Background-Impaired endothelium-mediated vasodilatation (EMVD) in congestive cardiac failure (CCF) has been linked to decreased nitric oxide (NO) bioavailability because of its interaction with vascular superoxide (O 2 ·Ϫ ), derived predominantly from NAD(P)H-dependent oxidases. When uncoupled from essential cofactors, endothelial nitric oxide synthase (eNOS) produces O 2 ·Ϫ . We studied the functional consequences of eNOS uncoupling in relation to EMVD in patients with CCF. Methods and Results-We employed the platelet as a compartmentalized ex-vivo model to examine O 2 ·Ϫ and NO production. When eNOS is functioning normally, incorporation of N -Nitro-L-Arginine methyl ester (L-NAME, 1 mmol/L), results in increased O 2 ·Ϫ detection, as inhibition of NO production prevents NO scavenging of O 2 ·Ϫ . This was observed in controls and 9 of the CCF patients, in whom O 2 ·Ϫ detection increased by 63% and 101%, respectively. In the remaining 9 CCF patients, incorporation of L-NAME reduced O 2 ·Ϫ production by 39%, indicating O 2 ·Ϫ production by eNOS uncoupling. Detection of platelet-derived NO was significantly greater in eNOS-coupled platelets compared with the uncoupled group (2.8Ϯ1.4 versus 0.9Ϯ0.4 pmol/10 8 platelets, Pϭ0.04). Endothelium-dependent and -independent vasodilator responses to acetylcholine and sodium nitroprusside recorded using venous occlusion plethysmography were significantly impaired in patients exhibiting eNOS uncoupling. Conclusions-This study provides first evidence that platelet eNOS can become uncoupled in human CCF. Impaired endothelium-dependent and -independent vasodilator responses and diminished platelet-derived NO production occurred in association with enzyme uncoupling.

Objective-Impaired flow-mediated dilation (FMD) occurs in disease states associated with atherosclerosis, including SLE.The primary hemodynamic determinant of FMD is wall shear stress, which is critically dependent on the forearm microcirculation. We explored the relationship between FMD, diastolic shear stress (DSS), and the forearm microcirculation in 32 patients with SLE and 19 controls. Methods and Results-DSS was calculated using (mean diastolic velocityϫ8ϫblood viscosity)/baseline brachial artery diameter. Doppler velocity envelopes from the first 15 seconds of reactive hyperemia were analyzed for resistive index (RI), and interrogated in the frequency domain to assess forearm microvascular hemodynamics. FMD was significantly impaired in SLE patients (median, 2.4%; range, Ϫ2.1% to 10.7% versus median 5.8%; range, 1.9% to 14%; PϽ0.001). DSS (dyne/cm 2 ) was significantly reduced in SLE patients (median, 18.5; range, 3.9 to 34.0 versus median 21.8; range, 14.1 to 58.7; Pϭ0.037). A strong correlation between FMD and DSS, r s ϭ0.65, Pϭ0.01 was found. Postischemic RI was not significantly different between the 2 groups; however, there were significant differences in the power-frequency spectrums of the Doppler velocity envelopes (PϽ0.05). Conclusions-These data suggest that in SLE, altered structure and function of the forearm microcirculation contributes to impaired FMD through a reduction in shear stress stimulus. Key Words: eigenvector Ⅲ flow-mediated dilation Ⅲ microcirculation Ⅲ shear stress Ⅲ systemic lupus erythematosus S ystemic lupus erythematosus (SLE) is the archetypal autoimmune disease, with a wide range of clinical manifestations. Among the clinical challenges of SLE, one of the most compelling is the high incidence of atherosclerosis in young women. In 1976, Urowitz et al showed a bimodal mortality pattern in SLE, with late deaths (comprising 45%) attributed to myocardial infarction. 1 Women with SLE have a high prevalence of coronary artery disease (CAD) 2 and an incidence of myocardial infarction up to 50 times higher than age-matched normals. 3 Classical risk factors are similar to those in the general population, 3 but the increased risk of atherosclerosis is not exclusively related to traditional Framingham risk factors alone, 4 with a recent report highlighting SLE itself as an independent risk. 5 Whereas several studies have highlighted the presence of subclinical atherosclerosis in SLE, 6,7 the pathogenesis is not fully understood. It has been proposed that autoimmune vascular injury in SLE may predispose to atherosclerotic plaque formation through mechanisms that promote endothelial dysfunction, the earliest precursor for plaque development. 8 -10 Flow-mediated dilation of the brachial artery (FMD) is used clinically as an indirect bioassay for endotheliumderived nitric oxide (NO) production. The primary hemodynamic determinant of FMD is wall shear stress, 11-13 and the degree of FMD has been shown to be proportional to both systolic and diastolic shear stress (DSS) in response to incr...

