Blood flow velocity changes in the middle cerebral artery as an index of the chronicity of hypertension

Hemodynamic parameters and diabetes mellitus in community-dwelling middle-aged adults and elders: a community-based study

Hemodynamic parameters have been correlated with stroke, hypertension, and arterial stenosis. While only a few small studies have examined the link between hemodynamics and diabetes mellitus (DM). This case-control study enrolled 417 DM patients and 3475 non-DM controls from a community-based cohort. Peak systolic velocity (PSV), end-diastolic velocity (EDV), blood flow velocity (MFV), pulsatility index (PI), and the resistance index (RI) of the common carotid arteries were measured by color Doppler ultrasonography. Generalized linear regression analyses showed that as compared to the non-DM controls, the age-sex-adjusted means of PSV, EDV, and MFV were - 3.28 cm/sec, - 1.94 cm/sec, and - 2.38 cm/sec, respectively, lower and the age-sex-adjusted means of RI and PI were 0.013 and 0.0061, respectively, higher for the DM cases (all p-values < 0.0005). As compared to the lowest quartiles, the multivariable-adjusted ORs of DM for the highest quartiles of PSV, EDV, MFV, RI, and PI were 0.59 (95% confidence interval [CI] 0.41-0.83), 0.45 (95% CI 0.31-0.66), 0.53 (95% CI 0.37-0.77), 1.61 (95% CI 1.15-2.25), and 1.58 (95% CI 1.12-2.23), respectively. More importantly, the additions of EDV significantly improved the predictabilities of the regression models on DM. As compared to the model contained conventional CVD risk factors alone, the area under the receiver operating curve (AUROC) increased by 1.00% (95% CI 0.29-1.73%; p = 0.0059) and 0.80% (95% CI 0.15-1.46%; p = 0.017) for models that added EDV in continuous and quartile scales, respectively. Additionally, the additions of PSV and MFV also significantly improved the predictabilities of the regression models (all 0.01 < p-value < 0.05). This study reveals a significant correlation between DM and altered hemodynamic parameters. Understanding this relationship could help identify individuals at higher risk of DM and facilitate targeted preventive strategies to reduce cardiovascular complications in DM patients.

Modeling essential hypertension with a closed-loop mathematical model for the entire human circulation

Arterial hypertension, defined as an increase in systemic arterial pressure, is a major risk factor for the development of diseases affecting the cardiovascular system. Every year, 9.4 million deaths worldwide are caused by complications arising from hypertension. Despite well-established approaches to diagnosis and treatment, fewer than half of all hypertensive patients have adequately controlled blood pressure. In this scenario, computational models of hypertension can be a practical approach for better quantifying the role played by different components of the cardiovascular system in the determination of this condition. In the present work we adopt a global closed-loop multi-scale mathematical model for the entire human circulation to reproduce a hypertensive scenario. In particular, we modify the model to reproduce alterations in the cardiovascular system that are cause and/or consequence of the hypertensive state. The adaptation does not only affect large systemic arteries and the heart but also the microcirculation, the pulmonary circulation and the venous system. Model outputs for the hypertensive scenario are validated through assessment of computational results against current knowledge on the impact of hypertension on the cardiovascular system.

The influence of contralateral circulation on computational fluid dynamics of intracranial arteries: simulated versus measured flow velocities

BACKGROUND

This study aimed to retrospectively evaluate the influence of contralateral anterior circulation on computational fluid dynamics (CFD) of intracranial arteries, by comparing the CFD values of flow velocities in unilateral anterior circulation with the measured values from phase-contrast magnetic resonance angiography (PC-MRA).

METHODS

We analyzed 21 unilateral anterior circulation models without proximal stenosis from 15 patients who performed both time-of-flight MRA (TOF-MRA) and PC-MRA. CFD was performed with the inflow boundary condition of a pulsatile flow of the internal carotid artery (ICA) obtained from PC-MRA. The outflow boundary condition was given as atmospheric pressure. Simulated flow velocities of the middle cerebral artery (MCA) and anterior cerebral artery (ACA) from CFD were compared with the measured values from PC-MRA.

RESULTS

The velocities of MCA were shown to be more accurately simulated on CFD than those of ACA (Spearman correlation coefficient 0.773 and 0.282, respectively). In four models with severe stenosis or occlusion of the contralateral ICA, the CFD values of ACA velocities were significantly lower (< 50%) than those measured with PC-MRA. ACA velocities were relatively accurately simulated in the models including similar diameters of both ACAs.

CONCLUSION

It may be necessary to consider the flow condition of the contralateral anterior circulation in CFD of intracranial arteries, especially in the ACA.

RELEVANCE STATEMENT

Incorporating the flow conditions of the contralateral circulation is of clinical importance for an accurate prediction of a rupture risk in Acom aneurysms as the bidirectional flow and accurate velocity of both ACAs can significantly impact the CFD results.

KEY POINTS

• CFD simulations using unilateral vascular models were relatively accurate for MCA. • Contralateral ICA steno-occlusion resulted in an underestimation of CFD velocity in ACA. • Contralateral flow may need to be considered in CFD simulations of ACA.

Increased pulsatility index of the basilar artery is a risk factor for neurological deterioration after stroke: a case control study

Background

Higher pulsatility of the middle cerebral artery (MCA) is known to be associated with stroke progression. We investigated whether pulsatility index (PI) of the basilar artery (BA) can predict neurological deterioration (ND) after acute cerebral infarction.

Methods

A total of 708 consecutive patients with acute ischemic stroke who had undergone transcranial Doppler (TCD) ultrasonography were included. ND was defined as an increase in the National Institutes of Health Stroke Scale scores by two or more points after admission. The patients were categorized into quartiles according to BA PI. Multivariable logistic regression analysis was performed to examine whether BA PI is independently associated with ND.

Results

BA PI was well correlated with the right (n = 474, r² = 0.573, P < 0.001) by Pearson correlation analysis although MCA PI could not be measured from right MCA (n = 234, 33.05%) and left MCA (n = 252, 35.59%) by TCD owing to insufficient temporal bone window. Multivariable logistic regression analysis including age, sex, cerebral atherosclerosis burden, National Institutes of Health Stroke Scale at admission, and the proportion of patients with current smoking status, hypertension, diabetes mellitus, atrial fibrillation revealed that the higher BA PI (odds ratio, 3.28; confidence interval, 1.07–10.17; P = 0.038) was independently associated with ND.

Conclusions

BA PI, which would be identified regardless of temporal window, could predict ND among acute stroke patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40885-022-00210-9.

Changes in ophthalmic artery Doppler during acute blood-pressure control in hypertensive pregnant women

OBJECTIVE

To examine the changes in ophthalmic artery Doppler indices and their association with changes in mean arterial blood pressure (MAP) and systolic (SBP) and diastolic (DBP) blood pressure, following acute antihypertensive treatment in women with hypertensive disorders of pregnancy presenting with high blood pressure.

METHODS

This was a prospective cohort study of 31 pregnant women presenting at 30 + 0 to 39 + 6 weeks' gestation for management of their hypertension. Paired maternal blood-pressure and ophthalmic-artery-Doppler measurements were performed prior to and at 30 min and 60 min after starting antihypertensive medication. In patients who did not achieve blood-pressure control (i.e. when blood pressure was < 140/90 mmHg) by 60 min, paired readings were continued up to 120 min. If blood-pressure control was still not achieved at that point, patients were admitted to hospital. Univariate linear regression was performed to determine the association of ophthalmic artery peak systolic velocity (PSV) ratio with SBP, DBP and MAP before treatment and after blood-pressure control. The longitudinal changes in MAP, SBP, DBP and PSV ratio from pretreatment to 30 min and 60 min after commencement of antihypertensives were examined by repeated measure, multilevel, linear mixed-effects analysis.

