Syndrome X and endothelial dysfunction

Endothelial dysfunction: from the particular to the general. Return to the «Old Paradigm»?

The vascular endothelium is a heterogeneous structure with diverse functions, being an active metabolic system. Endothelial cells mediate inflammatory and immune processes, regulate leukocyte adhesion, permeability and vascular tone, participate in the hemostasis system, stimulate the processes of angiogenesis. Endothelial dysfunction can initiate individual disorders, but more often it is a universal link in the pathogenesis of many diseases. Currently, endothelial dysfunction is presented as an imbalance between the production of vasodilating, angioprotective, antiproliferative factors, on the one hand, and vasoconstrictive, prothrombotic, proliferative factors, on the other hand. The manifestations of endothelial dysfunction, the direction and severity of these changes may vary depending on the disease. The review provides examples of combined endothelial disorders in the most studied and common diseases (essential hypertension, type 2 diabetes, systemic diseases of the connective tissue, atherosclerosis, and malignant tumors). Despite the presence of rare cases of isolated endothelial dysfunction, it can be argued that in the absolute majority of diseases, endothelial dysfunction has combined type of violations. The allocation of individual endothelial disorder spectra, typical for a specific disease, is problematic, due to the universality and nonspecificity of the manifestations of endothelial dysfunction. These conclusions allow us to return to the origins of this problem, considering endothelial dysfunction as a holistic concept, not limited to a certain range of its disorders.

Number and function of bone-marrow derived angiogenic cells and coronary flow reserve in women without obstructive coronary artery disease: a substudy of the NHLBI-sponsored Women's Ischemia Syndrome Evaluation (WISE)

BACKGROUND

In women with ischemia and no obstructive coronary artery disease, the Women's Ischemic Syndrome Evaluation (WISE) observed that microvascular coronary dysfunction (MCD) is the best independent predictor of adverse cardiovascular events. Since coronary microvascular tone is regulated in part by endothelium, we hypothesized that circulating endothelial cells (CEC), which reflect endothelial injury, and the number and function of bone-marrow derived angiogenic cells (BMDAC), which could help repair damaged endothelium, may serve as biomarkers for decreased coronary flow reserve (CFR) and MCD.

METHODS

We studied 32 women from the WISE cohort. CFR measurements in response to intracoronary adenosine were taken as an index of MCD. We enumerated BMDAC colonies and CEC in peripheral blood samples. BMDAC function was assessed by assay of migration of CD34+ cells toward SDF-1 and measurement of bioavailable nitric oxide (NO). These findings were compared with a healthy reference group and also entered into a multivariable model with CFR as the dependent variable.

RESULTS

Compared with a healthy reference group, women with MCD had lower numbers of BMDAC colonies [16 (0, 81) vs. 24 (14, 88); P = 0.01] and NO [936 (156, 1875) vs. 1168 (668, 1823); P = 0.02]. Multivariable regression analysis showed strong correlation of CFR to the combination of BMDAC colony count and CD34+ cell function (migration and NO) (R(2) = 0.45; P<0.05).

CONCLUSIONS

The BMDAC function and numbers of BMDAC colonies are decreased in symptomatic women with MCD and are independently associated with CFR. These circulating cells may provide mechanistic insights into MCD in women with ischemia.

Sex differences in presentation and outcome among patients with type 2 diabetes and coronary artery disease treated with contemporary medical therapy with or without prompt revascularization: a report from the BARI 2D Trial (Bypass Angioplasty Revascularization Investigation 2 Diabetes)

OBJECTIVES

This study evaluated differences in outcome among women and men enrolled in the BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) trial.

BACKGROUND

Women and men with coronary artery disease have different clinical presentations and outcomes that might be due to differences in management.

METHODS

We compared baseline variables, study interventions, and outcomes between women and men enrolled in the BARI 2D trial and randomized to aggressive medical therapy alone or aggressive medical therapy with prompt revascularization.

RESULTS

At enrollment, women were more likely than men to have angina (67% vs. 58%, p < 0.01) despite less disease on angiography (Myocardial Jeopardy Index 41 ± 24 vs. 46 ± 24, p < 0.01; number of significant lesions 2.3 ± 1.7 vs. 2.8 ± 1.8, p < 0.01). Over 5 years, no sex differences were observed in BARI 2D study outcomes after adjustment for difference in baseline variables (death/myocardial infarction/cerebrovascular accident: hazard ratio: 1.11, 99% confidence interval [CI]: 0.85 to 1.44). However, women reported more angina than men (adjusted odds ratio: 1.51, 99% CI: 1.21 to 1.89, p < 0.0001) and had lower scores for the Duke Activity Status Index (adjusted beta coefficient: -1.58, 99% CI: -2.84 to -0.32, p < 0.01).

CONCLUSIONS

There were no sex differences in death, myocardial infarction, or cerebrovascular accident among patients enrolled in the BARI 2D trial. However, compared with men, women had more symptoms and less anatomic disease at baseline, with persistence of higher angina rates and lower DASI scores after 5 years of medical therapy with or without prompt revascularization. (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes [BARI 2D]; NCT00006305).

