Assessment of vascular disease using arterial flow mediated dilatation

Arterial endothelial dysfunction occurs at all stages of atherosclerosis, both preceding structural atherosclerosis changes, as well as predisposing to clinical events in late obstructive disease. Endothelial dysfunction is thus well correlated with risks of vascular events. Release of endothelial nitric oxide has been shown to be a key player in normal endothelial function. Endothelial function can be measured in the coronary arteries and peripheral vascular tree by intra-arterial infusion of substances that promote release of nitric oxide, but this method is limited by its invasive nature which limits its widespread use in asymptomatic subjects. Flow mediated dilatation is a non invasive ultrasound-based method where arterial diameter is measured in response to an increase in shear stress, which causes release of nitric oxide from the endothelium and consequent endothelium dependent dilatation. Flow mediated dilatation has been shown to correlate with invasive measures of endothelial function, as well as with the presence and severity of the major traditional vascular risk factors. This noninvasive endothelial function testing has also demonstrated the potential reversibility of endothelial dysfunction by various strategies including cessation of smoking, weight loss in obese subjects, certain pharmacological agents (statins, ACE inhibitors), L-arginine and hormones.

Adenosine prevents neutrophil adhesion to human endothelial cells after hypoxia/reoxygenation

BACKGROUND

Neutrophil adhesion to vascular endothelium has been implicated in the pathogenesis of myocardial injury after ischaemia/reperfusion (IR) and the "no-reflow" phenomenon. Adenosine and sodium-nitroprusside (SNP) have been used clinically to ameliorate this injury. We set out to establish a human cellular model for the study of IR and to evaluate the effects of adenosine and SNP on neutrophil adhesion in vitro.

METHODS

Cultured human umbilical vein endothelial cells (HUVEC) were exposed to hypoxia (5% CO2, 95% N2) or normoxia (room air, 5% CO2) for 2 h, followed by reoxygenation for 30 min (IR condition). Human neutrophils were then added together with adenosine (50 microM), SNP (10 microM) or no additive (control). After incubation for 1 h, neutrophil adhesion to endothelial cells was quantified via automated cell counts. The experiment was repeated with the adenosine treatment alone, with and without the addition of the adenosine A2A receptor blocker ZM-241385.

RESULTS

Compared with baseline neutrophil adhesion after normoxia, hypoxia followed by reoxygenation increased adhesion to 189+/-43% (p=0.01), but this effect was prevented by the addition of adenosine (109+/-17%, p=NS compared to control conditions). SNP did not affect the increased adhesion caused by hypoxia (166+/-25%, p=NS). The addition of ZM-241385 did not inhibit the effect of adenosine on neutrophil adhesion after hypoxia/reoxygenation.

CONCLUSIONS

Exposure of human endothelial cells to hypoxia/reoxygenation causes increased neutrophil adhesion. This effect is prevented by adenosine, but not mediated by the A2A receptor. SNP does not prevent neutrophil adhesion after IR in vitro.

Urinary albumin levels in the normal range determine arterial wall thickness in adults with Type 2 diabetes: a FIELD substudy

AIM

Cardiovascular disease (CVD) rates are substantially higher among patients with Type 2 diabetes than in the general population. The objective of this study was to identify the determinants of carotid intima media thickness (IMT) in patients with Type 2 diabetes.

METHODS

We measured the thickness of the intima media layer of the carotid artery, a strong predictor of the risk of future vascular events, in 397 Type 2 diabetic patients drawn from the Fenofibrate Intervention and Event Lowering in Diabetes study, prior to treatment allocation.

RESULTS

The mean IMT was 0.78 mm [interquartile range (IQR) 0.23 mm], and the maximum IMT was 1.17 mm (IQR 0.36 mm). By multivariate analysis, age, sex, duration of diabetes, triglycerides, and total cholesterol were independently correlated with IMT, as was urine albumin-creatinine ratio (ACR) (P < 0.001). The effect of ACR on IMT was further examined by tertile. Clinically significant differences in IMT were associated with ACR > 0.65 mg/mmol, approximately one-fifth the standard clinical threshold for microalbuminuria (P < 0.01). Long-term diabetes, independent of other parameters, was associated with a 50% increase in age-related thickening.

