# Short- and Long-Term Effects of High-Intensity Interval Training vs. Moderate-Intensity Continuous Training on Left Ventricular Remodeling in Patients Early After ST-Segment Elevation Myocardial Infarction-The HIIT-EARLY Randomized Controlled Trial PMID: 35783836 Journal: Frontiers in cardiovascular medicine Published: 2022-06-17 Authors: Eser P, Trachsel LD, Marcin T, Herzig D, Freiburghaus I, De Marchi S, Zimmermann AJ, Schmid JP, Wilhelm M ## Question In optimally treated male patients early after STEMI, does 9 weeks of HIIT during cardiac rehabilitation produce better short- and long-term left ventricular remodeling and cardiorespiratory fitness outcomes than isocaloric MICT? ## Summary This randomized controlled trial compared HIIT with isocaloric moderate-intensity continuous training during ambulatory cardiac rehabilitation in male patients early after first STEMI treated with PCI and guideline-directed medical therapy. After a 3-week MICT run-in for familiarization and medication optimization, patients were randomized to 9 weeks of either MICT or a mixed schedule of two HIIT and one MICT session per week. HIIT did not improve left ventricular end-diastolic volume index or peak VO2 more than MICT. At 1-year follow-up, global longitudinal strain improved in MICT but not HIIT, and blood pressure increased more in HIIT, leading the authors to recommend caution with vigorous activity early after STEMI. ## Population - Male patients early after first STEMI treated with primary PCI and enrolled in ambulatory cardiac rehabilitation; 69 analyzed at randomization and end of CR. - Sample size: 73 - Age: Analysis sample age 56 +/- 10 years; median 55 years in HIIT and 59 years in MICT at randomization. - Sex: All male. - Fitness level: Cardiac rehabilitation patients; median peak VO2 at randomization was 26.5 ml/kg/min in HIIT and 27.7 ml/kg/min in MICT. - Health status: First STEMI treated with PCI within 4 weeks before inclusion; optimally treated with guideline-directed medical therapy; most had normal LV ejection fraction at randomization. ## Methodology - Single-center prospective randomized controlled trial integrated into a 12-week multidisciplinary ambulatory cardiac rehabilitation program with 1-year follow-up. - 12-week cardiac rehabilitation program with 3-week run-in and 9-week randomized intervention; 1-year follow-up after CR. - Ambulatory cardiac rehabilitation program at Bern University Hospital, Switzerland. - Randomized and controlled study design. ## Protocol - HIIT-EARLY HIIT. - Modality: Cycle ergometer. - Work intervals: 4 minutes above second ventilatory threshold, approximately 90-95% peak heart rate. - Recovery: 3 minutes active recovery below first ventilatory threshold. - Sets or repetitions: 4 intervals. - Intensity: Borg >=15 for HIIT; workload above second ventilatory threshold. - Session duration: 38 minutes including 10-minute warm-up and 3-minute cool-down. - Frequency: 2 HIIT sessions plus 1 MICT session per week during the 9-week randomized phase. - Program length: 9-week randomized intervention after 3-week MICT run-in. - Progression: Weekly workload adjustment to maintain Borg target and isocaloric regimens; next-session HIIT workload fine-tuned from end-session Borg score. - Moderate-intensity continuous training. - Modality: Cycle ergometer. - Work intervals: Continuous cycling endurance training. - Sets or repetitions: One continuous 38-minute endurance-training block including warm-up and cool-down. - Intensity: Initially first ventilatory threshold during run-in with Borg 12-13; during intervention weekly up-titration to Borg 13-14. - Session duration: 38 minutes including 5-minute warm-up and 3-minute cool-down during run-in. - Frequency: 3 sessions per week. - Program length: 3-week run-in for all participants; MICT group continued for 9-week randomized intervention. - Progression: Weekly up-titration to maintain target Borg scale and isocaloric exercise regimen. ## Outcomes ### LVEDVi Status: no clear change LVEDVi increased from randomization to end of CR in both groups, with no significant between-group difference; at 1 year, LVEDVi was not significantly different from randomization in either group. End-of-CR group x time interaction p = 0.557; 1-year group x time interaction p = 0.297. ### Global longitudinal strain Status: worse/safety concern GLS had no significant between-group difference at end of CR, but at 1 year MICT improved while HIIT did not, producing a significant group x time interaction. From randomization to 1-year follow-up, GLS changed by -1.0% (95% CI -1.8 to -0.1) in MICT and 0.3% (-0.5 to 1.2) in HIIT; group x time interaction p = 0.031, adjusted p = 0.021. ### Peak VO2 Status: improved Peak VO2 improved significantly over time in both groups, without significant group x time interactions. Peak VO2 improved from randomization to 1-year follow-up by 2.4 ml/kg/min (95% CI 1.0 to 3.7) in HIIT and 3.4 ml/kg/min (2.0 to 4.7) in MICT; group x time p = 0.138 at end of CR and p = 0.317 at 1 year. ### Blood pressure Status: worse/safety concern At 1-year follow-up, systolic BP increased in HIIT and was nearly unchanged in MICT, while diastolic BP increased in HIIT and decreased in MICT. Systolic BP change: HIIT +7.9 mmHg (95% CI 1.5 to 14.3), MICT -0.2 mmHg (-6.4 to 6.1), interaction p = 0.077. Diastolic BP change: HIIT +7.3 mmHg (3.3 to 11.4), MICT -1.3 mmHg (-5.2 to 2.7), interaction p = 0.003. ### Biomarkers of myocardial injury and inflammation Status: no clear change There were no significant group x time interactions for high-sensitive troponin T, NT-proBNP, or high-sensitive CRP. No significant group x time interactions were reported for biomarkers. ## Practical Insights - In early post-STEMI cardiac rehabilitation, HIIT should not be promoted as superior to isocaloric MICT for LV remodeling or fitness. - High-risk cardiac HIIT requires medical supervision, conservative exposure, and run-in/familiarization rather than direct consumer translation. - Possible long-term GLS and blood pressure signals should temper vigorous-exercise recommendations after STEMI. - MICT remains a defensible exercise option when patients prefer it or when HIIT safety is uncertain. ## Limitations - Target sample size was not reached. - Only male patients were included. - Physical activity during and after cardiac rehabilitation was not measured. - The HIIT arm also included one MICT session per week, so it was not a pure HIIT-only intervention. - Adverse event details were not fully described in this article. - Findings came from supervised cardiac rehabilitation and may not apply to unsupervised exercise. ## Safety And Adherence - One adverse event occurred in each group between randomization and end of CR; the article does not provide event details. - The trial used a 3-week MICT run-in for familiarization and safety before HIIT. - CPET was monitored by a cardiologist with continuous 12-channel ECG. - The authors caution that adverse long-term GLS changes after HIIT warrant caution with vigorous activities early after acute STEMI. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/35783836/) (pubmed) - [DOI](https://doi.org/10.3389/fcvm.2022.869501) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9247394/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.