RESULTS

Antihypertensive treatment was associated with a decrease in SBP, DBP, MAP and PSV ratio. At 60 min following antihypertensive treatment, the decrease in SBP, DBP, MAP and PSV ratio was 12.1 mmHg (95% CI, 9.0-15.1 mmHg; P < 0.0001), 9.1 mmHg (95% CI, 6.5-11.5 mmHg; P < 0.0001), 10.0 mmHg (95% CI, 7.6-12.4 mmHg; P < 0.0001) and 0.07 (95% CI, 0.03-0.11 mmHg; P < 0.001), respectively. From the total cohort, 20 (64.5%) women had achieved blood-pressure control at 60 min and another seven (22.6%) by 120 min from commencement of antihypertensive treatment. Four (12.9%) women did not achieve blood-pressure control during this period and were admitted to hospital. The relationship between PSV ratio and SBP, DBP and MAP was assessed before treatment (n = 31) and at the point of blood-pressure control in women in whom this was achieved by 120 min (n = 27). Prior to treatment, there was a significant association between PSV ratio and MAP (P < 0.0001, R²  = 0.39). This was primarily due to the association of PSV ratio with DBP (P < 0.0001, R²  = 0.39) and less so due to its association with SBP (P = 0.02, R²  = 0.16). At the point of achieving blood-pressure control, there was no significant association between PSV ratio and MAP (P = 0.7), DBP (P = 0.5) or SBP (P = 0.7).

CONCLUSIONS

Acute blood-pressure control in pregnancy is associated with a concomitant reduction in blood pressure and ophthalmic artery PSV ratio. In hypertensive pregnant women, there is a significant association of PSV ratio with MAP, SBP and DBP, which disappears after blood pressure is reduced to < 140/90 mmHg following antihypertensive treatment. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Peripheral Vascular Resistance in Cerebral Arteries in Patients With Carotid Atherosclerosis - Substudy Results of the Atherosclerotic Plaque Characteristics Associated With a Progression Rate of the Plaque and a Risk of Stroke in Patients With the Carotid Bifurcation Plaque Study (ANTIQUE)

OBJECTIVES

Transcranial color-coded duplex sonography (TCCS) enables to measure blood flow characteristics in cerebral vessels, including vascular resistance and pulsatility. The study aims to identify factors influencing pulsatility (PI) and resistance (RI) indices measured using TCCS in patients with carotid atherosclerosis.

METHODS

Self-sufficient patients with atherosclerotic plaque causing 20-70% carotid stenosis were consecutively enrolled to the study. All patients underwent duplex sonography of cervical arteries and TCCS with measurement of PI and RI in the middle cerebral artery, neurological, and physical examinations. Following data were recorded: age, gender, height, weight, body mass index, systolic and diastolic blood pressure, occurrence of current and previous diseases, surgery, medication, smoking, and daily dose of alcohol. Univariant and multivariant logistic regression analysis were used for identification of the factors influencing RI and PI.

RESULTS

Totally 1863 subjects were enrolled to the study: 139 healthy controls (54 males, age 55.52 ± 7.05 years) in derivation cohort and 1724 patients (777 males, age 68.73 ± 9.39 years) in validation cohort. The cut off value for RI was 0.63 and for PI 1.21. Independent factors for increased RI/PI were age (odds ratio [OR] = 1.108/1.105 per 1 year), occurrence of diabetes mellitus (OR = 1.767/2.170), arterial hypertension (OR = 1.700 for RI only), width of the carotid plaque (OR = 1.260 per 10% stenosis for RI only), and male gender (OR = 1.530 for PI only; P ˂.01 in all cases).

CONCLUSIONS

The independent predictors of increased cerebral arterial resistance and/or pulsatility in patients with carotid atherosclerosis were age, arterial hypertension, diabetes mellitus, carotid plaque width, and male gender.

Does vascular stiffness predict white matter hyperintensity burden in ischemic heart disease with preserved ejection fraction?

The survival rate of patients with ischemic heart disease (IHD) is increasing. However, survivors experience increased risk for neurological complications. The mechanisms for this increased risk are unknown. We tested the hypothesis that patients with IHD have greater carotid and cerebrovascular stiffness, and these indexes predict white matter small vessel disease. Fifty participants (age, 40-78 yr), 30 with IHD with preserved ejection fraction and 20 healthy age-matched controls, were studied using ultrasound imaging of the common carotid artery (CCA) and middle cerebral artery (MCA), as well as magnetic resonance imaging (T1, T2-FLAIR), to measure white matter lesion volume (WMLv). Carotid β-stiffness provided the primary measure of peripheral vascular stiffness. Carotid-cerebral pulse wave transit time (ccPWTT) provided a marker of cerebrovascular stiffness. Pulsatility index (PI) and resistive index (RI) of the MCA were calculated as measures of downstream cerebrovascular resistance. When compared with controls, patients with IHD exhibited greater β-stiffness [8.5 ± 3.3 vs. 6.8 ± 2.2 arbitrary units (AU); P = 0.04], MCA PI (1.1 ± 0.20 vs. 0.98 ± 0.18 AU; P = 0.02), and MCA RI (0.66 ± 0.06 vs. 0.62 ± 0.07 AU; P = 0.04). There was no difference in WMLv between IHD and control groups (0.95 ± 1.2 vs. 0.86 ± 1.4 mL; P = 0.81). In pooled patient data, WMLv correlated with both β-stiffness (R = 0.34, P = 0.02) and cerebrovascular ccPWTT (R = -0.43, P = 0.02); however, β-stiffness and ccPWTT were not associated (P = 0.13). In multivariate analysis, WMLv remained independently associated with ccPWTT (P = 0.02) and carotid β-stiffness (P = 0.04). Patients with IHD expressed greater β-stiffness and cerebral microvascular resistance. However, IHD did not increase risk of WMLv or cerebrovascular stiffness. Nonetheless, pooled data indicate that both carotid and cerebrovascular stiffness are independently associated with WMLv.NEW & NOTEWORTHY This study found that patients with ischemic heart disease (IHD) with preserved ejection fraction and normal blood pressures exhibit greater carotid β-stiffness, as well as middle cerebral artery pulsatility and resistive indexes, than controls. White matter lesion volume (WMLv) was not different between vascular pathology groups. Cerebrovascular pulse wave transit time (ccPWTT) and carotid β-stiffness independently associate with WMLv in pooled participant data, suggesting that regardless of heart disease history, ccPWTT and β-stiffness are associated with structural white matter damage.

