Texture-based speciation of otitis media-related bacterial biofilms from optical coherence tomography images using supervised classification

Otitis media (OM) is primarily a bacterial middle-ear infection prevalent among children worldwide. In recurrent and/or chronic OM cases, antibiotic-resistant bacterial biofilms can develop in the middle ear. A biofilm related to OM typically contains one or multiple bacterial strains, the most common include Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, and Staphylococcus aureus. Optical coherence tomography (OCT) has been used clinically to visualize the presence of bacterial biofilms in the middle ear. This study used OCT to compare microstructural image texture features from primary bacterial biofilms in vitro and in vivo. The proposed method applied supervised machine-learning-based frameworks (SVM, random forest (RF), and XGBoost) to classify and speciate multiclass bacterial biofilms from the texture features extracted from OCT B-Scan images obtained from in vitro cultures and from clinically-obtained in vivo images from human subjects. Our findings show that optimized SVM-RBF and XGBoost classifiers can help distinguish bacterial biofilms by incorporating clinical knowledge into classification decisions. Furthermore, both classifiers achieved more than 95% of AUC (area under receiver operating curve), detecting each biofilm class. These results demonstrate the potential for differentiating OM-causing bacterial biofilms through texture analysis of OCT images and a machine-learning framework, which could provide additional clinically relevant data during real-time in vivo characterization of ear infections.

Differentiation of otitis media-causing bacteria and biofilms via Raman spectroscopy and optical coherence tomography

In the management of otitis media (OM), identification of causative bacterial pathogens and knowledge of their biofilm formation can provide more targeted treatment approaches. Current clinical diagnostic methods rely on the visualization of the tympanic membrane and lack real-time assessment of the causative pathogen(s) and the nature of any biofilm that may reside behind the membrane and within the middle ear cavity. In recent years, optical coherence tomography (OCT) has been demonstrated as an improved in vivo diagnostic tool for visualization and morphological characterization of OM biofilms and middle ear effusions; but lacks specificity about the causative bacterial species. This study proposes the combination of OCT and Raman spectroscopy (RS) to examine differences in the refractive index, optical attenuation, and biochemical composition of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, and Pseudomonas aeruginosa; four of the leading otopathogens in OM. This combination provides a dual optical approach for identifying and differentiating OM-causing bacterial species under three different in vitro growth environments (i.e., agar-grown colonies, planktonic cells from liquid cultures, and biofilms). This study showed that RS was able to identify key biochemical variations to differentiate all four OM-causing bacteria. Additionally, biochemical spectral changes (RS) and differences in the mean attenuation coefficient (OCT) were able to distinguish the growth environment for each bacterial species.

Rapid potentiation of endothelium-dependent vasodilation by estradiol in postmenopausal women is mediated via cyclooxygenase 2

Estrogens influence cardiovascular function through direct and indirect effects and via genomic and nongenomic mechanisms. The pathways underlying the nongenomic mechanisms are not completely understood. Estrogen-induced responses in vascular cells have been shown to influence prostaglandins and cyclooxygenase (COX), a key enzyme in the production of prostaglandins, with two isoforms, COX-1 and COX-2. We investigated the effects of prostaglandins on the acute potentiation by 17beta-estradiol (E) of acetylcholine (ACh)-mediated vasodilation in the cutaneous vasculature. Using a double-blind placebo-controlled design, we assessed skin blood flow in 32 healthy, postmenopausal women by laser Doppler velocimetry with direct current iontophoresis of ACh and sodium nitroprusside before and after 6-wk treatment periods with aspirin (a nonspecific COX-1 and COX-2 inhibitor), diclofenac (predominantly a COX-2 inhibitor, which also inhibits COX-1), celecoxib (a specific COX-2 inhibitor), given at anti-inflammatory doses, or placebo. Blood flux values before iontophoresis of ACh did not differ between the treatment groups or after E administration, excluding a direct cutaneous vasodilator effect of the treatments or of E. Acute E administration enhanced the response to ACh after aspirin, diclofenac, and placebo; however, this effect was completely abolished with celecoxib treatment (P < 0.05). E had no effect on sodium nitroprusside-mediated vasodilation after any of the treatments. We conclude that the COX-2 pathway plays a specific role in the rapid E-induced potentiation of cholinergic vasodilation in postmenopausal women.

Estrogens and human cardiovascular physiology

The importance of estrogens for cardiovascular physiology in women is accepted, even if the clinical place for hormonal supplementation after menopause remains uncertain. However, although men produce significant quantities of estrogen, relatively little is known about the role of estrogens in the male cardiovascular system. Recent evidence about the epidemiology of cardiovascular disease, the mechanisms of action of estrogens, the biological actions of endogenously produced estrogens in men, and the acute and chronic effects of estrogens on the vasculature in both men and women, suggests that these hormones may well play an important role in normal male cardiovascular physiology. In addition, they may provide useful adjuncts to therapy in selected groups of men.

Experiences at menopause of women in a non-English-speaking community: a qualitative study

CONTEXT

It is important that clinicians appreciate the link between physiological disturbances and cultural meanings. The community surrounding the Baker Medical Research Institute in Melbourne, Australia includes a substantial number of women from a Greek-speaking background who attend the Menopause Clinic.

OBJECTIVE

To demonstrate how qualitative methodologies can assist with the development of clinical services by employing them to elucidate the role of cultural variables in the ways in which Greek women view menopause, aging, illness and medicine.

DESIGN

This was a qualitative study employing in-depth interviews on five separate occasions over 2 years, analyzed with thematic and ethnographic content analysis.

PATIENTS

Subjects were 40 Greek-speaking women attending the Clinic, aged 45-60 years.

RESULTS

There is an intricate association between experiences of the menopause and family relationships, problems raised by immigration and the cultural dislocation caused by it, beliefs and theories of the body, religion, and traditional approaches to healing and medicine. Many women had experienced unfavorable or unsatisfactory encounters with medicine in the past, reflecting lack of understanding of the women's experiences and failures of communication about clinical assessments and recommended treatments. Traditional therapies were often used without advising doctors.

CONCLUSIONS

The study emphasizes the potential utility of qualitative research methods for improving clinical practice by elaborating the specific requirements of particular groups, and thereby allowing doctors to deliver services that are more acceptable to patients from both a cultural and an ethical point of view, and also more effective. The process established for the evolution of our clinic may serve as a model for other clinics seeking to direct themselves to the needs of particular social groups or communities.

