South Asians have adverse cerebrovascular haemodynamics, despite equivalent blood pressure, compared with Europeans. This is due to their greater hyperglycaemia.
ABSTRACT 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.
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.
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).
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.
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ABSTRACT: BBZDR/Wor rat is a new model of type II diabetes with spontaneous obesity and clinical characteristics close to human diabetes. In this study the time-course of cerebroarterial dysfunction was characterized. Posterior cerebral arteries from BBZDR/Wor rats and their age-matched lean controls were pressurized to 70 mm Hg in an arteriograph. Effects of intraluminal pressure and different pharmacological agents on myogenic tone were evaluated. Pressure-myogenic tone curves in diabetic arteries were similar to that in non-diabetic arteries at pre-diabetic age, showed leftward shift at 4 weeks and were significantly different with higher myogenic tone at 5 and 8 months of diabetes. Age-dependent decrease in myogenic tone was observed in non-diabetic arteries. Dilation to histamine was similar to that in non-diabetic arteries at pre-diabetic and at 4 weeks but significantly reduced at 5 and 8 months of diabetes. Bradykinin-mediated dilation was significantly reduced in early and chronic diabetes, whereas (+/-)-S-nitroso-N-acetylpenicillamine (SNAP)-mediated dilation was decreased modestly at 8 months of diabetes. Sensitivity and constriction to 5-hydroxytryptamine were increased in early and chronic diabetes. Responses to bradykinin and 5-hydroxytryptamine were decreased and increased, respectively. Myogenic tone was significantly less sensitive to (lower pIC(50)) U-73122 than normal arteries at 4 weeks and 8 months of diabetes suggesting an increased activation of phospholipase C (PLC). This study shows that pressure-mediated autoregulation of cerebral arteries in type II diabetes operates at higher resistance. Endothelium-dependent dilation was decreased with chronic diabetes with increased sensitivity to constrictor agonist. Endothelium-independent dilation was modestly affected. Arterial hyper-reactivity to pressure and constrictor agonist were likely due to increased PLC activation.European Journal of Pharmacology 02/2008; 579(1-3):298-307. · 2.59 Impact Factor
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ABSTRACT: This study was designed to evaluate cerebral hemodynamic changes related to diabetes mellitus (DM) with transcranial Doppler ultrasonography (TCD). 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. 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). This study defines TCD findings of diabetes-related cerebral hemodynamic changes and suggests that the PI reflects microangiopathic changes of cerebral vessels.Stroke 06/2000; 31(5):1111-5. · 6.16 Impact Factor
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ABSTRACT: The relationship between intracranial vascular disease and cardiovascular risk factors such as smoking, hypertension, diabetes mellitus, and total serum cholesterol in patients with recent cerebral ischemia is not well established. We used transcranial Doppler (TCD) sonography tests as parameters of intracranial vascular disease and investigated the relationship between these parameters and conventional cardiovascular risk factors. We prospectively studied 598 patients with a minor ischemic stroke or transient ischemic attack (TIA). In all patients, flow velocities in the left and right middle cerebral artery (MCA), and cerebrovascular reactivity to CO2 were measured by means of TCD sonography. Student's t-test and linear regression analysis were used to determine the relationship between the baseline characteristics, vascular risk factors, and TCD parameters. After adjustment for other vascular risk factors, a statistically significant relationship with mean flow velocity in the MCA was found for age (3.5 cm/s/10 years of age; 95% CI, 2.5-4.5 cm/s/10 years of age; p < 0.0001), sex (-2.9 cm/s for male sex; 95% CI, -5.5 to -0.3 cm/s; p = 0.03), diabetes (5.6 cm/s for diabetics; 95% CI, 2.1-9.1 cm/s; p = 0.002), and total serum cholesterol (2.4 cm/s per mmol increase in total serum cholesterol; 95% CI, 1.4-3.5 cm/s; p < 0.0001). Total serum cholesterol and hypertension were related to cerebrovascular reactivity to CO2. Cerebral flow velocity is influenced by multiple interacting factors. Results of TCD investigations should be adjusted for age, sex, diabetes, and cholesterol when used for diagnostic or prognostic purposes.Journal of Clinical Ultrasound 02/2006; 34(2):70-6. · 0.70 Impact Factor