Cerebrovascular carbon dioxide reactivity and flow-mediated dilation in young healthy South Asian and Caucasian European men

South Asians living in the United Kingdom have a 1.5-fold greater risk of ischemic stroke than the general population. Impaired cerebrovascular carbon dioxide (CO₂) reactivity is an independent predictor of ischemic stroke and cardiovascular mortality. We sought to test the hypothesis that cerebrovascular CO₂ reactivity is reduced in South Asians. Middle cerebral artery blood velocity (MCA V_m) was measured at rest and during stepwise changes in end-tidal partial pressure of CO₂ (PETCO2) in South Asian (n = 16) and Caucasian European (n = 18) men who were young (~20 yr), healthy, and living in the United Kingdom. Incremental hypercapnia was delivered via the open-circuit steady-state method, with stages of 4 and 7% CO₂ (≈21% oxygen, nitrogen balanced). Cerebrovascular CO₂ reactivity was calculated as the change in MCA V_m relative to the change in PETCO2. MCA V_m was not different in South Asians [59 (9) cm/s, mean (standard deviation)] and Caucasian Europeans [61 (12) cm/s; P > 0.05]. Similarly, cerebrovascular CO₂ reactivity was not different between the groups [South Asian 2.53 (0.76) vs. Caucasian European 2.61 (0.81) cm·s^-1·mmHg^-1; P > 0.05]. Brachial artery flow-mediated dilation was lower in South Asians [5.48 (2.94)%] compared with Caucasian Europeans [7.41 (2.28)%; P < 0.05]; however, when corrected for shear rate no between-group differences in flow-mediated dilation were observed (P > 0.05). Flow-mediated dilation was not correlated with cerebrovascular CO₂ reactivity measures. In summary, cerebrovascular CO₂ reactivity and flow-mediated dilation corrected for shear rate are preserved in young healthy South Asian men living in the United Kingdom.NEW & NOTEWORTHY Previous reports have identified an increased risk of ischemic stroke and peripheral endothelial dysfunction in South Asians compared with Caucasian Europeans. The main finding of this study is that cerebrovascular carbon dioxide reactivity (an independent predictor of ischemic stroke) is not different in healthy young South Asian and Caucasian European men.

Cardiovascular risk factors as determinants of cerebral blood flow - a cross-sectional and 6-year follow-up study

Purpose: The parameters of cerebral blood flow are modulated by many factors. The aim of the study was to prospectively assess the relationship between the number of the established cardiovascular risk factors and hemodynamic parameters of cerebral blood flow.Material and methods: The study was cross-sectional baseline and 6-year follow-up data analysis. We analyzed data regarding cardiovascular risk factors, medications use, and ultrasonographically (transcranial Doppler) obtained mean cerebral blood flow velocity (mCBFV), pulsatility (PI), resistance (RI) indexes of middle cerebral artery.Results: After 6.0 ± 0.6 years of follow-up, there was increase in systolic (p = .047), and decrease in diastolic (p = .005) blood pressure, resulting in greater pulse pressure (p < .001). Although intima-media thickness increased during follow-up (p = .019), PI, RI and mCBFV did not differ between baseline and follow-up. In the cohort without follow-up (n = 112), we observed strong association between number of studied cardiovascular risk factors and lower mCBFV, and higher PI and RI (all p < .001), in the cohort with 6 year follow-up (n = 53), we confirmed similar association for mCBFV and PI (p = .002) at baseline, and mCBFV (p = .024) after follow-up. During follow-up, more patients were treated with vasoactive medications (p < .05). Also the median (interquartile range) of total number of taken drugs at follow-up 2 (1-3) was greater than at baseline 1 (0-2), (p < .001). The addition of vasoactive medications during follow-up was associated with increase of the mCBFV (0.012 ± 0.02 m/s, p = .013).Conclusion: The parameters of the cerebral blood flow are adversely influenced by accretion of cardiovascular risk factors, both at baseline and after 6 years of follow-up. The addition of a vasoactive medication during follow-up is associated with an increase of the mCBFV, a possibly beneficial effect.

Cocaine attenuates blood flow but not neuronal responses to stimulation while preserving neurovascular coupling for resting brain activity

Cocaine affects neuronal activity and constricts cerebral blood vessels, making it difficult to determine whether cocaine-induced changes in cerebral blood flow (CBF) reflect neuronal activation or its vasoactive effects. Here we assessed the effects of acute cocaine on both resting-state and stimulation responses to investigate cocaine's effects on neurovascular coupling and to differentiate its effects on neuronal activity from its vasoactive actions. We concurrently measured cortical field potentials via thinned-skull electroencephalography recordings and CBF with laser Doppler flowmetry in the rat's somatosensory cortex for both resting state and forepaw stimulation before and following cocaine administration (1 mg kg(-1), intravenously). Results show both resting-state field potentials and CBF were depressed after cocaine administration (19.8±4.7% and 52.1±13.4%, respectively) and these changes were strongly correlated with each other (r=0.81, P<0.001), indicating that cocaine did not affect neurovascular coupling at rest and that the reduction in resting CBF reflected reduction in synchronized spontaneous neuronal activity rather than vasoconstriction. In contrast, the forepaw stimulation-evoked neuronal activity was not changed by cocaine (P=0.244), whereas the CBF to the stimulation was reduced 49.9±2.6% (P=0.028) gradually recovering ∼20 min after cocaine injection, indicating that neurovascular coupling during stimulation was temporarily disrupted by cocaine. Neurovascular uncoupling by cocaine during stimulation but not during rest indicates that distinct processes might underlie neurovascular regulation for both stimulation and spontaneous activity. The greater reductions by cocaine to the stimulation-induced CBF increases than to the background CBF should be considered when interpreting functional MRI studies comparing activation responses between controls and cocaine abusers. Neurovascular uncoupling could contribute to cocaine's neurotoxicity, particularly for stimulation conditions when CBF might be insufficient to cover for the energetic demands of neuronal tissue.

Radial primary percutaneous coronary intervention is independently associated with decreased long-term mortality in high-risk ST-elevation myocardial infarction patients

AIM

To compare long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (PPCI) using radial and femoral arterial access.

METHODS AND RESULTS

The present study was an observational cohort study of patients with STEMI treated consecutively with PPCI between 2004 and 2011 at a single centre. The primary end point was all-cause mortality at a median follow-up of 3 years.Among 2727 patients, 1600 (58.7%) underwent PPCI via the femoral route. The femoral group was older (64.7 vs. 61.7 years; P < 0.0001), and had higher rates of diabetes (18.6% vs. 16.0%; P < 0.0001), previous PCI (11.2 vs. 7.8%; P = 0.004), previous myocardial infarction (15.3 vs. 8.3%; P < 0.0001) and cardiogenic shock (9.8 vs. 1.3%; P < 0.0001). Bleeding complications were more frequent in the femoral group (4.7 vs. 1.2%; P < 0.0001). The 5-year death rate was significantly higher in the femoral group than in the radial group (10.4 vs. 3.0%; P < 0.0001). After adjustment for confounding variables, bleeding complications [heart rate 2.07 (95% confidence interval 1.05-4.08)] and femoral access [heart rate 1.60 (95% confidence interval 1.02-2.53)] were independent predictors of all-cause mortality. After stratification using the propensity score, excess long-term mortality in patients treated via the femoral approach was predominantly in patients with a high baseline risk of death.

CONCLUSION

Patients undergoing PPCI via the femoral route are at a higher risk of adverse short-term and long-term outcomes than patients undergoing PPCI via the radial route. Patients with a high baseline risk may benefit most from radial access, and future outcome studies should focus on the most at-risk patients.

The value of transcranial Doppler derived pulsatility index for diagnosing cerebral small-vessel disease

Background:

The pulsatility index (PI), measured by transcranial Doppler (TCD) ultrasonography, can reflect vascular resistance induced by cerebral small-vessel disease (SVD). We evaluated the value of TCD-derived PI for diagnosing SVD as compared with magnetic resonance imaging (MRI).

Materials and Methods:

Fifty-six consecutive cases with SVD (based on MRI) and 48 controls with normal MRI underwent TCD. Based on MRI findings, patients were categorized into five subgroups of preventricular hyperintensity (PVH), deep white matter hyperintensity (DWMH), lacunar, pontin hyperintensity (PH), and PVH+DWMH+lacunar. The sensitivity and specificity of TCD in best PI cut-off points were calculated in each group.