Low-dose estrogen supplementation improves vascular function in hypogonadal men

It is widely accepted that in women, estrogens provide protection against the development of cardiovascular disease. However, the cardiovascular role of estrogens in men remains uncertain, despite preliminary evidence that endogenous estrogens produced by aromatization of androgenic precursors are of physiological importance. Hypogonadal men have very low levels of circulating estrogen. We studied the responsiveness of forearm resistance arteries to vasoconstrictor and vasodilator agents in 12 men (mean+/-SEM age, 68.7+/-2.6 years) rendered hypogonadal as a result of treatment for prostatic cancer, before and after 8 weeks of estrogen supplementation (estradiol valerate 1 mg daily; n=7) or placebo (n=5). Forearm blood flow was measured by venous occlusion plethysmography, and vasoactive agents were infused through a brachial artery cannula in doses that did not affect blood pressure or heart rate. Estrogen supplementation was well tolerated, with no adverse effects. After estrogen treatment, mean estradiol levels increased from <30 to 308+/-65 pmol/L, and both systolic and diastolic blood pressures were reduced. HDL cholesterol levels increased significantly, and vasoconstrictor responses to the NO synthase inhibitor N(G)-monomethyl-L-arginine (1, 2, 4 micromol/min) were enhanced. Vasoconstrictor responses to angiotensin II (8, 16, 32 ng/min) were markedly attenuated by estrogen treatment, as were vasoconstrictor responses to norepinephrine (25, 50, 100 ng/min). Estrogen did not alter the vasodilator responses to acetylcholine (9.25, 18.5, 37 microgram/min) or to the endothelium-independent agent sodium nitroprusside (1.6 microgram/min). Responses to all vasoactive agents were unchanged after administration of placebo. We conclude that low-dose estrogen supplementation in hypogonadal men is well tolerated, lowers blood pressure, and may affect vascular reactivity in a manner that is potentially beneficial, through several mechanisms, including enhancement of basal NO release and attenuation of vasoconstrictor responses to angiotensin II and norepinephrine. These findings suggest the need to consider a possible clinical role for estrogenic compounds in cardiovascular risk reduction in some groups of men.

Tamoxifen is an acute, estrogen-like, coronary vasodilator of porcine coronary arteries in vitro

Tamoxifen is a mixed estrogen antagonist and agonist. Observational data from breast cancer studies associate tamoxifen use with lesser rates of myocardial infarction. The authors sought to determine the acute vasoactive properties of tamoxifen compared with estradiol. Isolated coronary ring segments from female pigs were studied in organ baths. KCl-precontracted ring segments were exposed to increasing doses of both tamoxifen and estradiol (log-9-log-5 M ). Ring segments were also exposed to tamoxifen and estradiol in the presence of inhibitors of nitric oxide, glybenclamide, the hormone receptor antagonists ICI 182,780 and flutamide, and after de-endothelialization. Tamoxifen caused acute dilation of coronary arteries but less than estradiol. Tamoxifen-and estradiol-induced acute vasodilation was not nitric oxide- or endothelium-dependent, but was adenosine triphosphate-sensitive potassium channel-dependent. Tamoxifen-induced vasorelaxation was inhibited by antagonism of the classic estrogen receptor and antagonism of the androgen receptor with flutamide, whereas estrogen-induced vasorelaxation was inhibited partially by classic estrogen receptor antagonism but not by androgen receptor antagonism. Tamoxifen attenuated both the sensitivity of vasoconstriction to endothelin-1 and the maximal response. Tamoxifen and estradiol are both acute coronary vasodilators, with similar mechanisms of action. Tamoxifen also attenuates coronary vasoconstriction. Such properties may account for some of the observed cardiovascular clinical benefits seen in observational studies of tamoxifen use.

Variations in endothelial function and arterial compliance during the menstrual cycle

Female sex hormones have been implicated in the cardioprotection of premenopausal women. However, the cardiovascular actions of these hormones and the effects of their natural fluctuations during the menstrual cycle are not fully understood. We studied changes in vascular function during the menstrual cycle in 15 healthy premenopausal women. Four noninvasive procedures were performed during the early follicular (EF), late follicular (LF), early luteal (EL), and late luteal (LL) phases: flow-mediated dilatation (FMD) of the brachial artery during reactive hyperemia, laser Doppler velocimetry (LDV) with direct current iontophoresis of acetylcholine (ACh) and nitroprusside, whole body arterial compliance (WBAC), and pulse wave velocity. Hormone levels were consistent with predicted cycle phase and showed that all subjects ovulated during the cycle studied. FMD, LDV with ACh, and WBAC varied cyclically, with significant increases from the F to LF phase, sharp falls in the EL phase, and significant recoveries in the LL phase. These changes were most marked for FMD [EF, 8.8 +/- 0.6% (mean +/- SEM); LF, 10.0 +/- 0.7; EL, 4.2 +/- 0.6; LL, 8.6 +/- 0.9] and the LDV response to ACh (EF, 2.7 +/- 0.2 V/min; LF, 3.3 +/- 0.4; EL, 1.8 +/- 0.3; LL, 2.7 +/- 0.4). WBAC changed similarly (EF, 0.58 +/- 0.08 arbitrary units; LF, 0.84 +/- 0.06; EL, 0.65 +/- 0.05; LL, 0.68 +/- 0.06). Sodium nitroprusside-induced vasodilatation decreased significantly from EF to EL, with no other significant difference, and pulse wave velocity did not vary significantly over the four time points. Conductance and resistance artery endothelial reactivity and smooth muscle sensitivity to nitric oxide and arterial compliance are modulated significantly in response to the changing hormonal patterns of the menstrual cycle. These findings emphasize the importance of menstrual phase in the interpretation of data on endothelial function and may provide insights into the mechanisms underlying sex differences in cardiovascular risk and other disease processes in premenopausal women.

Mechanical strain stimulates a mitogenic response in coronary vascular smooth muscle cells via release of basic fibroblast growth factor

Mechanical strain has been shown to induce mitogenesis in a rat neonatal vascular smooth muscle (VSM) cell line in a response mediated predominantly by transcription, expression, and release of platelet-derived growth factor (PDGF). We examined the effect of cyclic mechanical strain and growth factor production on mitogenic response in ovine coronary artery smooth muscle cells. Vascular smooth muscle cells were cultured from explants of left anterior descending (LAD) coronary arteries from young sheep. Cells for experiments were grown on wells with silicone-elastomer bottoms, and subjected to strain (60 cycles/min) using a vacuum actuated strain device. Tritiated thymidine incorporation was used as a measure of DNA synthesis. Cell membrane damage was assessed with differentially permeable nuclear staining dyes. We observed an increase in tritiated thymidine incorporation in response to strain with a temporal response identical to that observed in response to exogenous growth factors (PDGF-BB and basic fibroblast growth factor [bFGF]). Supernatant medium obtained from stretched cells induced a twofold increase in DNA synthesis in unstretched cells. The mitogenic response was abolished by monoclonal antibodies to bFGF, but not by antibodies to PDGF-AB. Studies of fluorescent dye exclusion indicated the stretching protocol caused no cell membrane damage. Thus, mechanical strain is an important stimulus for growth factor release in coronary VSM cells. The mitogenic response is mediated by release of bFGF.

Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women

OBJECTIVES

Many women seek alternatives to hormonal therapies for the management of menopausal symptoms. Among the treatments currently popular are extracts of wild yam (Dioscorea villosa), which are applied topically in the form of a cream. These preparations are known to contain steroidal saponins, including diosgenin, which has been claimed to influence endogenous steroidogenesis. However, there have been no studies of the safety or efficacy of these preparations in the management of menopausal symptoms.

METHODS

We therefore conducted a double-blind, placebo-controlled, cross-over study of the effects of a wild yam cream in 23 healthy women suffering from troublesome symptoms of the menopause. After a 4-week baseline period, each woman was given active cream and matching placebo for 3 months in random order. Diaries were completed over the baseline period and for 1 week each month thereafter, and blood and saliva samples were collected at baseline and at 3 and 6 months, for measurement of lipids and hormones.

