Assessment and treatment of endothelial dysfunction in humans

Endothelial function in conduit and resistance arteries in men with coronary disease

The aims of this study were to determine whether non-invasive measurement of endothelial function in conduit arteries reflects that of subcutaneous resistance arteries measured in vitro and to examine whether there is an endothelial dysfunction also in resistance arteries in patients with a previous myocardial infarction. The brachial artery diameter responses to a hyperemic flow stimulus and an in vitro method, pressure myography, to directly evaluate flow-mediated responses in arteries obtained from biopsies of subcutaneous fat were measured in 25 patients with a previous myocardial infarction and in 8 aged matched healthy subjects. Flow-mediated dilatation of the brachial artery was more pronounced in the healthy group compared with the group with coronary disease, 5.1 +/- 2.5% and 2.6 +/- 2.1%, respectively (p < 0.05). The flow-mediated dilatation in subcutaneous arteries from CHD patients was significantly reduced compared to control subjects (e.g. percent change from initial preconstriction at maximum flow rate of 204 microl/min: 42 +/- 7% CHD (n = 25) versus 84 +/- 24% control (n = 8), ANOVA, p = 0.03). There was a significant correlation between flow-mediated dilatation of the brachial artery and maximum flow-mediated dilatation at microvascular level, (p < 0.01). In conclusion this study demonstrates endothelial dysfunction in both conduit and resistance circulation in patients after myocardial infarction compared to an aged-matched healthy control group. Furthermore, a significant and independent relationship between endothelial function by means of flow-mediated dilatation in large conduit arteries and resistance arteries was observed.

Relationship Between Carotid Artery Intima-Media Thickness and Brachial Artery Flow-Mediated Dilation in Middle-Aged Healthy Men

OBJECTIVES

We aimed to determine the relationship between carotid intima-media thickness (IMT) and brachial artery flow-mediated dilation (FMD) in healthy middle-age men.

BACKGROUND

Carotid IMT and brachial artery FMD are frequently used as surrogate measures of subclinical atherosclerosis. Whereas carotid IMT identifies early structural abnormalities, brachial artery FMD, considered a bioassay of endothelial function, measures functional vascular integrity. The relationship between carotid IMT and brachial artery FMD has not been well studied.

METHODS

We measured traditional risk factors, carotid IMT, and brachial artery FMD in 1,578 middle-aged men without known cardiovascular disease and analyzed the relationship between carotid IMT and brachial FMD.

RESULTS

Carotid IMT correlated with age, systolic blood pressure, body mass index, fasting glucose, total and low-density lipoprotein (LDL) cholesterol, and with the overall Framingham risk score (p < 0.001 for all), whereas impaired brachial artery FMD correlated with systolic and diastolic blood pressure (p < 0.01). No relationship was observed between carotid IMT and brachial artery FMD for the entire cohort (r = -0.006, p = 0.82) and in subgroups defined by traditional risk factors or by quintiles of carotid IMT and brachial FMD.

CONCLUSIONS

In middle-aged healthy men, there is no significant correlation between carotid IMT and brachial artery FMD. This finding suggests that these are unique, independent surrogates that measure different aspects and stages of early atherosclerosis. Further studies are needed to define their role in clinical research and in cardiovascular risk assessment.

Dose-dependent vasodilatory effects of acetylcholine and local warming on skin microcirculation

The assessment of the skin microvasculature response to iontophoretically applied acetylcholine (ACh) and local warming makes it possible to explore noninvasively in humans the functional integrity of endothelium. The present study aimed to examine whether these two stimuli of nitric oxide (NO) release have a dose-dependent vasorelaxant activity. For this purpose we assessed in healthy subjects using a laser-Doppler imaging system the increase in forearm blood flow following transdermal application of increasing amounts of ACh [with an iontophoretic current of either 0.28 mC/cm2 (n = 18), 0.56 mC/cm2 (n = 14), 1.4 mC/cm2 (n = 26), 7 mC/cm2 (n = 14), 28 mC/cm2 (n = 14), or 48 mC/cm2 (n = 6)] or graded warming of the skin [to either 37 degrees C (n = 8), 39 degrees C (n = 4) or 41 degrees C (n = 12)]. The maximal vasodilation was significantly smaller with the lowest dose than with the higher doses of ACh, and a plateau was reached with the 1.4 mC/cm2 dose. The skin blood flow responses to ACh were not dependent on the pulsed or continuous pattern of iontophoretic administration. The hyperemia induced by the local heating to 41 degrees C was significantly greater than that observed with the other temperatures. When measured in the same subjects, the magnitude of the maximal ACh-mediated skin blood flow increase was significantly smaller than the vasodilation associated with the warming to 41 degrees C. In summary, transdermally applied ACh and local heating of the skin induce a dose-dependent vasorelaxation. These techniques represent a unique means to investigate noninvasively the functional vasodilatory capacity of the skin microvasculature.

Cardiovascular risk factors and endothelial dysfunction

Endothelial dysfunction is a feature of atherosclerosis and is associated with CHD (coronary heart disease) risk factors. This study aimed to determine the relationship between the degree of endothelial dysfunction and calculated cardiovascular risk. Endothelial function, as determined by the ACh/NP (acetycholine/sodium nitroprusside response) ratio on brachial plethysmography, was compared with cardiovascular risk as calculated from the Framingham, PROCAM (Prospective Cardiovascular Munster) and MRFIT (Multiple Risk Factor Intervention Trial) algorithms in 246 (187 male) patients, including 44 (22%) with established CHD. Endothelial dysfunction correlated with the total number of risk factors (r2=0.22; P=0.002) and was related to LDL (low-density lipoprotein)-cholesterol in men and triacylglycerols (triglycerides) in women. The ACh/NP ratio correlated with the occurrence of diabetes, CHD and the LDL-cholesterol concentration (r2=0.58; P<0.001). Endothelial dysfunction was associated with presence of CHD on receiver-operating characteristic plot analysis (area=0.706+/-0.04; P=0.001). There was no correlation between ACh/NP ratio and CHD risk calculated with the Framingham algorithm in men, although both ACh and NP response correlated separately with risk in women. The endothelial ACh/NP ratio correlated with absolute risk in the PROCAM algorithm (r2=0.41; P<0.005). Intermediate results were obtained with MRFIT. Individual risk factors make different contributions to endothelial dysfunction compared with their role in risk calculators. The stronger relationship of endothelial dysfunction with PROCAM risk reflects the contribution of male sex, LDL-cholesterol and triacylglycerols to risk calculated by this algorithm.

Endothelial cell dysfunction and the vascular complications associated with type 2 diabetes: assessing the health of the endothelium

Diabetes-associated vascular complications are collectively the major clinical problems facing patients with diabetes and lead to the considerably higher mortality rate than that of the general population. People with diabetes have a much higher incidence of coronary artery disease as well as peripheral vascular diseases in part because of accelerated atherogenesis. Despite the introduction of new therapies, it has not been possible to effectively reduce the high cardiovascular morbidity and mortality associated with diabetes. Of additional concern is the recognition by the World Health Organization that we are facing a global epidemic of type 2 diabetes. Endothelial dysfunction is an early indicator of cardiovascular disease, including that seen in type 2 diabetes. A healthy endothelium, as defined in terms of the vasodilator/blood flow response to an endothelium-dependent vasodilator, is an important indicator of cardiovascular health and, therefore, a goal for corrective interventions. In this review we explore the cellular basis for endothelial dysfunction in an attempt to identify appropriate new targets and strategies for the treatment of diabetes. In addition, we consider the question of biomarkers for vascular disease and evaluate their usefulness for the early detection of and their role as contributors to vascular dysfunction.

The pathogenesis of atherosclerosis

Worldwide, more people die of the complications of atherosclerosis than of any other cause. It is not surprising, therefore, that enormous resources have been devoted to studying the pathogenesis of this condition. This article attempts to summarize present knowledge on the events that take place within the arterial wall during atherogenesis. Classical risk factors are not dealt with as they are the subjects of other parts of this book. First, we deal with the role of endothelial dysfunction and infection in initiating the atherosclerotic lesion. Then we describe the development of the lesion itself, with particular emphasis on the cell types involved and the interactions between them. The next section of the chapter deals with the events leading to thrombotic occlusion of the atherosclerotic vessel, the cause of heart attack and stroke. Finally, we describe the advantages--and limitations--of current animal models as they contribute to our understanding of atherosclerosis and its complications.

