Maximal Vasodilation Research Articles

Increased type IIA secretory phospholipase A2 expression contributes to oxidative stress in end-stage renal disease

End-stage renal disease (ESRD) patients exhibit increased in vivo oxidative stress conceivably contributing to cardiovascular mortality. The type IIA secretory phospholipase A(2) (sPLA(2)) has proatherogenic activity. We explored the hypothesis that sPLA(2) contributes to oxidative stress generation and endothelial dysfunction in ESRD patients and transgenic (tg) mice. Patients with ESRD had increased in vivo oxidative stress as assessed by plasma isoprostane levels (p < 0.001). Active sPLA(2) in plasma was substantially increased compared with healthy controls (1,156 +/- 65 versus 184 +/- 5 ng/dL, p < 0.001) and correlated with plasma isoprostanes (r = 0.61, p < 0.001). Correspondingly, human sPLA(2) tg mice display increased generation of reactive oxygen species within aortic vascular smooth muscle cells, leading to severe endothelial dysfunction (maximal vasodilation in response to 10 micromol/L acetylcholine, sPLA(2) 36 +/- 8%, controls 80 +/- 2% of phenylephrine-induced vasoconstriction). Increased vascular oxidative stress in sPLA(2) tg mice is dependent on the induction of vascular cyclooxygenase (COX)2 expression. Conversely, ESRD patients show increased formation of COX2-derived prostaglandins (p < 0.05) correlated with plasma sPLA(2) (r = 0.71, p < 0.05). Our data indicate that increased expression of sPLA(2) might represent a novel causative risk factor contributing to the increased cardiovascular disease morbidity and mortality in ESRD.

Roles of nitric oxide synthase isoforms in cutaneous vasodilation induced by local warming of the skin and whole body heat stress in humans

Nitric oxide (NO) participates in the cutaneous vasodilation caused by increased local skin temperature (Tloc) and whole body heat stress in humans. In forearm skin, endothelial NO synthase (eNOS) participates in vasodilation due to elevated Tloc and neuronal NO synthase (nNOS) participates in vasodilation due to heat stress. To explore the relative roles and interactions of these isoforms, we examined the effects of a relatively specific eNOS inhibitor, N(omega)-amino-l-arginine (LNAA), and a specific nNOS inhibitor, N(omega)-propyl-l-arginine (NPLA), both separately and in combination, on skin blood flow (SkBF) responses to increased Tloc and heat stress in two protocols. In each protocol, SkBF was monitored by laser-Doppler flowmetry (LDF) and mean arterial pressure (MAP) by Finapres. Cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Intradermal microdialysis was used to treat one site with 5 mM LNAA, another with 5 mM NPLA, a third with combined 5 mM LNAA and 5 mM NPLA (Mix), and a fourth site with Ringer only. In protocol 1, Tloc was controlled with combined LDF/local heating units. Tloc was increased from 34 degrees C to 41.5 degrees C to cause local vasodilation. In protocol 2, after a period of normothermia, whole body heat stress was induced (water-perfused suits). At the end of each protocol, all sites were perfused with 58 mM nitroprusside to effect maximal vasodilation for data normalization. In protocol 1, at Tloc = 34 degrees C, CVC did not differ between sites (P > 0.05). LNAA and Mix attenuated CVC increases at Tloc = 41.5 degrees C to similar extents (P < 0.05, LNAA or Mix vs. untreated or NPLA). In protocol 2, in normothermia, CVC did not differ between sites (P > 0.05). During heat stress, NPLA and Mix attenuated CVC increases to similar extents, but no significant attenuation occurred with LNAA (P < 0.05, NPLA or Mix vs. untreated or LNAA). In forearm skin, eNOS mediates the vasodilator response to increased Tloc and nNOS mediates the vasodilator response to heat stress. The two isoforms do not appear to interact during either response.

Arterial biomechanics after destruction of cytoskeleton by Cytochalasin D

Vascular smooth muscle is a major structural element of the arterial wall. We examined the effects of cytoskeleton destruction, after administration of Cytochalasin D, on the biomechanical properties of porcine common carotids. Compared to untreated, maximally dilated controls, Cytochalasin D-treated arteries have shown a marked increase in compliance in the elastin-dominated pressure range. After weakening the VSM stress-bearing cytoskeleton by Cytochalasin D the artery would expand, reaching a new equilibrium state. This study brings further evidence that VSM is under tension, even when it is under zero load and at maximal vasodilation. This residual tension was released upon partial destruction of the cytoskeleton with Cytochalasin D. From a biomechanical standpoint, this means that the zero stress states of the in-series and parallel elastic components are substantially different.

