Heart failure (HF) patients with diabetes may have a different functional response to exercise and may need to be considered as a separate cohort in the design and analysis of future trials of exercise training in HF patients, according to new data presented at the American College of Cardiology (ACC) Scientific Sessions 2015.  

Researchers at Duke University analyzed data from HF-ACTION trial, which randomly assigned 2,331 patients with HF to usual care with or without exercise. The cohort included 748 patients with diabetes (32%). Mean baseline peak VO2 was lower in patients with diabetes than those without the disease (13.4 mL/kg/minute vs. 15.6 mL/kg/minute; P<.001), as was mean 6-minute walk distance (339 meters vs. 377 meters; P<.001).

The researchers found that patients with diabetes had a smaller mean increase in peak VO2 among patients with diabetes than those without diabetes in the exercise arm (0.5 mL/kg/minute vs. 0.9 mL/kg/minute). Those with diabetes also had lower adherence to training (35.2% vs. 44.7%) and increased hospitalization/mortality, mortality and cardiovascular (CV) mortality/HF hospitalization.

Results also indicated a statistically significant interaction between diabetes and exercise training for change in peak VO2 (P=.02) but not 6-minute walk distance (P=.53).

“Heart failure patients with diabetes have both a reduced adherence and physiologic response to continuous aerobic exercise. Different modalities of training, such as interval training, warrants future research to identify effective modalities to improve functional capacity in this patient cohort,” said study investigator Adam Banks, MD, who is with Duke University Medical Center, Durham, North Carolina.

In HF-ACTION, diabetes was associated with older age, an increased prevalence of hypertension, worse HF symptoms, reduced health status and lower adherence to exercise training. The differences were even more profound in patients with insulin-dependent diabetes. In a previous analysis, exercise training modestly improved functional capacity in HF patients with reduced ejection fraction (HFrEF). 

HF-ACTION was a multicenter, randomized controlled trial of patients who had New York Heart Association (NYHA) class II to IV symptoms even with optimal HF therapy for at least 6 weeks. Dr. Banks and his colleagues explored whether comorbid diabetes was associated with an attenuated improvement in functional capacity or worse outcomes over a median follow-up of 2.5 years. 

“Our results confirmed our primary hypothesis that patients with both heart failure and diabetes mellitus would have a blunted response to exercise independently. We were somewhat surprised however that this was true despite adjusting for the diabetics reduced adherence to training,” Dr. Banks told Endocrinology Advisor

“The results are clinically relevant in that they confirm that diabetic patients have decreased baseline functional capacity, reduced response to aerobic exercise and an increased rate of hospitalization. This drives home that heart failure patient with diabetes, especially those on insulin, need to have closer follow-up with a multidisciplinary team to prevent re-hospitalization.”

He said the findings showed that continuous aerobic exercise has little effect in HF patients with diabetes and so further research should focus on different modalities of training to improve both adherence and physiologic exercise response. Dr. Banks noted that diabetes occurs in approximately 40% to 45% of patients with heart failure with reduced HFrEF.

This analysis has significant limitations because it is a retrospective analysis from a randomized controlled trial of exercise training. In addition, measures of glycemic control, such as HbA1c, were not recorded during the original trial. 

HF-ACTION had strict exclusion and inclusion criteria so the patients were likely healthier than the average HF patient. The exclusion criteria included major comorbidities or limitations that could interfere with exercise training, performing regular exercise training or using devices that limited the ability to achieve target heart rates.

Reference

  1. Banks AZ et al. Abstract 1252-204. Presented at: American College of Cardiology (ACC) 64th Annual Scientific Session & Expo; March 14-16, 2015; San Diego.