Endothelial dysfunction and diabetes

Endothelial function and dysfunction During the past two decades, there has been an increasing recognition of the importance of normal endothelial function in the maintenance of vascular homeostasis and vascular health. Abnormalities in the function of endothelium have been recognized in a number of conditions. One of the most important abnormalities of endothelial dysfunction appears to be changes in the bioavailability of nitric oxide. It now appears clear that abnormalities in endothelial dysfunction are associated with abnormalities in the production of nitric oxide and/or abnormalities in the rate of its degradation. Either way, loss of the functional availability of nitric oxide appears to be an important characteristic of endothelial dysfunction. Endothetial dysfunction and diabetes lmpaired endothcliul-dependent vasodilatation has been described in patients with type 1 and type 2 diabetes, and the degree of impairment may correlate with glycemic control Hyperglycemia itself appears to affect multiple mechanisms that increase atherosclerosis. Hyperglycemia enhances oxidation, thrombosis, inflammation, matrix production, and the formation of advanced glycation end-products and other metabolites that can potentially damage the vasculature. Treatment of endothelial dysfunction A number of trials have demonstrated that therapy with lipid lowering agents (statins) as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. These agents have also been shown to improve prognosis in patients with a number of underlying cardiac diseases and risk factors for cardiac disease. Therefore, it seems that interventions that lead to improvement in endothelial function can be associated with improvements in cardiovascular outcome. The role of antioxidant therapy is controversial. No data have been published regarding the effects of hormonal replacement therapy on endothelial dysfunction in postmenopausal women with type 2 diabetes.

Noninvasive identification of patients with early coronary atherosclerosis by assessment of digital reactive hyperemia

OBJECTIVES

We investigated the value of reactive hyperemia peripheral arterial tonometry (RH-PAT) as a noninvasive tool to identify individuals with coronary microvascular endothelial dysfunction.

BACKGROUND

Coronary endothelial dysfunction, a systemic disorder, represents an early stage of atherosclerosis; RH-PAT is a technique to assess peripheral microvascular endothelial function.

METHODS

Using RH-PAT, digital pulse volume changes during reactive hyperemia were assessed in 94 patients without obstructive coronary artery disease and either normal (n = 39) or abnormal (n = 55) coronary microvascular endothelial function; RH-PAT index, a measure of reactive hyperemia, was calculated as the ratio of the digital pulse volume during reactive hyperemia divided by that at baseline.

RESULTS

Average RH-PAT index was lower in patients with coronary endothelial dysfunction compared with those with normal coronary endothelial function (1.27 +/- 0.05 vs. 1.78 +/- 0.08: p < 0.001). An RH-PAT index <1.35 was found to have a sensitivity of 80% and a specificity of 85% to identify patients with coronary endothelial dysfunction.

CONCLUSIONS

Digital hyperemic response, as measured by RH-PAT, is attenuated in patients with coronary microvascular endothelial dysfunction, suggesting a role for RH-PAT as a noninvasive test to identify patients with this disorder.

Measurement of coronary vasomotor function: getting to the heart of the matter in cardiovascular research

Measurement of endothelial function in patients has emerged as a useful tool for cardiovascular research. Although no gold standard for the measurement of endothelial function exists, the measurement of flow-mediated dilation in the brachial artery, assessed with Doppler ultrasonography, is the most studied method. However, the assumption that endothelial dysfunction detected in brachial arteries is a manifestation of systemic endothelial dysfunction including the coronary circulation may not be entirely valid. Brachial and myocardial circulations differ in terms of the microvascular architecture, the pattern of blood flow and vascular resistance (e.g. shunt vessels occur in the hand but not in the myocardium), their metabolic regulation, type of receptors that contribute to humoral regulation and the pathways that are activated to induce hyperaemia. In this context, measuring coronary vasomotor function may be more useful than brachial artery measures to predict and assess potential myocardial damage related to limited vascular responsiveness. This review aims to provide an overview of the basic concept of coronary flow reserve and its different modalities of measurement, as well as its utility in cardiovascular research.

Arginine and endothelial and vascular health

The vascular endothelium is a crucial regulator of vascular function and homeostasis. Nitric oxide (NO) is an important paracrine substance released by the endothelium to regulate vasomotor tone. Risk factors for atherosclerosis, as well as atherosclerosis per se, are associated with endothelial dysfunction and decreased bioavailablilty of NO. Indeed, endothelial dysfunction is integral to the pathogenesis of atherosclerosis and other cardiovascular diseases. Moreover, endothelial dysfunction relates to an increased risk of adverse cardiovascular outcomes. L-Arginine is an essential amino acid required by the constitutive enzyme, endothelial NO oxide synthase (eNOS), to produce NO. Administration of L-arginine improves endothelial function in animal models and in humans with hypercholesterolemia and with atherosclerosis. Clinical trials to date support potential clinical applications of L-arginine in the treatment of coronary artery disease and peripheral arterial disease, as well as in the prevention of in-stent restenosis. The mechanism of benefit of L-arginine on endothelial function is unclear, because intracellular concentrations of L-arginine far exceed that required by eNOS. One potential explanation of this "arginine paradox" is that L-arginine restores endothelial function in atherosclerotic patients, in whom there are elevated levels of asymmetric dimethylarginine, an endogenous inhibitor of eNOS. Given the promising findings of early studies of L-arginine as a potential therapy for cardiovascular disorders, large-scale clinical trials are warranted.

Brachial artery reactivity in asymptomatic patients with type 2 diabetes mellitus and microalbuminuria (from the Detection of Ischemia in Asymptomatic Diabetics-brachial artery reactivity study)

Microalbuminuria is a novel atherosclerotic risk factor in patients with type 2 diabetes mellitus (DM) and predicts future cardiovascular events. Endothelial dysfunction and systemic inflammation have been proposed as common links between microalbuminuria and cardiovascular disease. However, no study has assessed the relation between microalbuminuria and vascular dysfunction as measured by brachial artery reactivity (BAR) in DM. We evaluated 143 patients (85 men; mean age 60.0 +/- 6.7 years) with DM (mean duration 8.2 +/- 7.4 years) enrolled in the Detection of Ischemia in Asymptomatic Diabetics study. Subjects were categorized as those with microalbuminuria (ratio of urinary albumin to creatinine 30 to 299 microg/mg creatinine, n = 28) and those with normoalbuminuria (ratio of urinary albumin to creatinine 0 to 29.9 microg/mg creatinine, n = 115). High-resolution ultrasound BAR testing was used to measure endothelium-dependent and endothelium-independent vasodilations. C-reactive protein was measured as a marker of systemic inflammation. Patients with microalbuminuria and normoalbuminuria had similar baseline characteristics, with the exception that those with microalbuminuria had a longer duration of DM (p = 0.03). Endothelium-dependent vasodilation at 1 minute (p = 0.01) and endothelium-independent vasodilation at 3 minutes (p = 0.007) were significantly less in patients with microalbuminuria. In addition, 96% of patients with microalbuminuria and 76% of those with normoalbuminuria had impaired endothelium-dependent vasodilation (<8%, p = 0.01). Microalbuminuria was an independent predictor of endothelium-dependent vasodilation in the entire cohort (p = 0.045) and after excluding patients on hormone replacement therapy (p = 0.01). Levels of C-reactive protein were significantly higher in patients with microalbuminuria than in those with normoalbuminuria (p = 0.02). We conclude that in DM the presence of microalbuminuria is associated with impaired endothelium-dependent and endothelium-independent vasodilations of the brachial artery and a higher degree of systemic inflammation. In addition, microalbuminuria is an independent predictor of endothelial dysfunction in asymptomatic patients with DM, especially in the absence of hormone replacement therapy.

