;115:3086-3094.

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