Sex, clinical symptoms, and angiographic findings in patients with diabetes mellitus and coronary artery disease (from the Bypass Angioplasty Revascularization Investigation [BARI] 2 Diabetes trial)

Previous studies have reported differences in presenting symptoms and angiographic characteristics between women and men undergoing evaluation for suspected coronary artery disease (CAD). We examined the relation between symptoms and extent of CAD in patients with type 2 diabetes mellitus and known CAD enrolled in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial. Of 1,775 patients (533 women, 30%, and 1,242 men, 70%), women were more likely than men to have angina (65% vs 56%, p <0.001) or an atypical angina/anginal equivalent (71% vs 58%, p <0.001). More women reported unstable angina (17% vs 13%, p = 0.047) or were in a higher Canadian Cardiology Society class compared to men (Canadian Cardiology Society classes II to IV 78% vs 68%, p = 0.002). Fewer women than men had no symptoms (14% vs 22%, p <0.001). Women had a lower mean myocardial jeopardy index (42.5 ± 24.3 vs 47.9 ± 24.3, p <0.001), smaller number of total significant lesions (2.3 ± 1.7 vs 2.7 ± 1.8, p <0.001), and fewer jeopardized left ventricular regions (p <0.001 for distribution) or long-term occlusions (29% vs 42%, p <0.001). After adjustment for relevant covariates, the odds of having CAD symptoms were still higher in women than men (odds ratio for angina 1.31, 95% confidence interval 1.02 to 1.69; odds ratio for atypical angina 1.52, 95% confidence interval 1.17 to 1.96). In conclusion, in a high-risk group of patients with known CAD and diabetes mellitus, women were more symptomatic than men but had less obstructive CAD. These data suggest that factors other than epicardial CAD severity influence symptom presentation in women in this population.

Serum ADMA concentration-- an independent factor determining FMD impairment in cardiac syndrome X

Mechanisms of decreased endogenous vascular reactivity in individuals with cardiac syndrome X (CSX) are not fully understood.

AIM

To evaluate the following serum markers: total nitric oxide (NO), asymmetric dimethylarginine (ADMA), platelet-derived growth factor (PDGF), and to establish their relation to ultrasound indexes of endothelial function and structural remodeling in CSX patients.

METHOD

The study group consisted of 43 CSX patients (mean age: 56.3 +/- 9 years), while the control group included 21 healthy subjects (mean age: 54.86 +/- 6.9 years). The high-resolution ultrasound was performed to measure: flow-mediated vasodilatation (FMD), nitroglycerine-mediated vasodilatation (NMD) and intima-media thickness (IMT) of carotid arteries.

RESULTS

In CSX patients, significantly lower FMD (9.06 +/- 3.2%) and significantly higher IMT (0.667 +/- 0.14 mm) values were observed compared to healthy individuals (17.42 +/- 8.4%, 0.571 +/- 0.2 mm; P < 0.05). Mean total NO serum concentration was significantly higher in the CSX group (48.2 +/- 18.2 micromol/L) as compared to controls (32.1 +/- 1.4 micromol/L; P < 0.0001). There were no differences in serum ADMA and PDGF levels. In CSX patients, FMD values correlated with NO (r = 0.323; P = 0.039) and ADMA (r = -0.387; P = 0.012) serum levels; however, there were no significant correlations between NO and ADMA concentrations.

CONCLUSION

Serum ADMA concentration is the only independent factor determining FMD impairment.

No effect of short-term arginine supplementation on nitric oxide production, metabolism and performance in intermittent exercise in athletes

Arginine supplementation has been shown to alleviate endothelial dysfunction and improve exercise performance through increasing nitric oxide production in patients with cardiopulmonary diseases. In addition, arginine supplementation could decrease accumulations of lactate and ammonia, metabolites involved in development of muscular fatigue. The aim of this study was to investigate the effect of short-term arginine supplementation on performance in intermittent anaerobic exercise and the underlying mechanism in well-trained male athletes. Ten elite male college judo athletes participated with a randomized crossover, placebo-controlled design. The subjects consumed 6 g/day arginine (ARG trial) or placebo (CON trial) for 3 days then performed an intermittent anaerobic exercise test on a cycle ergometer. Blood samples were collected before supplementation, before and during exercise and 0, 3, 6, 10, 30 and 60 min after exercise. ARG trial had significantly higher arginine concentrations than CON trial at the same time point before, during and after exercise. In both trials, nitrate and nitrite concentration was significantly higher during and 6 min after exercise comparing to the basal concentration. The increase in nitrate and nitrite concentration during exercise in both trials was parallel to the increase in plasma citrulline concentrations. There was no significant difference between the 2 trials in plasma nitrate and nitrite, lactate and ammonia concentrations and peak and average power in the exercise. The results of this study suggested that short-term arginine supplementation had no effect on nitric oxide production, lactate and ammonia metabolism and performance in intermittent anaerobic exercise in well-trained male athletes.