Effect of High-Dose Intracoronary Adenosine Administration During Primary Percutaneous Coronary Intervention in Acute Myocardial Infarction: A Randomized Controlled Trial

Effect of High-Dose Intracoronary Adenosine Administration During Primary Percutaneous Coronary Intervention in Acute Myocardial Infarction: A Randomized Controlled Trial

Flow-Mediated Dilation and Intima-Media Thickness of the Brachial and Axillary Arteries in Individuals With and Without Inducible Axillary Artery Compression

The presence of axillary artery aneurysm and/or thrombus in overhead throwing athletes has been linked, theoretically, with the finding of compression by the humeral head induced by a diagnostic arm maneuver. However, whether this intermittent compression is incidental or of pathological significance has yet to be determined. Flow-mediated vasodilation (FMD), intima-media thickness (IMT) and maximum vasodilatory capacity were measured locally (3rd portion of the axillary artery) and downstream (brachial artery) in individuals previously tested for inducible axillary artery compression (compressor group [COMP]: n = 8, mean (SD) age: 23 (4) y; “noncompressor” control group [NONCOMP]: n = 8, 26 (4) y). A high-resolution ultrasound machine recorded arterial diameter and blood flow velocity. A rapid inflation/deflation pneumatic cuff placed distal to the site of measurement induced reactive hyperemia. Custom-designed wall tracking software with synchronized Doppler waveform analysis detected changes in arterial diameter, blood flow velocity and shear rate from baseline to 3 min after cuff deflation. Glyceryl trinitrate and/or ischemic hand grip exercises were administered to induce maximum vasodilation. No significant differences in FMD, IMT or maximum vasodilator capacity were observed between groups at the axillary artery. However, the downstream brachial FMD response was significantly diminished in the COMP group (6.38 [3.28]%) compared with the NONCOMP group (10.38 [2.74]%; p = 0.006) despite a comparable shear rate between groups (COMP: 81.92 (44.55) s −1; NONCOMP: 83.18 (40.02) s −1; p = 0.961). Pooled data revealed a significant negative relationship (r = −0.52, p = 0.038) between the FMD response and degree of arterial compression. These results suggest a chronic change in downstream vascular function in individuals demonstrating clinically significant inducible axillary artery compression. (E-mail: c.stapleton@2005.ljmu.ac.uk)

Endothelium‐dependent Vasodilation in Myogenically Active Mouse Skeletal Muscle Arterioles: Role of EDH and K+ Channels

As smooth muscle cell (SMC) membrane potential (E(m)) is critical for vascular responsiveness, and arteriolar SMCs are depolarized at physiological intraluminal pressures, we hypothesized that myogenic tone impacts on dilation mediated by endothelium-derived hyperpolarization (EDH). Studies were performed on cannulated mouse cremaster arterioles [diameter, 33+/-2 microm (n=23) at 60 mmHg; SMC Em -34.6+/-1.2 mV (n=7)]. Myogenic activity was assessed as tone developed in response to intraluminal pressure. Functional observations were related to mRNA, protein expression, and anatomy. Acetylcholine concentration-response curves showed a modest shift following indomethacin (10 microM) and L-NAME (100 microM), although maximal vasodilation was achieved. Residual dilation was removed by apamin (1 microM) in combination with TRAM-34 (1 microM) or charybotoxin (0.1 microM), indicating the requirement of small (S) and intermediate (I) calcium-activated potassium channels (K(Ca)). Charybdotoxin, but not TRAM-34, caused vasoconstriction, presumably through the inhibition of SMC BK(Ca). Expression of SK3 and IK1 was confirmed by immunohistochemistry and polymerase chain reaction, while myoendothelial junctions were common, suggesting a high degree of cell coupling. Also consistent with a role for endothelial K(Ca) channels, acetylcholine increased endothelium [Ca(2 +)](i). Apamin and TRAM-34 similarly blocked EDH-mediated dilation at intraluminal pressures of 30 and 90 mmHg, suggesting that in mouse arterioles, SK(Ca -) and IK(Ca -) mediated mechanisms predominate and operate independently of physiological levels of myogenic activation.

