Acute effects of 17 beta-estradiol on the coronary microcirculation: observations in sedated, closed-chest domestic swine

Prognostic utility of sestamibi lung uptake does not require adjustment for stress-related variables: a retrospective cohort study

Background

Increased ^99mTc-sestamibi stress lung-to-heart ratio (sLHR) has been shown to predict cardiac outcomes similar to pulmonary uptake of thallium. Peak heart rate and use of pharmacologic stress affect the interpretation of lung thallium uptake. The current study was performed to determine whether ^99mTc-sestamibi sLHR measurements are affected by stress-related variables, and whether this in turn affects prognostic utility.

Methods

sLHR was determined in 718 patients undergoing ^99mTc-sestamibi SPECT stress imaging. sLHR was assessed in relation to demographics, hemodynamic variables and outcomes (mean follow up 5.6 ± 1.1 years).

Results

Mean sLHR was slightly greater in males than in females (P < 0.01) and also showed a weak negative correlation with age (P < 0.01) and systolic blood pressure (P < 0.01), but was unrelated to stress method or heart rate at the time of injection. In patients undergoing treadmill exercise, sLHR was also positively correlated with peak workload (P < 0.05) but inversely with double product (P < 0.05). The combined explanatory effect of sex, age and hemodynamic variables on sLHR was less than 10%. The risk of acute myocardial infarction (AMI) or death increased by a factor of 1.7–1.8 for each SD increase in unadjusted sLHR, and was unaffected by adjustment for sex, age and hemodynamic variables (hazard ratios 1.6–1.7). The area under the ROC curve for the unadjusted sLHR was 0.65 (95% CI 0.59–0.71, P < 0.0001) and was unchanged for the adjusted sLHR (0.65, 95% CI 0.61–0.72, P < 0.0001).

Conclusion

Stress-related variables have only a weak effect on measured sLHR. Unadjusted and adjusted sLHR provide equivalent prognostic information for prediction of AMI or death.

Animal models used in identifying gender-related differences

There is general agreement in the scientific community on the need to identify appropriate animal models that can be used to screen for gender-based differences. At the same time, there is a growing expectation for data from these models to mimic or be more predictive of the human experience. The species in this review will include nonhuman primates, rats, mice, rabbits, swine, hamsters, gerbils, quail, and fish. Although some of the models are unique, the gender-related differences, in most instances, may be correlated with man, due to the conservation of biological systems across species.

Impact of estradiol blood concentrations on skin capillary Laser Doppler flow in premenopausal women

OBJECTIVE AND METHOD

Estradiols are known to prevent cardiovascular diseases, but the underlying mechanisms remain unclear. We assessed the finger skin capillary blood flow in 20 premenopausal women with oral contraception noninvasively by Laser Doppler flowmetry (LDF). Blood flow was registered both under basal conditions and after 2 min of arterial occlusion. Furthermore, the combination with a beat-to-beat online finger blood pressure monitor allowed the calculation of the regional peripheral resistance (RPR). All measurements were performed in the menstrual phase. LDF and RPR were correlated to the estradiol whole blood levels.

RESULTS

Both baseline (r(2)=0.826; P<0.01) and vasodilation (r(2)=0.747; P<0.01) blood flux were significantly correlated to the corresponding estradiol concentrations. A multiple stepwise regression analysis (with age, height, weight, duration of oral contraception, nicotine pack years and estradiol levels in the equation) showed positive correlations between estradiol levels and (a) baseline (P<0.05) or (b) vasodilation (P<0.05) Laser Doppler flux or (c) time to reach the peak flux (r(2)=0.31; P<0.05). Furthermore, the minimal local vascular resistance was negatively correlated to the estradiol levels (r(2)=0.45; P<0.05).

CONCLUSION

The study provides evidence that both the baseline and the vasodilation capillary blood flux in women in the menstrual phase depend on the estradiol whole blood levels. Furthermore, the local vascular resistance shows a negative correlation to the hormonal state. Functional or structural alterations of the microvasculature may therefore contribute to the estradiol-associated cardiovascular protection.