Non-invasive assessment of microvascular endothelial function by laser Doppler flowmetry in patients with essential hypertension

The aim of the study was to investigate the endothelium-dependent vasodilation in the forearm skin using two non-invasive laser Doppler applications in patients with essential hypertension (EHT) and in normotensive (NT) control subjects. The effect of two consecutive doses of acetylcholine (ACh) and that of sodium nitroprusside (SNP) on the skin microcirculation, and thereafter the postocclusive reactive hyperaemic (PORH) response, were measured in 25 patients with essential hypertension and also in 25 control normotensive healthy subjects. The plasma von Willebrand factor (vWF) level and activity were also determined. The average peakflow in PORH was 287 +/- 31.5% (x +/- S.E.M.) in EHT and 410.28 +/- 35.08% in NT (P < 0.01). The average hyperaemic response to the two doses of ACh-iontophoresis was 206.36 +/- 33.97 and 568.76 +/- 54.23% in EHT and 444.24 +/- 80.28 and 804.12 +/- 93.07% in NT (P < 0.01, 0.05). The response to SNP was similar in the two groups. The vWF levels were 122.5 +/- 13.2 and 89.6 +/- 8.1% (P = 0.0595, NS), the activities were 80.8 +/- 5.5 and 68.9 +/- 6.1% (P = 0.157, NS) in EHT and in NT, respectively. These results demonstrate that essential hypertension is associated with endothelial dysfunction in the skin microcirculation of the forearm.

Amlodipine and atorvastatin in atherosclerosis: a review of the potential of combination therapy

Hypertension and hyperlipidaemia are major risk factors for the development of atherosclerosis. Calcium channel blockers (CCBs) have been used for decades and have established antihypertensive effects. Statins have been extensively used because of their potent lipid lowering properties. Amongst other factors, inflammation and oxidation are involved in enhanced progression of atherosclerosis and new lesion development. Therefore, research has been initiated focusing on the antioxidant and anti-inflammatory properties of CCBs and statins, beyond their primary effect, in order to evaluate the possible additive effects of combined treatment of CCBs with statins as antiatherosclerotic therapy. Clinical studies (e.g., the International Nifedipine Trial on Antiatherosclerotic Therapy [INTACT]) have demonstrated that the antiatherosclerotic action of CCBs is limited to the attenuation of the first stage of atherosclerogenesis (fatty streak formation or new lesion growth). The lesions that pre-existed at the start of CCB therapy did not demonstrate progression or regression on angiography. However, because the mechanisms of action of lipid-lowering drugs and CCBs, and their role in preventing the progression of atherosclerosis differ, it is conceivable to conclude that these two classes may have an additive or synergic effect, not only on new lesion formation but also on inhibiting the progression of established coronary atherosclerosis. Indeed, this combined effect of lipid-lowering therapy and CCBs on human coronary atherosclerosis has been reported in the Regression Growth Evaluation Statin Study (REGRESS) trial. This beneficial effect of combining CCBs with statins has now been replicated in transgenic atherosclerotic mice, where the combination of amlodipine and atorvastatin produced an additional 60% reduction of atherosclerosis compared with that observed with the statin alone. Serum markers of atherosclerosis and vascular integrity also improved most in the combination group. Synergistic effects of the combination of atorvastatin and amlodipine on acute nitric oxide release/endothelial function, and additive effects of the combination of amlodipine and atorvastatin in the improvement of arterial compliance in hypertensive hyperlipidaemic patients has been demonstrated. Collectively, these studies support the clinical antiatherosclerotic advantages of combination of CCBs and statins and in particular, of atorvastatin with amlodipine beyond their established antihyperlipidaemic and antihypertensive modes of action.

Successful treatment of symptomatic coronary endothelial dysfunction with enhanced external counterpulsation

Enhanced external counterpulsation (EECP) is a valuable therapeutic option for patients with coronary artery disease and refractory angina. Although the exact mechanisms by which this technique exerts favorable effects remain unclear, improvement in endothelial function is considered a potential mechanism contributing to the clinical benefit associated with EECP. We describe a young woman with severely symptomatic coronary endothelial dysfunction in the absence of obstructive coronary artery disease who experienced a dramatic and sustained reduction in symptoms in response to a standard 35-hour course of EECP.

Sildenafil does not improve nitric oxide-mediated endothelium-dependent vascular responses in smokers

AIMS

To examine the hypothesis that sildenafil, a phosphodiesterase type 5 inhibitor that inhibits cGMP breakdown, could enhance nitric oxide-mediated vasodilation and reverse endothelial dysfunction in chronic smokers.

METHODS

Flow-mediated dilation of the brachial artery and forearm postischemic reactive hyperemia (both nitric oxide-mediated responses) were measured before and after sildenafil 50 mg and placebo in a double-blind, randomized, crossover study in 9 men who were chronic smokers (21 +/- 3 pack years).

RESULTS

There was no significant change in flow-mediated dilation after either sildenafil (0.18%, 95%CI -1.7-2%) or placebo (0.24%, 95%CI -2.8-3.3%) (P = 0.88 and 0.8, respectively). Sildenafil had no significant effect on resting forearm blood flow or postischemic reactive hyperemia (P = 0.39 and 0.7, respectively). Resting heart rate and blood pressure were unaffected by sildenafil.

CONCLUSIONS

Acute sildenafil administration did not improve endothelial function in chronic smoking men.

Noninvasive tests for arterial structure, function, and compliance: Do they identify risk or diagnose disease?

BACKGROUND

Brachial artery reactivity (BAR), carotid intima-media thickness (IMT), and applanation tonometry for evaluation of total arterial compliance may provide information about preclinical vascular disease. We sought to determine whether these tests could be used to identify patients with coronary artery disease (CAD) without being influenced by their ability to identify those at risk for CAD developing.

METHODS

We studied 100 patients and compared 3 groups: 35 patients with known CAD; 34 patients with symptoms and risk factors but no CAD identified by stress echocardiography (risk group); and 31 control subjects. BAR and IMT were measured using standard methods, and total arterial compliance was calculated by the pulse-pressure method from simultaneous radial applanation tonometry and pulsed wave Doppler of the left ventricular outflow. Ischemia was identified as a new or worsening wall-motion abnormality induced by stress.

RESULTS

In a comparison between the control subjects and patients either at risk for developing CAD or with CAD, the predictors of risk for CAD were: age (P =.01); smoking history (P =.002); hypercholesterolemia (P =.002); and hypertension (P =.004) (model R = 0.82; P =.0001). The independent predictors of CAD were: IMT (P =.001); BAR (P =.04); sex (P =.005); and hypertension (P =.005) (model R = 0.80; P =.0001).

CONCLUSION

IMT, BAR, and traditional cardiovascular risk factors appear to identify patients at risk for CAD developing. However, only IMT was significantly different between patients at risk for developing CAD and those with overt CAD.

The effect of physical activity on endothelial function in man

Endothelial dysfunction occurs early in the atherosclerosis in response to elevated atherosclerotic risk factors, and endothelial dysfunction itself may exacerbate the atherosclerotic process. Treatments that reduce atherosclerotic risk factors also generally improve endothelial function. The present review seeks to summarize the effect of exercise training on endothelial function in human subjects. Cross-sectional studies comparing healthy physically active and inactive subjects as well as longitudinal exercise training studies of healthy individuals show little effect of exercise training on endothelial function. In contrast, both cross-section and longitudinal studies document improved endothelial function with exercise training in subjects with abnormal baseline endothelial function, including the elderly and patients with heart failure or coronary artery disease. Improvements in endothelial function with physical activity may explain some of the benefits of exercise in subjects with, or at risk for, vascular disease.

Aging attenuates vascular and metabolic plasticity but does not limit improvement in muscle VO(2) max

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 +/- 1 yr) and six sedentary old (67 +/- 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WR(max)) (young = 27 +/- 3, old = 24 +/- 4 W) and similar maximal quadriceps O(2) consumption (muscle Vo(2 max)) (young = 0.52 +/- 0.03, old = 0.42 +/- 0.05 l/min), which increased equally in both groups posttraining (WR(max), young = 38 +/- 1, old = 36 +/- 4 W, Muscle Vo(2 max), young = 0.71 +/- 0.1, old = 0.63 +/- 0.1 l/min). Before training, muscle blood flow was approximately 500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow approximately 700 ml/min, elevated arteriovenous O(2) difference approximately 1.3 ml/dl, and increased leg vascular resistance approximately 17 mmHg x ml(-1) x min(-1), whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WR(max) and muscle Vo(2 max), despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old.

Endothelial nitric oxide synthase gene polymorphisms in giant cell arteritis

OBJECTIVE

To examine potential associations of the Glu/Asp(298) polymorphism in exon 7 and the 4a/b polymorphism in intron 4 of the endothelial nitric oxide synthase (eNOS) gene with susceptibility to and clinical expression of giant cell arteritis (GCA), particularly in patients with versus those without ischemic complications.

