Active Voice: Failure to Improve Fitness in Cardiac Rehab Linked to Adherence and Clinical Outcomes in Heart Failure Patients
By Esmée Bakker, M.Sc., Dick Thijssen, Ph.D., and Thijs Eijsvogels, Ph.D.
Esmée Bakker, M.Sc., is a dual Ph.D. student at the Radboud University Medical Center in the Netherlands and at the Liverpool John Moores University in England. Her research is focused on the effects of sedentary behavior and physical activity behavior on cardiovascular health in the general population and in patients with cardiovascular diseases. She has been a student member of ACSM since 2015.
Dick Thijssen, Ph.D., is a professor at the Liverpool John Moores University and he also leads a research group at the Radboud University Medical Center. His research focuses on understanding the underlying mechanisms explaining the health and functional benefits of physical activity and sedentary behavior, specifically related to the role of hemodynamic stimuli mediating vascular adaptation. Dr. Thijssen is a former recipient of the ACSM Oded Bar-Or Award and the ACSM New Investigator Award.
Thijs Eijsvogels, Ph.D., is an exercise physiologist and assistant professor in the Department of Physiology of the Radboud University Medical Center. His research is focused on the benefits and potential deleterious effects of exercise across the whole spectrum of physical activity, from sedentary behavior to excessive volumes of exercise. Dr. Eijsvogels was a recipient of the 2017 ACSM New Investigator Award.
This commentary presents the authors’ views on the topic of their research article, which they and their colleagues authored. Their paper appeared in the February 2018 issue of Medicine & Science in Sports & Exercise® (MSSE).
Heart failure (HF) is diagnosed in one to two percent of the adult population and increases up to 10 percent at the age of 70 in developed countries. Cardiorespiratory fitness (CRF) is an important predictor for the progression of disease, where lower CRF is associated with an increased risk of cardiovascular events. Therefore, the American College of Sports Medicine (ACSM) recommends exercise training in HF patients. Nevertheless, significant heterogeneity exists in individual responses to exercise training during cardiac rehabilitation (CR), where some HF patients have no change or even a decline in CRF (nonresponders). It is unknown whether these nonresponders have a lower survival rate and a higher risk of morbidity compared to responders to CR.
Our study, as presented in our paper published in the February 2018 issue of MSSE, addresses this question. To build on this question, we also identified characteristics of HF patients who are at risk of becoming nonresponders. We included 155 HF patients; all received a program of supervised exercise training during CR and performed incremental bicycle ergometer tests to assess CRF before and after CR. The exercise training program consisted of two sessions per week at a moderate intensity for eight to 24 weeks. The median adherence to the supervised trainings session was 88 percent. Patients were defined as responders or nonresponders based on pre-to-post changes in VO2-peak; responders were defined as those exceeding an improvement of six percent or more, while nonresponders failed to reach that threshold at the end of CR. Patient characteristics, HF features and comorbidities were collected using electronic patient files. HF patients were followed up to maximal five years to assess incidence of hospitalization and all-cause mortality.
Our findings demonstrated that 55 percent of 155 HF patients did not increase CRF after the supervised CR program. More importantly, HF patients classified as nonresponders had nearly a 2.2-fold greater risk of all-cause mortality or unplanned hospitalization in comparison to responders; this was the case, even after statistical adjustment for possible confounders and baseline CRF. Nonresponders, especially those with lower CRF levels at baseline, showed the worst prognosis for unplanned hospitalization and all-cause mortality. These results reinforce the clinical importance of improving fitness during exercise training in the CR setting. We also found that patients who were older, had higher baseline VO2-peak, and were less adherent were at greater risk to become a nonresponders.
Our finding that nonresponse to CR training is associated with an increased risk for all-cause mortality or hospitalization has important clinical consequences. First, our observations support the importance of adherence to exercise training in HF patients, since it is a significant modifiable factor that affects both the potential functional and clinical benefits of CR. Secondly, higher age and higher baseline VO2-peak were associated with becoming a nonresponders. This knowledge can be used for early identification of nonresponders and, subsequently, alter exercise prescription strategies that are most likely to improve CRF. Nonresponders, for example, might benefit from high intensity interval training, resistance exercise training or a combination of aerobic and resistance training activities. Alternatively, one could increase training frequency in nonresponding HF patients. Such approaches may help prolong survival and reduce the risk for hospitalizations in this vulnerable patient group.
Taken together, our results may raise awareness for the negative health implications of nonresponse to exercise training and the importance of personalized exercise prescription for secondary prevention in HF patients.