CONCLUSIONS

IMT in people with Type 2 diabetes is independently and continuously related to urine albumin levels and to the duration of diabetes. These results support previous data linking urine albumin measurements within the normal range with increased ischaemic cardiac mortality in the setting of Type 2 diabetes, and strongly suggest that urine albumin levels within this range should trigger a formal evaluation for CVD.

Reperfusion injury in the human forearm is mild and not attenuated by short-term ischaemic preconditioning

1. Ischaemia-reperfusion (IR) injury is an important contributor to tissue damage and has been shown to be attenuated by preconditioning (PC) in some animal models. A recent report has suggested that the forearm can be used for the study of this phenomenon in humans. We aimed to reproduce and further characterize this model. 2. Healthy young adult volunteers (mean (+/-SEM) age 32+/-6 years) were studied on two occasions. During one visit, IR alone was induced by 10 min of upper arm cuff occlusion, whereas on another occasion a PC stimulus (three 3 min cuff inflations) preceded IR. Endothelial function in the ischaemic arm was assessed by measuring arterial flow-mediated dilatation (FMD) and by calculation of forearm blood flow at baseline and 15 and 60 min after IR. Systemic venous blood was sampled from the non-ischaemic arm at baseline, after PC and at 2, 15 and 30 min after IR to assess neutrophil/leucocyte (CD11b) and platelet (bound glycoprotein IIb/IIIa and fibrinogen) activation, as well as numbers of platelet-leucocyte complexes, which were determined by flow cytometry. Because of a lack of measurable effects, the IR experiment was repeated with 20 min ischaemia in six subjects. 3. Five females and eight males completed the study. Flow-mediated dilatation was significantly impaired 30 min after IR (4.1 vs 6.2% at baseline; P<0.05);however, this was not significantly attenuated by ischaemic PC (FMD reduction at 30 min compared with baseline was 2.1+/-0.5% with IR alone and 2.6+/-1.4% with IR after PC; NS). No significant effect was seen on the number of platelet-leucocyte aggregates or on white cell or platelet activation after IR alone or after IR with PC (P>0.6 for all comparisons). Similar results were obtained in six subjects studied subjected to 20 min ischaemia. 4. In conclusion, in healthy young adults, brief periods of skeletal muscle ischaemia lead to arterial endothelial dysfunction, but no significant platelet or white cell activation. Preconditioning does not attenuate this effect on the endothelium. Further experiments with longer ischaemia times and varying PC stimuli may be necessary to produce measurable effects; however, this may prove difficult in conscious human subjects.

Beauty is in the eye of the examiner: reaching agreement about physical signs and their value

Despite advances in other areas, evidence-based medicine is yet to make substantial inroads on the standard medical physical examination. We have reviewed the evidence about the accuracy and reliability of the physical examination and common clinical signs. The physical examination includes many signs of marginal accuracy and reproducibility. These may not be appreciated by clinicians and could adversely affect decisions about treatment and investigations or the teaching and examination of students and doctors-in-training. We provide a selected summary of the reliability and accuracy as well as important messages of key findings in the physical examination.

Overweight in children is associated with arterial endothelial dysfunction and intima-media thickening

OBJECTIVE

We sought to study arterial endothelial function and carotid intima-media thickness (IMT), both early markers of atherosclerosis, in overweight compared to normal children.

DESIGN

Case-control comparison.

SUBJECTS

A total of 36 asymptomatic overweight children (body mass index (BMI)>23; mean 25+/-3) aged 9-12 y and 36 age- and gender-matched nonobese healthy children (BMI<21) from a school community.

MEASUREMENTS

The key parameters were: BMI, arterial endothelial function (ultrasound-derived endothelium-dependent dilation) and carotid artery IMT. The secondary parameters measured included body fat content, waist-hip ratio (WHR), blood pressures, blood lipids, insulin and glucose.

