The Relationship Between Aerobic Exercise Capacity and Cardiac Dysfunction In T2D

In type 2 diabetes patients, treating diastolic function and myocardial perfusion reserve could improve aerobic exercise capacity and prevent heart failure. 

Heart failure is one of the most common complications in patients with T2D. Some of the difficulties that both asymptomatic and symptomatic patients can have are left ventricular diastolic dysfunction and cardiac remodeling. These patients are classified as having stage B heart failure. Individuals with T2D are known to have problems with cardiovascular exercises. The reduced peak of VO2 (the maximum rate of oxygen consumption measured during incremental exercise) is correlated with the development of cardiovascular diseases. The purpose of this study is to understand the link between cardiovascular dysfunction and T2D, and to understand if cardiovascular dysfunction markers are associated with the peak of VO2. Participants included in this study were between 18-75 with no prior diabetes history, no clinical symptoms of cardiovascular diseases. Exclusion criteria were no HF, no cardiovascular problems, and T1D.  

For the evaluation in these subjects’ performance, CMR, CPET, and transthoracic echocardiography were used. Normality was assessed using histograms, and q-q plots and Pearson correlation was used for the peak of VO2 in participants with and without type 2 diabetes. Linear modeling was performed for the evaluation of the dependence of T2D with aerobic activity. For this study, 259 subjects with T2D and 85 control subjects with age, sex, and ethnicity matched were recruited. Twelve T2D patients were ineligible; therefore, 247 were included in this study. Among the 85 controls, 7 were excluded after A1C analysis and CMR scan in which they resulted as pre-diabetic. So 78 healthy volunteers were used as case-control. Participants’ mean age was about 52 years old and with a BMI of 34 kg/m^2. Approximately 45% were women, and 37% were Black. The control group participants were similar for age, race, sex, and ethnicity.  

The T2D group had a higher proportion of individuals with a history of smoking and hypertension than control subjects; therefore, the antihypertensive and lipid-lowering medications were in higher concentrations than in control subjects. Compared to case-control subjects, the ones with T2D had higher glycated hemoglobin and lower total cholesterol and LDL. Performance of CMR, electrocardiography, and CPET showed that patients with T2D had similar absolute left ventricular (LV) volumes, but smaller indexed LV volumes and higher LV mass than control subjects. There was no significant difference between the two groups in T2D left ventricular global longitudinal strain (GLS) levels, and E/A ratios were lower in comparison with subject controls. There was no difference in LV PEDSR and LA EF in both groups. After the performance of stress and rest imaging in all subjects, the overall myocardial perfusion reserve (MPR) was lower in T2D subjects, 2.60 +- 1,24 vs. 3,54+- 1,15, respectively. Both absolute and body weight corrected peak VO2 were significantly lower in T2D in comparison with control subjects (18+- 6,6 vs. 27.8=-9.0 ml/kg/min, P<0,001) 

In assessing correlations with aerobic exercise capacity, the researchers observed significant correlations between age, peak VO2, LV EF, LV mass, LV GLS, and MPR in the patients with T2D. In both groups, with or without diabetes, a significant variable associated with peak VO2 was male sex, age, and white ethnicity. This study confirmed several markers of LV dysfunctions, and among these, MPR and LV were independently associated with peak VO2. In the control subjects, only LV mass was associated with peak VO2.  

Impaired MPR can be the cause of increased cardiovascular mortality, and treating even subclinical impairment in myocardial perfusion may lower risk of developing heart failure in people with T2D. Some strengths related to the study were the large sample size, the use of CPET for quantification of exercise capacity, and close matching of control groups. The study’s limitations were the risk of errors in measurements for the peak VO2 and imaging variables.     

Practice Pearls: 

• Ethnicity, sex, MPR, and diastolic function are essential determinants of aerobic exercise activity, independent of age, in T2D asymptomatic and symptomatic subjects. 
• Subjects with T2D have lower aerobic exercise capacity, high prevalence of LV systolic, diastolic dysfunction, and cardiac remodeling. 
• The reduced peak of VO2 is a risk factor indicator for the development of cardiovascular disease and mortality. 

Gaurav Gulsin, Joseph Henson, et al. “Cardiovascular Determinants of Aerobic Exercise Capacity in Adults with Type 2 Diabetes.” American Diabetes Association. July 17. 2020. Web. September 7, 2020. https://doi.org/10.2337/dc20-0706  

Joan Prifti, PharmD. Candidate, LECOM College of Pharmacy