Risk Factor Interaction in Cardiovascular and Cerebrovascular Disease

Estrogen increases cGMP in selected brain regions and in cerebral microvessels

We have previously reported that exogenous and endogenous estrogen can amplify residual cerebral blood flow during experimental cerebral ischemia. Because estrogen has been linked to nitric oxide and cyclic guanosine monophosphate (cGMP) signaling in noncerebral tissue, we tested the hypothesis that long-term 17beta-estradiol treatment increases basal cGMP in brain homogenates and cerebral microvessels in female rabbits. We also determined whether there are important baseline gender-specific differences in regional cGMP. Adult female rabbits were implanted with 17beta-estradiol pellets, 10 mg (F10, n = 10) or 50 mg (F50, n = 13), and compared with untreated females (F, n = 19) and males with negligible estrogen (M, n = 19) (plasma 17beta-estradiol levels of 4+/-4 pg/mL in M, 7+/-5 pg/mL in F, 141+/-74 pg/mL in F10, and 289 +/-10 pg/mL in F50). Cyclic GMP was determined by radioimmunoassay in cerebellum, hypothalamus, caudate nucleus, hippocampus, and cortex. Cerebral microvessels were harvested from additional cohorts of untreated males and females or estradiol-implanted females (n = 6 per group). Basal cGMP was higher in F versus M only in cerebellum. Estrogen-induced increases in regional cGMP were prominent in hippocampus at all doses (M = 43+/-26, F = 43+/-21, F10 = 84+/-24, F50 = 117+/-55 fmol/mg protein) and in cortex at the high dose (M = 78+/-55, F = 88+/-51, F10 = 69+/-34, F50 = 143+/-52 fmol/mg protein). Similarly, microvascular cGMP increased only in females treated with the 50 mg dose (M = 77+/-13, F = 86+/-25, F10O = 106+/-35, F50 = 192+/-88 fmol/mg protein). Therefore, 17beta-estradiol increases cGMP content in parenchymal regions that are known physiologic targets for reproductive steroids but are also areas of selective vulnerability to ischemic insult. Further, high doses of estrogenic steroids could amplify cGMP signaling within the cerebral microvasculature.

Age and sex differences in cerebral hemodynamics: a transcranial Doppler study

BACKGROUND AND PURPOSE

Hemodynamic factors seem to play an important role in the pathogenesis of cerebral ischemic events. The aim of this study was to evaluate whether changes in cerebrovascular reactivity occur in women after menopause.

METHODS

Using transcranial Doppler ultrasonography, we studied the changes of flow velocity after hypercapnia in the middle cerebral arteries of 45 healthy premenopausal women (mean age, 32.3 years; range, 20 to 47 years) and 40 postmenopausal women (mean age, 54.4 years; range, 48 to 64 years). The same measurements were recorded in two groups of healthy male subjects age matched with premenopausal (45 subjects) and postmenopausal women (40 subjects). Moreover, a subgroup of postmenopausal women aged 48 to 53 years (15 subjects) were compared with a group of 15 premenopausal women of the same age. We obtained hypercapnia with breath holding and evaluated cerebrovascular reactivity with the breath-holding index (BHI).

RESULTS

BHI was significantly lower in postmenopausal women (0.89+/-0.3) than in premenopausal women (1.59+/-0.3; P<0.0001) and in young (1.34+/-0.5; P<0.001) and old men (1.20+/-0.4; P<0.04). In the latter group, BHI was significantly lower than in premenopausal women (P<.0001). BHI values were also significantly lower in postmenopausal than in premenopausal women of the same age (0.81+/-0.1 versus 1.34+/-0.1; P<0.0001).

CONCLUSIONS

These findings suggest that the large reduction of cerebrovascular reactivity in postmenopausal women cannot be considered a simple factor related to aging but is probably influenced by hormonal changes. The alteration in cerebrovascular regulation could be involved in the increase of cerebrovascular disease in postmenopausal women.

Postischemic cerebral blood flow recovery in the female: effect of 17 beta-estradiol

Female reproductive hormones are considered to be protective agents in atherosclerotic vascular disease and stroke. The present study determined if there are unique cerebrovascular responses in female animals to global cerebral ischemia and if 17 beta-estradiol is important to postischemic outcome in brain. Three groups of anesthetized, sexually mature rabbits were treated with normotensive four-vessel occlusion (6 min) and 3 h of reperfusion: females chronically instrumented with 17 beta-estradiol implants (EFEM; n = 8, plasma estradiol level = 365 +/- 48 pg/ml), untreated females (FEM; n = 8, estradiol = 13 +/- 3 pg/ml), and untreated males (M; n = 8, estradiol < limit of radioimmunoassay). CBF (microspheres) and somatosensory evoked potential (SEP) amplitude were measured during ischemia/reperfusion. Baseline hemispheric blood flow and regional flow distribution were not altered by chronic estradiol treatment. Hemispheric blood flow was equivalently reduced during ischemia in FEM and M (6 +/- 1 and 9 +/- 2 ml min-1 100 g-1, respectively); however postischemic hyperemia was greater in FEM than M (CBF = 257 +/- 27 and 183 +/- 27 ml min-1 100 g-1. However, EFEM experienced higher CBF during ischemia (e.g., 13 +/- 2 ml min-1 100 g-1) and less hyperemia (134 +/- 4 ml min-1 100 g-1 in hemispheres) in numerous brain regions than FEM. CBF at 3 h reperfusion was not different among the groups. Recovery of SEPs was incomplete and similar in all groups. We conclude that chronic exogenous 17 beta-estradiol treatment increases CBF during global incomplete ischemia and ameliorates postischemic hyperemia in the female animal.

