Influence of High-Velocity Blood Flow on Right-to-Left Shunt in Patients with Patent Foramen Ovale during the Valsalva Maneuver

In this study, we investigated the changes in the right-to-left shunt (RLS) of the patent foramen ovale (PFO) at different phases of the Valsalva maneuver and analyzed the possible mechanisms. The study population consisted of 57 patients with symptoms highly suggestive of a PFO. These patients had been diagnosed with apsychia, migraine with aura, cerebral infarction, transient ischemic attack (TIA), and cerebral ischemia with unknown cause. Routine echocardiography was performed in all patients to rule out a cardiac malformation. Contrast-transcranial Doppler (c-TCD) and contrast-enhanced transthoracic echocardiography (c-TTE) were used to visualize and quantify the RLS. The standard apical four chamber view was used to observe the changes of E peak, A peak, and velocity-time integral (VTI) ratio of tricuspid blood flow during the strain phase and release phase of the Valsalva maneuver. Paired t-test was used to compare E peak, A peak, and VTI ratio of tricuspid blood flow during the different phases. The right-to-left shunt across the PFO (PFO-RLS) was graded in the two phases and compared by Kruskal-Wallis test. Compared with the strain phase of the Valsalva maneuver, the parameters of E, A, and VTI in diastolic period in patients with PFO-RLS at the release phase were significantly increased [54.30 ± 13.65 cm/s vs 100.35 ± 21.11 cm/s, 42.21 ± 12.32 cm/s vs 57.30 ± 18.88 cm/s, 10.34 ± 3.27 cm/s vs 19.58 ± 4.56 cm/s, respectively], and the difference was statistically significant. The positive consequence of PFO-RLS, as diagnosed by c-TTE with the Valsalva maneuver at the release phase of the Valsalva maneuver, was significantly higher than that at the strain phase of the Valsalva maneuver. At the beginning of release phase of the Valsalva maneuver, decreased intrathoracic pressure led to increased venous backflow into the right atrium. Thus, high-velocity blood flow rapidly pushed the PFO open, which resulted in a significant increase in the PFO-RLS. Therefore, the increase of the PFO-RLS during the Valsalva maneuver is caused by the impact of high-velocity blood flow the PFO.

Evaluation of global cardiac systolic performance and diastolic filling in central hypovolumia by lower body negative pressure with Doppler echocardiography

Objective ：To overall evaluate the change of global cardiac systolic performance and diastolic filling in hypovoleamia by LBNP, Methods：10 healthy male subjects were placed in a standard LBNP chamber. Baseline haemodynamic and echocardiographic measurements were made after a period of least 10 min resting supine within the chamber. Pressure was then decreased to -10,-20 and -30 mmHg, with each pressure maintained for 15 rain. The indices of four transvalvular and SVC flow were measured using Doppler echocardiography. Results ：The results showed that S wave, Re wave ,and VTI of SVC progressively decreased with increasing LBNP. At -30 mmHg stage, S wave decreased by 35.4 % （change of 0.21±0.03 m/s, P 〈 0.001）. This reduction in pre-load Was associated with a progressive decrease in SV（by 21.5 ± 4.5 ml at -30 mmHg,P 〈 0.001 ）, decrease in CO（by 1.2 ± 0.2 L min^-1 at -30 mmHg LBNP,P 〈 0.001 ）. The diastolic filling of mitral and tricuspid flow also reduced significantly. At -30 mmHg stage, the E wave of MVF and TVF decreased 31% and 32% respectively （change of 0.23 ± 0.05 m/s,P 〈 0.001 and 0.18 ± 0.01 m/s,P 〈 0.001）. VTI of MVF and TVF decreased 27% and 27.7% respectively（change of 5.55 ± 1.41cm,P 〈 0.01 and 4.25 ± 0.44 cm,P 〈 0.01）. A wave of both sides did not change significantly. Conclusion：Doppler indices changes in different LBNP stage can roughly reflect the degree of hypovoleamia caused by blood volume redistribution. The indices of Doppler echocardiography are more sensitive than traditional physiological indexes in evaluating cardiovascular responses of LBNP. Echocardiography techniques overall can evaluate the global cardiac function including systolic performance and diastolic filling.