Endothelin-1 Is a Key Mediator of Coronary Vasoconstriction in Patients With Transplant Coronary Arteriosclerosis

Transplant coronary arteriosclerosis (TCA) is the principal long-term complication in cardiac transplant recipients. The mediators responsible for vascular proliferation and vasoconstriction typical of TCA remain largely unknown. We tested whether endothelin-1 (ET-1), a potent vasoconstrictor and mitogen, contributes to the pathogenesis and manifestations of TCA. BQ-123, an ET-1 receptor-A antagonist, was infused into a coronary artery (40 nmol/min for 60 minutes) of 18 subjects, 6 + or - 4 years after transplantation. Vasomotor responses were measured in the infused artery and in a noninfused control artery in patients with (n=10) and without (n=8) advanced TCA (108 total coronary segments). Changes in diameters were compared at 15-minute intervals up to 60 minutes. Contribution of ET-1 to coronary constrictor tone was assessed by comparing vasodilation from BQ-123 with that of the maximal vasodilator nitroglycerin (200-microg intracoronary bolus). BQ-123 dilated coronary arteries of transplanted patients (8.4% at 60 minutes versus -0.4% in noninfused arteries, P<0.001). Dilation was greater for arteries with advanced TCA defined as diameter stenosis > or = 15% (dilation 15.2% with versus 0.6% without advanced TCA, P=0.004). Judged against the response to nitroglycerin, ET-1 accounted for 53.2% of coronary tone in advanced TCA but only 12.9% without advanced TCA. This study shows for the first time in humans that ET-1 is an important mediator of coronary vasoconstriction in TCA and accounts for >50% of the increased vasomotor tone. Therapeutic targeting of ET-1 may retard the development of TCA.

Simultaneous Occurrence and Interaction of Hypoperfusion and Embolism in a Patient With Severe Middle Cerebral Artery Stenosis

The coincidence of hemodynamic and embolic findings in patients with stroke from large artery stenosis has suggested an interaction of both pathologies. This has emerged into the hypothesis of an impaired washout of emboli in the presence of hypoperfusion. We propose an additional link between both pathologies. A 48-year-old woman presented with a recurrent symptomatic severe left middle cerebral artery stenosis. MRI depicted left hemispheric ischemic infarcts in the deep and subcortical white matter and in the cortical border zone. One-hour transcranial Doppler monitoring detected 64 microembolic signals distal to the arterial stenosis. Monitoring also revealed recurrent thrombus formation at the stenotic plaque with decline of poststenotic flow velocity followed by embolism with abrupt excessive flow velocity increase and subsequent normalization at the initial baseline level. Cerebrovascular reserve in the distribution territory of the stenosed artery as assessed by transcranial Doppler after carbon dioxide stimulation revealed a normal reserve capacity in periods with baseline poststenotic flow velocity and an exhausted reserve capacity when flow velocity was decreased due to stenotic thrombus formation. In our patient, adherent thrombus formation resulted in an increasing severity of the stenosis with subsequent vasodilatation and diminution of flow resistance in the depending vascular distribution territory. MRI suggested that adherent thrombi were predominantly washed into terminal supply and border zone brain regions, ie, into regions with supposed maximum vasodilatation and least flow resistance immediately before thrombus avulsion. Preferred wash-in of emboli into regions with low blood flow resistance might be an additional mechanism besides impaired washout in patients with severe large artery disease.

Akira Takeshita, MD, PhD

Akira Takeshita, MD, PhD, 69, Professor Emeritus of Cardiovascular Medicine and Director Emeritus of the Institute of Angiocardiology, Kyushu University Graduate School of Medicine, Japan, died on March 15, 2009 after a long illness. Dr Takeshita was an internationally recognized leader in cardiovascular medicine. His research focused on neural regulation and vascular biology. Dr Takeshita was born on January 24, 1940. He earned his MD degree from Kyushu University School of Medicine in 1965. His unique and international career started immediately after his graduation when, unlike many other Japanese physicians, especially at that time, he moved to the Tachikawa U.S. Air Force Hospital near Tokyo, where he was an intern and resident. He met Makiko, who was performing her externship in anesthesiology at the Hospital, and they married in 1968. They helped each other as the best partners in life and also as medical professionals, for 41 years until his death. In 1967, Dr Takeshita returned to Kyushu University where he trained in the Department of Cardiovascular Medicine. He then moved to Mount Sinai Hospital, Cleveland, in …

