Maximal Frequency Shift Research Articles

Hidden enemy of pulmonary arteries: COVID-19

It has been reported that COVID-19 may cause severe endothelial damage. Pulmonary Artery Stiffness (PAS) is a strong predictor of right ventricular function. PAS can reveal important information about the endothelial functions of the pulmonary bed. In this study, we aimed to elucidate the possible effect of COVID-19 on PAS. The study was performed by measuring PAS values with transthoracic echocardiography in 130 patients, 60 of whom had COVID-19 and 70 were controls. COVID-19 patients with positive polymerase chain reaction (PCR) test results were included in the study 3-6 months after their positivity. When the Maximal frequency shift (MFS) (Hz) results were examined, no significant difference was observed between the patient and control groups (2764±279.24 and 2664.8±673.91 p=0.340, respectively). There was a significant difference between the patient and control groups in favor of the patient group in pulmonary acceleration time (PAT) (msec) results (93.18±14.99 and 126.1±17.58, respectively, p<0.001). There was a significant difference between the patient and control groups in favor of the patient group in PAS (Hz/msec) results (30.28±5.07 and 21.57±7.04, respectively, p<0.001). It is possible that COVID-19 may have adverse effects on the pulmonary artery wall and bed. As a result of endothelial damage due to COVID-19, an increase in PAS values can be observed.

Site-specific imprinting of dengue virus non-structural 1 antigen on a polydopamine-based sensing film for early detection and prognosis of dengue

Serum levels of dengue virus (DENV) non-structural 1 (NS1) antigen can serve as a valuable prognostic indicator of severe dengue infections. A quartz crystal microbalance (QCM)-based biosensor with a biomimetic recognition element was designed to quantitatively detect DENV NS1 as an early disease biomarker. To mitigate the reliance on costly viral antigens during the molecular imprinting process, a synthetic peptide mimicking a DENV NS1 epitope was used as a surrogate template for the synthesis of an epitope-imprinted polydopamine (EMIPDA) sensing film on the biosensor surface. The maximal frequency shift for DENV NS1 was obtained with an EMIPDA film synthesised using 5 mg mL−1 of dopamine monomer and 0.5 mg mL−1 of peptide template. The EMIPDA-QCM biosensor achieved low detection and quantitation limits of 0.091 μg mL−1 and 0.436 μg mL−1, respectively, allowing acute-phase detection of dengue and prognosis of the disease progression. The EMIPDA-QCM biosensor exhibited remarkable selectivity with up to 68-fold larger frequency responses towards DENV NS1 compared to a major serum protein. The site-specific imprinting approach not only enhanced the biosensing performance but also enabled a 26-fold cost reduction for biosensor functionalisation, providing a cost-effective strategy for label-free biosensing of the dengue biomarker via the biopolymer film.

Fetal pulmonary artery stiffness is a strong predictor of persistent pulmonary hypertension of the newborn - An echocardiographic study

ObjectivePulmonary artery stiffness (PAS) is a strong and independent predictor of mortality in adult patients with pulmonary hypertension (PH). But the change in PAS during perinatal period remains unknown. Here, we aimed to explore the feasibility and performance of PAS on predicting persistent pulmonary hypertension of the newborn (PPHN). Methods1325 fetuses underwent a dedicated echocardiography screening for fetal heart defects during second trimester, third-trimester and neonatal period with the measurement of acceleration time (PAAT) and maximal frequency shift (MFS) of pulmonary artery flow. PAS (MFS/PAAT ratio) was calculated. ResultsSix fetuses were diagnosed as PPHN. Compared with the normal fetuses, those with PH had greater values of PAS during each period of time (second trimester, 52.6(46.2–54.5) vs. 32.4(28.0–39.4) kHz/s, p = 0.0003; third trimester, 52.9(46.1–55.3) vs. 29.7(27.3–33.3) kHz/s, p = 0.0002; neonatal period, 127.4(85.2–150.8) vs. 26.6(22.7–35.0) kHz/s, p < 0.0001). There was a statistically significant correlation between PAS and mean pulmonary artery pressure (p < 0.05) but no correlation between PAS and gestational age (p > 0.05) whether in normal fetuses or not. The area under receiver operating characteristic curve (AUC) of 0.97 for PAS during third trimester was superior to that for PAS during second trimester (AUC, 0.94) in predicting PPHN. The optimal cutoff value of PAS during third trimester was 37.40 KHz/s, with a sensitivity of 100%, a specificity of 91%, and an accuracy of 92%. ConclusionThere was a significant difference in PAS between normal fetuses and those with PH. PAS has a power performance on predicting PPHN.

