Researchers assigned 180 sedentary patients with chronic, stable heart failure 1:1:1 to receive HIIT (3 x 38 minutes/week), moderate continuous training (5 x 40 minutes/week), or a control group that was advised on physical activity guidelines. Participants in the two exercise groups had supervised workouts for three months in a clinic followed by nine months of home workouts delivered via telemedicine.
The primary goal of the trial was to evaluate peak oxygen consumption at three months, and researchers set a minimum clinically important between-group difference of 2.5 mL/kg/min.
At three months, there was a statistically significant difference in peak oxygen consumption from baseline between the HIIT (1.1 mL /kg/min) and moderate continuous training (1.6 mL/kg/min) groups, and between both groups and the control group, whose mean peak oxygen consumption declined (-0.6 mL/kg/min). However, none of the comparisons were significant at 12 months.
"HIIT performed 3 times a week was as effective as moderate continuous training five times a week," said senior study author Dr. Martin Halle, of the Center for Sports Cardiology at University Hospital Klinikum rechts der Isar at the Technical University of Munich, in Germany.
"The metabolic as well as functional adaptations induced during exercise are primarily triggered by intensity, and the higher the strain, the higher the effects on protein metabolism, myokines, etc.," Dr. Halle said by email. "That does make sense as the more you provoke a dysbalance, the more the cells are forced to adapt."
At three months, 45 participants (80.4%) in the HIIT group and 42 participants (76.4%) in the moderate continuous training group attended at least 70% of the exercise sessions at the clinic.
In the HIIT group, participants completed a median of 2.5 session or 96 minutes of exercise per week during the first three months of sessions in the clinic, while in the moderate continuous training group they completed a median of 4.4 sessions or 176 minutes per week.
Once participants had home-based training, median participation declined to 2.0 sessions per week in the HIIT group and 3.6 sessions per week in the moderate continuous training group.
Overall, a total of 102 patients (58%) experienced adverse events, including 52 people (30%) who had serious adverse events. There was no difference in serious adverse event rates between HITT and moderate continuous training.
Acute coronary syndrome was the most common cardiovascular adverse event, followed by worsening heart failure and atrial fibrillation. One cardiac death occurred in the HIIT group, but it wasn't related to training.
One limitation of the study is that the people evaluating participants were not blinded to treatment groups when administering exercise tests, the study team notes in JAMA. Researchers also lacked data from exercise echocardiography to assess changes in diastolic function during exercise.
Even so, the results underscore the importance of promoting exercise, with supervision when possible, said Dr. Dalane Kitzman, a professor in cardiovascular medicine and geriatrics at Wake Forest School of Medicine in Winston-Salem, North Carolina, who coauthored an editorial accompanying the study.
However, insurance may not reimburse for cardiac rehabilitation for heart failure patients with preserved ejection fraction, Dr. Kitzman said by email.
"So, in the meantime, physicians can encourage regular physical activity," Dr. Kitzman said.
SOURCE: https://bit.ly/3a0Uetb and https://bit.ly/3aPinCf JAMA, online February 9, 2021.
By Lisa Rapaport
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