RESULTS

The two groups were well matched for blood pressures, cholesterol and glucose levels, but BMI (P<0.0001), body fat (P=0.001), WHR (P<0.05), fasting blood insulin (P=0.001) and triglyceride levels (P<0.05) were higher in obese children. Overweight was associated with impaired arterial endothelial function (6.6+/-2.3 vs 9.7+/-3.0%, P<0.0001) and increased carotid IMT (0.49+/-0.04 mm vs 0.45+/-0.04 mm, P=0.006). The degree of endothelial dysfunction correlated with BMI (P<0.003) on multivariate analysis.

CONCLUSION

Obesity, even of mild-to-moderate degree, is independently associated with abnormal arterial function and structure in otherwise healthy young children.

Glucocorticoid treatment and cardiovascular disease

The propensity of glucocorticoids to produce hyperglycaemia, hypertension, dyslipidaemia, and central obesity has long been a cause for concern among physicians regarding possible adverse cardiovascular events. Should heart failure be added to this list of concerns?

Clinical criteria and the appropriate use of transthoracic echocardiography for the exclusion of infective endocarditis

BACKGROUND

Clinical guidelines currently suggest that transthoracic echocardiography (TTE) be carried out in all patients with suspected endocarditis, but the use of TTE where there is a low probability of infective endocarditis has a poor diagnostic yield. This screening approach may no longer be appropriate.

OBJECTIVE

To examine whether clinical criteria might aid decision making with respect to the use of TTE in possible endocarditis.

DESIGN

A retrospective review of patient records.

SETTING

Cardiology department of a tertiary referral centre.

PATIENTS

500 consecutive hospital inpatients referred for TTE to exclude endocarditis.

MAIN OUTCOME MEASURES

Evidence of endocardial vegetations on TTE and the presence of predetermined clinical criteria that may predispose to, or be suggestive of, endocarditis.

RESULTS

Evidence of infective endocarditis was detected on echocardiography in 43 of the 500 patients (8.6%). In 239 patients (48%), vegetations and certain prespecified clinical criteria were both absent. These criteria were: vasculitic/embolic phenomena; the presence of central venous access; a recent history of injected drug use; presence of a prosthetic valve; and positive blood cultures. The collective absence of these five criteria indicated a zero probability of TTE showing evidence of endocarditis.

CONCLUSIONS

The use of simple clinical criteria during the decision making process may avoid many unnecessary TTE examinations in hospital inpatients with a low probability of endocarditis.

Survivors of coarctation repair: fixed but not cured

While often considered to be cured, patients with repaired coarctation of the aorta frequently have premature morbidity and even mortality.

Increased aortic intima-media thickness: a marker of preclinical atherosclerosis in high-risk children

BACKGROUND

Autopsy studies in children have shown that atherosclerotic lesions begin to develop first in the intima of the aorta. Recent developments in ultrasound techniques have made it possible to visualize the intima-medial thickness of the abdominal aorta directly (aIMT). Therefore, we examined the feasibility of measuring aIMT in children and studied its value in distinguishing high-risk children from healthy controls compared with a more established marker of subclinical atherosclerosis, the common carotid artery intima-medial thickness (cIMT).

METHODS AND RESULTS

IMTs were measured using high-resolution (13 MHz) ultrasound in 88 children (aged 11+/-2 years); 16 had hypercholesterolemia (LDL cholesterol, 5.1+/-1.2 mmol/L), 44 had type 1 diabetes (mean duration, 4.4+/-3.1 years; LDL cholesterol, 2.3+/-0.7 mmol/L), and 28 were healthy (controls; LDL cholesterol, 2.5+/-0.8 mmol/L). High-risk children had significantly increased aIMTs and cIMTs (both P<0.001) compared with controls. In controls, aIMT was similar to cIMT (P=NS), but aIMT was higher than cIMT in the children with hypercholesterolemia and diabetes (both P<0.01). Both markers showed excellent and approximately equal between-observer (<4%) and between-subject variation (<5%).

CONCLUSIONS

Children with hypercholesterolemia and diabetes show increased IMTs compared with healthy controls, with a relatively greater increase in the aIMT than in the cIMT. Because atherosclerosis begins first in the intima of the aorta, these data suggest that the aIMT might provide the best currently available noninvasive marker of preclinical atherosclerosis in children.

