Type 1 diabetes associated with reduced exercise capacity, altered cardiac function among adolescents
Researchers in New Zealand found that adolescents with type 1 diabetes experienced a 10% reduction in exercise capacity along with an impaired left ventricular diastolic response to acute exercise compared with healthy adolescents.
Previous studies have examined the aerobic capacity and left ventricular stroke volume in adult patients with diabetes during exercise, but it was unknown whether otherwise healthy adolescent patients with diabetes have similar alterations in left ventricular function.
Silmara Gusso, PhD, from the Liggins Institute at the University of Auckland in New Zealand, and colleagues aimed to determine the left ventricular responses at rest and during acute exercise of adolescent patients with type 1 diabetes (n=53). They compared this group to a control group without diabetes (n=22).
Functional aerobic capacity (VO2 peak test), MRI assessment, resting left ventricular function and submaximal exercise left ventricular function were analyzed.
According to data, adolescents with diabetes were younger than control patients (P=.005) and had a higher resting heart rate (P=.02). Additionally, resting systolic BP was higher in adolescents with type 1 diabetes, while diastolic BP and mean arterial pressure remained similar at baseline.
Gusso and colleagues wrote that HbA1c in patients with diabetes was higher compared with the mean HbA1c over the previous year (P=.04). Patients with type 1 diabetes reported lower relative exercise capacity than control subjects (P=.03) and resting seating heart rate and systolic BP (both P=.02) were higher in adolescents with diabetes. This was also evident on peak systolic BP (P=.001) and mean arterial pressure (P=.05), they wrote.
In regard to left ventricular structure and function, the researchers found there were no differences in left ventricular mass, resting and acute exercise supine heart rates or ejection fractions between groups after adjustment for age, sex and fitness level.
Systolic BP was elevated among the diabetes group both at rest (P=.001) and during acute exercise (P=.03). Moreover, the supine diastolic BP was higher in the diabetes group during rest (P=.05) and exercise (P=.06).
“As a result, resting (P=.002) and acute exercise (P=.02) mean arterial pressures were both significantly elevated in the diabetes group,” researchers wrote.
Stroke volume decreased in patients with diabetes at rest (P=.02) and during acute exercise (P=.01). This reflected a lower end-diastolic volume (EDV), which was compensated at rest by a smaller end-systolic volume (ESV).
Researchers said these findings highlight the continuum of reduced exercise capacity in adolescents and adults with type 1 diabetes that worsens throughout the duration of diabetes.
“Importantly, the reduction in exercise capacity was associated with metabolic control, because subjects with higher levels of HbA1c showed worse fitness levels. The reduction in exercise capacity likely reflects the restrictions in cardiac output and, in particular, the abnormalities in stroke volume noted in this study,” researchers wrote.
They suggest more research in understanding the cardiovascular effects of diabetes and potential therapies needed for children and youth.
- Gusso S. Diabetes Care. 2012; doi: 10.2337/dc11-2331.
- This study was supported in part by grants from the Australasian Paediatric Endocrine Group, the National Heart Foundation of New Zealand, and the Maurice and Phyllis Paykel Trust. The researchers report no relevant financial disclosures.