RESULTS

The average age of the subjects was 53.3 +/- 1.1 (SEM) years and average time since last period 4.3 +/- 0.9 years. At baseline, the average body mass index was 27.3 +/- 0.8, cholesterol level 5.7 +/- 0.2 mmol/l and follicle stimulating hormone (FSH) level 74.2 +/- 5.1 IU/l; estradiol levels were undetectable in the majority of cases. After 3 months of treatment, no significant side-effects were reported with either active treatment or placebo, and there were no changes in weight, systolic or diastolic blood pressure, or levels of total serum cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, FSH, glucose, estradiol, or serum or salivary progesterone. Symptom scores showed a minor effect of both placebo and active treatment on diurnal flushing number and severity and total non-flushing symptom scores, and on nocturnal sweating after placebo, but no statistical difference between placebo and active creams.

CONCLUSIONS

This study suggests that short-term treatment with topical wild yam extract in women suffering from menopausal symptoms is free of side-effects, but appears to have little effect on menopausal symptoms. It emphasizes the importance of careful study of treatments for menopausal symptoms if women are to be adequately informed about the choices available to them.

Comparative effects of ACE inhibitors and an angiotensin receptor blocker on atherosclerosis and vascular function

BACKGROUND

Both angiotensin-converting enzyme inhibitors (ACE-I(s)) and angiotensin receptor blockers (ARB(s)) provide vascular protection. This study was designed to compare ACE-I(s) with widely differing tissue affinity (captopril and quinapril) and an ARB (losartan) on vascular protection against the adverse effects of high cholesterol.

METHODS AND RESULTS

Forty-two New Zealand rabbits on a 0.5% cholesterol diet were randomized into control, captopril (10 mg/kg/d), quinapril (0.3 mg/kg/d), and losartan (8 mg/kg/d) groups for 14 weeks. Captopril, quinapril, and losartan significantly attenuated aortic lipid lesions (P=0.001). Captopril and quinapril were more effective than losartan in preserving vascular relaxation.

CONCLUSIONS

Captopril, quinapril, and losartan had similar protective effects against atherogenesis. Captopril and quinapril were more effective than losartan in preserving vascular function. Increased bradykinin by ACE inhibition may be responsible for this improved vascular endothelial function.

Estrogen inhibits mechanical strain-induced mitogenesis in human vascular smooth muscle cells via down-regulation of Sp-1

OBJECTIVE

The cellular basis of the cardioprotective effects of estrogen are largely unknown. An inhibitory effect on vascular smooth muscle (VSM) growth has been proposed. We examined the effect of 17beta-estradiol (E2) on mechanical strain-induced mitogenesis in human fetal VSM cells.

METHODS AND RESULTS

Cells were grown on fibronectin-coated plates with silicone-elastomer bottoms, and exposed to cyclic mechanical strain (60 cycles/min), with and without E2 (1 nmol/l), for 48 h. [3H]-Thymidine incorporation was measured during the last 6 h. Strain induced 1.5-2 fold increases in DNA synthesis that were attenuated by antibodies to platelet-derived growth factor (PDGF) AA and BB. Strain also induced increases both in mRNA and protein levels of Sp-1, a transcription factor that binds to the PDGF-A gene promoter site. E2 attenuated strain-induced mitogenesis, and also increases in mRNA and protein levels of Sp-1. The estrogen receptor (ER) antagonist ICI 182,780 (100 nmol/l) reversed the inhibitory effect of E2 on strain-induced increases in DNA synthesis and Sp-1 protein. RT-PCR analysis showed presence of both ER-alpha and -beta in these cells.

CONCLUSIONS

Estrogen inhibits strain-induced mitogenesis in human VSM cells via an ER mediated process involving down-regulation of the transcription factor Sp-1.

Comparative effects of pretreatment with captopril and losartan on cardiovascular protection in a rat model of ischemia-reperfusion

OBJECTIVES

We sought to assess the comparative effects of pretreatment with captopril and losartan on myocardial infarct size and arrhythmias in a rat model of ischemia-reperfusion.

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) inhibit the renin-angiotensin system in different ways. However, the comparative effects of pretreatment with ACE inhibitors or ARBs on acute myocardial infarct size and arrhythmias are unknown.

METHODS

We randomly assigned 117 female Sprague-Dawley rats into three groups: group N was the normal control; group C was given 40 mg/kg body weight per day of captopril in drinking water; and group L was given 40 mg/kg per day of losartan in drinking water. After 10 weeks of pretreatment, 25 rats in each group were subjected to 17 min of left anterior descending coronary artery occlusion and 2 h of reperfusion with hemodynamic and electrocardiographic monitoring. Fourteen rats in each group had blood samples drawn and aortic rings removed to study vascular reactivity.

RESULTS

Mortality during ischemia and reperfusion was lower in combined groups L and C than in group N (4.2% vs. 19.2%, p = 0.042). Rats treated with losartan had significantly higher levels of angiotensin II in their plasma. Hemodynamic variables were not significantly different among the three groups. The thresholds of ventricular fibrillation (VF) before occlusion and after reperfusion were significantly higher in groups L and C than in group N (1.99 +/- 0.24 and 1.93 +/- 0.27 vs. 1.23 + 0.17 mA, p = 0.04; 2.13 +/- 0.25 and 1.78 +/- 0.22 vs. 0.95 +/- 0.11 mA, p = 0.001). The average episodes of ventricular tachycardia (VT) and VF per rat were significantly less in groups L and C than in group N (0.96 +/- 0.2 and 1.2 +/- 0.3 vs. 2.8 + 0.4 mA, p < 0.001). Myocardial infarct size was significantly smaller in groups L and C than in group N (34 +/- 3% and 35 +/- 3% vs. 44 +/- 3%, p = 0.031, 0.043). Endothelium-dependent vasorelaxation induced by a calcium ionophore (A23187) was increased in both groups but was only statistically significant in group C (p = 0.020).

CONCLUSIONS

Losartan and captopril have similar cardiovascular protective effects in a rat model of ischemia-reperfusion. They increased the threshold of VF, decreased mortality and decreased episodes of VT and VF, as well as decreased myocardial infarct size.