METHODS

Ninety-one consecutive patients with biopsy-proven GCA, who were residents of Reggio Emilia, Italy, and 133 population-based controls from the same geographic area were genotyped by polymerase chain reaction and allele-specific oligonucleotide techniques for eNOS polymorphisms in exon 7 and intron 4. The patients were separated into 2 subgroups according to the presence or absence of ischemic complications (visual loss and/or jaw claudication and/or aortic arch syndrome).

RESULTS

The distribution of the Glu/Asp(298) genotype differed significantly between GCA patients and controls (corrected P [P(corr)] = 0.003). Carriers of the Asp(298) allele (Asp/Asp or Glu/Asp) were significantly more frequent among the GCA patients than among the controls (P(corr) = 0.0002, odds ratio 3.3, 95% confidence interval 1.7-6.3). The distribution of the 4a/b genotype was similar in GCA patients and controls. No significant associations were found when GCA patients with and without ischemic complications were compared.

CONCLUSION

Our findings show that the Glu/Asp(298) polymorphism of the eNOS gene is associated with GCA susceptibility.

Evaluation of a novel sutureless anastomotic connector: From endothelial function to mid-term clinical and angiographic follow-up

OBJECTIVES

We evaluated the effect of the St Jude Medical sutureless anastomotic connector on endothelium-dependent and -independent saphenous vein graft relaxation, as well as on clinical outcomes and graft patency in patients.

METHODS

Human saphenous vein grafts were assigned to control or connector groups (loaded for 1 or 5 minutes; n = 18). Isometric dose-response curves to endothelium-dependent and -independent (sodium nitroprusside) vasodilators were constructed in saphenous vein grafts precontracted with phenylephrine. Thrombin-mediated vasorelaxation, an early determinant of saphenous vein graft failure, was also evaluated. Percent maximum relaxation was compared between groups. Patients in whom the St Jude Medical connector was employed underwent clinical follow-up, stress tests, and angiography 6 to 12 months postoperatively.

RESULTS

A23187-induced endothelium-mediated relaxation, sodium nitroprusside-induced endothelium-independent relaxation, and thrombin-mediated vasorelaxation did not differ between control and connector saphenous vein grafts at either time point studied. Twenty-seven patients received St Jude Medical connectors. There was no hospital mortality; patients were followed for 679 +/- 241 days. There was 1 late death; the connector saphenous vein graft was patent at postmortem. All connector saphenous vein grafts were patent at follow-up angiography. Four grafts had stenoses (30%-60%), without symptoms or requirement for intervention. All hand-sewn saphenous vein grafts were also patent.

CONCLUSIONS

The St Jude Medical connector does not impair endothelium-dependent vasorelaxation. In patients, patency of the connector saphenous vein grafts 6 to 12 months postoperatively was 100% but 22% of grafts had non-flow-limiting stenoses at or near the connector. Further long-term studies are required to confirm the safety of the St Jude Medical connector with regards to endothelial function and restenosis.

Endothelial function in obstructive sleep apnea and response to treatment

Impaired endothelium-dependent vascular relaxation is a prognostic marker of atherosclerosis and cardiovascular disease. We evaluated endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin (NTG)-induced dilation of the brachial artery with Doppler ultrasound in 28 men with obstructive sleep apnea (OSA) and 12 men without OSA. Subjects with OSA (apnea-hypopnea index; mean +/- SD, 46.0 +/- 14.5) had lower FMD compared with subjects without OSA (5.3 +/- 1.7% vs. 8.3 +/- 1.0%, p < 0.001), and major determinants of FMD were the apnea-hypopnea index and age. There was no significant difference in NTG-induced dilation. Subjects with OSA were randomized to nasal continuous positive airway pressure (nCPAP) or observation for 4 weeks. Subjects on nCPAP had significant increase in FMD, whereas those on observation had no change (4.4% vs. -0.8%, difference of 5.2%, p < 0.001). Neither group showed significant change in NTG-induced vasodilation. Eight subjects who used nCPAP for over 3 months were reassessed on withdrawing treatment for 1 week. On nCPAP withdrawal, FMD became lower than during treatment (p = 0.02) and were similar to baseline values. Our findings demonstrated that men with moderate/severe OSA have endothelial dysfunction and treatment with nCPAP could reverse the dysfunction; the effect, however, was dependent on ongoing use.

Impaired endothelium-dependent vasodilatation in subclinical hypothyroidism: beneficial effect of levothyroxine therapy

Subclinical hypothyroidism (sHT) is associated with enhanced cardiovascular risk. To test the hypothesis that patients with sHT are characterized by endothelial dysfunction and impaired nitric oxide (NO) availability, in 14 patients [serum cholesterol, 218 +/- 41 mg/dl (5.6 +/- 0.9 mM)] and 28 euthyroid subjects, subdivided into groups A and B [serum cholesterol, 170 +/- 19 mg/dl (4.4 +/- 0.5 mM) and 217 +/- 21 mg/dl (5.6 +/- 0.5 mM), respectively], we studied the forearm blood flow (strain-gauge plethysmography) response to intrabrachial acetylcholine, an endothelium-dependent vasodilator, at baseline and during infusion of N(G)-monomethyl-L-arginine (L-NMMA), a NO synthase inhibitor. Response to sodium nitroprusside and minimal forearm vascular resistances were also evaluated. In sHT patients, vasodilation to acetylcholine was reduced, compared with group B (+358 +/- 29% vs. +503 +/- 19%, P = 0.0003) and group A (663 +/- 65%, P = 0.02 vs. group B and P = 0.0002 vs. sHT). L-NMMA blunted the vasodilation to acetylcholine in groups A and B (49.1 +/- 6.3% and 42.7 +/- 5.5% maximal forearm blood flow reduction, respectively, P < 0.0001 vs. acetylcholine), whereas it was ineffective in sHT patients (12.8 +/- 2.5%). Response to sodium nitroprusside and minimal vascular resistances were similar. In sHT (n = 9) patients, 6 months of euthyroidism by levothyroxine replacement increased acetylcholine-vasodilation and restored L-NMMA inhibition. Patients with sHT are characterized by endothelial dysfunction resulting from a reduction in NO availability, an alteration partially independent of dyslipidemia and reversed by levothyroxine supplementation.

Coronary endothelial dysfunction is associated with an increased risk of cerebrovascular events

BACKGROUND

Stroke, mainly attributable to atherothrombotic disease, represents a leading cause of disability and death in the Western world. Endothelial dysfunction, which is considered a key factor in atherogenesis, is associated with an increased risk of cardiovascular events. However, the magnitude of the association between coronary endothelial dysfunction (CED) and cerebrovascular events is unknown. This study was performed to investigate the association between CED and cerebrovascular events.

METHODS AND RESULTS

We studied 503 patients without obstructive coronary artery disease (CAD) who underwent coronary endothelial function testing by intracoronary acetylcholine infusion. Patients were divided according to the presence (n=305) or absence (n=198) of CED, and medical records were examined for the occurrence of ischemic or hemorrhagic stroke or transient ischemic attack either before (prevalent) or after (incident) coronary endothelial function testing. Among the study population, a total of 25 cerebrovascular events were documented, 22 in patients with CED (15 prevalent) and 3 in patients without (all prevalent) (P=0.008). Multivariable logistic regression, which included traditional cerebrovascular disease-related risk factors, identified the presence of CED as the single strongest factor associated with cerebrovascular events (OR, 4.32; 95% CI, 1.26 to 14.83). Kaplan-Meier analysis indicated that patients with CED had a significantly higher cumulative cerebrovascular event rate than those without (P=0.04).

CONCLUSIONS

Presence of CED in patients without obstructive CAD is independently associated with an increased risk of cerebrovascular events. Thus, detection of this early stage of atherosclerosis may provide important information to identify patients who benefit from aggressive preventive strategies.

Effect of angiotensin-converting enzyme inhibition on endothelial function and insulin sensitivity in hypertensive patients

INTRODUCTION

Evidence suggests an association between insulin resistance, hypertension and impaired endothelial function. Studies have shown that insulin resistance precedes the development of hypertension. By improving insulin sensitivity, it may be possible to improve hypertension and the subsequent damage to vessel walls. Some data indicates beneficial effects of angiotensin-converting enzyme (ACE) inhibitors on insulin sensitivity and endothelial function. We aimed to investigate these effects of ACE inhibition in the same group of patients with essential hypertension.

