Fasting Blood Glucose Levels Are Related to Exercise Capacity in Patients
Fasting Blood Glucose Levels Are Related to Exercise Capacity in Patients
Background and Aim: Previous studies have demonstrated reduced exercise capacity in patients with diabetes mellitus. This study evaluated the relationship between fasting blood glucose (FBG) levels and exercise capacity in patients with coronary artery disease (CAD).
Methods: We evaluated 986 consecutive patients with CAD referred for bicycle spiroergometry combined with gated myocardial perfusion imaging. Maximum oxygen consumption (VO2max) and maximal watts were measured. Patients were divided into 4 FBG categories: <100 mg/dL (n = 611), 100 to 109 mg/dL (n = 144), 110 to 125 mg/dL (n = 102), and ≥126 mg/dL (n = 129). Differences in clinical characteristics, exercise hemodynamics, perfusion imaging, and univariate as well as multivariate predictors of exercise capacity were determined.
Results: Maximal watts and VO2max were significantly lower (P < .0001) in patients with higher FBG levels and were related to FBG values in univariate and multivariate analyses. Left ventricular volumes and ejection fractions did not differ between the FBG categories. Myocardial perfusion imaging showed a comparable degree of ischemia in the 4 FBG groups. However, patients with higher FBG levels had higher heart rate and blood pressure values at rest resulting in a higher rate-pressure product (values in the 4 FBG groups 8299 ± 2051, 8733 ± 2008, 9558 ± 2583, and 9588 ± 2468 beat/min × mm Hg, P < .0001), suggesting increased myocardial oxygen consumption per unit time at rest.
Conclusion: Exercise capacity in patients with CAD is related to FBG levels. Patients with impaired fasting glucose or an FBG level ≥126 mg/dL reached lower peak watts and lower VO2max values. This could be attributed to a higher myocardial oxygen consumption per unit time at rest and the inability to adapt their coronary flow adequately to higher metabolic demands during maximal exercise.
Cardiovascular diseasesincluding coronary artery disease (CAD)are the most common cause of death in men <65 years and the second most common cause in women. They are expected to be the main cause of death globally within the next 15 years owing to their rapidly increasing prevalence in developing countries and Eastern Europe and a rising incidence of obesity and diabetes in the western world. Exercise stress testing, often combined with myocardial perfusion imaging, is a validated examination in the follow-up of patients with a history of myocardial infarction or revascularization. Bicycle testing is not only useful in detecting myocardial ischemia but also provides important information on patients' exercise capacity and prognosis especially when combined with spiroergometry. Maximum oxygen consumption (VO2max) is an independent predictor of mortality particularly in patients with heart failure.
Diabetes mellitus (DM) is associated with a 2- to 4-fold increase in the risk of developing CAD. In patients with known CAD and diabetes, the rate of death is >70% over 10 years. According to the guidelines of the American Diabetes Association, a fasting blood glucose (FBG) level ≥126 mg/dL identifies individuals with diabetes. Fasting blood glucose levels between 110 and 125 mg/dL identify patients with impaired fasting glucose (IFG). Several authors have demonstratedeven in patients with CAD without diabetesthat there is a substantially increased mortality rate among patients with IFG.
The aims of our study were to (1) determine if exercise capacity is related to fasting glucose levels in patients with CAD and (2) investigate potential pathophysiologic mechanisms that could explain this relationship, including remodeling, ischemia, and hemodynamics.
Abstract and Introduction
Abstract
Background and Aim: Previous studies have demonstrated reduced exercise capacity in patients with diabetes mellitus. This study evaluated the relationship between fasting blood glucose (FBG) levels and exercise capacity in patients with coronary artery disease (CAD).
Methods: We evaluated 986 consecutive patients with CAD referred for bicycle spiroergometry combined with gated myocardial perfusion imaging. Maximum oxygen consumption (VO2max) and maximal watts were measured. Patients were divided into 4 FBG categories: <100 mg/dL (n = 611), 100 to 109 mg/dL (n = 144), 110 to 125 mg/dL (n = 102), and ≥126 mg/dL (n = 129). Differences in clinical characteristics, exercise hemodynamics, perfusion imaging, and univariate as well as multivariate predictors of exercise capacity were determined.
Results: Maximal watts and VO2max were significantly lower (P < .0001) in patients with higher FBG levels and were related to FBG values in univariate and multivariate analyses. Left ventricular volumes and ejection fractions did not differ between the FBG categories. Myocardial perfusion imaging showed a comparable degree of ischemia in the 4 FBG groups. However, patients with higher FBG levels had higher heart rate and blood pressure values at rest resulting in a higher rate-pressure product (values in the 4 FBG groups 8299 ± 2051, 8733 ± 2008, 9558 ± 2583, and 9588 ± 2468 beat/min × mm Hg, P < .0001), suggesting increased myocardial oxygen consumption per unit time at rest.
Conclusion: Exercise capacity in patients with CAD is related to FBG levels. Patients with impaired fasting glucose or an FBG level ≥126 mg/dL reached lower peak watts and lower VO2max values. This could be attributed to a higher myocardial oxygen consumption per unit time at rest and the inability to adapt their coronary flow adequately to higher metabolic demands during maximal exercise.
Introduction
Cardiovascular diseasesincluding coronary artery disease (CAD)are the most common cause of death in men <65 years and the second most common cause in women. They are expected to be the main cause of death globally within the next 15 years owing to their rapidly increasing prevalence in developing countries and Eastern Europe and a rising incidence of obesity and diabetes in the western world. Exercise stress testing, often combined with myocardial perfusion imaging, is a validated examination in the follow-up of patients with a history of myocardial infarction or revascularization. Bicycle testing is not only useful in detecting myocardial ischemia but also provides important information on patients' exercise capacity and prognosis especially when combined with spiroergometry. Maximum oxygen consumption (VO2max) is an independent predictor of mortality particularly in patients with heart failure.
Diabetes mellitus (DM) is associated with a 2- to 4-fold increase in the risk of developing CAD. In patients with known CAD and diabetes, the rate of death is >70% over 10 years. According to the guidelines of the American Diabetes Association, a fasting blood glucose (FBG) level ≥126 mg/dL identifies individuals with diabetes. Fasting blood glucose levels between 110 and 125 mg/dL identify patients with impaired fasting glucose (IFG). Several authors have demonstratedeven in patients with CAD without diabetesthat there is a substantially increased mortality rate among patients with IFG.
The aims of our study were to (1) determine if exercise capacity is related to fasting glucose levels in patients with CAD and (2) investigate potential pathophysiologic mechanisms that could explain this relationship, including remodeling, ischemia, and hemodynamics.
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