Matrix-dependent gene expression of egr-1 and PDGF A regulate angiotensin II-induced proliferation in human vascular smooth muscle cells

We have previously shown, in a neonatal rat cell line, that angiotensin II (Ang II)-induced proliferation in vascular smooth muscle cells is extracellular matrix (ECM) dependent. We hypothesized that such an effect might be mediated via differences in Ang II-induced increases in the transcriptional factor early growth response-1 (Egr-1) gene and, consequently, in platelet-derived growth factor (PDGF). Cultured human newborn aortic smooth muscle cells were studied on 4 different surfaces: (1) plastic, (2) laminin, (3) collagen, and (4) fibronectin. Ang II-induced increases in DNA synthesis were significantly greater on collagen (2.0+/-0.3-fold) and fibronectin (1.9+/-0.3-fold) than on laminin (1.0+/-0.2-fold) or plastic (1.4+/-0.2-fold). As with DNA synthesis, at 48 and 72 hours, Ang II-induced increases in cell numbers occurred only in cells grown on collagen and fibronectin culture plates and were blocked by an antagonist to the angiotensin type 1 (losartan, 10 micromol/L) but not the angiotensin type 2 (PD 123319, 10 micromol/L) receptor. Anti-PDGF AA antibody (6 microg/mL) blocked the increase in DNA synthesis by 60% to 64% in cells on collagen or fibronectin cultures but not on plastic cultures. When PDGF-AA (10 ng/mL) and Ang II were added together, DNA synthesis increased 2-fold and did not differ on the various ECM proteins. Increases in PDGF A-chain mRNA were observed only in cells grown on collagen (3.21+/-0.65-fold) and fibronectin (2.86+/-0.49-fold) plates 2 to 8 hours after the addition of Ang II and were blocked by losartan but not PD 123319. Expression of Egr-1, an early growth response gene, increased at 15 minutes, peaked at 30 minutes, and returned to normal after 2 hours with Ang II treatment. Ang II-induced increases in Egr-1 mRNA were greater on collagen (4. 82+/-0.66-fold at maximum) and fibronectin (4.01+/-0.56-fold) than on laminin (2.74+/-0.45-fold) or plastic (2.53+/-0.40-fold) and were blocked by losartan but not PD 123319. Thus, in human vascular smooth muscle cells in culture, Ang II-induced proliferation is mediated via the angiotensin type 1 receptor, dependent on ECM proteins, and regulated by differential gene expression of Egr-1 and PDGF-1.

Effects of L-arginine on atherogenesis and endothelial dysfunction due to secondhand smoke

Secondhand smoke (SHS) and hypercholesterolemia increase cardiovascular risk. We hypothesized that L-arginine, the precursor of nitric oxide (NO), might protect against atherogenesis and endothelial dysfunction caused by SHS. The effects of L-arginine supplementation (2.25% solution ad libitum) and SHS (smoking chambers for 10 weeks) were examined in 32 hypercholesterolemic rabbits. Eight normal rabbits served as controls. Acetylcholine- and nitroglycerin-induced vasorelaxation was assessed in aortic rings precontracted with norepinephrine. Hypercholesterolemia increased intimal lesion area (P=0.012), reduced endothelium-dependent relaxation (P=0.009), and reduced basal (P=0.005) and stimulated (P<0.0005) production of NOs. SHS increased intimal lesion area (P=0. 01) norepinephrine-induced contraction (P=0.001) and reduced endothelium-dependent relaxation (P=0.02). SHS-induced increase in norepinephrine contraction was abolished by the inhibition of NO synthase and removal of endothelium. L-Arginine improved endothelium-dependent relaxation (P=0.001) and attenuated SHS-induced endothelial dysfunction (P=0.007) and atherogenesis (P=0. 001). Basal production of nitrogen oxides correlated inversely with intimal lesion area (r=-0.66; P<0.0005) and stimulated production of NOs correlated with endothelium-dependent relaxation (r=-0.66; P<0. 001). SHS causes endothelial dysfunction and increased adrenergic responsiveness and atherogenesis in hypercholesterolemic rabbits. Chronic dietary supplementation with the NO precursor L-arginine mitigates these effects. The adverse vascular consequences of SHS appear to be mediated via deleterious effects on endothelial function.

Coronary vasodilator effects of BNP: mechanisms of action in coronary conductance and resistance arteries

Brain natriuretic peptide (BNP), a hormone secreted predominantly in ventricular myocytes, may influence coronary vascular tone. We studied the coronary vasodilatory response to BNP under physiological conditions and after preconstriction with endothelin-1 (ET-1) in anesthetized pigs. Average peak-flow velocity (APV) was measured using intracoronary Doppler, and cross-sectional area (CSA) was measured using intravascular ultrasound. Coronary blood flow (CBF) was calculated. Intracoronary BNP induced dose-dependent increases in CSA, APV, and CBF similar in magnitude to those induced by nitroglycerin (NTG). The magnitude of BNP-induced vasodilation was accentuated after preconstriction with ET-1. Pretreatment with either the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester or the cyclooxygenase inhibitor indomethacin attenuated the coronary vasodilator effect of BNP in resistance arteries without influencing epicardial vasodilation. Pretreatment with the ATP-sensitive potassium-channel blocker glibenclamide enhanced epicardial vasodilation in response to BNP. We conclude that BNP exerts coronary vasodilator effects, predominantly in epicardial conductance vessels. An accentuated vasodilatory response to BNP occurs in ET-1-preconstricted arteries. BNP-induced vasodilation in coronary resistance arteries may be partially mediated via nitric oxide and/or prostaglandin release.

Estrogen supplementation attenuates glucocorticoid and catecholamine responses to mental stress in perimenopausal women

Estrogens are reported to provide protection against the development of cardiovascular disease in women, but the mechanisms underlying these effects are not well defined. We hypothesized that estrogen might affect the hormonal responses to stress. We therefore studied cortisol, ACTH, epinephrine, norepinephrine, and norepinephrine spillover and hemodynamic responses to a 10-min mental arithmetic test in 12 perimenopausal women randomized to 8 weeks of estrogen supplementation (estradiol valerate, 2 mg daily; n = 7) or placebo (n = 5). Total body and forearm norepinephrine spillover were measured by radiotracer methodology. After supplementation with estradiol, the increases in both systolic and diastolic blood pressure in response to mental stress were reduced, and cortisol, ACTH, plasma epinephrine and norepinephrine, and total body norepinephrine spillover responses to stress were significantly attenuated (P < 0.05 in each case). Forearm norepinephrine spillover was unchanged by estrogen, and there was no change in any of the responses after placebo. We conclude that estrogen supplementation in perimenopausal women attenuates blood pressure, glucocorticoid, and catecholamine responses to psychological stress.

In-utero and neonatal exposure to secondhand smoke causes vascular dysfunction in newborn rats

OBJECTIVES

We sought to determine the effects of secondhand smoke (SHS) exposure on vascular reactivity in newborn and infant rats.

BACKGROUND

Secondhand smoke exposure increases cardiovascular risk. Secondhand smoke-induced endothelial dysfunction has been demonstrated in older teenagers and young adults. We have previously shown in adult rabbits that SHS induces atherogenesis and endothelial dysfunction. The effects of SHS on vascular function in the offspring of SHS-exposed mothers and in infants are unknown.

METHODS

In this study the effects of in-utero (21 days) and neonatal (28 days) exposure to SHS were examined in 80 rats, 4 weeks of age, in a 2-by-2 design study. Rats were exposed to sidestream smoke in smoking chambers. Aortic rings were excised and isometric force responses to phenylephrine, acetylcholine, A23187 and nitroglycerin were studied in organ baths.

RESULTS

Neonatal SHS exposure reduced animal weight (p=0.009). In-utero exposure increased the sensitivity (decreased the EC50) of aortic rings to phenylephrine (p < 0.0005), as did neonatal exposure (p=0.01). Maximal contraction to phenylephrine was reduced by in-utero exposure (p=0.04). In-utero SHS exposure reduced maximal endothelium-dependent relaxation to acetylcholine (p=0.04) and increased the EC50 (p=0.05), suggesting impaired sensitivity to acetylcholine. In-utero exposure decreased the sensitivity (increased the EC50) to the endothelium-independent vasodilator nitroglycerin (p=0.003).