Evaluation of post-stress left ventricular dysfunction and its relationship with perfusion abnormalities using gated SPECT in patients with cardiac syndrome X

OBJECTIVE

Cardiac syndrome X defines patients with typical angina, a positive exercise ECG stress test and angiographically documented normal coronary arteries. In previous studies, post-stress prolonged left ventricular dysfunction (PLVD) using gated SPECT (G-SPECT) had been well correlated with myocardial perfusion abnormalities and degree of stenotic vessels in CAG in patients with coronary artery disease. However, evaluation of left ventricular myocardial perfusion, wall motion and left ventricular ejection fraction (LVEF) in patients with cardiac syndrome X, using G-SPECT had not been studied yet. Thus, the aim of this study was to analyse PLVD using (99m)Tc-MIBI GSPECT in patients with cardiac syndrome X.

METHODS

Of the patients in whom G-SPECT was performed in our institution between 2004 and 2006, 17 patients with anginal chest pain, positive exercise ECG stress test and normal coronary angiograms were retrospectively included to the study (group I). Fifteen patients with normal myocardial perfusion and another 15 patients with ischaemia on G-SPECT were selected as control groups (groups II and III). (99m)Tc-MIBI G-SPECT was performed for all patients according to 2 day (stress-rest) protocol. Stress and rest LVEF were derived automatically (SLVEF and RLVEF). Difference LVEF (DLVEF) (stress-rest) was calculated. Semiquantitative analyses were made both for myocardial perfusion and wall motion (WM), using a 20-segment model and a 5-point scoring system. DLVEF, perfusion and WM scores of all groups were compared among three groups and relationship between DLVEF, perfusion and WM scores were evaluated.

RESULTS

Abnormal perfusion were detected in eight (47.1%) of patients, while the remaining nine (52.9%) had normal myocardial perfusion, in group I. Six of 17 (35.3%) patients in group I had post-stress WM abnormalities. Mean of DLVEF values were -3.1+/-3.0%, 4.4+/-2.0% and -6.0+/-5.1% in groups I, II and III, respectively (P<0.05 for group II vs. group I and group III; P>0.05 for group I vs. group III). LVEF response impairment (< or =5% increase from rest to post-stress images) was found in 17 (100%), seven (46.6%), 14 (93.3%) of patients in groups I, II and III, respectively.

CONCLUSION

Abnormal myocardial perfusion, concordant transient segmental WM abnormalities and LVEF response impairment are not uncommon in patients with cardiac syndrome X of this cohort of the study population. Therefore, post-stress prolonged stunning may be attributed to these findings in some of cardiac syndrome X patients as in true ischaemic patients. However, further studies with larger number of subjects and long-term follow-up are necessary to support these findings.

Brachial artery flow-mediated vasodilation in patients with cardiac syndrome X

Cardiac syndrome X (CSX) differs from coronary artery disease (CAD) and is characterized by angina, positive stress test, and patent coronary arteries. The probable mechanism is a microvascular disorder associated with endothelial dysfunction. In this study, brachial artery flow-mediated vasodilation was used as well as the endothelin-1 assay to assess endothelial function in patients with cardiac syndrome X (CSX), coronary artery disease (CAD), and healthy controls. All subjects underwent a 2-step brachial artery flow-related vasodilatation test. Serum endothelin-1, one of the most potent constricting factors, was measured for all participants. Patients with CSX had a lower brachial artery dilation ratio than controls but higher than that of CAD patients. Control subjects and CSX patients had higher endothelin-1 levels than CAD patients. CSX patients were found to have worse endothelial function than healthy volunteers, but patients with CAD had even worse endothelium function than CSX patients.

Reproducibility and Repeatability of Peripheral Microvascular Assessment Using Iontophoresis in Conjunction With Laser Doppler Imaging

Interrogation of peripheral vascular function is increasingly recognized as a noninvasive surrogate marker for coronary vascular function and carries with it important prognostic information regarding future cardiovascular risk. Laser Doppler imaging (LDI) is a completely noninvasive method for looking at peripheral microvascular function. We sought to look at reproducibility and repeatability of LDI-derived assessment of peripheral microvascular function between arms and 8 weeks apart. We used LDI in conjunction with iontophoretic application of ACh and SNP to look at endothelium-dependent and -independent microvascular function, respectively, in a mixture of women with cardiac syndrome X and healthy volunteers. We looked at variation between arms (n = 40) and variation at 8 weeks apart (n = 22). When measurements were corrected for skin resistance, there was nonsignificant variation between arms for ACh (2.7%) and SNP (3.8%) and nonsignificant temporal variation for ACh (3.5%) and SNP (4.7%). Construction of Bland-Altman plots reinforce that measurements have good repeatability. Elimination of the baseline perfusion response had deleterious effects on repeatability. LDI can be used to assess peripheral vascular response with good repeatability as long as measurements are corrected for skin resistance, which affects drug delivery. This has important implications for the future use of LDI.

Effects of Metformin on Microvascular Function and Exercise Tolerance in Women With Angina and Normal Coronary Arteries

OBJECTIVES

This study sought to determine whether metformin improves vascular function or myocardial ischemia in nondiabetic subjects.

BACKGROUND

Metformin prevents diabetes and may reduce coronary events in patients with diabetes, but effects on microvascular function and angina are not clear.