Endothelin-1 plus oxidized low-density lipoprotein, but neither alone, increase human monocyte adhesion to endothelial cells

Endothelin-1 is a potent vasoconstrictor and mitogenic peptide that is implicated in the atherosclerosis of apolipoprotein E-deficient mice and may promote atherogenesis in humans. We hypothesized that endothelin-1 might promote the adhesion of monocytes to endothelial cells, a key early event in atherosclerosis. We investigated the adhesion of primary human monocytes (isolated by elutriation) to human umbilical vein endothelial cell cultures after incubation with endothelin-1 (0.1 and 0.01 nM; approximately physiological concentrations), copper-oxidized low-density lipoprotein (LDL) (0.1 mg/ml) and a combination of the two. After a 4 h incubation with 0.1 or 0.01 nM endothelin-1 combined with oxidized LDL, adhesion was increased to 120+/-4% (P<0.001 compared with control) and 118+/-4% (P<0.002) respectively, whereas neither substance alone increased adhesion (92-104% of control values; not significant). Neither endothelin receptor A blockade nor co-incubation with anti-fibronectin antibody inhibited the pro-adhesive effects of endothelin-1 plus oxidized LDL (115+/-7% and 115+/-3% of control compared with 120+/-4% respectively; not significant). Endothelial cell expression of intercellular adhesion molecule-1, vascular adhesion molecule-1 and E-selectin were unchanged throughout the experiment. Therefore physiological concentrations of endothelin-1 and oxidized LDL may act synergistically to increase the adhesion of human monocytes to endothelial cells, contributing in part to the observed pro-atherogenic effects of endothelin-1.

Sex-related differences in the regulation of macrophage cholesterol metabolism

Men have an earlier onset and higher incidence of coronary heart disease than women, independent of environmental risk factor exposure. As a consequence, there has been considerable interest in the potential role of sex hormones in atherogenesis. An emerging body of evidence suggests that sex-specific tissue and cellular characteristics may mediate sex-specific responses to a variety of stimuli. Recent studies have shown that oestrogen, progesterone and androgens all regulate processes integral to human macrophage foam cell formation, a key event in atherogenesis, in a sex-specific manner; findings that may have important implications for understanding the sex gap in atherosclerosis. Physiological levels of 17beta-estradiol and progesterone are both associated with a female-specific reduction in cholesteryl ester accumulation in human macrophages. By contrast, androgens increase cholesteryl ester formation in male but not in female donor human macrophages. This review summarizes current data concerning the sex-specific effects of sex hormones on processes important to macrophage foam cell formation and the basic mechanisms responsible for the sex specificity of such effects. Future research in this promising field may eventually lead to the novel concept of 'sex-specific' treatments directed at inhibiting atherogenesis.

A double-blind, placebo-controlled, randomized clinical trial of transdermal dihydrotestosterone gel on muscular strength, mobility, and quality of life in older men with partial androgen deficiency

The efficacy and safety of androgen supplementation in older men remains controversial. Despite biochemical evidence of partial androgen deficiency in older men, controlled studies using T demonstrate equivocal benefits. Furthermore, the importance of aromatization and 5alpha reduction in androgen actions among older men remains unclear. Dihydrotestosterone is the highest potency natural androgen with the additional features that it is neither aromatizable nor susceptible to potency amplification by 5alpha reduction. Therefore, the effects of dihydrotestosterone may differ from those of T in older men. This study evaluated the efficacy and safety of 3 months treatment with transdermal dihydrotestosterone gel on muscle strength, mobility, and quality of life in ambulant, community-dwelling men aged 60 yr or older. Eligible men (plasma T < or =15 nmol/liter) were randomized to undergo daily dermal application of 70 mg dihydrotestosterone gel (n = 18) or vehicle (n = 19) and were studied before, monthly during, and 1 month after treatment. Among 33 (17 dihydrotestosterone, 16 placebo) men completing the study with a high degree of compliance, dihydrotestosterone had significant effects on circulating hormones (increased dihydrotestosterone; decreased total and free testosterone, LH, and FSH; unchanged SHBG and estradiol), lipid profiles (decreased total and low-density lipoprotein cholesterols; unchanged high-density lipoprotein cholesterol and triglycerides), hematopoiesis (increased hemoglobin, hematocrit, and red cell counts), and body composition (decreased skinfold thickness and fat mass; unchanged lean mass and waist to hip ratio). Muscle strength measured by isokinetic peak torque was increased in flexion of the dominant knee but not in knee extension or shoulder contraction, nor was there any significant change in gait, balance, or mobility tests, in cognitive function, or in quality of life scales. Dihydrotestosterone treatment had no adverse effects on prostate (unchanged prostate volumes and prostate-specific antigen) and cardiovascular (no adverse change in vascular reactivity or lipids) safety markers. We conclude that 3 months treatment with transdermal dihydrotestosterone gel demonstrates expected androgenic effects, short-term safety, and limited improvement in lower limb muscle strength but no change in physical functioning or cognitive function.