CONCLUSIONS

Secondhand smoke has detrimental effects on vascular smooth muscle function in the newborn.

Antioxidant diet preserves endothelium-dependent vasodilatation in resistance arteries of hypercholesterolemic rabbits exposed to environmental tobacco smoke

Environmental tobacco smoke (ETS) has been shown to impair endothelium-dependent vasodilation in vitro. This study was performed to investigate the effect of ETS on acetylcholine (ACh)-mediated blood pressure changes in vivo. Seventeen New Zealand White rabbits were fed a cholesterol diet (0.3%) for 13 weeks. Ten animals were exposed to ETS for 6 h/day, and seven animals were not exposed to ETS (non-ETS). Four of the ETS and three of the non-ETS-exposed rabbits received an antioxidant vitamin diet before and during their cholesterol diet for 21 weeks. Six rabbits served as healthy controls. To determine endothelium-dependent and independent blood pressure (BP) responses, BP was measured through a Tygon catheter, inserted into the right carotid artery at baseline and after each of three incremental intravenous doses of norepinephrine (NE; 1, 4, and 20 microg/kg), ACh (3.3, 10, and 30 microg/kg), and nitroglycerin (NTG; 1, 10, and 40 microg/kg). After NE, BP increases were significantly attenuated in the ETS group (p = 0.001) but not in animals receiving the antioxidant supplement. At both the middle and high ACh concentrations, ETS (p = 0.03 and p = 0.01, respectively) and hypercholesterolemia (p = 0.03 and p = 0.06, respectively) attenuated ACh-induced reductions in BP. At the highest ACh concentration, vitamins enhanced the reduction in BP (p = 0.002) and blocked the effect of ETS (p = 0.04). Neither ETS nor vitamins influenced NTG-induced decreases in BP. A combined antioxidant-vitamin diet can preserve endothelium-dependent vasodilatation in the hypercholesterolemic rabbit exposed to ETS.

Recent Advances in the Prevention of Coronary Artery Diseases: Focus on Primary Prevention

BACKGROUND: Several new strategies for prevention of coronary artery disease have emerged. This review examines the various approaches to primary prevention, and some aspects of secondary prevention. METHODS AND RESULTS: The role of aspirin, beta-blockers, exercise, diets, fish intake, vitamin E, and folic acid are discussed. The potential role of chlamydia in atherosclerosis, the protective effect of alcohol consumption, and the benefits of female sex hormones are also examined. An update on lipid-lowering therapy, and a summary of the recent major clinical trials establishing the use of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors in primary and secondary prevention of coronary artery disease, are provided. CONCLUSIONS: An aggressive approach to medical management of coronary artery disease a substantial reduction in risk.

Estrogen supplementation decreases norepinephrine-induced vasoconstriction and total body norepinephrine spillover in perimenopausal women

Estrogens are reported to provide protection against the development of cardiovascular disease in women, but the mechanisms underlying these effects are not well defined. We hypothesized that estrogen might reduce neural cardiovascular tone. We therefore studied responses to exogenous norepinephrine and norepinephrine spillover in 12 perimenopausal women randomized to 8 weeks of estrogen supplementation (estradiol valerate, 2 mg daily, n=7) or placebo (n=5). Forearm blood flow was measured by venous occlusion plethysmography, and vasoactive agents were infused through a brachial artery cannula in doses that did not influence blood pressure or heart rate. Total body and forearm norepinephrine spillover were measured by radiotracer methodology. Forearm vasoconstrictor responses to norepinephrine (25, 50, and 100 ng/min) were attenuated after estrogen supplementation (P=.002). Vasoconstrictor responses to angiotensin II (8, 16, and 32 ng/min) were unchanged postestrogen. There was a significant reduction in total body spillover of norepinephrine after estrogen supplementation (pre-estrogen, 700+/-152; postestrogen, 439+/-150 ng/min; P<.05), but there was no change after placebo. Total body clearance and forearm spillover of norepinephrine were unchanged by either estrogen or placebo. Estrogen supplementation also significantly decreased both systolic and diastolic blood pressures. Therefore, estrogen supplementation in perimenopausal women selectively attenuates vasoconstrictor responses to norepinephrine and reduces total body norepinephrine spillover, which is an index of sympathetic neural activity.

Effects of second-hand smoke and gender on infarct size of young rats exposed in utero and in the neonatal to adolescent period

OBJECTIVES

We sought to assess the effects of second-hand smoke (SHS) and gender on infarct size in young rats exposed in utero or in the neonatal to adolescent period, or both.

BACKGROUND

We previously demonstrated that exposure to SHS increases infarct size in a rat model of ischemia and reperfusion, with a dose-response relation. These results are consistent with epidemiologic studies demonstrating that SHS increases risk of death from heart disease.

METHODS

Thirty-one pregnant female rats were randomly divided into two groups: those exposed to SHS and a control group (non-SHS). After 3 weeks, each rat had given birth to 10 to 12 rats. One hundred one neonatal rats were divided into four groups according to exposure to SHS in utero (SHSu) and randomized to SHS exposure in the neonatal to adolescent period (SHSna). After 12 weeks, all rats were subjected to 17 min of left coronary artery occlusion and 2 h of reperfusion.

RESULTS

Birth mortality was higher in the SHSu group than in the non-SHSu group (11.9% vs. 2.8%, p < 0.001). Body weight of neonatal rats at 3 and 4 weeks in the two SHSu groups was lower than that of rats in the two non-SHSu groups (p < 0.001). Exposure to SHSna increased endothelin-1 levels in plasma (p = 0.001). In all 70 young rats who survived the neonatal period, infarct size (Infarct mass/Risk area x 100%) was greater in the SHSna groups than in the non-SHSna groups (p = 0.005) and in the male groups than in the female groups (p < 0.001).

CONCLUSIONS

Exposure to SHS in the neonatal to adolescent period and male gender increased myocardial infarct size in a young rat model of ischemia and reperfusion. These results are consistent with epidemiologic studies demonstrating that SHS increases the health risk to neonates and adolescents.

Physiological concentrations of estradiol attenuate endothelin 1-induced coronary vasoconstriction in vivo

BACKGROUND

Estrogens are cardioprotective hormones and are reported to have antianginal properties. We examined the effect of physiological concentrations of 17beta-estradiol on coronary reactivity in anesthetized female farm pigs.