MATERIALS AND METHODS

Nine non-smoking, untreated hypertensive patients (38.3+9 years, 4/5 male/female) and 12 age-matched healthy subjects (35.2+6.7 years, 5/7 male/female) were included in the study. Hypertensive patients were given enalapril maleate (5 40 mg/day) for six months. The following parameters were studied at baseline and at the end of treatment period. Whole body insulin sensitivity was measured by a formula derived from an oral glucose tolerance test and named as the insulin sensitivity index (ISI). Insulin was measured by chemiluminescence and glucose by a glucose oxidase method. Endothelial function was evaluated as flow-mediated dilatation (FMD) of the brachial artery by ultrasonography and expressed as a percentage change relative to baseline diameter. Endothelial- independent vasodilatation was measured after sublingual nitroglycerine.

RESULTS

FMD was impaired in the hypertensive group compared with healthy subjects (7.3+3.1% vs. 15.3+4.8%, p<0.0005), and ISI values were 1.18+0.6 vs. 4.4+0.9 (p<0.0001) respectively. Both insulin sensitivity and FMD improved after the treatment period compared with baseline values, FMD increased from 7.3+3.1% to 16.0+2.9% (p<0.0005) and ISI from 1.18+0.6 to 4.2+1.0 (p<0.0001). FMD and ISI showed a significant positive correlation (r=0.67, p<0.001) in the hypertensive group.

CONCLUSIONS

Patients with essential hypertension have impaired endothelial function and decreased whole body insulin sensitivity compared with healthy subjects. Treatment for six months with enalapril maleate seems to improve both FMD and ISI. This study confirms the beneficial effects of ACE inhibition on both endothelial function and insulin sensitivity tested in the same group of essential hypertensive patients. The mechanism of these favourable effects of ACE inhibition needs to be clarified.

Detection of endothelial dysfunction with brachial artery ultrasound scanning

The role of the endothelium in human disease recently has become the focus of intense scientific investigation. Impaired endothelial function is associated with a number of disease states, including cardiovascular disease (CVD) and its major risk factors. Endothelial dysfunction precedes overt vascular disease by years and may itself be a potentially modifiable CVD risk factor. Although no gold standard for the measurement of endothelial function exists, the measurement of flow-mediated dilation (FMD) in the brachial artery, assessed with Doppler ultrasonography, is the most studied method and shows the most promise for clinical application. It is a well-tolerated, noninvasive, and low-risk procedure. Brachial artery FMD after transient vascular occlusion may serve as an index of nitric oxide bioavailability, and its impairment correlates with coronary arterial abnormalities. These factors, with the wide availability of vascular ultrasound scanning in clinical practice, make brachial artery FMD an attractive screening tool for endothelial dysfunction. Present limitations of this procedure include the lack of a consensus definition of normal FMD and the variability among centers in both procedural technique and image analysis. However, these limitations are likely to be overcome with increasing experience and advances in technology, and with further refinements, the measurement of brachial artery FMD will likely become the clinical technique of choice for the evaluation of endothelial disease.

[Endothelial dysfunction and intima-media thickness in relation to cardiovascular risk factors in patients without clinical manifestations of atherosclerosis]

INTRODUCTION

Endothelial dysfunction and increased intima-media thickness are early findings in the development of atherosclerosis that can be assessed non-invasively by echography. The aim of this study was to investigate endothelial function and intima-media thickness, and the relation between these processes and cardiovascular risk factors in patients without clinical atherosclerosis.

PATIENTS AND METHOD

Fifty-two subjects were studied, 39 with one or more cardiovascular risk factors and 13 with none. Vascular echography was performed to analyze endothelium-dependent vascular dilatation in the brachial artery and intima-media thickness in the common carotid artery.

RESULTS

Compared to patients without risk factors, patients with cardiovascular risk factors more frequently had impaired vascular dilatation after ischemia, 11.98 4.61% vs 2.77 2.57%, (P<.0.001; mean difference = 9.21%, 95% CI of the difference 6.33-12.07%) and a greater intima-media thickness, 0.085 0.024% vs 0.057 0.014 cm (P < 0.0001; mean difference = 0.028 cm, 95% CI of the difference, 0.017-0.04 cm). There was a significant negative correlation between intimal-media thickness and endothelial dysfunction (r = -0.357; P<0.01). Linear regression analysis showed that intima-media thickness was independently related to age and the presence of hypertension, while endothelial function was related only with the presence of hypertension, smoking, and hyperlipoproteinemia.

CONCLUSIONS

In patients without clinical atherosclerotic disease, cardiovascular risk factors were associated with impaired endothelial function and increased intima-media thickness. There was a negative correlation between endothelial-dependent vascular dilatation and intima-media thickness.

Cardiovascular function in acromegaly

Even with modern treatment, acromegaly is associated with a 2- to 3-fold increase in mortality, mainly from vascular disease, which is probably a result of the long exposure of tissues to excess GH before diagnosis and treatment. There is accumulating evidence that effective treatment to lower serum GH levels to less than 1-2 ng/ml (glucose suppressed or random, respectively) and normalize IGF-I improves long-term outcome and survival. In addition to recognized cardiovascular risk factors of hypertension, type 2 diabetes mellitus, and dyslipidemia, there is accumulating evidence of specific structural and functional changes in the heart in acromegaly. Along with endothelial dysfunction, these changes may contribute to the increased mortality in this disease. There are specific structural changes in the myocardium with increased myocyte size and interstitial fibrosis of both ventricles. Left ventricular hypertrophy is common even in young patients with short duration of disease. Some of these structural changes can be reversed by effective treatment. Functionally, the main consequence of these changes is impaired left ventricular diastolic function, particularly when exercising, such that exercise tolerance is reduced. Diastolic function improves with treatment, but the effect on exercise tolerance is more variable, and more longitudinal data are required to assess the benefits. What scant data there are on rhythm changes suggest an increase in complex ventricular arrhythmias, possibly as a result of the disordered left ventricular architecture. The functional consequences of these changes are unclear, but they may provide a useful early marker for the ventricular remodeling that occurs in the acromegalic heart. Endothelial dysfunction, especially flow-mediated dilatation, is an early marker of atherosclerosis, and limited data imply that this is impaired in active acromegaly and can be improved with treatment. Similarly, early arterial structural changes, such as thickened intima media layer, appear more common in acromegalics, and there are hints that this may diminish with effective treatment, although more studies are required for a definite conclusion on this topic. In conclusion, impaired cardiac and endothelial structure and function in acromegaly are risk factors for vascular mortality and should be regarded as legitimate therapeutic targets in the overall management of this condition.

Endothelial dysfunction: a marker of atherosclerotic risk

Endothelial dysfunction is a systemic disorder and a key variable in the pathogenesis of atherosclerosis and its complications. Current evidence suggests that endothelial status is not determined solely by the individual risk factor burden but rather, may be regarded as an integrated index of all atherogenic and atheroprotective factors present in an individual, including known as well as yet-unknown variables and genetic predisposition. Endothelial dysfunction reflects a vascular phenotype prone to atherogenesis and may therefore serve as a marker of the inherent atherosclerotic risk in an individual. In line with this hypothesis, dysfunction of either the coronary or peripheral vascular endothelium was shown to constitute an independent predictor of cardiovascular events, providing valuable prognostic information additional to that derived from conventional risk factor assessment. Interventions like risk factor modification and treatment with various drugs, including statins and angiotensin-converting enzyme inhibitors, may improve endothelial function and thereby, potentially prognosis. Hence, given its reversibility and granted the availability of a diagnostic tool to identify patients at risk and to control the efficacy of therapy in clinical practice, endothelial dysfunction may be an attractive primary target in the effort to optimize individualized therapeutic strategies to reduce cardiovascular morbidity and mortality.