Elevated serum cholesterol is a risk factor for both coronary heart disease and thromboembolic stroke in Hawaiian Japanese men. Implications of shared risk

BACKGROUND AND PURPOSE

The relation between total serum cholesterol level and thromboembolic or nonhemorrhagic stroke is controversial. The Honolulu Heart Program cohort of Japanese-American men provides data which show that elevated serum cholesterol is an independent predictor of thromboembolic stroke as well as coronary heart disease (CHD). The data are presented to suggest that the association of elevated cholesterol with stroke is sometimes underestimated or underreported partly because of competing or shared risk with CHD, the other major atherosclerotic end point.

METHODS

The data are based on 6352 men (aged 51 to 74 years) at baseline examination (1971 to 1974) who were free of clinical CHD and stroke and were followed an average of 15 years for new cases of both end points. Relative risks of serum cholesterol for CHD and thromboembolic stroke were calculated, controlling for other major cardiovascular covariates.

RESULTS

There was a continuous and progressive increase in both CHD and thromboembolic stroke rates with increasing levels of serum cholesterol. The relative risk between the highest and lowest quartiles of serum cholesterol was 1.7 (95% confidence interval, 1.4 to 2.0) for CHD and 1.4 (95% confidence interval, 1.1 to 1.9) for thromboembolic stroke. There was a decline in the difference in relative risks between CHD and thromboembolic stroke in older men (aged 60 years and older) compared with younger men (aged younger than 60 years).

CONCLUSIONS

These data provide additional evidence that elevated serum cholesterol should be considered a primary risk factor for thromboembolic stroke, presumably through its effect on both coronary and cerebrovascular atherosclerosis. It is suggested that this association is sometimes underestimated or underreported partly because of shared or competing risk with CHD, the clinical manifestation of atherosclerosis that generally occurs earlier in life and with greater frequency than thromboembolic stroke.

Risk factors for carotid atherosclerosis and silent cerebral infarction in patients with coronary heart disease

In this study, the authors examined relations between coronary and carotid atherosclerosis and between coronary atherosclerosis and silent cerebral infarction. They ascertained the risk factors for carotid atherosclerosis and silent cerebral infarction complicating coronary heart disease (CHD) in 77 Japanese subjects. As coronary atherosclerosis progressed, the carotid ultrasonographic score and the brain computed tomographic score increased. Multivariate analyses showed that the significant and independent risk factors for carotid atherosclerosis in patients with CHD were age (p < 0.01) and apolipoprotein (apo) B (p < 0.05) and the factors for silent cerebral infarction were age (p < 0.05) and hypertension (p < 0.05). Their study confirms a positive relation between coronary atherosclerosis and carotid atherosclerosis and between coronary atherosclerosis and silent cerebral infarction in patients with CHD. Their data suggest that carotid atherosclerosis should be looked for in patients with CHD who are old and have a high value of apo B, and silent cerebral infarction should be looked for in those who are old and have hypertension, to prevent complicating symptomatic cerebral vascular disease (CVD). If severe carotid atherosclerosis or silent cerebral infarction are detected, antithrombotic medication should be given.

The US decline in stroke mortality: what does ecological analysis tell us?

We review a study in this issue that concludes, from analyses of ecological associations, that the use of medication to lower high blood pressure has caused at most a small decline in US stroke mortality rates. Our analysis suggests that other possible sources of the decline may be population-wide falls in levels of blood pressure, cigarette smoking, and coronary heart disease mortality, as well as improved treatment of cardiac and respiratory sequelae of stroke. Although the ecological method is powerful for answering questions about medical interventions' population-wide effects on disease, it must be used with care. Of particular concern are variables with meanings that differ between the ecological and the individual levels, the number of ecological units available for analysis, the sample size within the ecological units, and the range of independent variables used in ecological regression.

Brain magnetic resonance imaging and neuropsychologic evaluation of patients with idiopathic dilated cardiomyopathy

We compared brain magnetic resonance imaging and neuropsychologic performance in 20 neurologically asymptomatic patients suffering from idiopathic dilated cardiomyopathy (mean age 41 [range 18-49] years) and 20 age-matched controls (mean age 38 [range 28-49] years). Patients exhibited a significantly higher rate of cerebral infarcts (20% versus 0%, p less than 0.05) and cortical (50% versus 5%, p less than 0.01) and ventricular (55% versus 15%, p less than 0.02) atrophy than controls. Accordingly, semiquantitative volumetric measurements yielded a significantly increased ventricular-to-intracranial cavity ratio in the patients (6.2 +/- 2.9% versus 4.1 +/- 1.3%, p less than 0.01). This ratio and the cortical atrophy ratings correlated positively with disease duration (r = 0.63 and 0.54, p less than 0.05). Cognitive test performance was significantly worse in patients than in controls and was most impaired in those patients with morphologic cerebral abnormalities.

Management of coexistent carotid artery and coronary artery disease

At the present time staged carotid reconstruction several days before elective coronary artery bypass surgery seems to be the safest and most logical approach for patients with neurological symptoms, stable cardiac symptoms, and acceptable coronary anatomy. Combined procedures may well be necessary for those who have active neurological symptoms or bilateral carotid lesions in conjunction with diffuse or unstable coronary artery disease, but the incidence of neurological complications at the time of simultaneous operations could exceed the stroke risk for either carotid endarterectomy or coronary bypass alone. The asymptomatic patient with unilateral carotid stenosis who presents for coronary artery bypass might be best managed by myocardial revascularization followed by medical or surgical management of the carotid disease. In order to obtain optimal long-term results, both coronary disease and associated carotid disease require appropriate evaluation and medical and surgical management.