METHODS

We conducted an 8-week double-blind, randomized, placebo-controlled study of metformin 500 mg twice a day in 33 nondiabetic women with a prior history of normal coronary angiography but two consecutive positive (ST-segment depression > or =1 mm) exercise tolerance tests. All parameters were measured at baseline and at 8 weeks, together with an in vivo assessment of forearm (skin) microvascular function using laser Doppler imaging combined with iontophoresis.

RESULTS

In comparison with placebo (n = 17), metformin recipients (n = 16) showed significant reductions in weight and in homeostatic model assessment for insulin resistance (p < 0.05, intention to treat). Endothelium-dependent microvascular responses improved significantly with metformin (2-way repeated analysis of variance, p = 0.0003), but responses with placebo were unchanged (p = 0.50). A comparison of change in acetylcholine responses between metformin and placebo recipients was significant, whether analyzed by a 2-way analysis of variance (p < 0.0001) or change in area under curves (mean change +392 perfusion units, 95% confidence interval [CI] 20 to 764). Endothelium-independent responses were not altered. Maximal ST-segment depression (-0.84 mm, 95% CI -1.49 to -0.20, p = 0.013), Duke score (6.1 U, 95% CI 1.8 to 10.5, p = 0.008), and chest pain incidence (-0.11 episodes/day, 95% CI -0.22 to 0.00, p = 0.056) improved in metformin relative to placebo recipients.

CONCLUSIONS

Metformin may improve vascular function and decrease myocardial ischemia in nondiabetic women with chest pain and angiographically normal coronary arteries. Larger controlled trials of longer duration are warranted.

Microvascular function, metabolic syndrome, and novel risk factor status in women with cardiac syndrome X

To characterize microvascular function, candidate risk pathways, and metabolic syndrome prevalence in women with cardiac syndrome X, 52 nondiabetic women with angiographically normal epicardial arteries but >1 mm of planar ST depression during exercise testing (patients) and 24 healthy controls of similar age were recruited. In addition to fasting blood samples and anthropometric measurements, forearm cutaneous microvascular function after iontophoresis of acetylcholine and sodium nitroprusside was assessed by laser Doppler imaging. Despite body mass index correction and a larger proportion on statin therapy, patients had high levels of insulin (p=0.016), triglycerides (p=0.018), intercellular adhesion molecule-1 (p=0.021), von Willebrand factor (p=0.005), and leptin (p=0.005) and lower levels of high-density lipoprotein cholesterol (p=0.042) compared with controls. Consistent with these data, 30% of patients but only 8% of controls fulfilled criteria for the metabolic syndrome as defined by the National Cholesterol Education Program (p=0.015). Endothelium-dependent and -independent microvascular functions were markedly impaired in patients (p<0.001), and the odds ratio for cardiac syndrome X was 7.38 (95% confidence interval 2.2 to 24.7) if the acetylcholine response was <8,710 flux units. In conclusion, women with cardiac syndrome X more commonly have metabolic syndrome and related adiposity, metabolic, and inflammatory derangements. They also have significantly impaired skin microvascular function as assessed by laser Doppler imaging, consistent with generalized vascular dysfunction, a finding with potential diagnostic implications.

Frequency and severity of myocardial perfusion abnormalities using Tc-99m MIBI SPECT in cardiac syndrome X

Background

Cardiac syndrome X is defined by a typical angina pectoris with normal or near normal (stenosis <40%) coronary angiogram with or without electrocardiogram (ECG) change or atypical angina pectoris with normal or near normal coronary angiogram plus a positive none-invasive test (exercise tolerance test or myocardial perfusion scan) with or without ECG change. Studies with myocardial perfusion imaging on this syndrome have indicated some abnormal perfusion scan. We evaluated the role of myocardial perfusion imaging (MPI) and also the severity and extent of perfusion abnormality using Tc-99m MIBI Single Photon Emission Computed Tomography (SPECT) in these patients.

Methods

The study group consisted of 36 patients with cardiac syndrome X. The semiquantitative perfusion analysis was performed using exercise Tc-99m MIBI SPECT. The MPI results were analyzed by the number, location and severity of perfusion defects.

Results

Abnormal perfusion defects were detected in 13 (36.10%) cases, while the remaining 23 (63.90%) had normal cardiac imaging. Five of 13 (38.4%) abnormal studies showed multiple perfusion defects. The defects were localized in the apex in 3, apical segments in 4, midventricular segments in 12 and basal segments in 6 cases. Fourteen (56%) of all abnormal segments revealed mild, 7(28%) moderate and 4 (16%) severe reduction of tracer uptake. No fixed defects were identified. The vessel territories were approximately the same in all subjects. The Exercise treadmill test (ETT) was positive in 25(69%) and negative in 11(30%) patients. There was no consistent pattern as related to the extent of MPI defects or exercise test results.

Conclusion

Our study suggests that multiple perfusion abnormalities with different levels of severity are common in cardiac syndrome X, with more than 30 % of these patients having at least one abnormal perfusion segment. Our findings suggest that in these patients microvascular angina is probably more common than is generally believed.

