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07-06-2011 | Cardiology | Article

Adolescents with Type 2 diabetes have impaired CV exercise tolerance


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MedWire News: Adolescents with Type 2 diabetes have greater cardiovascular (CV) impairment during exercise compared with their nondiabetic peers, suggest Canadian study results.

This association seemed to be at least partially independent of body weight as obese nondiabetic teenagers had greater CV exercise tolerance than those who had Type 2 diabetes.

"Past studies in adults with Type 2 diabetes show that their heart and blood vessels' ability to adapt to exercise may be impaired," said lead author Teresa Pinto from Dalhousie University in Halifax, Nova Scotia.

"Our study shows that these changes in heart function may begin to happen very early after Type 2 diabetes occurs."

Pinto presented the study results at the Endocrine Society's 93rd Annual Meeting in Boston, USA. She described how the researchers assessed the CV exercise tolerance of a group of adolescents aged 12-20 years using a cycle ergonometer positioned in a magnetic resonance imaging (MRI) machine.

In total, the group consisted of 13 adolescents with Type 2 diabetes, 19 with no diabetes and of normal body weight (controls; body mass index [BMI] 18.5-24.9 kg/m2), and 27 with no diabetes but who were overweight or obese (BMI above 25 kg/m2).

The team measured cardiac and femoral flow before, during, and after exercise using the MRI machine.

Pinto and team found that the maximum heart rate achieved was significantly higher in controls than in the other two groups, despite all three groups having a similar exercise workload. Cardiac output was significantly lower during exercise, but not at rest in the Type 2 diabetes group compared with the overweight/obese and control groups (p<0.01, p<0.001, respectively).

During exercise, systolic volume increased by 11.1% in the control group, by 6.0% in the overweight/obese group, and by only 0.8% in the Type 2 diabetes group, while end diastolic volume decreased by 2.1%, 0.9%, and 6.1% in the control, overweight/obese, and Type 2 diabetes groups, respectively.

End systolic volume was also significantly lower in the diabetic compared with the other two groups during exercise (p<0.01).

"We showed that the heart's pumping function is strong, but it is not filling as well as normal between heart beats. This is known as diastolic dysfunction," Pinto said.

"Although this study did not determine the reason for this, we know that with diabetes, the heart can become stiffer, limiting its ability to stretch and expand."

Femoral artery flow per minute was also significantly lower in the Type 2 diabetes group than in the other two groups after exercise (p<0.05), notes the team.

"It appears that irrespective of weight, Type 2 diabetes seems to have a negative effect on the heart and blood vessels in adolescents," Pinto said.

"This impaired exercise capacity may be reversible with exercise training however, as some literature in adults suggests, but further studies are required to determine this."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Helen Albert

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