Cardiovascular structure and function in baboons with Type 1 diabetes -- a transvenous ultrasound study

Diabetes mellitus is an important risk factor for both macrovascular and cardiac disease in humans. The availability of a novel intravenous ultrasound probe allows detailed interrogation of a large proportion of the vasculature, as well as the heart, during the same examination. Six male baboons (Papio hamadryas) with Type 1 diabetes and known microangiopathy, and six control animals were studied. Vascular structure in the major large arteries and cardiac function were studied using transvenous ultrasound introduced via the right femoral vein and positioned under fluoroscopy. All arteries were examined for atherosclerotic plaque and for presence of increased intima-media thickness (IMT). Left ventricular function was assessed at rest and following infusions of dobutamine (positive inotrope) and esmolol (negative inotrope). The procedure was performed safely and successfully in all cases. No atherosclerotic plaque was seen in either diabetic or normal baboons. There was no difference in the aortic IMT (0.38+/-0.04 vs. 0.37+/-0.05 mm, normal vs. diabetic, P=NS) or in doppler flow in the renal or iliac arteries between diabetic and normal baboons. Left ventricular wall thickness and systolic tissue velocity were similar in the two groups at rest (6.9+/-2.5 vs. 6.2+/-1.4 cm/s, normal vs. diabetic, P=NS), after dobutamine (15.5+/-2.2 vs. 12.7+/-3.9 cm/s, normal vs. diabetic, P=NS), and after esmolol (4.3+/-1.0 vs. 5.6+/-1.0 cm/s, normal vs. diabetic, P=NS). In a high primate model of diabetes with microangiopathy, the presence of hyperglycemia for 7 years per se does not produce abnormalities of macrovascular or cardiac structure.

Evidence-based medicine: how good is the evidence?

The "evidence" in EBM must be of high quality in order to be useful, but this is not always the case. Even the "gold standard" of evidence-based medicine, the randomised clinical trial, is bedevilled by low inclusion rates and potentially important recruitment biases. "Real world" trials often do not give the same results as these highly artificial controlled clinical studies. Meta-analysis, the next most important level of evidence in EBM, may be unreliable, sometimes giving different results to subsequent large randomised trials. There is a bias in the hypotheses tested in large clinical trials, as the costs involved are usually covered by commercially interested companies. For this reason, trials of non-patentable compounds or therapies of no commercial interest may not be performed. The process of journal review and publication is capricious, slow and may have a selection bias towards positive studies, meaning that communication channels for the "evidence" are often unsatisfactory. For many rarer conditions and situations, there is simply no "high level" evidence, such as in paediatrics and subspecialty surgery.

The Mediterranean score of dietary habits in Chinese populations in four different geographical areas

OBJECTIVE

To compare the dietary intake of Chinese people living in Pan Yu, Hong Kong, San Francisco and Sydney with respect to cardiovascular health, using the Mediterranean diet score, examining the effects of age, gender, urbanization and acculturation on the diet score.

SUBJECTS

A total of 500 men and 510 women in Hong Kong were recruited as a territory-wide stratified random sample. Subjects were recruited in response to local advertisements for the other three sites: Pan Yu, 58 men, 95 women; San Francisco, 166 men, 192 women; Sydney, 95 men, 73 women.

