Homocysteine and pulsatility index of cerebral arteries.
ABSTRACT A pulsatility index (PI) represents vascular resistance distal to an examined artery. The purpose of the present study was to evaluate an association between plasma total homocysteine (tHcy) and PIs of the cerebral arteries in patients with ischemic stroke.
Consecutive patients with ischemic stroke referred to a neurovascular ultrasound laboratory were evaluated from March 2007 to February 2008. PI was defined as (peak systolic velocity-end-diastolic velocity)/mean flow velocity as recommended. Transcranial Doppler was examined in both middle cerebral arteries and vertebral arteries, and basilar arteries. All patients with ischemic stroke were subdivided according to the presence of proximal internal carotid arterial steno-occlusion (ICS).
The numbers of patients enrolled for the present analysis as ischemic stroke without and with ICS were 272 and 92, respectively. PIs measured in the cerebral arteries did not show a significant difference in the two groups, in spite of the fact that mean flow velocities of both basilar arteries and vertebral arteries were significantly elevated in the patients with ICS. Plasma tHcy was found to be independently associated with graded increases of PIs in all cerebral arteries in the patients without ICS, even adjusted for the potential confounders. However, there was no association between tHcy and PI in the patients with ICS.
Plasma tHcy was directly associated with increased cerebral arterial resistance. But in clinical situations when the cerebral arterial hemodynamics were altered as in the patients with ICS, the effect of tHcy on arterial remodeling could be obscured.
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ABSTRACT: Accumulating evidences suggest that homocysteine, a non-protein amino acid, is involved in vessel remodeling and blood flow at elevated level, although the exact mechanism is unclear. Here we hypothesized that homocysteine affects vein in such a way that vein develops arterial phenotype. We tested our hypothesis employing wild type (WT, C57BL/6J) and CBS+/- (cystathionine β-synthase heterozygote, a genetic model of hyperhomocysteinemia) supplemented with or without folic acid (FA, a homocysteine lowering agent). Vena cava blood flow was measured by ultrasound transonic flow probe. Tissue collagen and elastin were detected by histochemistry. Super oxide was detected by dihydroethidium (DHE) staining. Expressions of MMP-2, -9, -12, TIMP -2,-4, were measured by Western blot. MMP-13, TIMP-1, -3, and vein and aortic markers, EphB4 and EphrinB2, respectively were measured by RT-PCR. The results indicated relatively low blood flow and significant increase of collagen/elastin ratio in the CBS+/- mice compared to WT. Although FA treatment did not alter blood flow in CBS+/- mice, the collagen/elastin ratio was normalized. A relatively increased content of super oxide and gelatinase activity was observed in CBS+/- vena cava vs WT and normalized by FA treatment. Western blot analyses showed significant increase in MMP-9,-12 and decrease in TIMP-2, -4 expressions. Expressions of MMP-13, TIMP-1 and -3, Ephrin B2 were increased, whereas EphB4 was decreased with reverse change in FA treatment, with no change in MMP-13 and TIMP-1. We conclude that chronic HHcy causes vascular remodeling that expresses arterial phenotype in vein.International Journal of Physiology, Pathophysiology and Pharmacology 01/2011; 3(4):266-79.
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ABSTRACT: Transcranial Doppler (TCD) pulsatility index (PI) has traditionally been interpreted as a descriptor of distal cerebrovascular resistance (CVR). We sought to evaluate the relationship between PI and CVR in situations, where CVR increases (mild hypocapnia) and decreases (plateau waves of intracranial pressure-ICP). Recordings from patients with head-injury undergoing monitoring of arterial blood pressure (ABP), ICP, cerebral perfusion pressure (CPP), and TCD assessed cerebral blood flow velocities (FV) were analyzed. The Gosling pulsatility index (PI) was compared between baseline and ICP plateau waves (n = 20 patients) or short term (30-60 min) hypocapnia (n = 31). In addition, a modeling study was conducted with the "spectral" PI (calculated using fundamental harmonic of FV) resulting in a theoretical formula expressing the dependence of PI on balance of cerebrovascular impedances. PI increased significantly (p < 0.001) while CVR decreased (p < 0.001) during plateau waves. During hypocapnia PI and CVR increased (p < 0.001). The modeling formula explained more than 65% of the variability of Gosling PI and 90% of the variability of the "spectral" PI (R = 0.81 and R = 0.95, respectively). TCD pulsatility index can be easily and quickly assessed but is usually misinterpreted as a descriptor of CVR. The mathematical model presents a complex relationship between PI and multiple haemodynamic variables.Neurocritical Care 02/2012; 17(1):58-66. · 3.04 Impact Factor
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ABSTRACT: BACKGROUND: This study describes a new method for determining site-specific vascular shear stress using dynamic measures of shear rate and blood viscosity (BV) in the carotid arteries, and examines characteristics of carotid arterial shear stress among patients with lacunar infarction. METHODS: Vascular shear stress measurements were conducted in 37 patients (17 lacunar infarction patients and 20 control subjects) using duplex ultrasonography. Vessel wall diameters and velocities were measured in each arterial segment at peak-systolic (PS) and end-diastolic (ED) phases, for calculation of PS/ED shear rates. PS/ED shear stresses [dyne/cm2] were determined with PS/ED shear rates and shear-rate dependent BV values. For comparison, both values of hematocrit-derived BV and BV measurements at 300 s-1 were used for calculation of shear stress. RESULTS: All cardiovascular disease (CVD) risk factors including BV values were similar between the two groups. In both common carotid arteries, PS and ED shear stresses were significantly lower in the patients with lacunar infarction than in controls in multivariate models that included age, sex, and other major CVD risk factors. PS and ED shear stresses using the shear rate specific BV were 4.5% lower and 7.3% higher than those using the two other BVs, respectively. CONCLUSION: Lacunar infarction was associated with reduced carotid arterial shear stress. The use of estimated BV for calculating carotid arterial shear stress provides more accurate assessment of the hemodynamic contribution of shear stress than previous models that have arbitrarily assigned a constant value to this dynamic flow property.BMC Neurology 04/2013; 13(1):36. · 2.56 Impact Factor