Brachial artery flow-mediated dilation and myocardial perfusion in patients with cardiac syndrome X

We assessed the relation between systemic endothelial dysfunction abnormalities (brachial artery flow-mediated dilation) and myocardial perfusion abnormalities (single-photon emission computed tomography) in 41 patients who had cardiac syndrome X. Eighteen patients had normal perfusion scans and 18 had transient perfusion defects. Reverse redistribution was found in 5 patients. Patients who had myocardial perfusion defects had significantly lower flow-mediated dilation values (1.8%) than patients who had normal single-photon emission computed tomograms (3.9%, p = 0.012). Preserved systemic endothelial function appears to rule out the occurrence of transient single-photon emission computed tomographic defects in patients who have cardiac syndrome X.

Assessment of flow-mediated vasodilatation (FMD) of the brachial artery: effects of technical aspects of the FMD measurement on the FMD response

AIMS

The ability to assess endothelial function non-invasively with B-mode ultrasound has lead to its widespread application in a variety of studies. However, the absolute values obtained using this approach vary considerably across studies. We studied whether technical aspects of the methodology can explain the wide variety in absolute values across studies.

METHODS AND RESULTS

A literature search was performed to identify published reports on flow-mediated vasodilatation (FMD) of the brachial artery published between 1992 and 2001. Information on type of equipment (wall track/B-mode), location of the measurement (antecubital fossa/upper arm), occlusion site (lower/upper arm), occlusion duration (min), and occlusion pressure was extracted. Patient characteristics were also extracted. For the healthy populations, mean FMD varied from 0.20 to 19.2%; for the coronary heart disease (CHD) patients FMD varied from -1.3 to 14%; for subjects with diabetes mellitus FMD varied from 0.75 to 12%. Compared with occlusion at the upper arm, lower arm occlusion was related to decreased FMD (mean difference in FMD -2.47%; 95% CI 0.55-4.39). An occlusion duration of > or =4.5 min was related to an increased FMD compared with an occlusion time of < or =4 min (mean difference 1.30%; 95% CI 0.35-2.46). These findings were adjusted for other technical aspects of the methodology and for differences in risk factors between populations.

CONCLUSION

Mean FMD differs widely between studies. There is a great overlap between populations (healthy, CHD, diabetics). Our findings suggest that the technical aspects of the measurements, the location, and the duration of the occlusion may explain some of these differences, whereas type of equipment, location of the measurement, and occlusion pressure do not.

Decreased serum osteoprotegerin levels in patients with cardiac syndrome X

Receptor activator of nuclear factor KB (RANK) and osteoprotegerin (OPG) represent the ligand and decoy receptor, respectively, of a pleiotropic cytokine system that regulates bone metabolism and vascular biology. Several studies supported systemic microvascular abnormalities in patients with cardiac syndrome X (CSX). This study investigates serum OPG levels in healthy obese subjects and healthy lean controls affected by cardiac syndrome X.

METHODS

We compared the OPG levels in 8 patients with cardiac syndrome X [2 males, 6 females; age: 46+/-6 yr; body mass index (BMI): 30+/-5 kg/m2] with 24 obese subjects (8 males, 16 females; age: 38+/-5 yr; BMI: 35+/-5 kg/m2) and 15 healthy lean controls (6 males, 9 females; age: 36+/-5 yr; BMI: 23+/-2 kg/m2; BMI<25kg/m2).

RESULTS

Serum OPG levels in patients with cardiac syndrome X were lower than those in obese subjects and lean controls (11.45+/-8.36 pg/ml, 14.78+/-8.22 pg/ml, 19.24+/-6.96 pg/ml, respectively, cardiac syndrome X vs lean controls, p=0.039).

CONCLUSIONS

Serum OPG levels are lower in patients with CSX. Further studies on the mechanisms of OPG in microangiopathy may help to evaluate the OPG system role as a marker for disease activity, prognosis and response to therapy in cardiovascular diseases.

Effect of simvastatin on endothelial function in cardiac syndrome X patients

Patients with cardiac syndrome X with mild hypercholesterolemia were randomized to placebo (n = 20) or simvastatin 20 mg/day (n = 20). In the simvastatin group, there was a significant (26%; p < 0.0001) decrease in total cholesterol, a 38% (p < 0.0001) decrease in low-density lipoprotein cholesterol levels, and 7% a (p < 0.0001) increase in high-density lipoprotein cholesterol levels, without significant changes in triglyceride levels. Brachial artery flow-mediated dilation increased significantly (52% relative increase, p < 0.0001), and the time to > 1-mm ST-segment depression during stress testing was longer by the end of the study (p < 0.0001).

