Transplant Trial Watch

Effects of high-intensity interval training on cardiac remodelling, function and coronary microcirculation in de novo heart transplant patients: a substudy of the HITTS randomised controlled trial.

Rafique, M., et al.

BMJ Open Sport & Exercise Medicine 2023; 9(3): e001331.

They aim to assess if high-intensity interval training (HIT) results in structural and functional cardiac adaptation in de novo heart transplant recipients compared with standard care exercised-based rehabilitation.

Participants received either 9 months of HIT (four 4 min intervals at 85-95% peak effort with 3 min recovery at 60-70%) or moderate-intensity continuous training (MICT) (25 min of continuous training at 60-80% peak effort) which is the standard care recommended by the European Society of Cardiology.

81 adult de novo heart transplant (HTx) recipients

The primary outcomes were changes in left ventricular (LV) global longitudinal strain (GLS), and echo assessment of LV dimensions and end-diastolic volume (EDV). The secondary outcomes were the changes in index of microcirculatory resistance (IMR) and coronary flow reserve (CFR).

12 months posttransplantation.

CET Conclusions
This was a sub-study within a multicentre randomised control trial (HITTS), with these participants from a single centre in Norway and in which the cardiac assessments were performed by blinded investigators. The HITTS trial found that HIT early after HTx resulted in an improved VO2peak compared with MICT, as a result they are investigating the hypothesis that alterations to cardiac physiology may have partially caused this improvement. They found that LV GLS and EDV had statistically significant improvements as did IMR, suggesting that HIT early after HTx improves the microcirculatory function. However, these changes did not have a significant correlation with VO2peak at 12 months which was the primary endpoint of the original trial, making it harder to hold these changes are in part responsible for improved VO2peak. The main HITTS trial has robust methodology, but this, by the nature of being a sub-study, has limitations. Given the sample size was powered for VO2peak in the main HITTS trial, the result being a small sample size for the single centre sub-study. Despite limitations they find beneficial adaptions in the cardiovascular system as a result of the HIT, which they evaluate in more in-depth assessment than done in the original trial giving a possible mechanistic background to explain some of the improvements seen in the HITTS trial.

Trial registration - NCT01796379

Funding source
Non-industry funded