METHOD

Food-frequency questionnaire over a 7 week period. A high/healthy score was taken as > or =4 for men and >3 for women, representing a dietary pattern beneficial for cardiovascular health.

RESULTS

In Hong Kong, more women in the middle age group (35-54) had a high score than other age groups, and overall more women had high scores than men. In comparing the four geographical regions, Pan Yu had the highest number of subjects with high score, and Hong Kong had the lowest. With the exception of the younger population and men in Hong Kong, the percentage of the population with a high score in all sites is greater than among elderly Greeks consuming a more traditional heart-healthy Mediterranean diet.

CONCLUSION

Considerable variations in Chinese dietary patterns exist with respect to age, gender and geographic location. Overall, the Chinese diet is comparable to the Mediterranean diet and may be expected to have similar health benefits that have been documented for the traditional Mediterranean diet.

Oestradiol improves arterial endothelial function in healthy men receiving testosterone

OBJECTIVE

To assess prospectively the effects of low dose oestradiol on arterial endothelial and smooth muscle function in healthy men. Oestrogen use is associated with reduced cardiovascular disease in oestrogen-deficient women, however, the vascular effects of low-dose oestradiol in healthy men have not been investigated previously.

PATIENTS AND DESIGN

Twenty-three men (aged 32 +/- 8 years) were randomized to receive depot implants of testosterone (T) alone (group 1, n = 10), or T with either 10 mg (group 2, n = 7) or 20 mg (group 3, n = 6) of oestradiol (E).

MEASUREMENTS

Hormone levels, lipids and vascular reactivity were measured before, 1 month and 6 months after hormone implantation. Using high-resolution ultrasound, brachial artery diameter was measured at rest, during reactive hyperaemia (leading to flow-mediated dilatation, FMD, which is endothelium-dependent) and after sublingual nitroglycerin (GTN, an endothelium-independent dilator).

RESULTS

Oestradiol produced a dose-dependent increase in plasma oestradiol (at 1 month 96 +/- 7, 149 +/- 6, 192 +/- 23 pmol/l in the 3 groups, respectively, P < 0.001 by ANOVA for trend). Minor side-effects (gynaecomastia, nipple tenderness) indicated that 20 mg oestradiol was the maximum tolerated dose. There was also a dose-dependent increase in FMD with oestradiol dose: at 1 month, - 0.2, + 0.2 and + 1.8% for groups 1-3, respectively (P = 0.31 by ANOVA for trend); and at 6 months, - 0.8, + 0.4 and + 2.2% (P = 0.02). The rise in oestradiol levels following treatment correlated with the improvement in FMD (P = 0.01). GTN responses were similar in the 3 groups throughout the study.

CONCLUSION

In healthy young men, oestradiol supplementation is associated with enhanced arterial endothelial function, a key marker of vascular health.

Impaired vascular responses to nitroglycerin in subjects with coronary atherosclerosis

To study smooth muscle function in atherosclerosis, we calculated dose-response curves in patients with coronary artery disease and in controls by measuring changes in brachial artery diameter after incremental sublingual doses of nitroglycerin. The doses required to produce a 50% maximal dilator response were significantly higher in patients with coronary artery disease than in controls (p <0.002), suggesting smooth muscle dysfunction in atherosclerosis.

Androgenic anabolic steroids and arterial structure and function in male bodybuilders

OBJECTIVES

The study examined arterial and cardiac structure and function in bodybuilders using androgenic anabolic steroids (AAS), compared to non-steroid-using bodybuilder controls.

BACKGROUND

Adverse cardiovascular events have been reported in bodybuilders taking anabolic steroids. The cardiovascular effects of AAS, however, have not been investigated in detail.