Results:

The sensitivity and specificity of TCD in comparison with MRI with best PI cut-off points were as follows: In PVH with PI = 0.83, the sensitivity and specificity was 90% and 98%, respectively. In DWMH with PI = 0.79, the sensitivity and specificity was 75% and 87.5%, respectively. In lacunar with PI = 0.80, the sensitivity and specificity was 73% and 90%, respectively. In PH with PI = 0.69, the sensitivity and specificity was 92% and 87.5%, respectively. And, in PVH+DWMH+lacunar subgroup with PI = 0.83, the sensitivity and specificity was 90% and 96%, respectively.

Conclusions:

Increased TCD derived PI can accurately indicate the SVD. Hence, TCD can be used as a non-invasive and inexpensive method for diagnosing SVD, and TCD-derived PI can be considered as a physiologic index of the disease as well.

Central nervous system imaging in diabetic cerebrovascular diseases and white matter hyperintensities

Diabetes mellitus is an important vascular risk factor for cerebrovascular disease. This occurs through pathophysiologic changes to the microcirculation as arteriolosclerosis and to the macrocirculation as large artery atherosclerosis. Imaging techniques can provide detailed visualization of the cerebrovasculature using CT (computed tomography) angiography and MR (magnetic resonance) angiography. Newer techniques focused on advanced parenchymal imaging include CT perfusion, quantitative MRI, and diffusion tensor imaging; each identifies brain lesion burden due to diabetes mellitus. These imaging approaches have provided insights into the diabetes mellitus brain and cerebral circulation pathophysiology. Imaging has taught us that diabetics develop cerebral atrophy, silent infarcts, and white matter disease more rapidly than other patient populations. Longitudinal studies are needed to quantify the rate and extent of such structural brain and blood vessel changes and how they relate to cognitive decline. Diabetes prevention and treatment strategies will then be possible to slow the development of such changes.

Intima-media thickness of carotid artery and aortic pulse wave velocity as determinants of cerebral blood flow velocity

The current study aims to check the relationship between parameters derived from brachial blood pressure, the carotid artery intima-media thickness (IMT), pulse wave velocity (PWV) and mean cerebral blood flow velocity (mCBFV) in the middle cerebral artery (MCA). In consecutive adult outpatients we recorded the brachial systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), mean arterial blood pressure (MAP), PWV and IMT. mCBFV was assessed using Doppler ultrasound probe applied to the transtemporal window. The mean±s.d. age of 165 patients (50% women) was 56.7±11.8 years. Women and men differed significantly in SBP, PP, total cholesterol and mCBFV. Age (r=-0.44, P<0.001) and BMI (r=-0.25, P<0.01) were significantly and reversely related to mCBFV. Compared with healthy individuals, hypertensive (P<0.05) and diabetic (P<0.01) patients had lower mCBFV. IMT and PWV were related to mCBFV (IMT, r=-0.36; P<0.001, and PWV, r=-0.34; P<0.001). After adjustment for possible confounders, the relationship between mCBFV and PWV did not retain statistical significance (P=0.54). However, the relationship between mCBFV and IMT remained statistically significant (P=0.02). The association between lower CBFV and higher IMT may constitute a link between increased IMT and risk of cerebrovascular events.

Blood flow pattern in the middle cerebral artery in relation to indices of arterial stiffness in the systemic circulation

BACKGROUND

The brain is perfused at high-volume flow throughout systole and diastole. We explored the association of blood flow in the middle cerebral artery (MCA) with the pulsatile components of blood pressure in the systemic circulation and indices of arterial stiffness.

METHODS

We enrolled 334 untreated subjects (mean age, 50.9 years; 45.4% women) who had been referred for ambulatory blood pressure monitoring to Ruijin Hospital, Shanghai, China. We measured the MCA pulsatility index (PI) by transcranial Doppler ultrasonography. The indices of arterial stiffness included pulse pressure (brachial (bPP) and central (cPP) measured at the office and 24-h ambulatory (24-h PP)) and carotid-femoral (cf-PWV) and brachial-ankle (ba-PWV) pulse wave velocity. Effect sizes, expressed per 1 s.d., were adjusted for sex, age, heart rate, and mean pressure.

RESULTS

Women had faster MCA blood flow than men (68.0 vs. 58.3 cm/s), but lower PI (75.4 vs. 82.3%; P < 0.001). The five arterial stiffness indices were intercorrelated (r ≥ 0.37; P < 0.001). PI increased (P ≤ 0.045) with bPP (+6.78%), cPP (+5.56%), 24-h PP (+7.58%), cf-PWV (+1.59%), and ba-PWV (+3.46%). In explaining PI variance, bPP ranked first (partial r(2) = 0.25), 24-h PP second (0.20) and cPP third (0.14). In models including both cf-PWV and ba-PWV, only the latter was significant (-0.19%; P = 0.84 vs. +3.54%; P < 0.001). In models including both bPP and ba-PWV, only the former contributed to PI variance (+6.98%; P < 0.001 vs. -0.24%; P = 0.78).

CONCLUSION

MCA blood flow is closely associated with the pulsatile pressure in the systemic circulation, which depends on arterial stiffness as measured by PWV.

South Asians have adverse cerebrovascular haemodynamics, despite equivalent blood pressure, compared with Europeans. This is due to their greater hyperglycaemia

BACKGROUND

South Asians have a 1.5-fold increased stroke mortality compared with Europeans, despite similar blood pressures (BP). We hypothesized that it is the greater hyperglycaemia in South Asians that increases stroke risk, by adversely affecting cerebrovascular haemodynamics.

METHODS

A population-based sample of 149 Europeans and 151 South Asians underwent metabolic profiling and concurrent measurement of finger BP using a Finapres and middle cerebral artery (MCA) blood flow velocity using transcranial Doppler ultrasound. Cerebrovascular autoregulation, cerebrovascular resistance [resistive index (RI) and pulsatility index (PI)] were calculated. Means of cerebrovascular haemodynamic measures were compared by ethnicity, with the introduction of explanatory variables to a regression model to determine which variable could best account for ethnic differences.

RESULTS

Cerebrovascular resistance (RI) was 12.9 × 10(3) (0.9-24.8, P = 0.04) greater in South Asians than Europeans. Systolic, diastolic and mean MCA velocities were also higher in South Asians (mean velocity 41.4 ± 8.0 cm/s vs 38.0 ± 8.0 cm/s, respectively, P = 0.001). Low frequency gain, a measure of autoregulation, was worse in South Asians compared with Europeans (0.50 ± 0.01 cm/s mm/Hg vs 0.45 ± 0.01 cm/s mm/Hg, P = 0.01). RI positively correlated with HbA(1c) (r = 0.184; P < 0.01). Adjustment for BP could not explain the higher RI in South Asians, but adjustment for HbA(1c) abolished the ethnic difference in RI (5.8 × 10(3) (-6.5 to 18.1, P = 0.4).

CONCLUSIONS

Cerebrovascular resistance and autoregulation are worse in South Asians than in Europeans, despite equivalent resting BP. The greater hyperglycaemia in South Asians accounts for their adverse cerebrovascular resistance. This could explain excess stroke in South Asians but requires testing in longitudinal studies.