METHODS AND RESULTS

Epicardial coronary cross-sectional area (CSA) was assessed by two-dimensional intravascular ultrasound, average coronary peak flow velocity (APV) by intravascular Doppler velocimetry, and coronary blood flow (CBF) was calculated. Dose-response curves to intracoronary endothelin-1 (ET-1, 1 pmol/L to 10 nmol/L), the selective ET(B) receptor agonist sarafotoxin (1 pmol/L to 10 nmol/L), and serotonin (0.1 nmol/L to 1 micromol/L) were assessed before and after a 10-minute infusion of intracoronary estradiol (1 nmol/L). Before estradiol administration, ET-1 induced significant dose-dependent decreases in CSA, APV, and CBF. Estradiol attenuated ET-1-induced epicardial vasoconstriction (P<.001) as well as ET-1-induced decreases in APV (P=.05) and CBF (P=.012). In an additional five pigs, vehicle (DMSO) had no effect on ET-1-induced coronary vasoconstriction. Before estradiol administration, sarafotoxin induced no net change in CSA but induced increases in APV and CBF, the extent of which did not change significantly after estradiol. Serotonin induced small decreases in CSA but increased APV and CBF. Estradiol did not influence serotonin-induced changes in CSA, APV, or CBF.

CONCLUSIONS

We conclude that estradiol attenuates ET-1-induced vasoconstriction, possibly through effects on the ET(A) receptor, because selective ET(B) receptor-induced stimulation with sarafotoxin remained unchanged. Such an effect on the ET(A) receptor may relate to the antianginal properties of estrogens.

Premature coronary artery disease associated with a disruptive mutation in the estrogen receptor gene in a man

BACKGROUND

While estrogens protect against coronary artery disease in women, it is unclear whether they influence cardiovascular function in men. The present report describes coronary vascular abnormalities and the lipoprotein profile of a male patient with estrogen insensitivity caused by a disruptive mutation in the estrogen-receptor gene.

METHODS AND RESULTS

Stress thallium scintigraphy, echocardiography, and electron-beam computed tomography (CT) scanning of the coronary arteries and detailed lipoprotein analysis were performed. Electron-beam CT scanning of the coronary arteries showed calcium in the left anterior descending artery. Lipoprotein analysis showed relatively low levels of total (130 mg/dL), LDL (97 mg/dL), and HDL (34 mg/dL) cholesterol; apolipoprotein A-I (91.7 mg/dL); and lipoprotein(a) (4.1 nmol/L), but normal levels of triglycerides (97 mg/dL) and pre-beta-1-HDL cholesterol (61 microg/mL).

CONCLUSIONS

The absence of functional estrogen receptors may be a novel risk factor for coronary artery disease in men.

Hormonal therapy increases arterial compliance in postmenopausal women

OBJECTIVES

This study investigated the effects of hormonal therapy on large arterial properties.

BACKGROUND

Arterial stiffness is an emerging risk marker for coronary heart disease and is potentially modifiable. Postmenopausal use of hormonal therapy is associated with a lower risk of coronary heart disease.

METHODS

Total systemic arterial compliance (SAC) and pulse wave velocity (PWV) were determined in 26 premenopausal and 52 postmenopausal women, 26 of whom were taking hormonal therapy.

RESULTS

Arterial compliance was greater in the premenopausal group (mean +/- SEM 0.57 +/- 0.04 arbitrary compliance units [ACU]) than in the postmenopausal group not taking hormonal therapy (0.26 +/- 0.02 ACU, p = 0.001). Postmenopausal women taking hormonal therapy had a significantly increased total SAC compared with women not taking hormonal therapy (0.43 +/- 0.02 vs. 0.26 +/- 0.02 ACU, p = 0.001). PWV in the aortofemoral region in the premenopausal women was 6.0 +/- 0.2 vs. 8.9 +/- 0.3 m/s (p < 0.001) in untreated postmenopausal women. However, postmenopausal women taking hormonal therapy had a significantly lower PWV than those not taking hormonal therapy (7.9 +/- 0.2 vs. 8.9 +/- 0.3 m/s, p = 0.01). Eleven postmenopausal women had their hormone replacement therapy withdrawn for 4 weeks, resulting in a significant decrease in SAC and a significant increase in aortofemoral PWV.

CONCLUSIONS

The increased SAC and decreased PWV in women receiving hormonal therapy suggest that such therapy may decrease stiffness of the aorta and large arteries in postmenopausal women, with potential benefit for age-related cardiovascular disorders. The reduction of arterial compliance with age appears to be altered with hormonal therapy.

Sex hormones and vascular reactivity

It is increasingly recognized that sex steroids have, among many other effects, the ability to cause vasodilation. The vasodilatory effects of estradiol have been the best documented and described. At low concentrations, estradiol has the ability to improve impaired endothelium dependent (nitric oxide mediated) relaxation in estrogen deficient subjects. At high concentrations, estradiol causes vasodilation principally by endothelium independent mechanisms, in a gender independent fashion, which appear to involve a number of pathways such as ATP-dependent K+ channels. Testosterone also has ability, at higher doses, to cause vasodilation of the coronary circulation, in a gender independent fashion. The mechanisms of sex steroid-induced vasodilation are reviewed in this article.

Chronic dietary L-arginine prevents endothelial dysfunction secondary to environmental tobacco smoke in normocholesterolemic rabbits

Our goal was to determine whether environmental tobacco smoke causes endothelial dysfunction in the absence of hypercholesterolemia and whether such an effect can be prevented by supplementation with L-arginine. Environmental tobacco smoke exposure is associated with an increase in coronary artery disease events and mortality. We have previously demonstrated that environmental tobacco smoke causes endothelial dysfunction and atherosclerosis in rabbits with diet-induced hypercholesterolemia and atherosclerosis and that chronic dietary L-arginine supplementation prevents this. The effects of L-arginine supplementation (2.25% solution ad libitum) and environmental tobacco smoke (smoking chambers for 10 weeks) were examined with a 2 x 2 design in 32 rabbits fed a normal diet. Acetylcholine, calcium ionophore A23187, and nitroglycerin-induced vasorelaxation were assessed in aortic rings precontracted with phenylephrine. Endothelial L-arginine levels were measured by chromatography. Chronic L-arginine supplementation increased serum (P < .001) and endothelial (P = .003) L-arginine levels. Environmental tobacco smoke reduced endothelium-dependent acetylcholine-induced relaxation, and L-arginine blocked this adverse effect (P = .04). Environmental tobacco smoke tended to increase phenylephrine-induced contraction (P = .06). Neither environmental tobacco smoke nor L-arginine influenced A23187-induced relaxation nor endothelium-independent nitroglycerin-induced relaxation. Endothelial dysfunction secondary to environmental tobacco smoke may occur in the absence of diet-induced hypercholesterolemia and atherosclerosis. Chronic dietary supplementation with a nitric oxide donor such as L-arginine offsets the endothelial dysfunction associated with environmental tobacco smoke in normocholesterolemic rabbits, possibly through substrate loading of the nitric oxide pathway.

