# Heterogeneous Exercise Responses to High-Intensity Interval Training Are Associated With Varied Long-Term Cardiovascular Outcomes in Patients With Heart Failure: A 15-Year Follow-Up PMID: 40439155 Journal: Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease Published: 2025-06-03 Authors: Fu TC, Huang SC, Yuan SS, Wang CH, Wang JS, Tsai WC, Cherng WJ, Shyu YC, Hsu CC ## Question Are heterogeneous physiological responses to supervised HIIT in patients with heart failure associated with different long-term survival and cardiovascular readmission outcomes, and which HIIT-associated adaptations mediate those outcomes? ## Summary This retrospective cohort study followed 182 patients with heart failure who completed 36 supervised in-hospital HIIT sessions. About 21% did not improve peak oxygen consumption after HIIT. Responders had larger improvements in oxygen uptake efficiency, arteriovenous oxygen difference, skeletal muscle mass, peak heart rate, and heart rate reserve, and had better long-term cardiovascular event-free survival than nonresponders. ## Population - Adults with stable heart failure who completed 36 supervised in-hospital HIIT sessions in Taiwan. - Sample size: 182 - Age: Responders 57.5 years (95% CI 55.4-59.6); nonresponders 59.6 years (95% CI 56.0-63.2). - Sex: 49 female and 133 male overall, based on responder/nonresponder table counts. - Fitness level: Clinical heart failure cardiac rehabilitation population with low baseline VO2peak around 4.6-4.8 MET. - Health status: Heart failure, including reduced, midrange, and preserved ejection fraction phenotypes; stable symptoms/signs for at least 4 weeks before exercise. ## Methodology - Retrospective cohort study using registry data from three Chang Gung Medical Foundation institutes, classifying heart failure patients who completed 36 HIIT sessions as responders or nonresponders by change in peak oxygen consumption. - 36 HIIT sessions delivered 2-3 times weekly, followed observationally until May 31, 2024 or death; reported follow-up averaged 8.25 years in responders and 6.21 years in nonresponders. - In-hospital supervised cardiac rehabilitation program in three institutes in Taiwan, with long-term follow-up under heart failure care teams. ## Protocol - Supervised cycling HIIT. - Modality: Bicycle ergometer. - Work intervals: 3 minutes at 80% VO2peak. - Recovery: 3 minutes at 40% VO2peak. - Sets or repetitions: Alternating intervals for 30 minutes; exact count not explicitly stated. - Intensity: 80% and 40% of peak oxygen consumption. - Session duration: 30 minutes. - Frequency: 2-3 sessions per week. - Program length: 36 sessions. - HIIT nonresponder comparison. - Modality: Same supervised bicycle ergometer HIIT protocol. - Work intervals: 3 minutes at 80% VO2peak. - Recovery: 3 minutes at 40% VO2peak. - Sets or repetitions: Same 36-session HIIT protocol; group defined by no improvement or decrease in VO2peak. - Intensity: 80% and 40% of peak oxygen consumption. - Session duration: 30 minutes. - Frequency: 2-3 sessions per week. - Program length: 36 sessions. ## Outcomes ### Responder prevalence Status: mixed Of 182 HIIT completers, 143 were responders and 39 were nonresponders, giving a nonresponder prevalence of 21%. Responder classification was based on post-HIIT minus baseline VO2peak greater than 0 versus 0 or less. ### Cardiovascular event-free survival Status: improved Responders had better 14-year cardiovascular event-free survival than nonresponders. 91.3% versus 76.8%, P=0.037. ### Overall survival and cardiovascular readmission Status: no clear change Overall survival and cardiovascular readmissions were numerically better in responders but did not significantly differ across the full 14-year follow-up. Overall survival 83.7% versus 67.2%; readmissions 36.1% versus 46.7%; both not significant. ### Cardiorespiratory fitness Status: mixed Responders improved VO2peak, OUES, HRR, peak HR, and VE/VCO2 slope; nonresponders had significantly decreased VO2peak and nonsignificant adverse trends in some cardiorespiratory markers. Post-HIIT VO2peak 5.72 MET in responders versus 4.44 MET in nonresponders, P<0.001; OUES P=0.001; peak HR P=0.005; HRR P=0.007 between groups. ### Mediation analysis Status: improved VO2peak mediated the association between HIIT and all-cause death, and HRR mediated the association between HIIT and cardiovascular readmissions. VO2peak indirect path coefficient -30.96 (95% CI -81.05 to -2.96); HRR indirect path coefficient -2.96 (95% CI -7.81 to -0.02). ## Practical Insights - In clinical heart failure rehabilitation, a fixed HIIT protocol can produce heterogeneous physiological responses. - VO2peak and HRR are useful response markers to monitor after HIIT in heart failure populations. - Consumers with heart failure should not infer that unsupervised HIIT is appropriate; the evidence depends on medical screening and supervised cardiac rehabilitation. ## Limitations - Retrospective design limits causal inference. - No non-HIIT control group. - Nonresponder sample was relatively small. - Only patients completing all 36 sessions were included. - Exact exercise volume after HIIT during follow-up was not recorded. - Sleep quality was not provided. - Some measurements had missing data. ## Safety And Adherence - The main article did not report specific adverse event counts during training. - Participants were clinically screened and trained under supervised in-hospital cardiac rehabilitation. - Patients with decompensated heart failure, severe COPD, severe renal dysfunction, noncardiac disease prohibiting cycling, or ACSM absolute exercise contraindications were excluded. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/40439155/) (pubmed) - [DOI](https://doi.org/10.1161/JAHA.124.040330) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12229121/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.