Relationship between cerebral arterial pulsatility and carotid intima media thickness in diabetic and non-diabetic patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is considered a risk factor for atherosclerosis. The aim of the present study was to investigate the association of the pulsatility index (PI) of basilar artery (BA) and carotid intima media thickness (IMT) in diabetic and non-diabetic NAFLD patients. We compared a group of 80 stroke-free, diabetic and non-diabetic NAFLD patients and a control group of 26 healthy subjects without NAFLD. We then evaluated the PI of the BA by transcranial Doppler ultrasonography, and carotid IMT. The PI was significantly higher in diabetic NAFLD patients than in controls (p<0.003). Carotid IMT and asymmetrical dimethylarginine (ADMA) levels were higher in NAFLD patients than controls respectively (p<0.003, p<0.04). The PI of the BA was significantly correlated with age (R=0.369, p<0.001), male gender (R=0.207, p=0.035), diabetes (R=0.332, p=0.001), carotid IMT (R=0.296, p=0.002) and ADMA (R=0.349, p=0.015). A multiple regression analysis was performed with PI as the dependent variable with known clinical risk factors. Age (beta=3.54, p<0.001), diabetes (beta=2.32, p=0.022), gender (beta=2.20, p<0.03), ADMA (beta=2.25, p<0.031), and carotid IMT (beta=2.41, p<0.017), were independent predictive factors of BA PI. Adjustment for age and gender did not alter these relative risks, exhibiting a significant independent contribution to PI. The increased PI observed in this study represents enhanced cerebrovascular resistance, and we observed that the age, male gender, diabetes, ADMA levels, and carotid IMT were independent predictive factors of BA PI.

Cerebral arterial pulsatility and insulin resistance in type 2 diabetic patients

Diabetic patients have a threefold risk for cerebrovascular disease compared with nondiabetic controls. The aim of the present study was to investigate the association of insulin resistance with the pulsatility index (PI) of cerebral arteries in type 2 diabetic patients. We compared a group of 90 patients with stroke-free, type 2 diabetes and an age- and sex-matched control group of 45 healthy subjects without diabetes. We then evaluated the PI of the middle cerebral artery (MCA) by transcranial Doppler ultrasonography (TCD), and insulin resistance was determined by a short insulin tolerance test. The PI was significantly higher in diabetic patients than in healthy controls (p<0.05) and also higher in patients with insulin resistance than that seen in insulin sensitive diabetic patients (p<0.05). The PI of the MCA was significantly correlated with age (R=0.465, p<0.01), duration of diabetes (R=0.264, p=0.025) and hypertension (R=0.285, p=0.015) and inversely correlated with the insulin resistance index (Kitt: R=-0.359, p=0.030). A multiple regression analysis was performed with PI as the dependent variable and insulin resistance as an independent variable along with known clinical risk factors. Age (beta=0.393, p<0.01) and duration of diabetes (beta=0.274, p=0.043) exhibited a significant independent contribution to PI. PI could be a useful marker in the detection of diabetic cerebrovascular changes, and insulin resistance showed correlations with PI, but age and the duration of diabetes contributed independently to the variability in the PI.

Lacunar infarction in type 2 diabetes is associated with an elevated intracranial arterial pulsatility index

PURPOSE

The arterial pulsatility index (PI) is measured by transcranial Doppler ultrasonography (TCD) and is postulated to reflect the vascular resistance distal to the artery being examined. An increased PI of the intracranial artery is often reported with diabetes mellitus (DM), old age, hypertension, intracranial hypertension, vascular dementia, and small artery disease. Microvascular complication of DM, which may contribute to cerebral infarction, involves the small perforating artery and may influence the PI of the proximal artery.

MATERIALS AND METHODS

We performed a TCD examination in patients with type 2 DM with acute lacunar infarction (DML, n=35), type 2 DM without cerebral infarction (DMO, n=69), and in control cases with no DM or cerebral infarction (control group, n=41). We then compared the TCD findings among these groups.

RESULTS

The PI was significantly higher in the DML and DMO groups than in the control group (1.05, 0.93, 0.73. respectively, for the right middle cerebral artery; 1.04, 0.90, 0.73, respectively, for the left middle cerebral artery; 0.97, 0.89, 0.70, respectively, for the basilar artery). The PI was also significantly higher in the DML group than in the DMO group for both middle cerebral arteries. The flow velocity was comparable among the three groups.

CONCLUSION

The elevated PI of the intracranial arteries may reflect diabetic cerebral microvascular complications. The PI measurement using TCD may be a useful predictor of lacunar infarction in type 2 DM patients.

Prevalence and Risk Factors of Middle Cerebral Artery Stenosis in Asymptomatic Residents in Rongqi County, Guangdong

BACKGROUND

Intracranial atherosclerosis is the commonest vascular lesion for ischemic stroke in Asians. Most research on risk factors for middle cerebral artery (MCA) stenosis has been conducted in symptomatic patients with ischemic stroke or transient ischemic attack. The present study aimed to investigate risk factors for MCA stenosis in an asymptomatic population in Rongqi County in Southern China.

METHODS

We assessed 1,068 asymptomatic subjects over 50 years of age by transcranial Doppler. Medical history documentation and investigation of biochemical markers were performed for each subject. Multivariant, unconditioned, logistic regression analyses were employed to assess the risk factors associated with MCA stenosis.

RESULTS

MCA stenosis was found in 63 subjects (5.9%). Male gender, advancing age, hypertension, diabetes and systolic blood pressure were significant risk factors for MCA stenosis (p < 0.001). Based on logistic regression analyses, 4 factors emerged as independent risk factors (p < 0.001) of MCA stenosis: male gender [95% confidence interval (CI) = 1.49-4.66, OR = 2.63], age (95% CI = 1.01-1.06, OR = 1.04), hypertension (95% CI = 4.57-18.35, OR = 9.16) and diabetes mellitus (95% CI = 3.09-11.29, OR = 5.9).

CONCLUSION

MCA stenosis is relatively common among asymptomatic Chinese subjects. Male gender, advanced age, hypertension and diabetes mellitus are risk factors for MCA stenosis.

Relation of left ventricular hypertrophy to regional cerebral blood flow: single photon emission computed tomography abnormalities in essential hypertension

Several reports have shown that left ventricular hypertrophy (LVH) is an independent predictor of acute cerebrovascular events. The aim of the present study was to investigate the relationship between LVH and cerebral blood flow in middle-aged patients with essential hypertension. Forty never-treated hypertensive patients (24 men, 16 women, aged 50-60 years) without clinical evidence of target organ damage were studied. Regional cerebral blood flow was measured by means of single photon emission computed tomography of the brain. Twenty-nine patients showed echocardiographic criteria of LVH; 11 patients did not show this feature. No differences were found in regional cerebral blood flow ratio of all brain areas studied between hypertensives with or without LVH except for the striatum area. The regional cerebral blood flow ratio was significantly reduced in the striatum region of hypertensive patients with LVH, compared with patients without LVH (91.5+/-7.4 vs 98.1+/-8.3; P=.023). This relationship remained significant after adjusting for blood pressure. The authors conclude that the presence of LVH in middle-aged patients with essential hypertension is associated with a reduction of regional cerebral blood flow in the striatum area.

Evidencia científica en el tratamiento de la hipertensión arterial crónica en la prevención del ictus

Hypertension represents a relative risk of stroke up to 5 times. It is associated to ischaemic and haemorrhagic stroke. Hypertension produces an increase in brain vessels resistance and loss of the physiological mechanism of autoregulation, and it can be measured with transcranial doppler. Clinical trials have established that reducing blood pressure is effective in primary prevention of ischaemic and haemorrhagic stroke in hypertensive patients and in secondary prevention in hypertensive and non-hypertensive patients, even with small reductions in blood pressure. There is no evidence of superiority of a definite drug, although drugs that have proven efficacy in clinical trials are recommended in clinical practice.