C011 Expression and reproducibility of skin microvascular reactivity assessed with laser doppler flowmetry

The study of microvascular function can be routinely performed in humans using laser Doppler flowmetry (LDF) of the skin. Post-occlusive reactive hyperemia (PORH) and local thermal hyperemia (LTH) are used as tools to investigate endothelial and neurovascular microvascular functions. Sodium nitroprusside (SNP) iontophoresis is a commonly used technique to assess non endothelium-dependent skin microvascular function. However, there is no consensus over their reproducibility and variation over time, with room temperature, prandial status, and stress. Our objective was to test the reproducibility of those techniques on the finger and on the forearm, and their physiological variations. We performed local heating up to 44 °C, 5 min postocclusive hyperemia and SNP iontophoresis in fourteen healthy volunteers, at day 0, day 7 and month 6. We also tested the impact of a standard meal, of variations of room temperature, and of a psychological stress (Stroop test). Cutaneous blood flow was recorded with LDF probes. Data are expressed as cutaneous vascular conductance (CVC) in mV/mmHg, as % of maximal vasodilation and as a function of baseline. Reproducibility data are expressed as intra-subject coefficient of variation (CV) and intraclass correlation coefficients (ICC). One-week reproducibility of PORH and LTH on the finger pad is very good when expressed as CVC raw values (CV=12.6 to 23.7 %, ICC>0.71). On the dorsum of the finger and the forearm, reproducibility was better when expressed as a % of maximal vasodilation (CV=11.9 to 26.4 %, ICC>0.55). SNP iontophoresis did not lead to a vasodilation on the finger pad. On the dorsum and the forearm, its reproducibility was poor. Room temperature had a significant influence LTH and PORH hyperemia parameters, especially on the finger pad. Reproducibility was very good for both PORH and LTH, but the way of expressing data plays a key role. Reproducibility of SNP iontophoresis was poor. Room temperature (especially when elevated) influenced both PORH and LTH responses on the finger pad, highlighting the need for temperature-controlled conditions while performing these tests.

Prognostic impact of microembolic signals in arterial sources of embolism

Sir I read with interest the review by Ritter et al. [3] regarding the prevalence and prognostic impact of microembolic signals (MES) in arterial sources of cerebral embolism. I wish to comment on some important issues related to this review. Emboli originating from an atherosclerotic stenotic plaque are considered to play an important etiological role in subsequent cerebral ischemic events [2], and the detection of MES may help in clinical decision-making, especially in patients previously considered to have asymptomatic arterial stenoses. However, this approach is still not widely accepted and appears to be looking at ‘only one side of the picture.’ Cerebral ischemic events secondary to hemodynamic disturbances (hypoperfusion) in patients with significant stenotic lesions constitute an important clinical group, and these patients can be easily evaluated with transcranial Doppler and assessment of cerebral autoregulation (CA). CA is the inherent ability of the cerebral blood vessels to maintain the blood flow over a wide range of systemic blood pressure and various provocative stimuli [6] and can be assessed by testing the vasomotor reactivity (VMR). Flow velocities obtained in real-time by TCD can reflect cerebral blood flow volume (CBFV), and the velocity changes can be proportionate to the changes in CBFV if certain parameters are known and remain constant (e.g., angle of insonation, perfusion territory, and arterial diameter) and the effect of only one stimulus is observed [5]. Evaluation of VMR to various ‘challenges’ and maneuvers may help in the prognostic assessment of patients with significant stenosis in the cervico-cranial cerebral arteries. Silverstrini et al. [4] demonstrated a significantly higher risk of subsequent cerebral ischemic events in patients with asymptomatic carotid stenosis and having impaired VMR, assessed by breath-holding index. VMR can be easily assessed by monitoring the blood flow velocities (by TCD) during voluntary breath-holding in any intracranial artery distal to the stenosis. Elevation of carbon-dioxide levels in blood during breath-holding is a strong vasodilatory stimulus and results in significant augmentation of flow velocities in the intracranial arteries. However, the arteries distal to the segment with significant stenosis tend to maintain maximal vasodilation and may not dilate further in response to hypercapnia, reflected by a blunted response in the blood flow velocities. The response may be further affected, in some cases, due to ‘intracranial steal phenomenon’ known as ‘reversed Robin Hood syndrome’ [1]. I propose that, in addition to the MES monitoring, patients with hemodynamically significant stenosis in the cervical or intracranial cerebral arteries should be evaluated for VMR by TCD. Assessment of VMR in the arterial segments distal to the atherosclerotic segment would reveal, at least to some extent, the ‘other side of the picture’ and help in better understanding of cerebral hemodynamics and the pathogenic mechanisms of cerebral ischemia in these patients. Well-designed prospective studies would, however, be needed to test the feasibility and efficacy of this approach in clinical decision-making.

