Document Detail

Impaired exercise performance but normal skeletal muscle characteristics in female syndrome X patients.
MedLine Citation:
PMID:  10426336     Owner:  NLM     Status:  MEDLINE    
Pathophysiologic mechanisms in syndrome X (anginal chest pain, positive exercise stress test, and angiographically normal coronary arteries) have been extensively studied. Recent reports suggest an ischemic origin of the pain to be less probable. Other contributing mechanisms that have been hypothesized are enhanced sympathetic drive or sensitivity or an abnormal muscle metabolism. Our aim in this study was to characterize exercise performance, skeletal muscle characteristics, and sympathetic control of blood flow in patients with syndrome X. Seven female patients aged 50 to 65 years and 5 matched controls were tested. Exercise test was performed according to clinical routine. Plasma catecholamine and blood lactate levels were measured before, during, and after exercise. Autonomic blood flow control was measured plethysmographically in the resting contralateral forearm during isometric handgrip. Muscle biopsy specimens were obtained at rest from the lateral part of Musculus vastus at midthigh. The biopsy samples were investigated for the relative number of different fiber types, phosphagen content, and energy charge, calculated as (adenosine triphosphate +/- 1/2 adenosine diphosphate)/[adenosine triphosphate +/- adenosine diphosphate +/- adenosine monophosphate]). Exercise capacity was markedly decreased in syndrome X compared with controls (85 +/- 14 vs 156 +/- 11 W, p <0.0005) and all patients discontinued exercise because of chest pain (Borg CR-10, 5 +/- 3). Peak heart rate was lower in syndrome X (150 +/- 18 vs 176 +/- 7 beats/min, p <0.01), whereas systolic blood pressure and double product did not differ. Peak norepinephrine plasma levels were lower than in controls (11 +/- 6 vs 24 +/- 13 nmol/L, p <0.04), whereas peak blood lactate levels did not differ. Blood flow increase in the resting forearm during isometric handgrip was similar to that in controls. The proportion of different fiber types, phosphagen content, and energy charge were normal. Thus, patients with syndrome X have a reduced physical exercise capacity but no skeletal muscle abnormalities. Catecholamine hypersensitivity may contribute to their condition.
B E Eriksson; E Jansson; L Kaijser; C Sylvén
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of cardiology     Volume:  84     ISSN:  0002-9149     ISO Abbreviation:  Am. J. Cardiol.     Publication Date:  1999 Jul 
Date Detail:
Created Date:  1999-08-04     Completed Date:  1999-08-04     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0207277     Medline TA:  Am J Cardiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  176-80     Citation Subset:  AIM; IM    
Department of Cardiology, Huddinge University Hospital, Karolinska Institutet, Stockholm, Sweden.
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MeSH Terms
Biopsy, Needle
Catecholamines / blood
Energy Metabolism
Exercise Test
Lactic Acid / blood
Microvascular Angina / blood,  physiopathology*
Middle Aged
Muscle, Skeletal / blood supply,  chemistry,  physiopathology*
Reg. No./Substance:
0/Catecholamines; 50-21-5/Lactic Acid

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