Underperfusion May Play Role in Poor Exercise Capacity in Diabetics


MONTREAL — Patients with type 2 diabetes had abnormally elevated pulmonary capillary wedge pressure and reduced myocardial perfusion indexes during exercise testing in a small pilot study.

This inverse correlation was present even in the absence of obstructive coronary artery disease or diastolic dysfunction, Dr. Marcus Chen and colleagues reported in a poster at the annual meeting of the American Society of Nuclear Cardiology.

People with type 2 diabetes and no known cardiovascular disease are known to have a reduced ability to exercise, but the mechanism of impairment is not well established. One possibility is that exercise capacity is impaired due to relative cardiac underperfusion, Dr. Chen, a cardiology fellow at the University of Colorado at Denver and Health Sciences Center, said in an interview.

The study included seven women with uncomplicated type 2 diabetes for an average of 3 years, and seven nondiabetic women matched for age (42 years vs. 43 years); weight (body mass index of 28 kg/m

Myocardial perfusion index (MPI) was determined from stress and rest mean pixel counts in 17 cardiac segments using 4D-SPECT software corrected for dose, decay, and time of imaging. On a separate day, subjects had an internal jugular pulmonary artery catheter placed, and hemodynamics were continuously monitored during graded bicycle maximal exercise stress testing.

Mean pulmonary capillary wedge pressure (PCWP) rose significantly more steeply and to a greater level with exercise in the diabetic patients than in the controls. At maximal exercise, PCWP was 22.3 mm Hg in those with diabetes, compared with 18.1 mm Hg in controls, the authors reported. No subjects in either group had visual myocardial perfusion defects.

Stress counts normalized to myocardial mass were significantly lower in the diabetic group than in controls (4.28 vs. 6.60).

Total MPI as an absolute number did not differ between groups. But when total MPI was normalized to myocardial mass, BMI, and peak exercise double product, it was significantly lower in the diabetes group, compared with controls (11.0 vs. 17.5). Peak exercise double product is a measure of stress workload, derived by multiplying the heart rate by the systolic blood pressure.

The inverse correlation between elevated wedge pressure and decreased normalized MPI was statistically significant. The findings suggest the presence of cardiac dysfunction during exercise in subjects with type 2 diabetes, the authors concluded.

The investigators acknowledged that the study was small and included only women, but reported that women were chosen because it's been suggested that diabetic women have worse exercise impairments than diabetic men relative to their nondiabetic counterparts. Future studies will expand the cohort, they said.

The findings suggest the presence of cardiac dysfunction during exercise in patients with type 2 diabetes. DR. CHEN

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