Endothelial dysfunction and the metabolic syndrome

The metabolic syndrome is a highly prevalent multifaceted clinical entity produced through the interaction of genetic, hormonal, and lifestyle factors. A distinctive constellation of abnormalities precedes and predicts the accelerated development of inflammation and coagulation represent emerging risk contributors associated with obesity and insulin resistance, central components of the metabolic syndrome, which act in concert with traditional abnormalities to increase cardiovascular risk. The initiation and progression of atherosclerosis may have its origins in impaired endothelial function that can be detected at the earliest stages of development of the syndrome. The basic elements of the metabolic syndrome and accelerated phase of atherogenesis are often silent partners that present many years before the onset of type 2 diabetes mellitus. The ability to detect and monitor subclinical vascular disease, as a reflection of the multiple factors that contribute to impair arterial wall integrity, holds potential to further refine cardiovascular risk stratification. Noninvasive assessment of vascular health may also aid the clinical decision-making process by guiding therapeutic interventions to optimize vascular protection in the metabolic syndrome.

The Endothelium in Health and Disease-A Target for Therapeutic Intervention

In this review we discuss the contribution of NO, prostacyclin and endothelium-derived relaxing factor--endothelium-derived hyperpolarizing factor, or EDHF, to vascular function. We also explore the hypotheses (1): that tissues can store NO as nitrosothiols (RSNOs) and (2) that such RSNO stores can be modulated by physiological and pathophysiological processes. Notably in the microcirculation, EDHF appears to play an important role in the regulation of vascular tone. Leading candidates for EDHF include extracellular potassium (K+), an epoxygenase product, hydrogen peroxide and/or a contribution from myoendothelial gap junctions. Data from our laboratory indicate that in mouse vessels, different endothelium-dependent vasodilators, such as acetylcholine and protease-activated receptor (PAR) agonists, release different endothelium-derived relaxing factors. The combination of two K-channel toxins, apamin and charybdotoxin, inhibits EDHF activity in most protocols. Endothelial dysfunction is considered as the major risk factor and a very early indicator of cardiovascular disease including the cardiovascular complications of type I & types II diabetes. Impaired endothelium-dependent vasodilatation results primarily from a decreased synthesis of endothelium-derived nitric oxide (NO) and/or an increase in the production of reactive oxygen species such as superoxide. We have shown that the administration of tetrahydrobiopterin, an important co-factor for nitric oxide synthase (NOS) partially restores endothelial function (1) in leptin-deficient mice (db/db) with spontaneous type II diabetes, as well as (2) in human vascular tissue harvested for coronary artery bypass grafting (CABG). These data suggest that a deficiency in the availability of tetrahydrobiopterin plays an important role in vascular dysfunction associated with Type II diabetes. In addition, changes in the contribution of EDHF occur in vascular tissue from the db/db mice suggesting a compensatory increase in EDHF production; whether this alteration in EDHF production is physiological or pathophysiological remains controversial.

Markers of endothelial function in pediatric stem cell transplantation for acute leukemia

BACKGROUND

Endothelial cells and leukocytes intimately interact in inflammation and coagulation processes, so that dysregulation of their function may lead to both cellular damage and thrombosis, which may occur as complications of bone marrow transplantation (BMT). Partially conflicting evidence about endothelial markers and their relationships with clinical complications after BMT has been reported in the literature. Since almost all studies were carried out in adults, we evaluated some recent available markers of endothelial cell function in pediatric patients undergoing stem cell transplantation (SCT) for acute leukemia.

PROCEDURE

We studied the variation in circulating serum endothelial-selectin (ES), leukocyte-selectin (LS), thrombomodulin (TM), von Willebrand factor (vWF), nitrate + nitrite (NO(2) (-)/NO(3) (-)), endothelin-1 (EN), and tissue factor (TF) in 21 pediatric patients undergoing SCT for acute leukemia.

RESULTS

ES and LS significantly lowered following SCT and returned to pre-SCT levels 4 weeks after the procedure. NO(2) (-)/NO(3) (-) markedly increased following SCT. Also, TM and vWF increased, although such changes did not reach statistical significance. EN and TF did not appreciably change. A strong correlation was observed between white blood cell (WBC) count and both ES and LS, as well as between such selectins. TM significantly correlated with both selectins and NO(2) (-)/NO(3) (-). The pre-conditioning levels of TM and vWF in patients undergoing major complications, considered altogether, were significantly lower and higher, respectively, than in uncomplicated patients. NO(2) (-)/NO(3) (-) levels 3 and 4 weeks post-SCT were significantly lower in patients suffering from veno occlusive disease. Both selectins were significantly higher in allo- than in auto-transplanted patients 4 weeks after SCT.

CONCLUSIONS

Our data support the hypothesis of severe endothelial damage after conditioning and SCT, particularly allogeneic. However, the increase in TM, which has strong anticoagulant properties, and metabolites of NO, involved also in protective actions, may reflect regeneration of the anti-thrombotic endothelial function. This could take place after transitory functional impairment, rather than pure endothelial damage.

Nitric oxide, atherosclerosis and the clinical relevance of endothelial dysfunction

The endothelium plays a key role in vascular homeostasis through the release of a variety of autocrine and paracrine substances, the best characterized being nitric oxide. A healthy endothelium acts to prevent atherosclerosis development and its complications through a complex and favorable effect on vasomotion, platelet and leukocyte adhesion and plaque stabilization. The assessment of endothelial function in humans has generally involved the description of vasomotor responses, but more widely includes physiological, biochemical and genetic markers that characterize the interaction of the endothelium with platelets, leukocytes and the coagulation system. Stable markers of inflammation such as high sensitivity C-reactive protein are indirect and potentially useful measures of endothelial function for example. Attenuation of the effect of nitric oxide accounts for the majority of what is described as endothelial dysfunction. This occurs in response to atherosclerosis or its risk factors. Much remains to be learned about the molecular and genetic pathophysiological mechanisms of endothelial cell abnormalities. However, pharmacological intervention with a growing list of medications can favorably modify endothelial function, paralleling beneficial effects on cardiovascular morbidity and mortality. In addition, several small studies have provided tantalizing evidence that measures of endothelial health might provide prognostic information about an individual patient's risk of subsequent events. As such, the sum of this evidence makes the clinical assessment of endothelial function an attractive surrogate marker of atherosclerosis disease activity. The review will focus on the role of nitric oxide in atherosclerosis and the clinical relevance of these findings.

Beyond lipid lowering: the role of statins in vascular protection

The introduction of the hydroxy methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in 1987 was a major advance in the prevention and treatment of cardiovascular disease. Several landmark clinical trials have demonstrated the benefit of lipid lowering with statins for the primary and secondary prevention of coronary heart disease (CHD), namely The Scandinavian Simvastatin Survival Study (4S), Cholesterol And Recurrent Events (CARE), Long-term Intervention with Pravastatin in Ischemic Disease (LIPID), West of Scotland Coronary Prevention Study (WOSCOPS) and Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TexCAPS). Although it is widely accepted that the majority of clinical benefit obtained with statins is a direct result of their lipid-lowering properties, these agents appear to display additional cholesterol-independent or pleiotropic effects on various aspects of cardiovascular disease, including improving endothelial function, decreasing vascular inflammation and enhancing plaque stability. Although the full impact of statin therapy on each of these processes is not fully understood, ongoing studies with current and new statins are likely to shed further light on the potential cholesterol-independent benefits of these agents.

Morphologic rather than functional or mechanical sonographic parameters of the brachial artery are related to angiographically evident coronary atherosclerosis

OBJECTIVES

The purpose of this study was to determine the relationship among coronary atherosclerosis and functional, morphologic, and mechanical parameters assessed noninvasively within the brachial artery (BA).

BACKGROUND

Flow-mediated vasodilation (FMD) of the BA, intima-media thickness (IMT) of the carotid artery, and distensibility of the aorta have been correlated with the presence of coronary artery disease (CAD).

METHODS

The BA was examined with high-resolution ultrasound (13 MHz) in 117 male patients, in whom coronary angiography was performed. Coronary artery disease (> or =30% diameter stenosis in > or =1 major branch) was found in 84 patients, and 33 patients had smooth coronary arteries (non-CAD). Wall cross-sectional area (WCSA) was calculated from resting diameter and IMT.

