Cardiac Rehabilitation in Acute Coronary Syndrome

Introduction

Cardiac rehabilitation to enhance functional capacity is crucial to favorably influence the clinical evolution of acute coronary syndrome, which is related to sudden, reduced blood flow to the heart. With 17.9 million cases of acute coronary syndrome recorded in 2019, it is one of the world’s major causes of death. The adoption of multifactorial interventions has been advocated by the World Health Organization (WHO). Combining aerobic training to improve cardiovascular and cardiopulmonary outcomes with resistance training to improve strength outcomes has been the recommended approach. More recently, neuromuscular training, encompassing sport-specific and fundamental training including resistance, balance, core strength, dynamic stability, agility, and plyometrics has shown beneficial effects in cardiopulmonary outcomes in a wide population, including athletes, young people, and adult people with chronic conditions. However, this method of training has not been evaluated in patients with cardiovascular disease having symptoms of acute coronary syndrome. This study, therefore, investigated neuromuscular training as part of cardiac rehabilitation in acute coronary syndrome

Methods

To study the best type of cardiac rehabilitation in acute coronary syndrome, neuromuscular training, and classic strength training were compared. This study conducted a randomized, double-blind, parallel clinical trial in a university health clinic in Spain.

Eligible patients were diagnosed with acute coronary syndrome, between 18 and 80 years and had moderate or low cardiac risk, based on cardiopulmonary exercise testing (CPET)

Patients with a diagnosis of ACS were recruited, meeting the inclusion criteria of being between 18–80 years old, with moderate or low cardiac risk, based on cardiopulmonary exercise testing (CPET) and the guidelines by the American Heart Association.

Participants were randomly assigned to one of two groups: the intervention group performing neuromuscular training or the control group assigned classic strength training. People in both groups participated in 20 sessions (twice per week) of a 60-minute exercise regimen based on the FITT-VP model (Frequency, Intensity, Time, Type, Volume, Progression) from the American College of Sports Medicine (ACSM). The sessions followed the following structure:

Warm-up: 10 minutes
Endurance Training: 20 minutes, either on a treadmill or a bicycle ergometer. A continuous or interval training was done, based on the risk profile of each participant
Resistance Training: 20 minutes
- Neuromuscular training group: Exercises aimed at improving trunk stabilization, movement patterns, upper-limb dissociation from the trunk, and dynamic control of hip and knee motions.
- Classic strength training group: General strength training targeting major muscle groups, progressing from open-chain to closed-chain exercises.
Cool-down and stretching: 10 minutes Patients’ heart rate and oxygen saturation were monitored continuously throughout training. Measurements of blood pressure were obtained at the beginning of the session, after the endurance training, and after the resistance training. Similarly, perceived exertion was assessed using the Borg scale at the beginning of the session and after each training phase.

The primary outcome was the Incremental Shuttle Walking Test (ISWT). This is a test used to measure functional capacity and predict the VO2 max. Secondary outcomes included the Chester Step Test (CST), 30-Second Chair Stand Test (30CST), and hip flexor strength using dynamometry. Assessments were held at baseline, immediately post-intervention, and at the 6-month follow-up.

Results

30 participants were included and equally divided into the neuromuscular or classic strength training group. The mean age of the participants was approximately 55 years. The body mass index was 31 and 28 in the neuromuscular and classic strengthening groups respectively. They had a normal mean oxygen saturation at baseline of 97%.

Rehabilitation in Acute Coronary Syndrome — From: Valtueña-Gimeno et al., Physiotherapy (2024)

The results indicate that, regarding the primary outcome, the neuromuscular training group improved more than the classic strengthening group. A difference of 155m in favor of the neuromuscular group was found at the end of the program (10 weeks). Six months after the end of the trial, this difference was 214 meters, also in favor of the participants who followed the neuromuscular training program.

The secondary outcomes partially supported the findings of the primary analysis. The CST and hip flexor strength outcomes improved significantly in the neuromuscular training group. The 30-second chair stand test did not show significant between-group differences.

Questions and thoughts

Is there a superior exercise mode for rehabilitation in acute coronary syndrome, based on the results of this preliminary RCT?

Regarding the primary outcome functional capacity, measured by the ISWT, the neuromuscular training yielded the best results. According to Houchen-Wolloff et al. (2015), the minimal clinically important difference (MCID) of the ISWT is 70 meters. This MCID was established in a population that followed cardiac rehabilitation. This was found in patients who rated their exercise tolerance following the program as ‘slightly better’. Preferably, we would attain a level of people feeling ‘better’ instead of ‘slightly better’. In the same study, people who were better achieved an increase of approximately 85 meters. With a between-group difference of 155 and 214 at the end of the intervention and 6 months later respectively, the results of the current RCT after following the neuromuscular program seem promising.

At baseline, the groups were different in terms of their ISWT scores. The neuromuscular group had a better ISWT score compared to the classical strengthening group. The authors point to the expectation that lower scores would give more room for improvement in the classical group, yet it did not happen in their trial. Bringing up this, they want to highlight the effect of the neuromuscular training. I see it the other way around. People in the intervention group had better functional capacity at baseline, compared to the control group. Meaning they had probably better capability to improve their functional capacity even more since they had a better basis to start from. The difference at baseline was approximately 100 meters. This is already more than the proposed 70-85 meters MCID. In my opinion, the participants in the neuromuscular training group were thus better positioned to increase their functional capacity even more. A well-balanced RCT should confirm whether true meaningful between-group differences in favor of the neuromuscular training group can be achieved.

Talk nerdy to me

Patients were recruited in a private hospital tertiary care setting. You should take this into account when extrapolating these findings to your practice. Only a few participants were included, which may be a limitation, but is understandable given this is a preliminary study. The conclusions should now have to be confirmed in a larger trial.

However the trial yielded important differences, the confidence intervals for the primary outcome were wide and at 10 weeks the confidence interval was just not significant since it crossed zero. A wide confidence interval means that some people only improved a little, while others improved largely. Some may thus have not experienced meaningful changes. At 6 months following the trial, the confidence interval was significant and the lower border approached the MCID. Still, this indicates that some people did not attain the MCID of 70-85 meters. For a preliminary study including only 30 participants, the results seem promising. The approach of neuromuscular training should now be analyzed in further, larger trials before hard conclusions are drawn. Ideally, a responder analysis should be conducted to understand who is likely to improve following a neuromuscular training program for rehabilitation in acute coronary syndrome.

Take home messages

This preliminary RCT compared classic strength training to neuromuscular training for functional capacity rehabilitation in acute coronary syndrome. The findings indicate that more benefit is achieved in people following the neuromuscular training program. The results should now be confirmed in larger RCTs. The present study gives us an interesting direction of how to design exercise programs for the rehabilitation in acute coronary syndrome.