Not all patients with angina have myocardial ischemia. A sizable minority-up to 30% of angina patients studied at tertiary referral centers-have normal coronary angiograms. Such patients often undergo an expensive and...
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Not all patients with angina have myocardial ischemia. A sizable minority-up to 30% of angina patients studied at tertiary referral centers-have normal coronary angiograms. Such patients often undergo an expensive and extensive array of testing and treatment. Yet the prognosis is generally good, and symptomatic management may be effective.
The combination of angina pectoris, angiographically normal epicardial coronary arteries, and a positive exercise test is referred to as syndrome X. Previous studies have demonstrated an impaired coronary flow reserve...
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The combination of angina pectoris, angiographically normal epicardial coronary arteries, and a positive exercise test is referred to as syndrome X. Previous studies have demonstrated an impaired coronary flow reserve and a peripheral vascular dysfunction, suggesting that vascular abnormalities in syndrome X may not be confined to the heart. The aim of this study was to investigate whether any vascular disorder of syndrome X is due to intrinsic structural or functional disturbances in resistance arteries. We compared 16 patients with syndrome X (56.6 +/- 1.2 years, 3 men) with 15 matched control subjects. Myocardial blood flow was measured with N-13-ammonia positron emission tomography. Forearm blood flow was measured in the brachial artery with high-resolution ultrasound. Gluteal subcutaneous resistance arteries were dissected and mounted on a myograph for measurement of active tension development, lumen diameter, and media thickness. Baseline myocardial blood flow was similar in patients and controls, but dipyridamole-induced hyperemia was decreased in patients (1.67 +/- 0.13 vs 2.31 +/- 0.12 ml/min/g, p <0.01). Patients and controls had similar baseline forearm blood flow, but hyperemic flow after transient occlusion of the brachial artery was impaired in patients (198 +/- 20 vs 273 +/- 32 ml/min, p < 0.05). isolated resistance arteries showed no differences in constriction to noradrenaline, or relaxation to acetylcholine, dipyridamole, or nitroglycerin. Furthermore, the ratio between media thickness and lumen diameter were similar in syndrome X patients and controls. Our data show that when compared with a well-matched control group, syndrome X patients have a decreased coronary and peripheral vasodilator capacity. However, this is not reflected by functional abnormalities or structural changes as evaluated in subcutaneous resistance arteries. We conclude that syndrome X is not a generalized intrinsic abnormality of the resistance circulation. (C) 1999 by Excerp
OBJECTIVES The purpose of this study was to investigate the relationship between arterial and coronary sinus endothelin (ET) concentrations and coronary vasomotor responses during rapid atrial pacing in patients with ...
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OBJECTIVES The purpose of this study was to investigate the relationship between arterial and coronary sinus endothelin (ET) concentrations and coronary vasomotor responses during rapid atrial pacing in patients with chest pain and normal coronary arteriograms (CPNA). BACKGROUND Plasma ET concentrations are significantly higher in CPNA patients than in healthy control subjects. METHODS We investigated 19 carefully characterized CPNA patients (14 women;mean age 53 +/- 9 years) of whom 10 had positive electrocardiographic responses to exercise. The percentage fall in coronary vascular resistance (%***) after 10 min of rapid atrial pacing was determined using a thermodilution pacing catheter. Plasma ET concentrations were measured by radioimmunoassay on simultaneously drawn arterial and coronary sinus samples. RESULTS No significant differences in ET concentrations were observed between men and women, but a strong statistical trend suggested that %*** was lower in women than men (27[23 to 31]% vs. 34[29 to 45]%-median[interquartile range];p = 0.07). Simple regression analysis including only the women (n = 14) suggested a significant relationship between baseline arterial ET concentrations and %*** (R-2 = 0.34;p = 0.06). Furthermore, stepwise multivariate regression analysis of the group as a whole indicated that both gender (p = 0.03) and baseline arterial ET concentration (p = 0.02) were independently predictive of %*** (R-2 = 0.44;overall p = 0.02);this relationship predicts that women with high ET levels would have the lowest %*** during pacing. CONCLUSIONS These data support the hypothesis that elevated ET activity may be associated with reduced coronary flow responses during rapid atrial pacing in CPNA patients. (C) 1999 by the American College of Cardiology.
Syndrome X may be caused by a coronary microvascular dysfunction, possibly due to abnormalities in coronary endothelial function. Previous studies suggested that endothelin-l (ET-1) might be involved in the pathogenes...
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Syndrome X may be caused by a coronary microvascular dysfunction, possibly due to abnormalities in coronary endothelial function. Previous studies suggested that endothelin-l (ET-1) might be involved in the pathogenesis of syndrome X. Baseline arterial and coronary sinus ET-I levels were measured in 13 patients with syndrome X (10 women, 52 +/- 7 years) and in 8 control patients (5 women, 46 +/- 11 years). ET-I was also measured after atrial pacing in 12 patients with syndrome X and all controls. To simultaneously assess the activity of nitric oxide, guanosine 3'-5'-cyclic monophosphate (cGMP) was also measured in 11 patients with syndrome X and 7 controls. Baseline arterial (2.27 +/- 0.46 vs 1.90 +/- 0.22 pg/ml, p < 0.05) and coronary sinus (2.03 +/- 0.43 vs 1.68 +/- 0.28 pg/ml, p = 0.06) ET-I plasma levels were higher in patients than in controls. After pacing, arterial ET-I levels did not change in either group and coronary sinus ET-1 levels were also unchanged in controls. In contrast, coronary sinus ET-I increased significantly in response to atrial pacing in patients with syndrome X (p = 0.023), and differences between coronary sinus ET-I levels of patients with syndrome X and controls after pacing became highly significant (2.22 +/- 0.45 vs 1.69 +/- 0.20 pg/ml, respectively, p = 0.006). No significant differences in arterial and coronary sinus cGMP concentrations were found between the 2 groups, both at baseline and after pacing. Our findings suggest that an increased vasoconstrictor activity of microvascular endothelium is present in at least some patients with syndrome X and may be involved in the pathogenesis of the syndrome. (C) 1999 by Excerpta Medico, Inc.
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