A large-scale study on relationship between cerebral blood flow velocity and blood pressure in a natural population

In order to verify the relationship between blood pressure and cerebral blood flow velocity in sub-clinical natural population, 1294 middle-aged and old Beijing rural residents were investigated in autumn 2002. For all subjects, systolic blood flow velocities (V(s)) in common carotid artery (CCA), internal carotid artery (ICA) and middle cerebral artery (MCA) were detected with trans-cranial Doppler. Key factors such as anthropometry, medication use, blood pressure and blood biochemical analysis were investigated at the same time. After controlling for age, gender, diabetes, hypercholesterolaemia, smoking and body mass index, multivariate analysis showed that systolic blood pressure (SBP) correlated positively with V(s) at MCA and slight negatively correlated with at CCA. As blood pressure rose by 10 mm Hg, the V(s) at MCA increased by 1.63 cm/s. Duration of hypertension (HD) negatively correlated with V(s) at MCA (P<0.01). The V(s) at MCA in early-stage and chronic hypertensive patients were 92.9+/-1.9 and 84.1+/-2.3 cm/s, respectively. Antihypertensive treatment could modify the V(s) at MCA towards a normal level by lowering blood pressure. In conclusion, the effect of hypertension on cerebral blood flow is complex. V(s) at MCA positively correlated with SBP, but negatively related to HD. Antihypertensive treatment might be helpful to keep cerebral blood flow at a normal level.

Pulsatility index at the cervical internal carotid artery as a parameter of microangiopathy in patients with type 2 diabetes

OBJECTIVE

Although carotid intima-media thickness is a well-recognized indicator of atherosclerosis, it may not be an appropriate indicator of microangiopathy. We evaluated the parameters of extracranial carotid artery (CA) duplex ultrasonographic scanning in relation to microalbuminuria, which is an indicator of microangiopathy in patients with diabetes. The relationships of CA stenosis, hypertension, and dyslipidemia with microalbuminuria were also evaluated.

METHODS

Among 234 patients who were hospitalized for controlling type 2 diabetes during a 20-month period, those with major cerebrovascular, cardiac, or renal disease were excluded, leaving 159 patients who did not have any acute symptoms enrolled in this cross-sectional study. The parameters of extracranial CA duplex ultrasonographic scanning and urine albumin-to-creatinine ratio (u-ACR) were extracted, and their relationships were analyzed. Each patient's status with regard to CA stenosis, hypertension, and dyslipidemia was also examined for the effects on u-ACR.

RESULTS

Of the 159 patients, 29 (18.2%) had some CA stenosis, and there were significantly more hypertensive patients in this group (P=.007). The value of u-ACR was significantly higher in patients with dyslipidemia (P<.001) but not in those with CA stenosis or hypertension. With univariate analysis, significant correlations of u-ACR were observed with age, right end-diastolic velocity, and the bilateral pulsatility index (PI). Among these factors, multivariate analysis was made, and only age and PI proved to be independent factors correlated with u-ACR (P<.0001). With a PI cutoff of 1.15, 89.3% specificity with 49.1% sensitivity was obtained for detecting microalbuminuria.

CONCLUSIONS

The PI at the cervical internal CA can indicate microangiopathy because of its strong correlation with microalbuminuria in patients with type 2 diabetes, and it is thought to reflect the microangiopathy of cerebral vessels.

Gender and risk factor dependence of cerebral blood flow velocity in Chinese adults

BACKGROUND AND PURPOSE

The objective of this study is to determine if and how cerebral blood flow velocity and stroke risk factors are related in a stroke free population.

METHODS

This cross-sectional study recruited 1323 stroke-free subjects, aged 42-73 years, from a county region in China. Systolic blood flow velocities in cerebral arteries were detected with trans-cranial Doppler. Key factors, such as anthropometry, life-style, medication use, blood pressure and blood biochemical analysis were investigated at the same time.

RESULTS

In women, even controlled for major cardiovascular risk factors, cerebral blood flow velocities of common carotid artery, internal carotid artery, middle cerebral artery, anterior cerebral artery and posterior cerebral arteries decreased significantly with age (from 43.8 to 39.3, 48.0 to 42.6, 97.7 to 82.8, 79.2 to 69.4 and 44.1 to 39.7 cm/s in the range of 42-73 years old, p < 0.01 for each). In men, however, this inverse trend only existed in common carotid artery (from 45.6 to 41.7 cm/s, p < 0.01). Multivariate regression showed that most established cardiovascular risk factors (e.g. hypertension, hypercholesterolemia, diabetes mellitus and overweight/obesity) were associated with decreased blood flow velocity in the extra-cranial arteries. However, this association was not present (e.g. diabetes and overweight/obesity) or was inversed (e.g. hypertension and hypercholesterolemia) in the intra-cranial arteries.

CONCLUSION

Extra-cranial blood flow velocity is significantly and inversely related to age and cardiovascular risk factors. The relationship between intra-cranial blood flow and risk factors changes and may depend on gender. These finding may have importance in the determination of mechanisms of stroke.

Diagnostic tools for the study of vascular cognitive dysfunction in hypertension and antihypertensive drug research

Arterial hypertension is one of the main risk factors for cerebrovascular diseases, and antihypertensive treatment has significantly reduced their associated mortality. However, morbidity has not been reduced to a similar extent and a still increasing number of patients suffers from recurring strokes and from the disabling consequences of cerebrovascular diseases and develops progressive cognitive impairment. It is still debated to what extent antihypertensive treatment may prevent the development of cognitive dysfunction, due to the lack of a focused approach to vascular cognitive impairment, to the lack of a systematic study of the early phases of dementia, and to the use of diagnostic tests that are not sensitive and specific for a slow onset clinical condition, such as dementia. The aim of the present expert consensus report is to enlist the diagnostic tools that are currently available to assess mild cognitive impairment (MCI) and early dementia and that are sensitive and specific enough to be used in observational, longitudinal, and interventional clinical research studies, aiming to investigate the impact of antihypertensive drugs on vascular dementia (VD).

Cerebral hemodynamics and silent cerebral white matter lesions in middle-aged essential hypertensive patients

Cerebral white matter lesions (WML) represent a subclinical form of ischemic brain damage that have been associated with risk of future stroke. Studies have shown an association between WML and impaired cerebral autoregulation in hypertensives who had previously suffered a stroke. The aim of the study was to evaluate cerebral hemodynamics in asymptomatic hypertensives according to the presence or absence of WML. Fifty never-treated essential hypertensives (32 men, 18 women), aged 50-60 years, without clinical evidence of target organ damage were studied. All patients underwent 24-h ambulatory blood pressure monitoring, and brain-magnetic resonance imaging to establish the presence or absence of WML. Baseline cerebral blood flow velocity (CBF), pulsatility index (PI; differences between systolic and diastolic velocities), and CBF after acetazolamide infusion (vasomotor reactivity of cerebral vessels), were measured by transcranial Doppler ultrasonography in both left and right middle cerebral arteries, and averaged. Twenty hypertensive patients (40%) were found to have WML on brain resonance. No differences were observed on resting and stimulating CBF between hypertensives with and without WML. In contrast, patients with WML exhibited significantly higher PI compared with hypertensives without WML (0.79 +/- 0.13 vs 0.66 +/- 0.12; p = 0.003). Moreover, PI correlated with 24-h pulse pressure (r = 0.361; p = 0.015). We conclude that the presence of silent WML in middle-aged hypertensives is associated with increased cerebrovascular pulsatility. This increased pulsatility is also associated with higher pulse pressure values, suggesting a pathogenetic link between pulse pressure, pulsatility and the development of WML.