Assessment of systemic inflammation and infective pathogen burden in patients with cardiac syndrome X

Inflammation plays a key role in coronary artery disease (CAD), but whether it is involved in the pathogenesis of syndrome X (SX) is not known. Thus, we assessed the presence of systemic inflammation in patients with SX and its possible relation to infections from Helicobacter pylori, Chlamydia pneumoniae, cytomegalovirus, and Epstein-Barr virus. We studied 55 patients with SX (57 +/- 8 years old; 27 women), 49 with stable angina and obstructive CAD (56 +/- 8 years old; 24 women), and 60 healthy controls (57 +/- 11 years old; 24 women). Plasma levels of high-sensitivity C-reactive protein and interleukin-1 receptor antagonist were measured in all patients. Infection from Helicobacter pylori, Chlamydia pneumoniae, cytomegalovirus, and Epstein-Barr virus was assessed in 43 patients with SX, 40 patients with CAD, and in 39 controls. Patients with SX had lower serum levels of C-reactive protein than did patients with CAD (4.06 +/- 6.8 vs 5.99 +/- 7.8 mg/L, p = 0.013) but higher levels of C-reactive protein than did controls (1.75 +/- 1.98 mg/L; p = 0.008). Plasma levels of interleukin-1 receptor antagonist were higher in patients with CAD (570 +/- 738 pg/ml) and patients with SX (494 +/- 677 pg/ml) than in controls (254 +/- 174, pg/ml; p = 0.0003 vs CAD and p = 0.013 vs SX) but did not differ significantly between patients with CAD or SX (p = 0.20). There were no differences across groups in the prevalence of infection from Helicobacter pylori, Chlamydia pneumoniae, cytomegalovirus, and Epstein-Barr virus and in the prevalence of 1, 2, 3, and 4 infections (p = 0.99). Among patients with SX, no correlation was found between markers of inflammation and indexes of disease activity (angina episodes, exercise test results). Our data show evidence of increased low-grade systemic inflammation in patients with cardiac SX, which was unrelated to an increased infectious pathogen burden.

Hypothalamic digoxin, hemispheric chemical dominance and syndrome X with multiple lacunar state. A hypothesis

This study assessed the changes in digoxin and some other metabolites of the isoprenoid pathway in metabolic syndrome X presenting with multiple lacunar state. The isoprenoid pathway and digoxin status was also studied for comparison in individuals of differing hemispheric dominance to find out the role of cerebral dominance in the genesis of syndrome X. There was an increase in plasma HMG CoA reductase activity with a consequent increase in serum digoxin, which caused a reduction in RBC membrane Na(+)-K+ ATPase activity. There was an increase in serum tryptophan and its metabolites and a decrease in tyrosine and its metabolites. Serum magnesium was decreased with consequent alteration in the metabolism of glycosaminoglycans and glycolipids. Increase in dolichol, another product of the isoprenoid pathway, resulted in alteration in glycoprotein metabolism. Changes in the composition of membrane glycosaminoglycans, glycoproteins and cholesterol: phospholipid ratio were also observed in this disorder leading to decreased lysosomal stability. Decrease in ubiquinone, another isoprenoid metabolite, resulted in alteration in the free radical generation. Membrane Na(+)-K+ ATPase inhibition due to digoxin, altered membrane structure, increased tryptophan catabolites and decreased tyrosine catabolites can lead to increased intracellular calcium and reduced intracellular magnesium which can account for the symptoms of syndrome X. The biochemical patterns including hyperdigoxinemia observed in syndrome X correlated with those obtained in right hemispheric chemical dominance. Right hemispheric chemical dominance is a predisposing factor for syndrome X with multiple lacunar state.

C-reactive protein, clinical presentation, and ischemic activity in patients with chest pain and normal coronary angiograms

OBJECTIVES

We sought to investigate the relationship among C-reactive protein (hs-CRP), clinical characteristics, exercise stress test responses, and ST-segment changes during daily life in patients with typical chest pain and normal coronary angiograms (CPNCA).

BACKGROUND

Patients with CPNCA have coronary microvascular endothelial dysfunction and myocardial ischemia. Elevated hs-CRP levels have been related to atherogenesis and endothelial dysfunction. The relationship between hs-CRP and disease activity has not been previously investigated in CPNCA patients.

METHODS

We studied 137 consecutive CPNCA patients (mean age, 57 +/- 9; 33 men). All completed standardized angina questionnaires, underwent exercise stress testing, 24-h ambulatory electrocardiogram (ECG) monitoring (Holter), and hs-CRP measurements at study entry.

RESULTS

C-reactive protein levels (mg/l) were higher in patients with frequent (2.9 +/- 3.3) and prolonged (3.9 +/- 4.1) chest pain episodes, and in those with ST-segment depression on exercise testing (2.6 +/- 2.8) and Holter monitoring (3.4 +/- 3.1) compared with patients with occasional (1.3 +/- 1.2; p = 0.002) or shorter chest pain (1.5 +/- 1.3; p < 0.001) episodes, negative exercise stress testing (1.1 +/- 1.1; p < 0.001), and no ST-segment shifts on Holter monitoring (0.9 +/- 0.7; p < 0.001). Moreover, we found a correlation between hs-CRP concentration and number of ischemic episodes during Holter monitoring (r = 0.65; p < 0.001) and with the magnitude of ST-segment depression on exercise testing (r = -0.43; p < 0.001). The hs-CRP was the only independent variable (multivariate logistic regression) capable of predicting positive findings on Holter monitoring (odds ratio [OR], 3.8; confidence interval [CI], 2.3 to 6.2) and exercise testing (OR, 1.7; CI, 1.2 to 2.2).