Right ventricular-pulmonary arterial uncoupling in mild-to-moderate asthma

Objective Persistent pulmonary hypertension and resulting right ventricular (RV) failure are highly encountered phenomenon in severe pulmonary diseases. However, in this study, we aimed to examine the effects of mild-to-moderate asthma on RV functions, pulmonary arterial stiffness (PAS), and coupling of RV to the pulmonary artery (PA) in the absence of overt pulmonary hypertension. Methods We enrolled 53 patients with mild-to-moderate asthma, and 50 healthy control subjects. A comprehensive two dimensional transthoracic echocardiography was performed on each individual. The parameters measuring RV function were all examined. PAS was calculated by dividing maximal frequency shift of pulmonary flow by pulmonary acceleration time. RV-PA coupling was estimated by the tricuspid annular plane systolic excursion (TAPSE) to pulmonary artery systolic pressure (PASP) ratio (TAPSE/PASP). Results Baseline demographics, clinical and laboratory parameters of both groups were similar (p > 0.05). Most of conventional echocardiographic parameters measuring RV function were impaired in patients with asthma compared to control subjects. PAS values were significantly higher in the asthma group [24 (21–26) vs. 20 (18–22), p < 0.001], and TAPSE/PASP ratio was significantly lower in the asthma group versus the control group [0.81 ± 0.08 vs. 0.96 ± 0.11, p < 0.001]. Multilinear regression analysis revealed PAS, TAPSE, and PASP as independent predictors of TAPSE/PASP ratio. Conclusion Mild-to-moderate asthma was shown to be associated with both subclinical RV dysfunction and increased PAS values. TAPSE/PASP ratio was also markedly decreased, suggesting RV-PA uncoupling even in the absence of overt pulmonary hypertension. PAS referring RV afterload was shown to be an independent predictor of TAPSE/PASP ratio.

Feasibility of Echocardiographic Estimation of Pulmonary Artery Stiffness in Horses

Pulmonary artery stiffness (PAS) is an index of pulmonary artery elasticity that permits to evaluate the pulmonary vascular bed in humans. It can early detect an increase in pulmonary artery stiffness as a consequence of remodeling of the vessel wall caused by chronic pulmonary and congenital heart diseases. This remodeling can occur also in horses with chronic respiratory diseases. Thus, PAS could be a useful echocardiographic parameter also in horses. However, in literature, there are no studies regarding PAS in horses. The aim of this study is to evaluate the feasibility of PAS in horses. Fifteen healthy horses were included in this prospective study. Maximal frequency shift and acceleration time were measured from the pulsed-wave Doppler trace of the pulmonary artery flow, obtained from the right parasternal short-axis view at the level of the pulmonary artery, and then PAS was calculated as the ratio of Maximal frequency shift to acceleration time. The low variability assessed for intra- and inter-observer variability, day-to-day variability and image acquisition variability suggests that PAS can be measured consistently in horses. Further studies could be useful to assess the clinical usefulness of PAS in unhealthy horses, such as those affected by chronic respiratory diseases.

Multi-functional polarization conversion manipulation via graphene-based metasurface reflectors

In this work, we present an efficient polarization conversion device via using a hollow graphene metasurface. The platform can simultaneously realize a series of excellent performances, including the broadband x-to-y cross polarization conversion (CPC) function with near unity polarization conversion ratio (PCR), dual-frequency linear-to-circular polarization conversion (LTC-PC) function, and highly sensitive polarization conversion function manipulation under wide oblique incidence angle range. For instance, the proposed device obtains an x-to-y CPC function with the bandwidth up to 1.83 THz (χPCR ≥98.8%). Moreover, the x-to-y CPC function can be switched to LTC-PC function via artificially tuning the Fermi energy of graphene. The maximal frequency shift sensitivity (S) of polarization conversion function reaches 23.09 THz/eV, suggesting a frequency shift of 2.309 THz for the LTC-PC function when the chemical potential is changed by 0.1 eV. Based on these superior performances, the polarization converter can hold potential applications in integrated and compact devices, such as polarization sensor, switches and other optical polarization control components.

