Effects of age on ventricular performance during graded supine exercise |
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| Authors: | D L Mann B S Denenberg A K Gash P T Makler A A Bove |
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| Affiliation: | 1. Cardiology Section, Department of Medicine, Temple University Medical School Philadelphia, Pa., USA;2. Cardiovascular Division, Mayo Clinic Rochester, Minn. USA.;1. Department of Bridge Engineering, Tongji University, Shanghai 200092, China;2. Department of Civil and Environmental Engineering, Waseda University, Tokyo 169-8555, Japan;3. Department of Civil and Environmental Engineering, Engineering Research Center for Advanced Technology for Large Structural Systems (ATLSS Center), Lehigh University, 117 ATLSS Dr., Bethlehem, PA 18015-4729, USA;1. School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, China;2. Information Materials and Intelligent Sensing Laboratory of Anhui Province, Anhui University, Hefei, 230601, China;3. Anhui Province Key Laboratory of Wetland Ecosystem Protection and Restoration, Anhui University, Hefei, 230601, China;4. State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan, 430079, China;5. Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo, 315211, China;1. Department of Pediatrics, School of Medicine, Universidad Nacional de Colombia, Bogota, Colombia;2. Department of Pediatric Pulmonology and Pediatric Critical Care Medicine, School of Medicine, Universidad El Bosque, Bogota, Colombia;3. Department of Internal Medicine, School of Medicine, Universidad Nacional de Colombia, Bogota, Colombia;4. Division of Pediatric Pulmonary, Sleep Medicine and Integrative Systems Biology, Center for Genetic Research, Children’s National Medical Center, George Washington University, Washington, D.C.;1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;2. Center for Hypergravity Experiment and Interdisciplinary Research, Zhejiang University, Hangzhou, Zhejiang 310058, China;3. MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, Zhejiang 310058, China;1. Baylor College of Medicine, Houston, TX, USA;2. David Geffen School of Medicine at UCLA, Los Angeles, CA, USA;3. Clinical Research Institute of Southern Oregon, Medford, OR, USA;4. University of North Carolina School of Medicine, Chapel Hill, NC, USA;5. Clinical Research of Rock Hill, Rock Hill, SC, USA;6. Queen''s University, Kingston, ON, Canada;7. P3 Research Ltd., Newtown, Wellington, New Zealand;8. AstraZeneca (Former Employee of Pearl Therapeutics Inc.), Gaithersburg, MD, USA;9. Pearl Therapeutics Inc., Morristown, NJ, USA;10. AstraZeneca, Morristown, NJ, USA |
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| Abstract: | To assess the effects of age on ventricular performance, graded supine exercise tests with equilibrium radionuclide ventriculography were performed in six normal subjects of mean age 37 +/- 4 years and in eight normal subjects with a mean age of 59 +/- 2 years. At a standard submaximal work load, older subjects had a similar heart rate (older: 126 +/- 10, younger: 128 +/- 5 bpm) and systolic blood pressure responses (older: 198 +/- 24, younger: 202 +/- 24 mm Hg). Cardiac output counts increased appropriately in both groups during submaximal exercise. However, when expressed as percent change from resting values, the increases in cardiac output (older: 125 +/- 14, younger: 75 +/- 10 L/min; p less than 0.05) were greater for the older subjects. The percent change in end-diastolic counts (older: 8.4 +/- 5, younger: -2.8 +/- 4), stroke counts (older: 26 +/- 6, younger: 8.6 +/- 4), and ejection fraction (older: 18 +/- 3, younger: 11 +/- 1%) in proceeding from rest to exercise Stage III (600 kg-m/min) was greater for the older subjects. Age-related differences in each of these measurements were significant at p less than 0.05. These findings suggest that cardiac output during exercise is maintained by an increased heart rate in younger subjects, and by a combination of increased heart rate and the Frank-Starling mechanism in older individuals. Since the heart rate and mean blood pressure response to exercise were similar in both groups, the use of the Frank-Starling mechanism during exercise in older subjects suggests that age-related differences in ventricular preload are important in modulating the performance of the aging left ventricle. |
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