Dietary enrichment with wild blueberries ( Vaccinium angustifolium) affects the vascular reactivity in the aorta of young spontaneously hypertensive rats

We have previously reported on the positive effects of wild blueberries on arterial contractile response to α 1 adrenergic stimuli and on endothelium-mediated vasorelaxation. Our present study was designed to evaluate the effects of the dietary enrichment with wild blueberries on aortic function and reactivity in the developmental phase of essential hypertension in spontaneously hypertensive rats (SHR). We investigated the possible influence blueberries may have on the acetylcholine (Ach)-induced endothelium-dependent vasorelaxation and phenylephrine-induced vasoconstriction in young SHRs, as well as the contribution of the nitric oxide (NO) synthase and cyclooxygenase (COX) pathways in each of the above responses in an animal model with dysfunctional endothelium. Vascular ring studies were conducted in 3-mm isolated rat aortic ring preparations to investigate vasoconstriction induced by l-Phenylephrine (Phe, 10 −8 to 3×10 −6M) and vasorelaxation induced by acetylcholine (Ach, 10 −9 to 3×10 −6M). The major findings of our study were that in Phe-induced vasoconstriction, SHR-BB aortas relaxed to a greater degree in comparison to controls when mefenamic acid (MFA) was present and that the incubation with this COX inhibitor failed to restore — and in fact decreased — the maximum vasodilator response to Ach, in comparison to controls. Our vessel reactivity index ( pD 2) observations indicate that blueberries appear to modulate cell membrane–agonist (Ach) interactions primarily in response to Ach in the young SHR model, but not to the α 1 adrenoreceptor agonist. Incorporating wild blueberries in the diet seems to affect the endothelium-dependent vasorelaxation by modulating alternative metabolic pathway(s) (such as affecting the production/activity of COX-derived products) in the young SHR aorta.

Bubble Formation and Endothelial Function Before and After 3 Months of Dive Training

It has been suggested that repeated compression-decompression cycles reduce diver susceptibility to decompression sickness (DCS). This study examined whether intensive scuba dive training would reduce bubble formation and modulate endothelial function as shown by skin circulation. There were 22 military divers who were studied before and after a 90-d program of physical training and open-sea air diving (mean 67 dives total). Skin blood flow in the forearm was measured at rest (baseline), during post-occlusive hyperemia (endothelium-dependent vasodilatation), and with local heating to 42 degrees C (maximal vasodilatation). Subjects were also examined by pulsed Doppler for venous bubbles 30, 60, and 90 min after surfacing from a hyperbaric exposure to 400 kPa (30 msw) for 30 min in a dry chamber. None of the divers experienced DCS during the training period. There was no change in weight, body mass index, maximal oxygen uptake, or endothelial function. Bubble grades by the Kisman Integrated Severity Score were significantly decreased immediately after the diving training period (3.6 +/- 9.2 vs. 16.4 +/- 14.3) and increased 3 mo after this period (10.3 +/- 13.9 vs. 3.6 +/- 9.2). The results highlight that repeated scuba dives and regular physical exercise activity reduce bubble formation and probably have a protective effect against DCS risk. Although this phenomenon has been observed for decades, the mechanism remains complex and the results cannot elucidate the effects of physical exercise and NO production. Bubble formation could activate the stress response which could be the basis for diving acclimatization.