Effects of angiotensin receptor neprilysin inhibition on pulmonary arterial stiffness in heart failure with reduced ejection fraction.

The sacubitril/valsartan combination is an important agent used in the treatment of heart failure with reduced ejection fraction (HFrEF). Pulmonary artery stiffness (PAS) is an index developed to evaluate the pulmonary vascular bed. Changes in pulmonary vascular structures in HFrEF patients can affect PAS. In this study, we aimed to investigate the effect of sacubitril/valsartan on PAS in HFrEF patients. One hundred fifty HFrEF patients, who received sacubitril/valsartan therapy and continued for at least 6months without interruption, were examined retrospectively. N-terminal pro-B-type natriuretic peptide levels (NT-proBNP), NYHA classes, Minnesota Living with Heart Failure Questionnaire (MLWHFQ) scores, New York Heart Association (NYHA) functional classes and echocardiograpic parameters such as left ventricular ejection fraction (LVEF), mean pulmonary artery pressure (mPAP), right ventricle myocardial performance index (RV-MPI), Tricuspid annular plane systolic excursion (TAPSE), right ventricular fractional area change (RV-FAC) and PAS changes were evaluated before and 6months after sacubitril/valsartan treatment. PAS was calculated by using the maximal frequency shift and acceleration time of the pulmonary artery flow trace measured in the echocardiogram. PAS values were significantly reduced (23.8 ± 2.8 vs 19.1 ± 3.1kHz/ms, p < 0.001) after the sacubitril/valsartan treatment. Sacubitril/valsartan treatment was associated with significant improvements in NYHA class and MLWHFQ scores; significant reductions in the NT-proBNP levels, mPAP, and RV-MPI, and significant increases in LVEF, TAPSE, and RV-FAC (p < 0.05). The significant reduction in the PAS value was significantly correlated with the improvements in the MLWFQ scores, NT-proBNP levels, mPAP, RV-MPI, TAPSE and RV-FAC. In HFrEF patients, switching from angiotensin-converting enzyme inhibitor/angiotensin II receptor blocker therapy to sacubitril/valsartan may result in reduction in PAS.

Echocardiographic assessment of pulmonary arterial stiffness in human immunodeficiency virus-infected patients.

Pulmonary hypertension (PH) is one of the complications of human immunodeficiency virus (HIV) infection. Despite the emergence of effective therapies, pulmonary arterial hypertension is commonly seen, especially at advanced stages. At the time of diagnosis, a majority of patients are at New York Heart Association-Functional Class III or IV. Many of the current screening modalities are dependent on detecting a rise in pulmonary arterial pressure (PAP). However, high capacitance of the pulmonary circulation implies that early microcirculation loss is not accompanied by a change in resting PAP. Therefore, we aimed to demonstrate early changes in pulmonary vascular disease in HIV-infected patients with a new echocardiographic parameter, called as pulmonary arterial stiffness (PAS). Thirty-six HIV-infected patients and 36 age- and sex-matched healthy control subjects were enrolled in this study. PAS was calculated echocardiographically by using maximal frequency shift and acceleration time of the pulmonary artery flow trace. There was no significant difference in diastolic functions, right ventricular diameters, systolic PAP, inferior vena cava widths, right atrial area, and tricuspid annular plane systolic excursion values between the two groups. However, PAS was calculated as 24.3±6.4Hz/msn in HIV-infected patients and 19.3±3.1Hz/msn in healthy control group (P<0.001). Increase in PAS was correlated with duration of HIV infection (P<0.05). Our results suggest that HIV infection affects pulmonary vascular bed starting early onset of disease and this can be demonstrated by an easy-to-measure echocardiographic parameter.

Evaluation of pulmonary artery stiffness in newly diagnosed adult patients with asthma.

There are limited studies on the effects of asthma on cardiac function. Right ventricular dysfunction and pulmonary hypertension are cardiovascular complications that may be seen in advanced stages of the disease. Pulmonary artery stiffness (PAS), is a promising, relatively new echocardiographic index that has been reported to increase in right ventricular failure, providing information about pulmonary vascular bed. In this study, we aimed to evaluate PAS, a marker of pulmonary artery elasticity, in adult-onset asthma. Ninety-nine nonsmokers who had a new asthma diagnosis between the ages of 18 and 65years and 97 healthy controls with similar age and sex distribution were included in the study. PAS was calculated by dividing the maximal frequency shift of pulmonary flow (MFS) in pulmonary acceleration time (PAT). Clinical and demographic characteristics of both groups were similar (P˃0.05). PAS values were higher in the asthma group than in the control group (25.2±4.5 vs 22.4±4.1, P ˂0.001). TAPSE was lower in the case group (24.9±2.0 vs 25.5±2.1, P=0.043), while RV MPI was higher (0.36±0.07 vs 0.32±0.06, P ˂0.001). In the multivariate linear regression analysis, RV MPI, RV Em, and TAPSE variables were independent predictors of PAS. In our study, PAS values were higher in patients with newly diagnosed adult asthma and we found a significant weak correlation between PAS values and subclinical right ventricular dysfunction.

