Purpose: Type 2 diabetes mellitus (T2DM) is associated with chronotropic incompetence (CI), which may lead to a worse prognosis. It remains uncertain whether CI in T2DM patients is related to patient characteristics that are modifiable by exercise interventions.
Methods: From 33 male T2DM patients and 18 healthy subjects not taking β-blockers, calcium-antagonists, and/or diuretics, a fasting blood sample was collected, followed by an oral glucose tolerance test, maximal cardiopulmonary exercise test, and body composition analysis. Chronotropic incompetence was defined as the inability to achieve a maximal chronotropic response index (maxCRI) ≥ 0.80 during exercise testing. By univariate correlations and multivariate regression analysis, relationships between exercise tolerance, body composition, glycemic control, and maxCRI were examined.
Results: MaxCRI was significantly lower in T2DM patients (0.85 ± 0.17) vs healthy controls (1.02 ± 0.17, P < .01): Chronotropic incompetence was prevalent in 14 T2DM patients (42%) and 1 healthy subject (6%, P < .05). Significant (P < .05) univariate correlations between maxCRI and body mass index (r = -0.59), blood high-density lipoprotein cholesterol (r = 0.34), HbA1c (r = -0.33) and insulin level (r = -0.48), HOMA-IR index (r = -0.45), trunk adipose tissue mass (r = -0.45), waist circumference (r = -0.58), peak cycling power output (r = 0.42), and oxygen uptake (r = 0.33) were found (P < .05). Independent significant relations were found between maxCRI and waist circumference (P < .01) and peak cycling power output (P < .05).
Conclusions: Chronotropic incompetence in male T2DM patients is independently related to exercise tolerance and adipose tissue mass. These data provide further insight into the etiology of CI in male T2DM patients and show that exercise interventions might impact predictors of CI.