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NCT Number: NCT07546227

HIIT Versus Moderate Continuous Training in ACHD

This study is a single center randomized controlled trial evaluating the effect of an exercise training intervention (interval training or moderate continuous training) compared to usual care (no training) on exercise capacity in patients with congenital heart disease (CHD).

Our primary aim is to determine the impact of interval training (IT) compared to moderate continuous exercise training (MCT) versus controls (no exercise) on exercise capacity as measured by peak VO2. Secondary aims are to: 1) assess the safety of exercise training in CHD, 2) evaluate the effect of exercise training on cardiac structure and function and 3) assess the effects of exercise training on quality of life and long-term physical activity.

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Key information

Conditions

Adult Congenital Heart Disease Behavior Cardiovascular Abnormalities Cardiovascular Diseases Congenital Abnormalities Congenital, Hereditary, and Neonatal Diseases and Abnormalities Heart Defects, Congenital Heart Diseases Motor Activity

Age range

16 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Jim Pattison Center for Cardiac Rehabilitation

Edmonton, Alberta, T6G 2B7, Canada

About this study

Adults with congenital heart disease (ACHD) have reduced exercise capacity which is an independent predictor of adverse outcome including hospitalization and mortality in this patient population. When aerobic exercise capacity is measured by cardiopulmonary exercise testing (CPET), peak oxygen consumption (peak VO2) averages 22ml/kg/min in ACHD, less than half of age matched controls, and similar to patients with heart failure. Factors contributing to low exercise capacity include central factors related to abnormal cardiac anatomy, ventricular systolic and diastolic dysfunction, valvular abnormalities, pulmonary hypertension, chronotropic incompetence and impaired pulmonary function as well as peripheral factors such as skeletal muscle conditioning. Clinicians may further contribute to reluctance around exercise by failing to encourage physical activity or giving inappropriate exercise restrictions to ACHD.

The aim of our study was to explore the efficacy of HIIT compared to MCT on aerobic exercise capacity as measured by peak VO2 in ACHD patients. Secondary aims were to determine the effect of exercise on various physiologic variables, to assess the safety of HIIT in ACHD, to evaluate the effect of exercise training on cardiac structure and function as assessed by cardiac MRI and to measure the impact of exercise training on quality of life (QoL).

This was a single center randomized controlled trial designed in accordance with CONSORT guidelines. Participants were randomized with a 1:1:1 ratio into three groups: HIIT, MCT or control group. Randomization occurred by clusters defined by week of attendance in the clinic. Permuted blocks of 3, 6, and 9 were used to ensure a similar number of weeks randomized to the three groups, with randomization sequence generated by one author (AM). Participants were enrolled by a study coordinator who assigned participants to one of the three groups. Participants underwent testing at baseline and after 12 weeks of the intervention.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Medically stable patients aged 16 or great with congenital heart disease.

Exclusion criteria

  • Uncorrected cyanotic congential heart disease (SpO2 </= 85%)
  • Severe outflow tract obstruction (peak Doppler gradient >50 mmHg)
  • Sustained arrhythmia

Treatment and study plan

Exercise intervention

Other

Participants will take part in 3 exercise sessions per week of either HIIT or MCT training.

Primary outcomes

  1. Change in peak VO2 from baseline to 12 weeks post enrollment

    Time frame: From enrollment to the end of the 12 week treatment

    Participants will complete a cardiopulmonary exercise test at baseline and after 12 weeks to determine peak VO2 values.

Secondary outcomes

  1. Determination of adverse events

    Time frame: Participants will be monitored throughout the exercise training and one hour afterward.

    High intensity exercise has the potential to transiently increase the risk of arrhythmias and myocardial infarction in susceptible persons. Participants will be monitored throughout exercise for any adverse events defined as cardiac arrest, myocardial infarction, sustained ventricular or suprraventricular arrhythmias or heart failure.

  2. Cardiac adaptation

    Time frame: Cardiac MRI's will be performed at baseline with follow-up scans at 4 weeks of starting and at completion of the 12 week intervention.

    Cardiac MRI will be used to assess right ventricular volumes and ejection fraction. Pulmonary regurgitation fraction, left ventricular volumes and ejection fraction will also be assess.

  3. The effect of exercise training on quality of life.

    Time frame: Participants will complete questionnaires during study visits or be sent a link by email to complete the questionnaires on-line at baseline, 3 months (after exercise training intervention) and 6 months after randomization.

    Participants will complete a quality of life questionnaire, satisfaction with life scale and New York Heart Association (NYHA) Functional Classification.

  4. Impact of exercise program on physical activity levels.

    Time frame: Participants will wear the accelerometers at baseline and 6 months after randomization to collect data for 4 days.

    Participants will wear SenseWear arm bands (accelerometers) to describe baseline physical activity levels and to assess long-term changes in physical activity 6 months after randomization. Data will be acquired for 4 days at each time-point and change from baseline compared between exercise training groups and usual care.

Sponsors and collaborators

Lead sponsor

University of Alberta

Other

Registry information

Official study title

Physical Activity in Tetralogy: A Randomized Trial of Interval Training Versus Moderate Continuous Training

Acronym: PhiT

Important dates

Study start
2015
Primary completion
2023
Study completion
2024
First posted
Apr 22, 2026
Registry last updated
Apr 29, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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