Author + information
- Siri M. Hollekim-Strand, MSc,
- Marit R. Bjørgaas, MD, PhD,
- Grethe Albrektsen, PhD,
- Arnt E. Tjønna, PhD,
- Ulrik Wisløff, PhD and
- Charlotte B. Ingul, MD, PhD∗ ()
- ↵∗Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Olav Kyrres gate 3, 7491 Trondheim, Norway
Left ventricular diastolic dysfunction (DD) may lead to heart failure and is found in approximately 50% of asymptomatic patients with type 2 diabetes mellitus (T2DM). Little is known about the effect of exercise on DD in T2DM (1), but moderate-intensity exercise (MIE) seems insufficient to improve myocardial function. Studies indicate that high-intensity interval exercise (HIIE) is more effective than MIE in reducing cardiovascular risk factors in T2DM and in reversing left ventricular remodeling in patients with post-infarction heart failure. The aim of this study was to compare the effect of HIIE (4 × 4–min interval, 90% to 95% maximal heart rate, 40 min/bout, 3/week) and MIE according to current guidelines (≥10 min/bout, 210 min/week) on DD, defined as peak early diastolic tissue Doppler velocity (e′) <8 cm/s (2), and other cardiovascular risk factors in patients with T2DM and DD. Our hypothesis was that HIIE, more than MIE, would improve these measures.
We prescreened 83 patients for DD who had T2DM for <10 years and no known cardiovascular disease. A total of 47 patients (55.9 ± 6.0 years; 36% female; duration of T2DM: 3.6 ± 2.5 years) met the inclusion criteria (e′ <8 cm/s). The subjects were randomized to home-based MIE (n = 23) and supervised HIIE (n = 24) and tested at baseline, 12 weeks (MIE, n = 17; HIIE, n = 20), and 1 year (MIE, n = 16; HIIE, n = 16). The patients in the MIE group were younger than those in the HIIE group (mean 54.7 ± 5.3 vs. 58.6 ± 5.0 years) but did not differ by sex (35.3% vs. 40.0% female) or duration of T2DM (3.0 ± 2.6 vs. 4.2 ± 2.3 years). After 12 weeks, exercise was home based in both groups.
Repeated-measures analysis of variance models (generalized linear model, linear mixed model) were applied to compare intervention groups with respect to mean change in outcome variables. Results from baseline to 12 weeks are shown in Table 1.
Both groups showed improved diastolic function (e′) at rest, but HIIE showed more improvement than MIE. Only HIIE improved transmitral peak early diastolic velocity (E), diastolic filling pressure (E/e′), and E/A ratio. A higher proportion of patients in the HIIE group had improved diastolic function to e′ >8 cm/s during the 12-week period (80.0% vs. 41.2%; p = 0.02, chi-square test). During exercise, only HIIE improved diastolic function (E). Lack of improvement in e′ during exercise may be explained by the use of different echocardiographic methods at rest and during exercise.
A nonsignificant decrease in e′ at rest was seen from 12 weeks to 1 year (−0.45 and −0.24 cm/s for HIIE and MIE, respectively). However, in contrast to the MIE group, the HIIE group still had improved diastolic function (e′) compared with baseline. Improvement in E was sustained in the HIIE group after 1 year.
After 12 weeks, HIIE but not MIE improved systolic function at rest (peak systolic tissue Doppler velocity, S′; global strain and global strain rate) and during exercise (global strain rate).
At baseline, mean peak oxygen consumption (Vo2peak) (n = 37) was approximately 16% lower compared with a healthy population (the Nord-Trøndelag Health Study [HUNT] study). Both intervention groups increased Vo2peak, but HIIE did so more than MIE. The improvement in Vo2peak was sustained at 1 year in the HIIE group, but not in the MIE group, despite a significant decrease from 12 weeks to 1 year (−1.68 vs. −0.19 ml/kg/min, respectively).
After 12 weeks, waist circumference was reduced in both groups, whereas only HIIE reduced body mass index. From 12 weeks to 1 year, the MIE group, but not the HIIE group, had increased waist circumference (2.01 vs. −0.12 cm) and tended toward increased body mass index (0.58 vs. −0.12 kg/m2). Body fat percent did not improve after 12 weeks but was reduced in the HIIE group after 1 year (mean change −1.31%). Twelve weeks of HIIE improved flow-mediated dilation (incomplete data due to impaired ultrasound image quality), hemoglobin A1c, and high-sensitivity C-reactive protein level. Improved flow-mediated dilation and hemoglobin A1c were not sustained after 1 year. No significant changes were seen for other variables.
Limitations of this study include the small size, significant dropout rate (albeit similar to other studies in this arena), lack of a control group without exercise, and supervised exercise in only the HIIE group, which could introduce better compliance.
This pilot evaluation, one of the first randomized studies to assess the effect of exercise intensity on DD in patients with T2DM, shows that HIIE may modify the natural history of diabetic cardiac dysfunction. In patients with T2DM and DD, HIIE was more effective than MIE in improving diastolic and systolic function as well as Vo2peak. This indicates that exercise intensity is an important factor in improving cardiac function in early stages of T2DM and DD. Larger studies in the future should explore whether this is an effective and low-cost intervention in these patients with few other good therapeutic options.
Please note: This study was funded by the Liaison Committee between the Central Norway Regional Health Authority (Stjørdal, Norway) and the Norwegian University of Science and Technology (Trondheim, Norway) and K. G. Jebsen Foundation for Medical Research, Center for Exercise in Medicine, at Norwegian University of Science and Technology (Trondheim, Norway). The funders had no role in the design and conduct of the study. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation