Effect of High-Intensity Interval Training in De Novo Heart Transplant Recipients - 3-year Results from the HITTS Randomized Controlled Trial

Abstract

The HITTS study (High -intensity Interval Training in de novo Heart Transplant Recipients in Scandinavia) is a randomized controlled trial designed to assess the effect of high-intensity interval training (HIT) versus moderate intensity continuous training (MICT) on exercise capacity in de novo heart transplant recipients. The primary endpoint was the change in oxygen consumption (VO2peak) at the end of the intervention period, which began 3 months after heart transplantation (HTx). After the 9-month long intervention period, we reported a between-group difference in VO2peak of 1.8 ml/kg/min in favor of HIT (p = 0.04).We found that HIT was safe, well tolerated and efficient. The HITTS study is the first randomized controlled trial to assess the effectiveness of HIT in de novo heart transplant recipients. However, long-term effects of commencing HIT soon after HTx remain unknown. In this extension of the HITTS trial, our aim was to examine whether the benefits of 9 months of supervised HIT training persist two years after the end of the intervention. In the HITTS study, we randomized 81 adult de novo heart transplant recipients to 9 months of HIT (4 × 4 min intervals at 85-95% of peak heart rate (HR) or 9 months of MICT (60-80% of peak HR). The mean ± SD age was 49 ±13 and 73 % were men. Before the start of the intervention and at follow-up shortly after the intervention, we measured VO2peak, isokinetic muscle strength, body composition, left ventricular function by echo, biomarkers, and health-related quality of life (HRQoL). For the extension study, the measurements will be repeated 3 years after enrollment. VO2peak is measured with breath-by-breath gas exchange on a treadmill or bicycle ergometer. The last patient is scheduled to complete his/her 3-year follow-up at Nov 14th, 2019. Data will be available for presentation at ISHLT 2020. The primary outcome is the long-term effect of HIT vs MICT on aerobic exercise capacity as assessed by VO2peak. Secondary outcomes are: Isokinetic muscular strength in the lower limbs by a dynamometer, body composition (bio-impedance analysis), left ventricular function by echo, heart rate response during the cardiopulmonary exercise test, relevant circulation biomarkers (renal function, NT-proBNP and cardiac troponins), HRQoL, tolerability, safety and adverse events.