Reduced dietary potassium reversibly enhances vasopressor response to stress in African Americans

Acute vasopressor responses to stress are adrenergically mediated and hence potentially subject to differential modulation by dietary potassium and sodium. The greater vasopressor responsiveness in blacks compared with whites might then be consequent not only to a high dietary salt intake but also to a marginally reduced dietary potassium intake. Under controlled metabolic conditions, we compared acute vasopressor responses to cold and mental stress in black and white normotensive men during three successive dietary periods: (1) while dietary potassium was reduced (30 mmol K+/70 kg per day) and salt was restricted (10 to 14 days); (2) while salt was loaded (15 to 250 mmol Na+/70 kg per day) (7 days); and (3) while salt loading was continued and potassium was either supplemented (70 mmol K+/70 kg per day) (7 to 21 days) in 9 blacks and 6 whites or continued reduced (30 mmol K+/70 kg per day) (28 days) in 4 blacks (time controls). At the lower potassium intake, cold-induced increase in forearm vascular resistance in blacks was twice that in whites during both salt restriction and salt loading. Normalization of dietary potassium attenuated cold-induced increases in both forearm vascular resistance and systolic and diastolic blood pressures in blacks but only in systolic pressure in whites. In blacks but not in whites, normalization of dietary potassium attenuated mental stress-induced increases in systolic and diastolic pressures. In normotensive blacks but not whites, a marginally reduced dietary intake of potassium reversibly enhances adrenergically mediated vasopressor responsiveness to stress. That responsiveness so enhanced over time might contribute to the pathogenesis of hypertension in blacks.

Testosterone worsens endothelial dysfunction associated with hypercholesterolemia and environmental tobacco smoke exposure in male rabbit aorta

OBJECTIVES

To assess the effects of interaction of sex hormones, hypercholesterolemia (HC) and environmental tobacco smoke (ETS) exposure on endothelium-dependent relaxation, we examined vascular reactivity in vitro in an animal model of atherogenesis.

BACKGROUND

Animal and human studies indicate the presence of interactions between classic coronary artery disease risk factors and endothelium-dependent relaxation. Sex hormones have also been shown to influence release of endothelium-derived relaxing factor.

METHODS

New Zealand White rabbits were randomized to receive either an HC diet (n = 8) or ETS exposure plus HC diet (n = 8). Eight rabbits receiving a normal diet, without exposure to ETS, served as the control group. The HC diet consisted of 3% soybean oil and 0.3% cholesterol by weight over 13 weeks. The source of ETS was sidestream smoke of 4 cigarettes/15 min, 6 h/day, 5 days/week over 10 weeks in a smoking chamber. Rabbits were killed, and fresh aortic rings were harvested and maintained in oxygenated Krebs solution in an organ bath at 37 degrees C. Rings were precontracted with norepinephrine and exposed to acetylcholine in increasing doses, and isometric tension was recorded. Rings were also exposed to physiologic concentrations (1 nmol/liter) of either 17-beta-estradiol, testosterone or progesterone before pre-contraction with norepinephrine and relaxation with acetylcholine. Endothelium-independent relaxation was studied using nitroglycerin. The surface area of the ring covered by lipids was measured by Sudan IV staining.

RESULTS

HC and ETS significantly reduced endothelium-dependent relaxation (p = 0.01 and p < 0.0005, respectively) and caused atherogenesis (p < 0.0005 and p = 0.047, respectively) but did not affect endothelium-independent relaxation. Incubation with estradiol and estradiol plus progesterone did not influence endothelium-dependent relaxation. Testosterone reduced endothelium-dependent relaxation (p = 0.049) and augmented the endothelial dysfunction associated with ETS exposure and HC (p = 0.03).

CONCLUSIONS

Both HC and ETS are atherogenic and impair endothelial function but do not affect endothelium-independent relaxation. Physiologic levels of estradiol and estradiol plus progesterone do not affect endothelium-dependent relaxation. Physiologic levels of testosterone impair relaxation and augment the endothelial dysfunction associated with ETS exposure and HC.

Use of intravascular ultrasound in evaluating repeated balloon rupture during coronary stenting

Balloon rupture during coronary angioplasty is a well-recognized complication of PTCA. Coronary angiography commonly fails to elicit the cause of balloon perforation. We present a case with multiple balloon rupture during additional high-pressure inflations of a Palmaz-Schatz stent where intravascular ultrasound was useful in revealing a calcified lesion protruding through the struts of the stent.

Testosterone induces dilation of canine coronary conductance and resistance arteries in vivo

BACKGROUND

Although estrogens have been shown to be vasoactive hormones, the vascular effects of testosterone are not well defined. Like estrogen, testosterone causes relaxation of isolated rabbit coronary arterial segments. We examined the vasodilator effects of testosterone in vivo in the coronary circulation and the potential mechanisms of its actions.

METHODS AND RESULTS

Using simultaneous intravascular two-dimensional and Doppler ultrasound, we examined the effect of intracoronary testosterone in coronary conductance and resistance arteries in 10 anesthetized dogs (5 male, 5 female). We also assessed the contribution of NO, prostaglandins, ATP-sensitive K+ channels, and classic estrogen receptors to testosterone-induced vasodilation. Testosterone induced a significant increase in cross-sectional area, average coronary peak flow velocity, and calculated volumetric coronary blood flow at the 0.1 and 1 mumol/L concentrations. This effect was independent of sex. Pretreatment with N omega-nitro-L-arginine methyl ester to block NO synthesis decreased testosterone-induced increase in cross-sectional area, average coronary peak flow velocity, and coronary blood flow. Pretreatment with glybenclamide to assess the role of ATP-sensitive K+ channels did not influence testosterone-induced dilation in epicardial arteries but did attenuate its effect in the microcirculation. Pretreatment with indomethacin or the classic estrogen-receptor antagonist ICI 182,780 did not alter testosterone-induced changes.

CONCLUSIONS

Short-term administration of testosterone induces a sex-independent vasodilation in coronary conductance and resistance arteries in vivo. Acute testosterone-induced coronary vasodilation of epicardial and resistance vessels is mediated in part by endothelium-derived NO. ATP-sensitive K+ channels appear to play a role in the vasodilatory effect of testosterone in resistance arteries.

Comparison of adenosine to dipyridamole in degree of coronary hyperemic response in heart transplant recipients

Transplant coronary vasculopathy is associated with endothelial dysfunction. Microvascular function, assessed as coronary flow reserve, has been reported to be normal. We used intracoronary ultrasound technology to simultaneously assess conductance and resistance vessel function in response to standard dosages of the vasodilators adenosine and dipyridamole. Coronary hemodynamic changes were assessed in 11 heart transplant recipients, at a mean duration of 784 +/- 516 days after transplantation, using a 3.2Fr or 4.3Fr, 30-MHz ultrasound imaging catheter over a 0.014-inch Doppler guidewire. Measures of coronary average peak flow velocity (APV) and coronary cross-sectional area (CSA) were used to calculate volumetric flow during intravenous infusions of adenosine (140 micrograms/kg/min over 4 minutes) and dipyridamole (140 micrograms/kg/min over 4 minutes). Flow reserve was assessed as a ratio of maximal pharmacologically induced flow to steady baseline flow before infusion. Increase in APV (261.9% vs 194.6%, p = 0.005), lumenal CSA (+11.8% vs +4.2%, p = 0.01), peak volumetric blood flow (515.8 vs 317.2 ml/min, p = 0.007), and coronary flow reserve (2.93 +/- 0.74 vs 1.99 +/- 0.53, p < 0.001) were higher with adenosine than dipyridamole. Both agents caused similar decreases in systemic blood pressure and little change in heart rate. Adenosine appears to be a more potent coronary vasodilator than dipyridamole in denervated human transplant subjects. Adenosine has a vasodilator effect at the epicardial and microvascular levels, resulting in an overall increase in volumetric flow. Flow reserve in response to both endothelium-independent agents is decreased in comparison with previously established values, but the attenuation is greater with dipyridamole.