Impaired FMD (flow-mediated dilatation) has traditionally been recognized as an indirect marker of NO bioactivity, occurring in disease states such as DM (diabetes mellitus). Endothelium-dependent FMD is a homoeostatic response to short-term increases in local shear stress. Microvascular dysfunction in DM influences blood flow velocity patterns. We explored the determinants of the FMD response in relation to evoked DSS (diastolic shear stress) and forearm microcirculation haemodynamics by quantifying changes in Doppler flow velocity waveforms between groups. Forty patients with uncomplicated Type 1 DM and 32 controls underwent B-mode and Doppler ultrasound scanning to interrogate the brachial artery. Postischaemic Doppler velocity spectral envelopes were recorded and a wavelet-based time-frequency spectral analysis method was employed to track change in distal microcirculatory haemodynamics. No difference in baseline brachial artery diameter was evident between the groups (4.15 compared with 3.94 mm, P=0.23). FMD was significantly impaired in patients with Type 1 DM (3.95 compared with 7.75%, P<0.001). Endothelium-independent dilatation in response to GTN (glyceryl trinitrate) was also significantly impaired (12.07 compared with 18.77%, P<0.001). DSS (dyn/cm2) was significantly reduced in the patient group (mean 20.19 compared with 29.5, P=0.001). Wavelet interrogation of postischaemic flow velocity waveforms identified significant differences between groups. In conclusion, DSS, microcirculatory function and endothelium-independent vasodilatation in response to GTN are important determinants that impact on the magnitude of FMD response and are impaired in patients with Type 1 DM. Impaired FMD response is multifactorial in origin and cannot be attributed solely to a diminished NO bioavailability.

Alteration in the physical properties of arterial blood vessels act as the substrate for end-organ damage and the occurrence of vascular events in hypertension. Structural and functional alteration in the microcirculation represents a prevalent and characteristic abnormality described in the earliest stages of hypertension. In addition to lowering arterial pressure, the importance of reversing structural abnormalities and restoring endothelial function has recently been emphasized. The normalization of microvascular function does not always correlate with blood pressure reduction and might depend on the class of antihypertensive agent employed. Because altered resistance vessel structure and function is a recognized hallmark of hypertension, institution of drug therapy that corrects the associated pathogenic vascular abnormalities is a rational, if unproven, clinical goal.

M icrovascular changes occur early in diabetes mellitus. Doppler ultrasound enables non-invasive identification of ocular microvascular haemodynamics through interrogation of blood flow velocity waveforms. Wave decomposition permits the spectrum of sinusoidal components comprising flow velocity waveforms to be quantified. We hypothesised that comprehensive interrogation of waveforms would be more sensitive in identifying microvascular abnormalities than traditional analysis employing the resistive index.Thirty-four subjects with type 2 diabetes and 20 healthy controls between 30 and 70 years old were recruited. Doppler flow velocity waveform signals were captured from the ophthalmic and carotid arteries under standardised conditions. The signals were analysed using a wave decomposition algorithm and the sinusoidal components of average waveforms were compared between groups at both arterial sites.The diabetes group displayed significant differences in the lower frequency sinusoidal components of both the ophthalmic artery (p<0.001) and, to a lesser extent, the carotid artery (p<0.05) waveforms compared with controls, with no difference noted in the resistive index at either site.We conclude that wave decomposition analysis of Doppler flow velocity waveforms, recorded in proximity of the terminal vascular bed of interest, can identify subtle microvascular haemodynamic abnormalities not detected by traditional methods of analysis. Br J Diabetes Vasc Dis 2011;11:243-248