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      Impaired Exercise Capacity in Diabetic Patients after Coronary Bypass Surgery: Effects of Diastolic and Endothelial Function

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          Objectives: The aims of this study were to clarify the influence of cardiac diastolic and peripheral vascular function on the exercise capacity of patients with coronary bypass surgery (CABG) and diabetes mellitus (DM) by tissue Doppler imaging (TDI) and flow-mediated vasodilatation (FMD), and to investigate interrelations between exercise capacity and LV diastolic function, endothelial function and biochemical parameters. Methods: We analyzed the exercise capacity, TDI at the mitral annulus and FMD in 51 uncomplicated first-time CABG survivors (23 DM) at an average interval of 21.6 ± 12.2 months after surgery. Results: Diabetics had lower E’, A’, VO<sub>2</sub>peak, (a-v)O<sub>2</sub> difference, and higher E/E’ ratios (p < 0.05) than non-DM patients, but not FMD (p = 0.17). The A and E/E’ ratios correlated negatively with VO<sub>2</sub>peak after age adjustment (r = –0.336, p = 0.024). In addition, HbA<sub>1c</sub>, and triglyceride also correlated negatively with VO<sub>2</sub>peak (r = –0.377, –0.307, respectively, p < 0.05). Conclusions: Diabetics after CABG had more advanced diastolic dysfunction and oxygen extraction impairment than non-DM. It suggests these factors could contribute to lower exercise capacity, risk of developing heart failure despite preserved systolic function and poorer long-term survival of diabetic patients after CABG.

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          Most cited references 27

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          Effect of exercise on coronary endothelial function in patients with coronary artery disease.

          Studies of the cardioprotective effects of exercise training in patients with coronary artery disease have yielded contradictory results. Exercise training has been associated with improvement in myocardial perfusion even in patients who have progression of coronary atherosclerosis. We therefore conducted a prospective study of the effect of exercise training on endothelial function in patients with coronary artery disease. We randomly assigned 19 patients with coronary endothelial dysfunction, indicated by abnormal acetylcholine-induced vasoconstriction, to an exercise-training group (10 patients) or a control group (9 patients). To reduce confounding, patients with coronary risk factors that could be influenced by exercise training (such as diabetes, hypertension, hypercholesterolemia, and smoking) were excluded. In an initial study and after four weeks, the changes in vascular diameter in response to the intracoronary infusion of increasing doses of acetylcholine (0.072, 0.72, and 7.2 microg per minute) were assessed. The mean peak flow velocity was measured by Doppler velocimetry, and the diameter of epicardial coronary vessels was measured by quantitative coronary angiography. In the initial study, the two groups had similar vasoconstrictive responses to acetylcholine. After four weeks of exercise training, coronary-artery constriction in response to acetylcholine at a dose of 7.2 microg per minute was reduced by 54 percent (from a mean [+/-SE] decrease in the luminal diameter of 0.41+/-0.05 mm in the initial study to a decrease of 0.19+/-0.07 mm at four weeks; P<0.05 for the comparison with the change in the control group). In the exercise-training group, the increases in mean peak flow velocity in response to 0.072, 0.72, and 7.2 microg of acetylcholine per minute were 12+/-7, 36+/-11, and 78+/-16 percent, respectively, in the initial study. After four weeks of exercise, the increases in response to acetylcholine were 27+/-7, 73+/-19, and 142+/-28 percent (P<0.01 for the comparison with the control group). Coronary blood-flow reserve (the ratio of the mean peak flow velocity after adenosine infusion to the resting velocity) increased by 29 percent after four weeks of exercise (from 2.8+/-0.2 in the initial study to 3.6+/-0.2 after four weeks; P<0.01 for the comparison with the control group). Exercise training improves endothelium-dependent vasodilatation both in epicardial coronary vessels and in resistance vessels in patients with coronary artery disease.
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            Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation.

            This study investigated the prognostic importance of measured peak oxygen intake (VO(2peak)) in women with known coronary heart disease referred for outpatient cardiac rehabilitation. Exercise capacity is a powerful predictor of prognosis in men with known or suspected coronary disease. Similar findings are described in women, but fewer studies have utilized measured VO(2peak), the most accurate measure of exercise capacity. A single-center design took data from 2,380 women, age 59.7 +/- 9.5 years (1,052 myocardial infarctions, 620 coronary bypass procedures, and 708 with proven ischemic heart disease), who underwent cardiorespiratory exercise testing. They were followed for an average of 6.1 +/- 5 years (median 4.5 years, range 0.4 to 25 years) until cardiac and all-cause death. We recorded 95 cardiac deaths and 209 all-cause deaths. Measured VO(2peak) was an independent predictor of risk, values > or =13 ml/kg/min (3.7 multiples of resting metabolic rate) conferring a 50% reduction in cardiac mortality (hazard ratio [HR] 0.5, p = 0.001). Considered as a continuous variable, a 1 ml/kg/min advantage in initial VO(2peak) was associated with a 10% lower cardiac mortality. Adverse predictors were diabetes (HR 2.73, p = 0.0005) and antiarrhythmic therapy (HR 3.93, p = 0.0001). As in men, measured VO(2peak) is a strong independent predictor of cardiac mortality in women referred for cardiac rehabilitation.
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              Exercise training normalizes vascular dysfunction and improves central adiposity in obese adolescents.

              We sought to characterize the impact of obesity on vascular function in adolescents and to determine whether an exercise program reverses abnormalities in endothelial function. Obesity, a major modifiable risk factor for cardiovascular disease, is epidemic in Western societies, with rapid rates of increase in the young. Atherosclerosis begins in childhood, and endothelial dysfunction is its earliest detectable manifestation. The influence of eight weeks of circuit training (CT) was examined in 19 obese subjects (14.3 +/- 1.5 years), using a randomized, crossover protocol. Functional capacity and muscular strength were assessed by standard techniques. Body composition was examined using anthropometric measures and dual-energy X-ray absorptiometry. Conduit vessel endothelial function was assessed using high-resolution ultrasound and flow-mediated dilation (FMD) of the brachial artery. Circuit training decreased abdominal and trunk fat and significantly improved fitness and muscular strength (p < 0.05). In the obese group, FMD was significantly impaired relative to control subjects (n = 20) at entry (5.3 +/- 0.9% vs. 8.9 +/- 1.5%, p < 0.05) and was normalized after CT (8.8 +/- 0.8%, p < 0.05). Circuit training improved functional capacity, muscular strength, and body composition in obese adolescents. Furthermore, conduit vessel function was normalized after exercise training. If vascular dysfunction is an integral component of the pathogenesis of vascular disease, this study supports the value of an exercise program in the management of obese adolescents.

                Author and article information

                S. Karger AG
                June 2008
                04 December 2007
                : 110
                : 3
                : 191-198
                Departments of aInternal Medicine, bNuclear Medicine and cSurgery, National Taiwan University Hospital, College of Medicine, dSchool and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, eInstitute and Faculty of Physical Therapy, National Yang-Ming University and fDepartment of Surgery, Far Eastern Memorial Hospital, Taipei, Taiwan
                111929 Cardiology 2008;110:191–198
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 3, Tables: 6, References: 46, Pages: 8
                Original Research


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