Significance of heterogenity in endothel-dependent vasodilatation occurrence in healthy individuals with or without coronary risk factors

Brachial artery flow-mediated dilation (FMD) is extensively used for non-invasive assessment of endothelial function. Traditionally, FMD is calculated as a percent change of arterial diameter from the baseline value at an arbitrary time point after cuff deflation (usually 60 seconds). Considerable individual differences in brachial artery temporal response to hyperemic stimulus have been observed, potentially influenced by the presence of atherosclerotic risk factors (RF). The importance of such differences for the evaluation of endothelial function has not been well established. The aim of the study was to determine the time course of maximal brachial artery endothelium-dependent dilation in healthy adults with and without RF, to explore the correlation of RF with brachial artery temporal response and to evaluate the importance of individual differences in temporal response for the assessment of endothelial function. A total of 115 healthy volunteers were included in the study. Out of them, 58 had no RF (26 men, mean age 44 +/-14 years) and 57 had at least one RF (29 men, mean age 45 +/-14 years). High-resolution color Doppler vascular ultrasound was used for brachial artery imaging. To determine maximal arterial diameter after cuff deflation and the time-point of maximal vasodilation off-line sequential measurements were performed every 10 seconds from 0 to 240 seconds after cuff release. True maximal FMD value was calculated as a percent change of the true maximal diameter from the baseline, and compared with FMD value calculated assuming that every participant reached maximal dilation at 60 seconds post cuff deflation (FMD60). Correlation of different RF with brachial artery temporal response was assessed. A maximal brachial artery endothelium-dependent vasodilation occurred from 30-120 seconds after cuff release, and the mean time of endothelium-dependent dilation was 68 +/-20 seconds. Individuals without RF had faster endothelium-dependent dilation (mean time 62 +/-17 seconds), and a shorter time-span (30 to 100 seconds), than participants with RF (mean time 75 +/-21 seconds, time-span 40 to 120 seconds) (p < 0.001). Time when the maximal endothelium-dependent dilation occurred was independently associated with age, serum lipid fractions (total cholesterol, LDL and HDL cholesterol), smoking, physical activity and C-reactive protein. True maximal FMD value in the whole group (6.7 +/-3.0%) was significantly higher (p < 0.001) than FMD60 (5.2 +/-3.5%). The same results were demonstrated for individuals with RF (4.9 +/- 1.7% vs 3.1 +/- 2.3%, p < 0.001) and without RF (8.4 +/- 2.9% vs 7.2 +/- 3.2%, p < 0.05). The temporal response of endothelium-dependent dilation is influenced by the presence of coronary FR and individually heterogeneous. When calculated according to the commonly used approach, i.e. 60 seconds after cuff deflation, FMD is significantly lower than the true maximal FMD. The routinely used measurement time-points for FMD assessment may not be adequate for the detection of true peak vasodilation in individual persons. More precise evaluation of endothelial function can be achieved with sequential measurement of arterial diameter after hyperemic stimulus.

Abstract 3726: Right Ventricular Microcirculatory Changes in Pulmonary Hypertension-Associated Right Heart Failure Imaged by Three-Dimensional Confocal Microscopy

Background: Right ventricular (RV) ischemia occurs in pulmonary hypertension (PH) patients despite normal coronary angiograms. O 2 supply-demand balance in the pressure-overloaded RV is determined by the interplay between reduced coronary perfusion (due to systemic hypotension and compression of coronary vessels) and a wall stress-related increase in myocardial O 2 consumption. The role of capillary rarefaction, which is involved in pressure overload induced left heart failure, has not been investigated in PH-associated RV failure. Methods: Rats received a single dose of the VEGF receptor blocker SU5416 and were exposed to 4 wks of normobaric hypoxia and 2 wks of sea level room air. This regimen induces angioproliferative changes in the pulmonary circulation, severe PH and RV failure. At 6 wks, the rats received intravital injections of Texas-Red conjugated tomato lectin, which is an N-acetylglucosamine specific marker of blood vessels in rodents. After circulation of the lectin for 5 min, papaverin was injected to promote maximal vasodilation of all perfused blood vessels. Animals were exsanguinated and perfusion-fixed with paraformaldehyde. After overnight fixation, 300 μm thick transverse sections of the myocardium were bleached in a methanol/DMSO mixture and nuclei were stained using DAPI. Prior to 3-dimensional imaging under a confocal microscope, further tissue clearing was achieved using organic solvents. Results: Z-stacks of 2-dimensional images were made in whole-mount cardiac specimens, using a step size of 0.32 μm. 3-dimensional reconstruction allowed quantification of the total capillary volume, which was reduced in the PH model compared to controls (2.9±1% vs. 5.7±1% of tissue volume, p&lt;0.05). The reconstructions showed a remarkable increased morphological heterogeneity of the capillaries in the failing RV. In contrast, images of the LV microcirculation in the SU5416 treated animals were not different from those of controls. Conclusions: RV failure in experimental PH is associated with capillary rarefaction. 3-dimensional imaging of the myocardial microcirculation can be achieved using intravital injections of tomato lectin and subsequent confocal imaging.