CONCLUSIONS

The hs-CRP correlates with symptoms and ECG markers of myocardial ischemia in CPNCA patients. Whether hs-CRP is related to the pathogenesis of angina in these patients deserves further investigation.

Differential mononuclear cell activity and endothelial inflammation in coronary artery disease and cardiac syndrome X

BACKGROUND

Circulating mononuclear cells could be activated with endothelial inflammation in patients with coronary artery disease (CAD). In some patients with normal coronary angiograms, myocardial ischemia could also present with coronary microvascular dysfunction (cardiac syndrome X). This study was undertaken to investigate whether mononuclear cell activation and endothelial inflammation can present in syndrome X patients.

METHODS

We evaluated the biochemical parameters, circulating soluble adhesion molecules, circulating superoxide free radicals, and mononuclear cell activity in 32 patients with syndrome X, 34 with angiographically documented CAD, and 17 age- and gender-matched healthy control subjects.

RESULTS

Compared to that in control subjects, plasma high-density lipoprotein was reduced (P<0.001) and insulin to glucose ratio increased (P=0.02) in CAD patients. Circulating level of soluble intracellular adhesion molecule-1 was significantly higher in both syndrome X and CAD patients than in control subjects (P<0.01), whereas the levels of soluble vascular cell adhesion molecule (P=0.02) and von Willebrand factor (P=0.01) were increased in CAD patients only. The peak (P<0.001) and total counts of superoxide free radicals in whole blood (P<0.001) was significantly higher in syndrome X patients than in the other two groups. However, phorbol-12-myristate-13-acetate-induced superoxide free radical generation of mononuclear cells was increased in CAD (10.5+/-4.6%, P=0.01) but not in syndrome X patients (8.7+/-2.0%) as compared with control subjects (7.7+/-0.5%).

CONCLUSIONS

The results indicated that the activity of mononuclear cells was increased with significant endothelial inflammation and injury in CAD patients. In syndrome X patients, though circulating superoxide free radicals were increased, there was minimal endothelial inflammation without mononuclear cell activation. The relatively preserved lipid and metabolic profiles might contribute to less vascular inflammation in syndrome X patients.

[Cardiovascular syndrome X and endothelial dysfunction]

Up to 30% of patients with chest pain who undergo coronary arteriography, have completely normal coronary angiograms. The subgroup with typical angina and a positive response to stress testing is generally included under the diagnosis of cardiovascular syndrome X. Several causes and mechanisms have been investigated in the past twenty years, to explain both chest pain and ischemic angina-like ST segment depression that are commonly observed in these patients. Clinical and pathogenic heterogeneity appears to be the main features of the syndrome. Among the suggested pathophysiological mechanisms, endothelial dysfunction of the coronary microcirculation features prominently. In this review, we present the available evidence regarding endothelial dysfunction in cardiovascular syndrome X.

Long-term angiotensin-converting enzyme inhibition reduces plasma asymmetric dimethylarginine and improves endothelial nitric oxide bioavailability and coronary microvascular function in patients with syndrome X

Angiotensin-converting enzyme (ACE) inhibition has been shown to improve clinical myocardial ischemia in patients with syndrome X (angina pectoris, positive treadmill exercise test, normal coronary angiograms, and no evidence of coronary spasm). This study was conducted to investigate the effects of long-term ACE inhibitors on endothelial nitric oxide (NO) metabolism and coronary microvascular function in patients with syndrome X. After a 2-week washout period, 20 patients with syndrome X were randomized to receive either enalapril, an ACE inhibitor, 5 mg twice daily (n = 10) or placebo (n = 10) in a double-blind design for 8 weeks. Another 6 age- and gender-matched subjects with negative treadmill exercise tests were also studied as controls. Compared with control subjects, patients with syndrome X had significantly reduced coronary flow reserve, reduced plasma levels of nitrate and nitrite (NOx), and a reduced plasma L-arginine to asymmetric dimethylarginine (ADMA) ratio (an index of systemic NO metabolism), as well as reduced endothelial function. These patients also had increased plasma levels of ADMA, which is an endogenous inhibitor of NO synthase and of von Willebrand factor, a marker of endothelial injury. Baseline characteristics including exercise performance and coronary flow reserve were similar between enalapril and placebo groups. After an 8-week treatment period, exercise duration (p = 0.001) and coronary flow reserve (p = 0.001) significantly improved with enalapril but not with placebo. Enalapril treatment, but not placebo, reduced plasma von Willebrand factor (p = 0.03) and ADMA levels (p = 0.01) and increased NOx levels (p = 0.01) and the ratio of L-arginine to ADMA (p <0.01). In patients with syndrome X, the plasma NOx level was positively and ADMA level inversely correlated with coronary flow reserve before and after the treatment. In conclusion, long-term ACE inhibitor treatment with enalapril improved coronary microvascular function as well as myocardial ischemia in patients with syndrome X. This may be related to the improvement of endothelial NO bioavailability with the reduction of plasma ADMA levels.