RESULTS

The BA-WCSA (5.3 +/- 1.5 mm(2) vs. 4.4 +/- 1.4 mm(2), p = 0.002) and IMT (0.37 +/- 0.07 mm vs. 0.31 +/- 0.07 mm, p < 0.001) were significantly greater in patients with CAD compared with non-CAD patients. Flow-mediated vasodilation and distensibility were similar among groups. Using logistic regression analyses adjusting for age, positive family history, hypertension, hypercholesterolemia, smoking, FMD, and distensibility, only WCSA (p < 0.01) and IMT (p < 0.001) correlated independently with the presence of CAD.

CONCLUSIONS

Morphologic but not functional and mechanical parameters of the BA are associated with the presence of CAD. Among BA sonographic parameters, IMT and WCSA seem to be the most accurate ones for the estimation of coronary atherosclerotic risk.

Eicosapentaenoic acid improves endothelial function in hypertriglyceridemic subjects despite increased lipid oxidizability

BACKGROUND

Epidemiologic investigations suggest that fish oil, which contains eicosapentaenoic acid (EPA), has favorable cardiovascular effects. Fish oil improves endothelial function in subjects with hypercholesterolemia or diabetes. However, controversy persists regarding relationships between primary hypertriglyceridemia and endothelial dysfunction. Moreover, lipoproteins are more susceptible to oxidation in vitro after incorporation of fish oil.

METHODS

We determined the effects of EPA on serum lipids, susceptibility of low-density lipoproteins (LDL) and very-low-density lipoproteins (VLDL) to oxidation, and endothelial function in hypertriglyceridemic (HTG) subjects. In 8 men with untreated primary hypertriglyceridemia (plasma triglyceride between 150 and 500 mg/dL) and 7 control subjects (triglyceride below 150 mg/dL), forearm blood flow (FBF) responses were tested. In HTG subjects, this was repeated 3 months after initiation of EPA (1800 mg/day). Cu2+-induced oxidation of VLDL and LDL was determined by serial measurement of conjugated dienes. We used lag time, which corresponded to the period when the lipoproteins were resistant to oxidation, as a parameter of oxidizability. FBF responses to acetylcholine and sodium nitroprusside were determined by strain-gauge plethysmography.

RESULTS

Plasma triglyceride in HTG subjects fell 31% with EPA supplementation. Before EPA, VLDL and LDL lag times in HTG subjects were shorter than in control subjects. EPA further reduced lag time for VLDL but not LDL. The FBF response to acetylcholine (but not to nitroprusside) was significantly less in HTG subjects before EPA than in control subjects. EPA normalized the FBF response to acetylcholine.

CONCLUSIONS

EPA improves endothelial function in HTG subjects despite increasing in VLDL oxidizability.

Temporal heterogeneity of endothelium-dependent and -independent dilatation of brachial artery in patients with coronary artery disease

BACKGROUND

Endothelial function is routinely assessed with high frequency ultrasound of the brachial artery. Fixed time points (1' post-occlusion and 3' post-nitrate) are commonly used to assess dynamic changes in brachial artery diameter. The underlying assumption is the lack of variability in temporal response to both endothelium-dependent and -independent stimuli.

OBJECTIVE

To evaluate the temporal course of endothelium-dependent (flow-mediated) and endothelium-independent (nitrate-induced) vasodilation of the brachial artery in patients with coronary artery disease (CAD) using high resolution (10 MHz) ultrasound.

METHODS

Thirty-seven patients with angiographically assessed CAD were prospectively enrolled in the study. End-diastolic, two-dimensional, long axis ultrasonographic images of the brachial artery were digitally stored on-line every 10 s, from baseline up to 4' during flow-mediated and up to 7' during 300 micrograms sublingual nitrate-induced vasodilation of the brachial artery.

RESULTS

The mean percent endothelium-dependent flow-mediated maximal dilation (FMD) measured at 60 s was lower than the mean peak FMD (4.8 +/- 4.1 vs. 6.6 +/- 5.2%; p < 0.01). By 60 s only eight patients (35%) reached their maximum FMD response. The mean time to reach peak FMD was 87 +/- 33 s. The mean time for the peak nitrate dilation was 291 +/- 73 s. The peak nitrate-induced percent dilation was higher than that measured at 3 min (12.2 +/- 6.7 vs. 5.4 +/- 4.5%; p < 0.001). By 190 s, only four patients (11%) reached their maximum nitrate response.

CONCLUSION

The routinely used measurement time points for evaluation of FMD and endothelium-independent vasodilation may not be adequate to detect the peak responses of individual patients with CAD.

A rapid and reproducible on line automated technique to determine endothelial function

OBJECTIVE

To evaluate clinically a new on line, automated technique to measure flow mediated dilatation (FMD) as a marker of endothelial function.

DESIGN

Prospective study.

PATIENTS

12 healthy volunteers and 12 patients with significant, angiographically documented coronary artery disease.

INTERVENTIONS

Brachial arteries were imaged using a standard vascular ultrasound system with a 5-12 MHz linear transducer. Arterial diameter was measured on line (in real time) by connecting the ultrasound system to a personal computer equipped with a frame grabber and artery wall detection software (VIA) specially developed by the authors' group. By using this new technique, FMD was measured following 4.5 minutes of ischaemia of the proximal forearm in all subjects on two separate days.

RESULTS

The mean (SD) day to day variability in FMD measurements was 0.90 (0.48)%,which compares very favourably with current methods. The FMD measurement was available within seconds of completing the scan.

CONCLUSIONS

Personal computer based automated techniques to assess FMD involve image acquisition and recording after which a second (off line) image interpretation session is required. The need for off line analysis makes current methods time consuming and increases the variability of measurement. This on line, automated analysis technique for FMD assessment reduces the variability and greatly increases the speed of measurement. Using this system may mean that fewer patients will be required in clinical trials assessing the effects of interventions on endothelial function. Adopting this method may also facilitate the screening of larger numbers of subjects for endothelial dysfunction.

Prognostic role of reversible endothelial dysfunction in hypertensive postmenopausal women

OBJECTIVES

; The aim of the present study was to assess whether optimized antihypertensive treatment is effective in modifying endothelial function and whether an improvement in flow-mediated vasodilation (FMD) in response to treatment, as an expression of reversible endothelial dysfunction, could predict a more favorable prognosis in a population of postmenopausal women.

BACKGROUND

Hypertensive postmenopausal women have been shown to have abnormal endothelium-dependent vascular function. However, FMD may change over time, according to antihypertensive treatment; the prognostic value of these changes has not been investigated.

METHODS

A total of 400 consecutive postmenopausal women with mild-to-moderate hypertension and impaired FMD underwent ultrasonography of the brachial artery at baseline and after six months, while optimal control of blood pressure was achieved using antihypertensive therapy. They were then followed up for a mean period of 67 months (range 57 to 78). Endothelial function was measured as FMD of the brachial artery, using high-resolution ultrasound.

RESULTS

After six months of treatment, FMD had not changed (< or = 10% relative to baseline) in 150 (37.5%) of 400 women (group 1), whereas it had significantly improved (>10% relative to baseline) in the remaining 250 women (62.5%) (group 2). During follow-up, we noticed 32 events (3.50 per 100 person-years) in group 1 and 15 events (0.51 per 100 person-years) in group 2 (p < 0.0001).

CONCLUSIONS

This study demonstrates that a significant improvement in endothelial function may be obtained after six months of antihypertensive therapy and clearly identifies patients who possibly have a more favorable prognosis.

Blunted vasodilatory responses in the cutaneous microcirculation of cigarette smokers

OBJECTIVE

The present study was undertaken to investigate whether chronic smoking alters the vasodilatory capacity in the microcirculation.

METHODS

We assessed, in habitual cigarette smokers, the forearm skin blood flow response to iontophoretically applied acetylcholine (endothelium-dependent vasodilator) and sodium nitroprusside. Postocclusive forearm reactive hyperemia was also explored. The skin blood flow responses were determined with a laser-Doppler flowmeter that allowed us to scan the surface after acetylcholine and sodium nitroprusside application.

RESULTS

Forty healthy male volunteers were included. Twenty subjects were aged 20 to 35 years and 20 subjects were aged 40 to 60 years. We studied the following 4 groups of 10 subjects each: group 1, younger smokers (mean of 7.2 pack-years); group 2, older smokers (mean of 30 pack-years); group 3, younger nonsmokers; and group 4, older nonsmokers. On the day of the experiment, the subjects of groups 1 and 2 were asked to smoke at least 15 cigarettes from the morning until the afternoon, when the experiments were performed. No significant difference in the studied parameters was observed between younger smokers and younger nonsmokers. In older smokers, however, both acetylcholine- and sodium nitroprusside-induced skin blood flow increases were significantly attenuated in comparison with nonsmokers. Heart rate also was significantly blunted by long-term cigarette smoking in older subjects.