Abnormal brain activation to visual stimulation in cocaine abusers

Chronic cocaine abuse has been associated with cerebrovascular pathology. This is likely to reflect its vasoactive effects; cocaine produces vasoconstriction and reduces cerebral blood flow. We propose that cerebrovascular pathology in chronic cocaine abusers would result in abnormal BOLD [blood oxygenation level dependent] responses to activation stimuli. Here, we used fMRI to compared the BOLD response to photic visual stimulation in neurologically intact active cocaine abusers to that in non-drug-using healthy controls. Cocaine abusers showed a significantly enhanced positive BOLD response to photic stimulation when compared to control subjects. The enhanced activation in the cocaine abusers could result from low resting cerebral blood flow secondary to increased vasoconstriction and/or from low oxidative metabolism during activation. Alternatively, the larger signal intensity in the cocaine abusers could result from inefficient neuronal processing as has been shown to occur in other conditions of cerebral pathology. These findings provide evidence of cerebral dysfunction with chronic cocaine abuse, which could reflect cerebral blood flow or neuronal changes. Further studies are required to determine if the cerebrovascular changes we observed in the cocaine abusers recover with detoxification and to assess their functional consequences.

Methadone treatment induces attenuation of cerebrovascular deficits associated with the prolonged abuse of cocaine and heroin

Opiate replacement therapy has been useful in reducing heroin use and in keeping patients in treatment programs. However, neuropsychological and neurophysiological effects of this treatment regimen have not been evaluated systematically. To determine whether methadone treatment reduces the magnitude of cerebral blood flow alternations in polysubstance (heroin and cocaine) abusers, we compared blood flow parameters in control subjects (n=26), polysubstance abusers (n=28) maintained on methadone for 24 weeks, and polysubstance abusers (n=22) who were not seeking treatment. Blood flow velocity was recorded from the anterior and middle cerebral arteries using transcranial Doppler sonography on an outpatient visit. The pulsatility index, a measure of cerebrovascular resistance, was significantly (p&<0.05) increased in both groups of polysubstance abusers compared to control subjects. Increased pulsatility in the two groups of substance abusers suggests constriction of the small cortical arteries. Nevertheless, the methadone-maintained polysubstance abusers had significantly lower pulsatility values than the nontreatment substance-abusing group. These findings suggest that maintenance on methadone might have significant beneficial neurovascular effects on this population of patients.

Online monitoring of cerebral hemodynamics during hemodialysis

BACKGROUND

Several factors, including anemia, diabetes, and hypertension, potentially could disturb the cerebral autoregulation mechanism in hemodialysis (HD) patients. This study examined the effect of hemodynamic and rheological changes on mean cerebral blood flow (CBF) velocity (MV) during HD.

METHODS

Continuous online monitoring of MV and pulsatility index in the middle cerebral artery were performed in 18 HD patients by transcranial Doppler ultrasound during the entire HD period (range, 3 to 4 hours). In addition, blood pressure, hematocrit (Hct), and relative decrease in blood volume were continuously monitored. Blood samples were obtained at the beginning and end of HD to measure hemorheological variables.

RESULTS

After HD, Hct increased significantly from 33.6% +/- 5.9% to 41.4% +/- 5.7% (P < 0.001). Blood and plasma viscosity increased significantly from 3.33 +/- 0.77 to 4.36 +/- 1.3 mPa.s (P < 0.001) and from 1.35 +/- 0.29 to 1.54 +/- 0.38 mPa.s (P < 0.001), respectively. The change in MV (DeltaMV) was not significantly different from zero and correlated significantly with change in Hct. During HD, mean arterial pressure (MAP) in 15 patients changed within the normal range (group I), whereas 3 patients developed hypotension (group II) and their MAP decreased from 99 +/- 5 to 60 +/- 8 mm Hg (P < 0.05). In both groups, DeltaMV were not significant.

CONCLUSION

Results of this study suggest that CBF does not appear to be diminished significantly during HD.

Dynamics of cerebral blood flow autoregulation in hypertensive patients

In hypertensive patients, the upper and lower limits of cerebral autoregulation are shifted to higher levels. However, the dynamics of cerebral autoregulation in hypertensive patients are less well known. We compared the dynamics of cerebral autoregulation in 21 treated hypertensive patients (13 men and 8 women; mean age: 48.9+/-13.6 years) and in 21 normotensive subjects (13 men and 8 women; mean age: 51+/-14.5 years) by transcranial Doppler (TCD) of the middle cerebral artery (MCA) during the acute decrease in blood pressure induced by standing up after 2 min in squatting position. MCA maximal outline blood flow velocity (FV), blood pressure (Finapres) and end-tidal PCO2 were continuously monitored and computerised. A cerebral vascular resistance index (CR) was calculated as follows: mean arterial BP/MCA mean FV with normalised changes in CR per second during the blood pressure decrease (CR slope). The CR slope reflecting the rate of cerebral autoregulation did not differ between the two groups and within the hypertensive patients [well controlled (8 patients) and not controlled (13 patients)]. The time to maximum decrease of CR (T1) and the time to full recovery of CR after the initial drop (T2) were also similar in the two groups (controls T1: 11.3+/-3.1 s, T2: 12+/-5.9 s; hypertensive T1: 11.7+/-2.5 s, T2: 10.7+/-4.5 s) and within hypertensive patients. These findings suggest that the dynamics of cerebral autoregulation are well preserved in hypertensive patients, with no difference according to the efficiency of treatment of hypertension.

Cerebral blood flow pulsatility deficits in HIV+ poly substance abusers: differences associated with antiviral medications

This study examines the influence of HIV-seropositivity and antiviral medications on cerebral blood flow in cocaine abusers. Forty-five HIV negative (HIV-) cocaine abusers, 36 HIV positive (HIV+) cocaine abusers (CD4; mean 378, +/-229) and 27 control HIV- subjects were studied. Blood flow velocity and pulsatility were determined for the anterior and middle cerebral arteries using transcranial Doppler sonography (TCD). Psychological assessments, which included the psychiatric symptom checklist (SCL-90R), hopelessness (Beck) and well-being (Ellison) questionnaires revealed greater psychiatric distress in HIV+ cocaine abusers than the other groups. HIV- cocaine abusers and HIV+ cocaine abusers not receiving antiviral medications (n=25 of 36) had elevated pulsatility values, indicating increased resistance in the cerebral blood vessels in comparison to control subjects. HIV+ cocaine abusers using antiviral medications (n=11 of 36) had pulsatility values similar to HIV- control subjects. Interestingly, there was no significant relationship between intensity of psychiatric distress reported by HIV+ cocaine abusers and perfusion deficits. Our findings suggest that unmedicated HIV+ cocaine abusers have cerebrovascular deficits, which are similar to HIV- cocaine abusers. In addition, the use of antiviral medications appears to be associated with a reduction of these deficits in HIV+ cocaine abusers. Nevertheless, more studies will be needed before any conclusion can be reached regarding possible beneficial effects of these agents on the cerebral vasculature.

Transcranial Doppler pulsatility indices as a measure of diffuse small-vessel disease

BACKGROUND AND PURPOSE

Elevation in pulsatility indices (PIs) as measured by transcranial Doppler (TCD) have been postulated to reflect downstream increased vascular resistance caused by small-vessel ischemic disease.

METHODS

The authors retrospectively compared TCD PIs and magnetic resonance imaging (MRI) manifestations of small-vessel disease in 55 consecutive patients who underwent TCD studies and brain MRI within 6 months of each other during a 2-year period.