Maternal Thyroid Disease and Neonatal Low Birth Weight: A Systematic Review and Meta-Analysis

Objective: Thyroid disorder is a common endocrine complication in pregnant women: the association between neonatal low birth weight (LBW) and thyroid dysfunction during pregnancy has not been definitely confirmed. We conduct a systematic literature review and meta-analysis of the adverse fetal complication of LBW in maternal thyroid disease, including overt and subclinical hyperthyroidism and hypothyroidism. Methods: Relevant studies in English published between 1990 and 2016 were identified by searching PubMed, Medicine, and Embase databases. Cohort studies that evaluated the association between LBW infants and overt and subclinical hyperthyroidism or hypothyroidism during pregnancy and included a healthy pregnancy reference group were selected. The combined odds ratio (OR) with 95% confidence intervals (CI) were calculated to evaluate this relationship. Results: A total of 11 cohort studies (1,171,052 participants) assessed the association between maternal thyroid disease and LBW infants. An increased risk for LBW in hyperthyroidism pregnancies was demonstrated (OR: 1.30, 95% CI 1.11 - 1.54;p = 0.02). No significant increased risk for LBW was detected in subclinical hyperthyroidism (OR 1.03;95% CI 0.72 - 1.48;p = 0.87), or hypothyroidism pregnancies (overt: OR 0.98;95% CI 0.88 - 1.10;p = 0.75;subclinical: OR 1.29;95% CI 0.81 - 2.04;p = 0.28). Conclusion: Data show a higher trend towards an increased risk of LBW among infants from maternal hyperthyroidism pregnancies. No association was seen in subclinical cases of hyperthyroidism or hypothyroidism during pregnancy.

High-thermoelectric performance of TiO_(2-x)fabricated under high pressure at high temperatures

We present the work about the initiative fabrication of multi-scale hierarchical TiO2-x by our strategy,combining high pressure and high temperature(HPHT)reactive sintering with appropriate ratio of coarse Ti to nanosized TiO_(2).Ubiquitous lattice defects engineering has also been achieved in our samples by HPHT.The thermoelectric performance was significantly enhanced,and rather low thermal conductivity(1.60 W m^(-1)K^(-1))for titanium oxide was reported here for TiO1.76.Correspondingly,a high dimensionless figure of merit(zT)up to 0.33 at 700℃was realized in it.As far as we know,this value is an enhancement of 43%of the ever best result about nonstoichiometric TiO_(2)and the result is also exciting for oxide thermoelectric materials.The moderate power factor,the significantly reduced thermal conductivity and the remarkable synergy between electrical properties and thermal conductivity are responsible for the excellent thermoelectric performance.We develop a facile strategy for preparing multi-scale hierarchical TiO_(2-x)and its superior ability to optimize thermoelectric performance has been demonstrated here.

Thermoelectric properties of In-substituted Ge-based clathrates prepared by HPHT

Bulk materials Ba_(8)Ga_(16)In_(x)Ge_(30-x)(x=0.5,1.0,1.5)were prepared by High-Pressure and High-Temperature(HPHT)method and the crystal structure has been confirmed by X-ray diffraction and cell refinement.The actual In composition was much lower than the starting composition,and lattice constants increased with the increase of substitution.As the temperature increased,the Seebeck coefficient and electrical resistivity increased first and then decreased,while the thermal conductivity was the opposite,which leads to significant enhancement on thermoelectric properties of the clathrates.The substitution of indium elements decreased the seebeck coefficient and electrical resistivity,and also changed the microstructure of the compounds.A minimum thermal conductivity of 0.84Wm^(-1)1K^(-1)was obtained,and a good ZT value of 0.52 was achieved.The grain boundaries and lattice defects generated by high pressure can effectively scatter phonons of different frequencies,which reduce the lattice thermal conductivity.