METHODS

We recruited 20 male bodybuilders (aged 35 +/- 3 years), 10 actively using AAS and 10 who denied ever using steroids. Serum lipid and hormone levels, carotid intima-media thickness (IMT), arterial reactivity, and left ventricular (LV) dimensions were measured. Vessel diameter was measured by ultrasound at rest, during reactive hyperemia (an endothelium-dependent response, leading to flow-mediated dilation, FMD), and after sublingual nitroglycerin (GTN, an endothelium-independent dilator). Arterial reactivity was also measured in 10 age-matched non-bodybuilding sedentary controls.

RESULTS

Use of AAS was associated with significant decreases in high density lipoprotein cholesterol, sex hormone binding globulin, testosterone and gonadotrophin levels, and significant increases in LV mass and self-reported physical strength (p < 0.05). Carotid IMT (0.60 +/- 0.04 mm vs. 0.63 +/- 0.07 mm), arterial FMD (4.7 +/- 1.4% vs. 4.1 +/- 0.7%) and GTN responses (11.0 +/- 1.9% vs. 14.4 +/- 1.7%) were similar in both bodybuilding groups (p > 0.2). The GTN responses were significantly lower and carotid IMT significantly higher in both bodybuilding groups, however, compared with the non-bodybuilding sedentary controls (p = 0.01).

CONCLUSIONS

Although high-level bodybuilding is associated with impaired vascular reactivity and increased arterial thickening, the use of AAS per se is not associated with significant abnormalities of arterial structure or function.

Flow-mediated dilatation

Arterial endothelial dysfunction is one of the key early events in atherogenesis, preceding structural atherosclerotic changes. It is also important in the late stages of obstructive atherosclerosis, predisposing to constriction and/or thrombosis. Endothelial function can be measured in coronary arteries and in the periphery by measuring vasomotor function after intra-arterial infusion of pharmacologic substances which enhance the release of endothelial nitric oxide. The disadvantage of these methods is their invasive nature, which generally makes them unsuitable for studies involving asymptomatic subjects. For this reason, noninvasive tests of endothelial function have been developed. In the most widely used of these, an ultrasound-based method, arterial diameter is measured in response to an increase in shear stress, which causes endothelium-dependent dilatation. Endothelial function assessed by this method correlates with invasive testing of coronary endothelial function, as well as with the severity and extent of coronary atherosclerosis. This noninvasive endothelial function testing has provided valuable insights into early atherogenesis, as well as into the potential reversibility of endothelial dysfunction by various strategies, including pharmacological agents (lipid lowering, ACE inhibition), L-arginine, antioxidants and hormones.

Inhaled nitric oxide and prevention of pulmonary hypertension after congenital heart surgery: a randomised double-blind study

BACKGROUND

Pulmonary hypertensive crises (PHTC) are a major cause of morbidity and mortality after congenital heart surgery. Inhaled nitric oxide is frequently used as rescue therapy. We did a randomised double-blind study to investigate the role of routinely administered inhaled nitric oxide to prevent pulmonary hypertension in infants at high risk.

METHODS

We enrolled 124 infants (64 male, 60 female; median age 3 months [IQR 1-5]), 76% with large ventricular or atrioventricular septal defects, who had high pulmonary flow, pressure, or both, and were undergoing corrective surgery for congenital heart disease. They were randomly assigned continuous low-dose inhaled nitric oxide (n=63) or placebo (n=61) from surgery until just before extubation. We measured the numbers of PHTC, time on study gas, and hours spent in intensive care. Analysis was done by intention to treat.

FINDINGS

Compared with placebo, infants receiving inhaled nitric oxide had fewer PHTC (median four [IQR 0-12] vs seven [1-19]; relative risk, unadjusted 0.66, p<0.001, adjusted for dispersion 0.65, p=0.045) and shorter times until criteria for extubation were met (80 [38-121] vs 112 h [63-164], p=0.019). Time taken to wean infants off study gas was 35% longer in the nitric oxide group than in the placebo group (p=0.19), but the total time on the study gas was still 30 h shorter for the nitric oxide group (87 [43-125] vs 117 h [67-168], p=0.023). No important toxic effects arose.

INTERPRETATION

In infants at high risk of pulmonary hypertension, routine use of inhaled nitric oxide after congenital heart surgery can lessen the risk of pulmonary hypertensive crises and shorten the postoperative course, with no toxic effects.