CONCLUSION

These data show that the vasodilatory response of the skin microvasculature is impaired in subjects who have smoked cigarettes for many years. This abnormality involves both endothelium-dependent and endothelium-independent responses.

Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy

A hypothesis is presented based on a coalescence of anthropological estimations of Homo sapiens' phenotypes in the Late Paleolithic era 10,000 years ago, with Darwinian natural selection synergized with Neel's idea of the so-called thrifty gene. It is proposed that humans inherited genes that were evolved to support a physically active lifestyle. It is further postulated that physical inactivity in sedentary societies directly contributes to multiple chronic health disorders. Therefore, it is imperative to identify the underlying genetic and cellular/biochemical bases of why sedentary living produces chronic health conditions. This will allow society to improve its ability to effect beneficial lifestyle changes and hence improve the overall quality of living. To win the war against physical inactivity and the myriad of chronic health conditions produced because of physical inactivity, a multifactorial approach is needed, which includes successful preventive medicine, drug development, optimal target selection, and efficacious clinical therapy. All of these approaches require a thorough understanding of fundamental biology and how the dysregulated molecular circuitry caused by physical inactivity produces clinically overt disease. The purpose of this review is to summarize the vast armamentarium at our disposal in the form of the extensive scientific basis underlying how physical inactivity affects at least 20 of the most deadly chronic disorders. We hope that this information will provide readers with a starting point for developing additional strategies of their own in the ongoing war against inactivity-induced chronic health conditions.

Abciximab attenuates coronary microvascular endothelial dysfunction after coronary stenting

BACKGROUND

Platelet glycoprotein IIb/IIIa receptor blockade with abciximab decreases ischemic events after percutaneous coronary intervention (PCI); however, the mechanism of this benefit has not been fully elucidated. The present study was designed to assess endothelium-dependent vasomotion after coronary stenting and to determine if abciximab alters this response.

METHODS AND RESULTS

The study group consisted of 48 patients (59+/-10 years of age) with discrete coronary stenoses who underwent stenting alone (n=28) or stenting plus abciximab (n=20). A control group consisted of 31 additional patients who had vasomotor testing on a non-PCI vessel. Coronary blood flow (CBF) was measured (0.014-inch Doppler wire) 30 minutes after uncomplicated PCI and in response to the intracoronary infusion of acetylcholine (Ach) (10(-7), 10(-6) mol/L Ach) and adenosine (24 microg). Ach-mediated increase in CBF was impaired after stent insertion when compared with the control group (41+/-52% versus 70+/-48%; P<0.05). The stenting plus abciximab group demonstrated a superior CBF response to Ach compared with the stenting alone group (83+/-93% versus 41+/-52%; P<0.05), with no difference between groups in the peak flow or percent change in flow to adenosine. By multivariate analysis, concomitant administration of abciximab was strongly predictive of the change in CBF to Ach (P<0.005).

CONCLUSIONS

Abciximab preserves the CBF response to Ach after coronary stenting. The preservation of microvascular endothelial function may help explain the beneficial clinical effect of this agent in patients undergoing PCI.

Endothelin blockade potentiates endothelial protective effects of ACE inhibitors in saphenous veins

BACKGROUND

Angiotensin II and endothelin-1 are potent endothelium-derived contracting factors. The effects of acute endothelin antagonism on endothelial function in saphenous vein from patients treated with and without angiotensin-converting enzyme inhibitors were compared.

METHODS

Vascular segments of saphenous vein were obtained perioperatively from 14 patients on angiotensin-converting enzyme inhibitors and 29 controls. In vitro endothelium-dependent and -independent responses to acetylcholine and sodium nitroprusside were assessed by constructing isometric dose-response curves in precontracted rings in the presence and absence of bosentan (endothelinA/B receptor antagonist) and BQ-123 (endothelinA antagonist) using isolated organ baths. Percent maximum relaxation and sensitivity were compared between interventions.

RESULTS

Endothelium-dependent relaxation to acetylcholine was augmented in the angiotensin-converting enzyme inhibitor-treated group (p < 0.005). Both specific and mixed endothelin receptor blockade improved acetylcholine-mediated relaxation in the angiotensin-converting enzyme inhibitor-treated and untreated groups (p < 0.02). The effects of these antagonists were endothelium specific as endothelium-independent responses to sodium nitroprusside remain unaltered.

CONCLUSIONS

These data demonstrate that (1) chronic angiotensin-converting enzyme inhibition improves endothelial function in saphenous veins, and (2) this effect can be further augmented by acute endothelin blockade. These data suggest that antagonism of both angiotensin II and endothelin may be important in attenuating saphenous vein arteriosclerosis.

Toward a new definition of atherosclerosis including hypertension: a proposal

Atherosclerosis is a very complex disease and while research about its aetiology and development advances, it is more difficult to understand its pathology. Because of this atherosclerosis is not easy to define. Old and even new definitions are incomplete. Most of them do not take into consideration the endothelium on both sides, and some risk factors such as high blood pressure are ignored. Here we present a proposal for a redefinition of atherosclerosis and look forward to having a better understanding about the why and how of this lethal disease.

The endothelium in clinical cardiac transplantation

Cardiac transplantation is the most successful therapy for refractory heart failure, but clinical transplantation is still confronted with the problems of acute rejection and acute pump failure. The limiting factor in achieving prolonged survival remains cardiac allograft vasculopathy. In recent years it has become apparent that from brain death onward, the cardiac endothelium plays a key role in these acute and chronic events. Brain death is associated with an inflammatory response that primes the endothelium for cumulative injury during the subsequent stages of ischemic cold storage, reperfusion and allorecognition. As a structural and functional interface, the endothelium is the site at which inflammatory cells move from the bloodstream through the vessel wall into the parenchyma. The endothelium interacts with the complement system, the coagulation and inflammatory cascades, circulating leukocytes, the immune system, the smooth muscle in the vessel wall, and the surrounding matrix and cardiomyocytes. A better understanding of its many roles may lead to expansion of our therapeutic possibilities and better outcomes overall. This article reviews the possible roles of the endothelium in relation to cardiac transplantation, and discusses the diagnostic and therapeutic modalities that are available to date.

Insulin causes endothelial dysfunction in humans: sites and mechanisms

BACKGROUND

Insulin resistance is often accompanied by hyperinsulinemia and may predispose to atherosclerosis. Endothelium plays a central role in atherogenesis. The in vivo effects of hyperinsulinemia on endothelial function of large conduit arteries are unknown.

METHODS AND RESULTS

Twenty-five healthy subjects were enrolled for study. In study A (n=9), subjects underwent both a time-control saline study and a euglycemic low-dose insulin (insulin approximately 110 pmol/L) clamp for 6 hours. Study B (n=5) was identical to study A except that the euglycemic clamp was performed at high physiological insulin concentrations (approximately 440 pmol/L). In study C (n=7), subjects underwent two 4-hour euglycemic insulin (approximately 110 pmol/L) clamps with and without the concomitant infusion of an antioxidant (vitamin C). In study D (n=4), two saline time-control studies were performed with and without the concomitant infusion of vitamin C. In all studies, both at baseline and throughout the experimental period, endothelium-dependent (flow-mediated) and endothelium-independent (nitroglycerin-induced) vasodilation was assessed in femoral and brachial arteries by echo Doppler. Both low (study A) and high physiological (study B) hyperinsulinemia abolished endothelium-dependent vasodilation, whereas endothelium-independent vasodilation was unaffected. Vitamin C fully restored insulin-impaired endothelial function without affecting endothelium-independent vasodilation (study C). Vitamin C had no effects on endothelium-dependent or endothelium-independent vasodilation during saline control studies (study D).

CONCLUSIONS

Modest hyperinsulinemia, mimicking fasting hyperinsulinemia of insulin-resistant states, abrogates endothelium-dependent vasodilation in large conduit arteries, probably by increasing oxidant stress. These data may provide a novel pathophysiological basis to the epidemiological link between hyperinsulinemia/insulin-resistance and atherosclerosis in humans.