Original Research
Association of Exercise Intolerance in Type 2 Diabetes With Skeletal Muscle Blood Flow Reserve

https://doi.org/10.1016/j.jcmg.2014.12.033Get rights and content
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Abstract

Objectives

This study sought to investigate the association of exercise intolerance in type 2 diabetes (T2DM) with skeletal muscle capillary blood flow (CBF) reserve.

Background

Exercise intolerance in T2DM strongly predicts adverse prognosis, but associations with muscle blood flow independent of cardiac dysfunction are undefined.

Methods

In 134 T2DM patients without cardiovascular disease, left ventricular function and contrast-enhanced ultrasound of the quadriceps (for CBF; i.e., product of capillary blood volume and velocity) were assessed at rest and immediately following treadmill exercise for peak oxygen uptake (Vo2peak). Left ventricular systolic and diastolic functional reserve indexes were derived from changes in systolic and early diastolic color tissue Doppler velocities. Cardiac index reserve and its constituents (stroke volume and chronotropic indexes) and left ventricular filling pressure (ratio of early diastolic mitral inflow and annular velocities) were also measured.

Results

Vo2peak correlated with muscle CBF reserve (β = 0.16, p = 0.005) independent of cardiac index reserve and clinical covariates. This was explained by higher muscle capillary blood velocity reserve (β = 0.18, p = 0.002), rather than blood volume reserve (p > 0.10) in patients with higher Vo2peak. A concurrent association of Vo2peak with cardiac index reserve (β = 0.20, p < 0.001) appeared to reflect chronotropic index (β = 0.15, p = 0.012) rather than stroke volume index reserve (p > 0.10), although the systolic functional reserve index was also identified as an independent correlate (β = 0.16, p = 0.028). No associations of Vo2peak with diastolic functional reserve were identified (p > 0.10).

Conclusions

Vo2peak is associated with muscle CBF reserve in T2DM, independent of parallel associations with cardiac functional reserve. This is consistent with a multifactorial basis for exercise intolerance in T2DM.

Key Words

contrast agents
diabetic cardiomyopathies
echocardiography
exercise test
perfusion

Abbreviations and Acronyms

BP
blood pressure
CBF
capillary blood flow
ECG
electrocardiography
E/Em
ratio of early diastolic mitral inflow and septal annular velocities
Em
early diastolic tissue velocity
HbA1c
glycosylated hemoglobin
LV
left ventricular
MAP
mean arterial pressure
Sm
systolic tissue velocity
SVI
stroke volume index
T2DM
type 2 diabetes mellitus
Vo2peak
peak exercise oxygen uptake

Cited by (0)

This work was supported in part by a Centre of Clinical Research Excellence award from the National Health and Medical Research Council, Canberra, Australia. The authors have reported that they have no relationships relevant to the contents of this paper to disclose. Sherif Nagueh, MD, served as Guest Editor for this paper.