Elasticity Properties of Pulmonary Artery in Patients with Bicuspid Aortic Valve

Although the vascular complications of bicuspid aortic valve (BAV) disease cause significant morbidity and mortality, the role of pulmonary artery in this pathogenesis is less understood. We aimed to assess the elastic properties of pulmonary artery with echocardiography in patients with BAV. Thirty patients with BAV (26 males) were enrolled in this study. The presence of aortic stenosis was accepted as exclusion criteria. Thirty-two healthy subjects (27 males) with no any history of cardiovascular disease comprised the control group. In all patients, maximal frequency shift (MFS) and acceleration time (AcT) of the pulmonary artery flow trace were measured echocardiographically in parasternal short-axis view. Subsequently, pulmonary artery stiffness (PAS) was calculated by using the following formula PAS (kHz/sec) = MFS/AcT. There were no significant differences in baseline demographic characteristics of the study population. Aortic strain and aortic distensibility index were lower, and aortic stiffness index (SI) higher, in patients with BAV. The PAS was significantly increased in patients with BAV compared with control subjects with tricuspid aortic valve (11.08 ± 2.27 vs. 7.11 ± 1.54, P < 0.001). There was a significant correlation between aortic diameters, aortic elasticity indexes, and PAS. Multivariate linear regression analysis, the only significant independent factor affecting the PAS was SI (β = 0.547, P < 0.001). We demonstrated that elastic properties of pulmonary artery tend to be impaired as in the aorta in patients with BAV disease.

GW24-e0413 Pulmonary artery stiffness in patients with heart failure

ObjectivesThere is increasing recognition that pulmonary artery stiffness (PAS) is an important determinant of right ventricular afterload in pulmonary arterial hypertension. Pulmonary hypertension and right ventricular dysfunction are usually being...

Impact of Pulmonary Artery Stiffness on Right Ventricular Function and Tricuspid Regurgitation after Successful Percutaneous Balloon Mitral Valvuloplasty: The Importance of Early Intervention

We assessed impact of pulmonary artery stiffness (PAS) on the long-term right ventricular (RV) function and tricuspid regurgitation (TR) changes after percutaneous balloon mitral valvuloplasty (PBMV). Using Doppler echocardiography, PAS was calculated by dividing maximal frequency shift of pulmonary flow by the acceleration time, and mitral area, RV function, and degree of TR severity were evaluated before, immediately after, 6 months, and 12 months after successful PBMV in 81 consecutive patients. Compared with control subjects patients with mitral stenosis (MS) had significant higher PAS (P < 0.001). The PAS was significantly lower in patients with progressive RV function improvement and regression of TR (P < 0.001). PAS was significantly correlated with the degree of pulmonary artery systolic pressure (PASP), tricuspid annular plane systolic excursion (TAPSE), and E/E'm ratio (P < 0.0001, <0.0001, and < 0.001, respectively). Multivariate regression analysis showed that the PAS is an independent predictor of TR regression and sustained RV functional improvement after successful PBMV (P < 0.0001). The changes in RV function and TR after successful PBMV were significantly correlated with the degree of PAS. Despite a sustained increase in mitral valve area, some patients showed no regression of TR, and progressive RV dysfunction suggests a significant role of PAS on RV function and the degree of TR regression in patients with MS suggests that PBMV must be performed early, utilizing PAS as a noninvasive parameter for proper timing for PBMV.