RESULTS

Correlations between TCD middle cerebral artery PIs and MRI measures were as follows: periventricular hyperintensity (PVH) = 0.52 (P < .0001), deep white matter hyperintensity (DWMH) = 0.54 (P < .0001), lacunar disease = 0.31 (P = .02), and combined PVH/DWMH/lacunes = 0.54 (P < .0001). Correlation between pontine ischemia and vertebrobasilar PIs was 0.46 (P = .0004). Univariate analysis showed that age, elevated PI, and hypertension strongly correlated with white matter disease measures. After adjusting for these factors in a multivariate Poisson regression analysis, PI remained an independent predictor of white matter disease. Receiver operator curve analyses identified PI cut points that allowed discrimination of PVH with 89% sensitivity and 86% specificity and discrimination of DWMH with 70% sensitivity and 73% specificity.

CONCLUSIONS

Elevation in PIs as measured by TCD shows strong correlation with MRI evidence of small-vessel disease. TCD may be a useful physiologic index of the presence and severity of diffuse small-vessel disease.

Antiviral medications improve cerebrovascular perfusion in HIV+ non-drug users and HIV+ cocaine abusers

Antiviral medications have been useful in delaying the time course of HIV infection. Antiviral medications have also been reported to delay or reduce symptoms associated with AIDS related dementia and to improve cortical perfusion. The mechanism for this improvement is unclear. Thus, this report studies the effects of antiviral medications on cerebral blood flow velocity in HIV+ cocaine abusers, HIV+ control individuals and appropriate control individuals. Thirty-two unmedicated HIV+ individuals (28 cocaine abusers and 4 control individuals), 22 HIV+ individuals using antiviral medications (16 cocaine abusers and 6 HIV+ control individuals), 47 HIV- cocaine abusers, and 27 control HIV- subjects were studied. Blood flow velocities were determined for the anterior and middle cerebral arteries using transcranial Doppler sonography. HIV+ individuals on antiviral medications had lower pulsatility values, suggesting decreased resistance in the cerebral blood vessels, in comparison to HIV+ individuals not taking antiviral medications. HIV+ cocaine abusers and HIV+ control individuals using antiviral medications had pulsatility values similar to HIV- control subjects. Antiviral medications appear to reduce these cerebrovascular perfusion deficits in HIV+ individuals. The antiviral medications appear to have a direct neuroprotective effect in addition to their antiviral effects. The neuroprotective role of antiviral medications requires further investigation.

Effect of exogenous melatonin on vascular reactivity and nitric oxide in postmenopausal women: role of hormone replacement therapy

OBJECTIVE

Several effects of melatonin are modulated by gonadal steroids and are reduced in ageing women. Administration of melatonin reduces internal carotid artery pulsatility index (PI), and blood pressure in young individuals. Whether these effects are conserved in postmenopausal women and are influenced by hormone replacement therapy (HRT), was herein investigated.

DESIGN

Randomised, double-blind placebo controlled study.

PATIENTS

Twenty-three postmenopausal women of which 11 were unreplaced with HRT and 12 on the oestrogenic phase of continuous transdermal estradiol (50 microg/day) plus cyclic medroxyprogesterone acetate (5 mg/day x 12 days every 28 days).

MEASUREMENTS

Internal carotid PI, by colour Doppler, and supine blood pressure were evaluated 90, 180 and 240 minutes following the oral administration of melatonin (1 mg) or placebo. Levels of nitrites/nitrates (NOx), the stable derivatives of nitric oxide, were also evaluated in samples collected 90 minutes following the administration of placebo or melatonin.

RESULTS

In women not on replacement therapy melatonin was ineffective. In HRT-treated women, melatonin reduced internal carotid artery PI (P = 0.005). The effect was maximal within 90 minutes, and maintained for at least 240 minutes, with melatonin levels in the nocturnal physiological range. Systolic and diastolic blood pressures were reduced of 8 mmHg (P = 0.038) and 4 mmHg (P = 0.045), respectively, while NOx levels were significantly increased (P = 0.024).

CONCLUSIONS

The circulatory response to melatonin is conserved in postmenopausal women with but not without hormone replacement therapy. Maintenance of the cardiovascular response to melatonin, may be implicated in the reduced cardiovascular risk of postmenopausal women with hormone replacement therapy.

Arterial pulsatility as an index of cerebral microangiopathy in diabetes

BACKGROUND AND PURPOSE

This study was designed to evaluate cerebral hemodynamic changes related to diabetes mellitus (DM) with transcranial Doppler ultrasonography (TCD).

METHODS

We measured the flow velocities and the Gosling pulsatility index (PI) of the middle cerebral artery (MCA), extracranial internal carotid artery (ICA), and basilar artery (BA) in 56 stroke-free, normotensive patients with type 2 DM and 70 age- and gender-matched healthy volunteers. Patients were divided into 2 groups according to the presence of microvascular complications such as retinopathy, nephropathy, and neuropathy.

RESULTS

Patients showed slightly lower hematocrit and higher serum fibrinogen levels than control subjects, but other clinical profiles, including stroke risk factors except for diabetes, were comparable between patients and controls. The flow velocity of the ICA but not the MCA and BA in patients regardless of the complication was significantly higher than that in controls. The PIs of the MCA and ICA were significantly higher in patients with complication than those without complication, as well as in controls. The PI of the BA was also significantly higher, even in patients without complication, than in controls. The PIs of the MCA and ICA but not the BA were closely correlated with the duration of DM (r(2)=0.46 and 0.34, respectively).

CONCLUSIONS

This study defines TCD findings of diabetes-related cerebral hemodynamic changes and suggests that the PI reflects microangiopathic changes of cerebral vessels.

Effect of desogestrel-containing oral contraceptives on vascular reactivity and catecholamine levels

The modifications induced by new oral contraceptives (OC) on blood pressure, great vessel vascular reactivity by color Doppler, and catecholamine levels were investigated. Young healthy women not taking OC (n = 22; controls) or receiving, for > or = 6 months, OC containing desogestrel with either 30 micrograms (n = 14) or 20 micrograms of EE (n = 8) were enrolled. Blood pressure measured at rest in supine position was similar between controls and OC users. The pulsatility index (PI), an indirect index of resistance to blood flow, of axillary artery was significantly higher (p < 0.05) in 30 micrograms than in 20 micrograms EE OC users or controls. A similar trend, albeit not significant, was observed for the internal carotid artery PI. Norepinephrine (p < 0.01) and dopamine (p < 0.05) but not epinephrine levels, were lower in 30 micrograms EE OC users than in 20 micrograms EE OC users or controls. Thus, both 20 micrograms and 30 micrograms EE OC had no negative effect on blood pressure, but the 30 micrograms EE OC tended to increase great vessel resistance to blood flow, independently of catecholamine levels.

Gosling's Doppler pulsatility index revisited

In Doppler sonography, the physiological meaning of Gosling's pulsatility index (PI) as a measure of downstream resistance is still under dispute. We deliver the theoretical derivation of its physiological significance. We present a mathematical model based on the linked theories of critical closing pressure (CCP) and cerebrovascular impedance, verified in preterm neonates. Mathematical transformation results in a series of equations interrelating several physiological parameters. Instead of indicating cerebrovascular resistance, PI is linked to the ratio of cerebrovascular impedances at the heart rate and at zero frequency. Next to arterial blood pressure, CCP is the principal determinant of PI. PI is identical to the ratio of the alternate and the direct component of the effective driving force. Thus, PI has no distinctive physiological meaning by itself. At present, our model is confined to physiological conditions where the lowest velocity is the end diastolic, and always more than zero.