Abnormal subendocardial perfusion in cardiac syndrome X detected by cardiovascular magnetic resonance imaging

BACKGROUND

In cardiac syndrome X (a syndrome characterized by typical angina, abnormal exercise-test results, and normal coronary arteries), conventional investigations have not found that chest pain is due to myocardial ischemia. Magnetic resonance techniques have higher resolution and therefore may be more sensitive.

METHODS

We performed myocardial-perfusion cardiovascular magnetic resonance imaging in 20 patients with syndrome X and 10 matched controls, both at rest and during an infusion of adenosine. Quantitative perfusion analysis was performed by using the normalized upslope of myocardial signal enhancement to derive the myocardial perfusion index and the myocardial-perfusion reserve index (defined as the ratio of the myocardial perfusion index during stress to the index at rest).

RESULTS

In the controls, the myocardial perfusion index increased in both myocardial layers with adenosine (in the subendocardium, from a mean [+/-SD] of 0.12+/-0.03 to 0.16+/-0.03 [P=0.02]; in the subepicardium, from 0.11+/-0.02 to 0.17+/-0.05 [P=0.002]); in patients with syndrome X, the myocardial perfusion index did not change significantly in the subendocardium (0.13+/-0.02 vs. 0.14+/-0.03, P=0.11; P=0.09 as compared with controls) but increased in the subepicardium (from 0.11+/-0.02 to 0.20+/-0.04, P<0.001; P=0.11 for the comparison with controls). Adenosine provoked chest pain in 95 percent of patients with syndrome X and 40 percent of controls (P<0.001).

CONCLUSIONS

In patients with syndrome X, cardiovascular magnetic resonance imaging demonstrates subendocardial hypoperfusion during the intravenous administration of adenosine, which is associated with intense chest pain. These data support the notion that the chest pain may have an ischemic cause.

Nutraceuticals: vitamins and other nutrients in coronary heart disease

Nutraceuticals and specifically vitamins, oils and herbs are increasingly being taken by patients. Some supplements may improve cardiovascular outcome, most are unproved, and some could potentially cause harm. Marine lipid supplementation needs to be considered in all patients who have manifest coronary heart disease. For most supplements more data are needed before confident recommendations can be made.

Circulating N-terminal brain natriuretic peptide precursor and endothelin levels in patients with syndrome X and left bundle branch block with preserved systolic function

BACKGROUND

Deterioration of left ventricular function during follow-up was reported in some patients with syndrome X and concomitant left bundle branch block. The patients with syndrome X and left bundle branch block has been frequently presented with elevated Endothelin-1 (ET-1) level while brain natriuretic peptide (BNP) (a sensitive marker of left ventricular dysfunction) has not been measured in patients with syndrome X.

METHODS

The purpose of the present study was to assess left ventricular diastolic function, levels of N-terminal Brain Natriuretic Peptide (NT-proBNP) precursor and biochemical parameters of endothelial function in patients with syndrome X complicated by left bundle branch block but preserved left ventricular systolic function (group A, n=8). The echocardiographic and neurohormonal measures in these patients were compared to those in patients with syndrome X without left bundle branch block (group B, n=13), and controls (group C, n=15).

RESULTS

At rest and after exercise the serum concentration of NT-proBNP was significantly higher in group A than in the controls (at rest: 232+/-96 vs. 133+/-23 fmol/ml, P=0.03; after exercise: 313+/-96 vs. 180+/-33 fmol/ml, P=0.02). The highest concentration of endothelin-1 was also found in group A, being significantly higher than in the controls (6.81 vs. 4.52 pg/ml, P<0.05). Mitral flow abnormalities were detected in left bundle branch block patients. Accordingly, the lowest E/A ratio was in group A and it differed significantly from that in group C (0.85 vs. 1.1, P<0.05). E/A ratio inversely correlated with plasma NT-proBNP concentration in patients with left bundle branch block (r=-0.48, P=0.02).

CONCLUSIONS

Elevated NT-proBNP and endothelin-1 plasma concentrations were demonstrated in patients with syndrome X complicated by left bundle branch block even when left ventricular systolic function was still preserved. In this subgroup the magnitude of left ventricular diastolic dysfunction correlated with the increase of BNP level which reflects neurohormonal activation.

Dietary modulation of endothelial function: implications for cardiovascular disease

The vascular endothelium is the primary site of dysfunction in many diseases, particularly cardiovascular disease. A variety of risk factors, including smoking, hypercholesterolemia, hyperhomocysteinemia, hypertension, and diabetes mellitus, adversely affect endothelial function. Emerging evidence suggests an important role of dietary factors in modulating endothelial function. In particular, n-3 fatty acids, antioxidant vitamins (especially vitamins E and C), folic acid, and L-arginine appear to have beneficial effects on vascular endothelial function, either by decreasing endothelial activation or by improving endothelium-dependent vasodilation in patients at high risk of cardiovascular disease as well as in healthy subjects. These effects may serve as one potential mechanism through which these nutrients reduce the risk of cardiovascular disease, as observed in epidemiologic studies and several clinical trials. This article reviews clinical and experimental evidence regarding the role of these nutrients in modulating endothelial function and their potential to prevent cardiovascular disease.