Investigation of internal nonhomogenous volumes of perturbation as tuning and miniaturization elements for cavity resonators

AbstractIn this article, we investigate the tuning and miniaturization performance induced by a volume perturbation inserted in a cavity resonator. The volume perturbation is either a rectangular perturbation centrally located, called central postperturbation (CPP) or dually, a hole shaped in an annular extruded volume, called side annular perturbation (SAP). The tuning and miniaturization mechanism is fully described using the small perturbation theory. This serves the analytical evaluation of the frequency shift resulting from the insertion of the perturbation volume in the cavity resonator. The impact of these perturbations is assessed also by HFSS simulations and measurements of 72 different cavity resonators. An idle cavity resonator characterized by a resonance frequency of 4 GHz is tuned from 1 to 6 GHz. A maximal frequency shift of 3 GHz and 2 GHz is measured for respectively the resonator with CPP and SAP, resulting in a total tuning range of 125%. Additionally, the CPP serves miniaturization purposes, as cavity resonators with a resonance frequency as low as 1 GHz were measured, derived from an idle cavity resonator at 4 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:491–496, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26578

1134 Right ventricular function and its relation to pulmonary artery stiffness in patients with systemic lupus erythematosus

Background: Pulmonary hypertension and right heart failure are severe complications of systemic lupus erythematosus (SLE). The potential mechanisms of these complications are multifactorial and may include increased pulmonary artery stiffness (PAS). In this study, we tested the hypothesis suggesting that the PAS is increased in patients with SLE, which may determine right ventricular myocardial performance index (RV MPI) as an echocardiographic parameter summarizing right ventricular function in these patients. Methods: We studied 24 patients with SLE with no cardiac symptoms (age: 33.6±8.4 years) and 24 normal control subjects by echocardiography. RV MPI, defined as the sum of isovolumetric contraction and relaxation time divided by ejection time, was measured by using Doppler echocardiography. To estimate PAS, echocardiographic records of the pulmonary flow trace were obtained and maximal frequency shift of pulmonary flow divided by acceleration time. Correlation between RV MPI and the PAS, right ventricular ejection fraction, age, heart rate, body surface area and the duration of disease were determined by linear regression analysis. Results: Patients versus control subjects had increased PAS and RV MPI. In linear regression analysis, RV MPI was significantly correlated with PAS and the duration of disease (r=0.62, p<0.005 and r=0.53, p<0.01). Conclusions: These results suggest that the increased PAS may be an important pathogenetic factor, which may contribute the RV dysfunction in patients with SLE.

Spontaneous otoacoustic emissions in two gecko species, Gekko gecko and Eublepharis macularius.

Spontaneous otoacoustic emissions (SPOAE) of the gecko species Gekko gecko and Eublepharis macularius appear as broad spectral peaks (bandwidth 44 to 170 Hz) between 1 and 4.5 kHz that have peak levels of -7 to 10 dB SPL. Most ears showed SPOAE at many frequencies. In some ears, the peaks were superimposed on a broad baseline emission. The instantaneous frequency of any emission varied rapidly within its bandwidth limits and frequencies in the center of the band occurred most commonly, but not with higher levels than frequencies on the periphery of the band. SPOAE were temperature dependent, rising in frequency with an increase in temperature and falling with a decrease in temperature (rate of change from 54 to 107 Hz/degrees C), with no systematic changes in peak level except that at the temperature extremes, the SPOAE disappeared into the noise. External tones suppressed SPOAE peak level in a frequency-dependent way. Isosuppression tuning curves were V-shaped. In restricted frequency ranges, facilitation also occurred. External tones also caused shifts in the frequency of SPOAE; frequency "pushing" was more common than "pulling." The maximal frequency shift observed was 313 Hz. In general, the SPOAE characteristics strongly resemble those already reported in the bobtail lizard Tiliqua rugosa.

Aortic stiffness: A new Doppler echocardiographic measure predictive of systolic blood pressure in children

Aortic stiffness, the maximal frequency shift in the descending aorta divided by the Doppler acceleration time, was studied in 384 eleven year old twin children. The extent to which this measurement provided a prediction of systolic blood pressure that was independent of body size, heart rate, cardiac contractility and left ventricular mass was investigated. Aortic stiffness, after adjustment for height and weight, correlated significantly with systolic blood pressure (r = 0.22, p < 0.01), but not with diastolic blood pressure. The short- (r = 0.82) and longer- (r = 0.68) term reproducibility of aortic stiffness was high.This measure appears to be a more powerful predictor of systolic blood pressure than is left ventricular mass. Aortic stiffness is a highly reproducible Doppler variable that may explain in part the contribution of the aortic wall elastic properties to the level of systolic blood pressure in preadolescent children at rest.