No Gain For Interval Training vs Standard Training in Heart Failure: SMARTEX-HF

Larry Hand

January 20, 2017

TRONDHEIM, NORWAY — High-intensity interval training (HIIT) did not prove to be superior to moderate continuous training (MCT) in the first randomized multicenter trial evaluating HIIT in chronic heart-failure patients with reduced ejection fraction[1].

"For patients with stable heart failure, the beneficial effect of a systematic supervised training program was larger than just giving general advice on regular exercise, irrespective of whether they used interval training or continuous activity of moderate to high intensity," primary author Dr Øyvind Ellingsen (St Olavs Hospital, Trondheim University Hospital) told heartwire from Medscape.

"Even if patients get positive effects after 12 weeks, physical activity and functional improvement seem to subside when the program is over, so we need to think more carefully about how to motivate our patients to maintain good exercise habits after rehabilitation," he said.

Ellingsen and colleagues conducted the SMARTEX Heart Failure Study, a randomized, controlled trial, at nine European centers between June 2009 and July 2014. They included 215 patients in their analysis from outpatient heart-failure clinics, referrals to cardiac rehabilitation, public announcements, and hospital registries.

They based their investigation on a previous smaller study[2] that found that HIIT exercise performed in intervals of 1 to 4 minutes was superior to MCT in heart-failure patients, according to their article, published January 12, 2017 in Circulation.

They randomized the patients, median age 60 and 81% male, to HIIT (n=77), MCT (n=65), or recommended regular exercise (RRE, n=73). At baseline, all patients were on optimal medical treatment, median left ventricular ejection fraction (LVEF) was 29%, and median peak oxygen uptake was 17.1 mL×kg1×min-1.

HIIT consisted of three supervised sessions a week of treadmill or bicycle exercise performed at 4-minute intervals with a goal of achieving 90% to 95% of maximal heart rate and separated by 3-minute recovery periods. Sessions lasted 38 minutes including warm-up and cooldown.

MCT consisted also of three supervised sessions a week of treadmill or bicycle exercise with a goal of achieving 60% to 70% maximal heart rate and lasting 47 minutes.

Patients randomized to RRE were advised to exercise at home with a goal of achieving 50% to 70% of maximal heart rate and attend a session of moderate-intensity training every 3 weeks.

Supervised training sessions stopped after 12 weeks in all three groups, but investigators stayed in contact by phone during the remainder of the 52 weeks of follow-up.

The researchers found median adherence to supervised training sessions to be 35 of 36 sessions. However, eight patients completed fewer than 24 sessions.

They also found that 51% of patients in the HIIT group exercised at a lower intensity than prescribed, while 80% of patients in the MCT group exercised at a higher intensity than prescribed.

For the primary end point of change in left ventricular end-diastolic diameter (LVEDD), the researchers found no significant differences. Change in LVEDD in HIIT patients came out to be -1.2 mm compared with MCT but -2.28 mm compared with RRE.

They found no other significant differences in echocardiographic measurements, and at 1 year they found no significant differences between groups.

They also found no significant differences in serious adverse events, although the study was not powered for safety evaluation, and no significant differences in quality-of-life measures.

"Interest, advice, and encouragement from cardiologists and other clinicians may be much more important than we think when it comes to establishing and maintaining good exercise habits and other positive lifestyle changes," Ellingsen told heartwire.

"Interval training might be a new remedy in the toolbox, a nice variation for those motivated, although it was not proved to be as effective as predicted from experimental and smaller clinical studies," he continued. "Our results also support the notion that exercise could stretch our zone of comfort a bit while exercising without doing any harm. This seems to be true even in heart failure, provided they are under good supervision, as all heart-failure patients should be."

Dr Luc Vanhees (University Hospitals of Leuven, Belgium), senior author of a previous study[3] cited in this new article, told heartwire , "These data in HF patients confirm our findings in patients with coronary artery disease. If the volume and intensity of continuous aerobic exercise is sufficiently high and the intensity of HITT feasible to do, no differences in training effect will be found. These two larger studies do not confirm the earlier reported different effects in much smaller groups of patients.

"The prescription of intensity should be based on the individual assessment of patients' capacity, possibilities, and preferences for type of exercise," he continued. "Whether continuous or interval training should be used is therefore of less importance. Accurate intensity of exercise seems to be the crucial factor."

This research was supported by the Norwegian University of Science and Technology (NTNU); Norwegian Health Association; Danish Research Council; Central Norwegian Health Authority/NTNU; Else-Kröner-Fresenius-Stiftung, and Société Luxembourgeoise. Ellingsen reported no relevant financial relationships. Disclosures for the coauthors are listed in the paper.

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