Lifestyle modifications for hypertension. The many benefits are worth the effort

Any approach to antihypertensive therapy should include lifestyle modifications. In the beginning, emphasis should be on weight loss and exercise, along with moderation of alcohol use and cessation of smoking. Patients should be encouraged to consume fresh rather than processed (and thus high-salt) foods and to limit use of salt in cooking and at the table. Even if patients eventually require antihypertensive medications, lifestyle modifications should continue, since there is evidence that such measures minimize the number and dose of medications required.

Estrogen enhances basal nitric oxide release in the forearm vasculature in perimenopausal women

The mechanisms of estrogen-induced cardiovascular protection are incompletely understood. Acute estrogen administration enhances acetylcholine-induced vasorelaxation, suggesting that endothelium-dependent factors may be important. The effect of long-term estrogen supplementation on endothelial function has not been well defined. In this double-blind, randomized study, we examined endothelial function in forearm resistance arteries in 11 perimenopausal women before and after 8 weeks of estrogen supplementation (estradiol valerate, 2 mg daily, n = 6) or placebo (n = 5). Forearm blood flow was measured by venous-occlusion plethysmography, and vasoactive agents were infused through a brachial artery cannula in doses that did not influence blood pressure or heart rate. Estrogen supplementation significantly reduced systolic and diastolic pressures but had no effect on plasma lipoproteins. Estrogen did not alter the vasodilator responses to acetylcholine at doses of 9.25, 18.5, and 37 micrograms/min (rise in forearm blood flow before estrogen: 263 +/- 72%, 288 +/- 66%, and 383 +/- 84%, respectively; after estrogen: 205 +/- 34%, 260 +/- 44%, and 359 +/- 54%, P > .05.). Vasodilator responses to the endothelium-independent agent sodium nitroprusside (1.6 micrograms/min) were also unchanged after estrogen supplementation. However, estrogen enhanced vasoconstrictor responses to the nitric oxide synthase inhibitor NG-mono-methyl-L-arginine at doses of 1, 2, and 4 mumol/min (fall in fore-arm blood flow before estrogen: 13 +/- 9%, 20 +/- 7%, and 26 +/- 8%, respectively; after estrogen: 18 +/- 9%, 36 +/- 7%, and 47 +/- 7%, P = .04). Responses to vasoactive agents were unchanged after administration of placebo. Thus, in perimenopausal women, estrogen supplementation reduces blood pressure and enhances basal but not acetylcholine-induced nitric oxide release in fore-arm resistance arteries.

Angiographically silent atherosclerosis detected by intravascular ultrasound in patients with familial hypercholesterolemia and familial combined hyperlipidemia: correlation with high density lipoproteins

OBJECTIVES

This study sought to evaluate the extent of atherosclerosis in coronary and iliac arteries in patients with heterozygous familial hypercholesterolemia or familial combined hyperlipidemia, using intravascular ultrasound imaging.

BACKGROUND

Intravascular ultrasound imaging provides cross-sectional tomographic views of the vessel wall and allows quantitative assessment of atherosclerosis.

METHODS

Forty-eight nonsmoking, asymptomatic patients with heterozygous familial hypercholesterolemia or familial combined hyperlipidemia underwent intravascular ultrasound imaging of the left anterior descending coronary, left main coronary and common iliac arteries. Angiography showed only minimal or no narrowing in these vessels. Intravascular ultrasound images obtained during catheter pullback underwent morphometric analysis. Plaque burden was expressed as the mean and maximal intimal index (ratio of plaque area and area within the internal elastic lamina) and as the percent of vessel surface covered by plaque.

RESULTS

Intravascular ultrasound detected plaque more frequently than angiography in the left anterior descending (80% vs. 29%, respectively), left main (44% vs. 16%) and iliac arteries (33% vs. 27%). Plaque burden was higher in the left anterior descending (mean intimal index [+/- SD] 0.25 +/- 0.16) than in the left main (0.11 +/- 0.16, p < 0.001) and iliac arteries (0.02 +/- 0.04, p < 0.001). Angiography detected lumen narrowing only in coronary arteries with a maximal intimal index > or = 0.42 (left anterior descending artery) and > or = 0.43 (left main artery). The area within the internal elastic lamina increased with plaque area in the left anterior descending (r = 0.82, p < 0.001) and left main arteries (r = 0.53, p < 0.001). By stepwise multiple regression analysis, the strongest predictor for plaque burden in the left anterior descending artery was the level of high density lipoprotein (HDL) cholesterol and total/HDL cholesterol ratio for the left main artery.

CONCLUSIONS

In patients with heterozygous familial hypercholesterolemia and familial combined hyperlipidemia, extensive coronary plaque is present despite minimal or no angiographic changes. Compensatory vessel enlargement and diffuse involvement with eccentric plaque may account for the lack of angiographic changes. Levels of HDL cholesterol and total/HDL cholesterol ratio are far more powerful predictors of coronary plaque burden than are low density lipoprotein cholesterol levels in these patients with early, asymptomatic disease.

Coronary vasodilation induced by angiotensin-converting enzyme inhibition in vivo: differential contribution of nitric oxide and bradykinin in conductance and resistance arteries

BACKGROUND

We studied in coronary conductance and resistance arteries the coronary vasodilator effects of the angiotensin-converting enzyme inhibitor ramiprilat and the contribution of nitric oxide, bradykinin, and prostaglandins to this vasodilation.

METHODS AND RESEARCH

In seven anesthetized dogs, a Doppler guidewire was placed in the circumflex coronary artery to measure coronary flow velocity, and an ultrasound imaging catheter was introduced over the Doppler wire to measure coronary cross-sectional area. Drugs were infused directly into the left main coronary artery to minimize systemic effects. Ramiprilat increased both epicardial cross-sectional area and coronary blood flow velocity, resulting in an increase in absolute coronary blood flow. Pretreatment with N omega-nitro-L-arginine methyl ester (100 micromol/L intracoronary) to block nitric oxide synthase attenuated ramiprilat-induced increase in epicardial coronary cross-sectional area (P<.05) but not in coronary flow velocity or coronary blood flow. In contrast, pretreatment with the selective bradykinin antagonist HOE 140 (10 micromol/L) attenuated ramiprilat-induced increase in flow velocity (P<.025) and coronary blood flow (P<.05) but not epicardial coronary cross-sectional area. Pretreatment with indomethacin (5 mg/kg body wt IV) did not alter ramiprilat-induced increase in epicardial cross-sectional area, nor did it significantly influence coronary blood flow.

CONCLUSIONS

Other than decreasing angiotensin II production, acute ramiprilat-induced vasodilation in canine coronary conductance arteries is mediated in part by nitric oxide. Ramiprilat-induced vasodilation in resistance arteries is in part mediated by the action of bradykinin.

In vitro quantification of radiofrequency ablation lesion size using intracardiac echocardiography in dogs

The results of this study demonstrate that real-time ultrasonic evaluation of radiofrequency lesion creation and lesion size is feasible.