C-reactive protein: the underlying cause of microvascular dysfunction in rheumatoid arthritis

RA is a chronic autoimmune inflammatory condition associated with increased cardiovascular morbidity and mortality. Endothelial dysfunction, a marker of early atherosclerotic disease, occurs in some inflammatory diseases but this relationship has not been previously explored within the microvasculature of patients with RA. We therefore assessed forearm microvascular endothelial function in patients with RA and determined its relationship to RA disease activity and inflammation. A total of 128 RA patients with no previous history of cardiovascular disease were evaluated. Endothelium-dependent and -independent forearm skin microvascular function was measured using laser Doppler imaging after iontophoretic delivery of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. Parameters of RA disease activity and inflammation were also checked. There was a significant negative correlation between the level of inflammation measured by log(10)CRP and maximum vasodilatation measured by peak ACh response (r(2) = -0.209, P = 0.018, Pearson correlation test). In a multiple regression model, age (beta = -0.449, P < 0.0001) and log(10)CRP (beta = -0.193, P = 0.026) were independently negatively associated with ACh responses. When RA patients were sub-divided according to their systemic inflammatory status (CRP > 10 mg/l vs CRP </= 10 mg/l), the high CRP group showed lower vasodilator responses to ACh [P = 0.018, analysis of variance (ANOVA)] and SNP (P = 0.05, ANOVA) than the low CRP group. In this large cross-sectional study, we found for the first time systemic inflammation (CRP) to be independently associated with microvascular dysfunction in patients with RA. This strong correlation was independent of other conventional vascular risk factors.

Enhancement of endothelial nitric oxide synthase production reverses vascular dysfunction and inflammation in the hindlimbs of a rat model of diabetes

Reduced bioavailability of nitric oxide (NO) is a hallmark of diabetes mellitus-induced vascular complications. In the present study we investigated whether a pharmacological increase of endothelial NO synthase (eNOS) production can restore the impaired hindlimb flow in a rat model of severe diabetes. A model of diabetes mellitus was induced in male Sprague-Dawley rats by a single injection of streptozotozin. Rats were treated chronically with the eNOS transcription enhancer AVE3085 (10 mg [kg body weight](-1) day(-1); p.o.) or vehicle for 48 days and compared with controls. Endothelial function and arterial BP were investigated in vivo using an autoperfused hindlimb model and TIP-catheter measurement, respectively. Protein production of eNOS, total and phosphorylated vasodilator-stimulated phosphoprotein (VASP) were assessed in their quadriceps muscle tissue, whereas cyclic GMP (cGMP) concentrations were assessed in blood plasma. RNA levels of intracellular and vascular cell adhesion molecules (ICAM-1 and VCAM-1) were measured by real-time PCR. Untreated diabetic rats showed significantly reduced quadriceps muscle contents of eNOS (-64%) and phosphorylated VASP (-26%) protein associated with impaired vascular function (maximum vasodilatation: -30%, p < 0.05) and enhanced production of ICAM-1 (+121%) and VCAM-1 (+156%). Chronic treatment with AVE3085 did not alter arterial BP or severe hyperglycaemia, but did lead to significantly increased production of eNOS (+95%), cGMP (+128%) and VASP phosphorylation (+65%) as well as to improved vascular function (+36%) associated with reduced production of ICAM-1 (-36%) and VCAM-1 (-58%). In a rat model of severe diabetes, pharmacological enhancement of impaired eNOS production and NO-cGMP signalling by AVE3085 restores altered hindlimb blood flow and prevents vascular inflammation.

