Feasibility of high-intensity interval training in patients with left ventricular assist devices: a pilot study
Question
Can stable patients on chronic LVAD support complete a short CPX-guided HIIT program without major adverse events, and what are the observed effects on aerobic capacity and left ventricular remodelling?
Summary
This uncontrolled pilot study tested whether stable patients with durable left ventricular assist devices could complete a short, personalized, physician-supervised HIIT program. Fifteen patients began training and twelve completed post-training testing. The protocol was feasible for selected stable LVAD patients, with no major adverse events, high prescribed workload completion, improved oxygen uptake at ventilatory threshold, but no improvement in VO2peak or quality-of-life scores.
Methodology
- 15 stable adults with durable LVAD support enrolled in a single-arm HIIT pilot study.
- 15 participants.
- Upright cycle ergometer.
- Work intervals: 30 s high-intensity interval.
- Recovery: 4 min active recovery.
- Intensity: Sessions 1-3: 80% baseline PPO intervals; session 4 onward: 100% PPO intervals if tolerated. Warm-up and recovery also prescribed as percentages of PPO.
- 30 min.
- 3 sessions/week.
- 5 weeks.
- Prospective single-arm pilot feasibility study.
- Prescribed workload completed, VO2 at ventilatory threshold, VO2peak, and Left ventricular end-diastolic volume were tracked.
Outcomes
Feasibility/workload completion
Participants completed a median 90% of total prescribed workload and a median of 13 sessions.
90% (IQR 78%, 99%); median sessions 13, range 6-15.
Safety
No major adverse events occurred during 204 supervised sessions; one minor asymptomatic supraventricular tachycardia event was managed by lower workloads.
Descriptive safety outcome; no inferential P value.
VO2 at ventilatory threshold
Submaximal oxygen uptake improved after HIIT.
7.1 (6.5, 9.1) to 8.5 (7.7, 9.3) mL/kg/min; P = 0.04.
Work rate at ventilatory threshold
Submaximal work rate improved after HIIT.
44 (14, 54) to 55 (21, 66) W; P = 0.054.
VO2peak
Peak oxygen uptake did not improve.
11.9 (9.5, 14.8) to 12.0 (10.0, 15.0) mL/kg/min; P = 0.6.
Left ventricular end-diastolic volume
LV end-diastolic volume decreased in the paired turndown echocardiogram subset.
168 (144, 216) to 159 (124, 212) mL; n = 7 in text, table labelled N = 8; P = 0.02.
KCCQ quality of life
KCCQ overall summary and physical limitation scores did not significantly improve.
Overall summary 72 (60, 79) to 64 (53, 84), P = 0.5; physical limitation 75 (62, 88) to 75 (62, 92), P = 0.51.
Insights
- In selected stable LVAD patients, very short work intervals with long active recoveries can be feasible under physician supervision.
- CPX-derived workload may be preferable to heart-rate prescription when chronotropic incompetence and impaired heart-rate recovery are common.
- Clinical HIIT protocols need built-in regression rules for intolerance or arrhythmia signals.
- Improved submaximal capacity may matter even when VO2peak and short-term quality-of-life scores do not change.
Limitations
- No control group.
- Small pilot sample.
- Only selected stable LVAD patients were enrolled; 25% of screened patients entered the study.
- No progressive workload increases after session 4.
- Short 5-week intervention.
- Some patients trained at RPE below 13.
- White patients were under-represented.
- Not directly translatable to unsupervised or non-clinical exercise settings.
Safety
- No major adverse events occurred during 204 supervised sessions.
- No sessions were discontinued by the supervising physician.
- One participant had recurrent asymptomatic supraventricular tachycardia after the session 4 workload increase and completed all sessions using lower induction workloads.
- Two participants withdrew early because of training intolerance.
- One participant was urgently listed for transplant because of LVAD malfunction.