Exercise has long been recognised as a key factor in maintaining a healthy heart and reducing the risk of coronary artery disease (CAD). A recent study called the CENIT trial has provided some valuable insights into the benefits of high-intensity interval training (HIIT) for patients with established CAD. Published in the European Journal of Preventive Cardiology, this research reveals how HIIT can counteract disease progression and promote cardiovascular health. 

Coronary artery disease occurs when atherosclerosis, or plaque, builds up in the arteries that supply blood to the heart. Over time, plaques can increase in volume and become unstable and rupture leading to a stroke or a heart attack. Atheroma volume, which measures the amount of plaque present in the arteries, is a crucial indicator of CAD severity and has been shown to increase the likelihood of future cardiac events.

To better understand the impact of exercise on CAD, let’s examine the exercise interventions in the CENIT trial. The study consisted of two groups: the high-intensity interval training (HIIT) group and the control group. Each group had a specific exercise program.

1. High-Intensity Interval Training (HIIT) Group: Participants in the HIIT group engaged in two supervised exercise sessions per week for a duration of 6 months. Each session began with a 10-minute warm-up at a moderate intensity (around 60% to 70% of peak heart rate). This was followed by four intervals of intense exercise, lasting for four minutes each, at an intensity of 85% to 95% of peak heart rate. Active recovery periods, lasting for three minutes at a moderate intensity, were included between intervals. The sessions concluded with a 5-minute cooldown period. The HIIT sessions involved activities such as walking or running on a treadmill, bicycling, or other exercises that engaged large muscle groups. Participants were encouraged to use a wearable device to track their heart rate and activity levels during the HIIT sessions. This allowed them to maintain the desired intensity and monitor their progress. In addition to the supervised sessions, participants were advised to engage in home-based endurance training. This included performing intervals and any other physical activities that involved dynamic work with large muscle groups.
2. Control Group: The control group followed contemporary preventive guidelines for physical activity without receiving further supervision. They were encouraged to engage in regular physical activity of moderate intensity for 30-60 minutes on more than 5 days per week. Not only was this exercise not supervised but it was not monitored unlike in the intervention group.

The CENIT trial focused on the effects of supervised HIIT on coronary plaque geometry in patients with stable CAD who had undergone percutaneous coronary intervention (PCI). Here’s what they found:

1. Regression of Atheroma Volume: Patients who participated in 6 months of supervised HIIT experienced significant regression in atheroma volume compared to those following standard preventive guidelines. This means that the plaque buildup in their arteries was reduced, potentially lowering their risk of future coronary events.
2. Improved Cardiorespiratory Fitness: The HIIT group exhibited a significant improvement in peak oxygen consumption (VO2peak), which measures cardiorespiratory fitness. By increasing VO2peak, HIIT enhances the overall health of the cardiovascular system.
3. Positive Body Composition Changes: Patients in the HIIT group also experienced reductions in body mass index (BMI) and waist circumference. These improvements in body composition are important markers of metabolic health and can contribute to a reduced risk of CAD and related complications.

The findings from the CENIT trial provide reasonable evidence for the effectiveness of HIIT in managing CAD and improving cardiovascular health. It is, however, difficult to tease out from the study whether it was the supervision of exercise, or wearing a monitor that someone else was tracking or the HIIT that had the greatest benefits. Based on these results, here are some key takeaways to consider:

1. Consult An Experienced Personal Trainer: If you have established CAD or are at risk for heart disease, consult a very experienced personal trainer who is confident in managing patients who have stable heart disease. They can provide personalised recommendations based on your health status and previous exercise experience.
2. Embrace High-Intensity Interval Training (HIIT): Consider incorporating supervised HIIT sessions into your exercise routine under professional supervision. HIIT involves short bursts of intense exercise alternated with active recovery periods, making it an efficient and time-effective workout option. But note, the intervention group did not just do HIIT, they also did low-intensity exercise. 
3. Prioritise Exercise: HIIT’s positive impact on atheroma volume regression, improved cardiorespiratory fitness, and positive body composition changes highlight the importance of exercise as a core component of cardiac rehabilitation programs. When compared to another study looking at the effects of high-intensity statin on plaque lipid volume, high-intensity exercise combined with low-intensity exercise had an effect comparable effect to that of a high-intensity statin.
4. Monitor Your Exercise: The intervention group wore a wearable and knew they were being monitored. Use a wearable and get an accountability partner to keep you on track. 

The CENIT trial provides evidence that high-intensity interval training, supervised by a personal trainer and the wearing of a fitness tracker can effectively counteract disease progression and improve cardiovascular health in patients with established coronary artery disease. Participating in supervised HIIT sessions can lead to a reduction in atheroma volume, improved cardiorespiratory fitness, and positive body composition changes.

Dr J Hugh Coyne

Private GP

Parsons Green