Papaverine solution improves preservation of saphenous vein grafts used during cardiac surgery

The purpose of this study was to assess the viability and dilator response of the saphenous vein segments harvested during cardiac surgery.The saphenous veins were incubated with either normal saline (group A) or papaverine solutions (group B). The viability of saphenous vein endothelial cells was assessed by counting the number of total cells. Maximal endothelium-dependent vasodilator response to acetylcholine was also investigated.Cell viability of vein samples was decreased after 4 hours of incubation with normal saline (34 ± 6.5%) as compared to solution containing papaverine (92 ± 3.7%). By 24 hours, the viabilities of the endothelial cells incubated with saline and papaverine solutions were 22 ± 4.5% and 87 ± 5%, respectively.There was significant difference in vasodilatation responses to acetylcholine between saline-incubated and papaverine-incubated groups. By 4 hours of incubation, the relaxation response to acetylcholine significantly deteriorated in group A when compared to the initial value (P < 0.001). Furthermore, the decrease in this vasorelaxation response has also continued throughout the observation period and the values obtained by 24 hours were observed to be significantly lower than those obtained at the end of 4 hours (P < 0.01). In contrast, although a decrease was noticed in group B over time, this decrease was not statistically significant (P, not significant).We thus conclude that the use of papaverine solution improves endothelial cell viability and is associated with preservation of the maximal endothelial-dependent vasodilator response of a vein segment.

Diminished coronary flow velocity reserve and aortic distensibility in elderly patients with chest pain and negative coronary angiograms

Aging is a dominant process that alters vascular stiffness, endothelial function and coronary flow regulation. The objective of our work was to assess simultaneously the elastic properties of the descending aorta and coronary flow velocity reserve (CFR) during the same transesophageal echocardiography (TEE) in elderly patients. The following patients with normal epicardial coronary arteries were compared: 30 subjects under 55 years of age (group 1) and 17 patients over 55 years (group 2). A complete TEE examination was carried out in all patients, and the following aortic elastic properties were calculated from aortic diameter and blood pressure data: aortic elastic modulus [E(p)] and Young's circumferential static elastic modulus [E(s)]. Doppler evaluation of left anterior descending coronary flow velocity was performed in resting conditions and after administration of 0.56 mg/Kg dipyridamole over 4 min. Peak coronary flow velocities were measured at the 6th minute at maximum vasodilation. CFR was estimated as the ratio of hyperemic to basal peak diastolic coronary flow velocities. Peak hyperemic diastolic coronary flow velocities were significantly decreased (139.1+/-35.6 cm/s vs 105.7+/-39.7 cm/s, p<0.01) in patients >55 years. CFR was decreased (2.67+/-1.05 vs 2.13+/-0.56, p<0.05), whereas E(p) (in 103 mmHg, 0.59+/-0.49 vs 0.94+/-0.65, p<0.05) and E(s) (in 103 mmHg, 5.70+/-4.30 vs 8.47+/-5.14, p<0.05) were increased in patients >55 years. A correlation was found between CFR and E(p) (r=-0.20, p<0.05). CFR and aortic distensibility are altered in elderly patients. There is a relationship between these functional parameters.

Venous endothelial function in heart failure: Comparison with healthy controls and effect of clinical compensation

Endothelial function has been extensively evaluated at the arterial bed in several cardiovascular scenarios. Venous endothelial dysfunction, however, has not been thoroughly explored particularly in heart failure (HF). To characterize venous endothelial function in severe HF. Venous endothelial function was evaluated by the dorsal hand vein technique using a tripod holding a linear variable differential transformer. Dorsal hand veins were pre-constricted with phenylephrine and dose-response curves were constructed after acetylcholine and sodium nitroprusside administration. Maximum vasodilator response to acetylcholine, a marker of endothelium-dependent venodilation, was significantly lower (47+/-53% versus 102+/-54%, respectively, p=0.0004) in HF (n=27) patients compared to healthy controls (n=20). No difference in the endothelium-independent venodilator response was observed (p=0.87). Maximum vasodilator response to acetylcholine was also significantly lower on admission compared to the response immediately before hospital discharge in patients with acute decompensated HF (p<0.01). Improvement in venous endothelial function paralleled weight loss (mean difference of -3.8 kg, p<0.01) and improvement in the 6-minute walk test (mean difference of 107 m, p<0.01). There was no significant change in angiotensin-converting enzyme inhibitor or beta-blocker use during hospital stay. HF patients experience marked endothelium-dependent venous dysfunction with partial recovery during in-hospital management.