On the scattering of evanescent waves into sound

1987 ◽  
Vol 184 ◽  
pp. 101-121 ◽  
Author(s):  
J. E. Ffowcs Williams ◽  
D. C. Hill

This paper concerns the conversion of momentum and energy from evanescent surface waves into sound. Exact results are obtained from surface waves of specified form on a confined region of an otherwise rigid plane surface. The model chosen is simple enough for exact analysis while approximating some of what we believe to be significant aspects of sound generation by vibrating surface panels.We find that the evanescent wave approaching an edge gives up all of its energy into sound, a sound which is beamed mainly parallel to the direction of the surface-wave phase velocity. The surface remains energetically inactive, but exerts a force on the fluid in the opposite direction to the incoming wave. This force is balanced by a nonlinear mean pressure gradient in the field of the evanescent wave, and by momentum in the sound field.Sound is also produced when a similar evanescent wave emerges from an edge. The surface has then to provide the necessary energy for both waves. These waves induce a mean axial force at the boundary which forces the fluid in the direction of the receding evanescent wave.A similar wave travelling across a finite panel in the otherwise rigid plane surface is observed to have some characteristics of the previous two cases, but there is no axial force arising from the mean pressure gradient.These results are applied to the problem of a semi-infinite tensioned membrane, and the energy radiation under light fluid loading is determined for the case of high and low free membrane wave speeds.

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
K Piayda ◽  
A Wimmer ◽  
H Sievert ◽  
K Hellhammer ◽  
S Afzal ◽  
...  

Abstract Background In the era of transcatheter aortic valve replacement (TAVR), there is renewed interest in percutaneous balloon aortic valvuloplasty (BAV), which may qualify as the primary treatment option of choice in special clinical situations. Success of BAV is commonly defined as a significant mean pressure gradient reduction after the procedure. Purpose To evaluate the correlation of the mean pressure gradient reduction and increase in the aortic valve area (AVA) in different flow and gradient patterns of severe aortic stenosis (AS). Methods Consecutive patients from 01/2010 to 03/2018 undergoing BAV were divided into normal-flow high-gradient (NFHG), low-flow low-gradient (LFLG) and paradoxical low-flow low-gradient (pLFLG) AS. Baseline characteristics, hemodynamic and clinical information were collected and compared. Additionally, the clinical pathway of patients (BAV as a stand-alone procedure or BAV as a bridge to aortic valve replacement) was followed-up. Results One-hundred-fifty-six patients were grouped into NFHG (n=68, 43.5%), LFLG (n=68, 43.5%) and pLFLG (n=20, 12.8%) AS. Underlying reasons for BAV and not TAVR/SAVR as the primary treatment option are displayed in Figure 1. Spearman correlation revealed that the mean pressure gradient reduction had a moderate correlation with the increase in the AVA in patients with NFHG AS (r: 0.529, p<0.001) but showed no association in patients with LFLG (r: 0.145, p=0.239) and pLFLG (r: 0.030, p=0.889) AS. Underlying reasons for patients to undergo BAV and not TAVR/SAVR varied between groups, however cardiogenic shock or refractory heart failure (overall 46.8%) were the most common ones. After the procedure, independent of the hemodynamic AS entity, patients showed a functional improvement, represented by substantially lower NYHA class levels (p<0.001), lower NT-pro BNP levels (p=0.003) and a numerical but non-significant improvement in other echocardiographic parameters like the left ventricular ejection fraction (p=0.163) and tricuspid annular plane systolic excursion (TAPSE, p=0.066). An unplanned cardiac re-admission due to heart failure was necessary in 23.7% patients. Less than half of the patients (44.2%) received BAV as a bridge to TAVR/SAVR (median time to bridge 64 days). Survival was significantly increased in patients having BAV as a staged procedure (log-rank p<0.001). Conclusion In daily clinical practice, the mean pressure gradient reduction might be an adequate surrogate of BAV success in patients with NFHG AS but is not suitable for patients with other hemodynamic entities of AS. In those patients, TTE should be directly performed in the catheter laboratory to correctly assess the increase of the AVA. BAV as a staged procedure in selected clinical scenarios increases survival and is a considerable option in all flow states of severe AS. (NCT04053192) Figure 1 Funding Acknowledgement Type of funding source: None


2009 ◽  
Vol 7 (3-4) ◽  
pp. 0-0
Author(s):  
Sigitas Čibiras ◽  
Eugenijus Kosinskas

Sigitas Čibiras, Eugenijus KosinskasVilniaus universiteto Širdies ir kraujagyslių ligų klinika, Vilniaus universiteto ligoninės Santariškių klinikos, Santariškių g. 2, LT-08661 VilniusE-mail: [email protected] Įvadas Darbo tikslas – apibendrinti 20 metų patirtį ir įvertinti įgimtos plaučių arterijos (PA) stenozės balioninės valvuloplastikos (BPV) tiesioginius, tarpinius ir vėlyvuosius rezultatus. Ligoniai ir metodai 1987–2007 metais Vilniaus širdies ligų klinikoje buvo atlikta 101 BPV, ligonių amžius nuo 1 paros iki – 39 metų. BPV atlikta esant spaudimo per PA vožtuvą skirtumui > 30 mm Hg. Ligoniai prieš BPV suskirstyti į dvi grupes pagal tai, ar pradinis spaudimo per PA vožtuvą skirtumas <50 mm Hg (1 gruoė), ar > 50 mm Hg (2 grupė). Analizuotas duomenų kitimas tiesiogiai po BPV, tarpiniu laikotarpiu (iki dvejų metų po BVP), vėlyvuoju laikotarpiu (praėjus daugiau kaip dvejiems metams). Ligoniai po BPV buvo suskirstyti į dvi grupes: turintys liekamąjį spaudimo skirtumą iki 36 mm Hg ir daugiau kaip 36 mm Hg. Rezultatai BPV atlikta 18 pacientų, kurių spaudimo per PA vožtuvą skirtumas < 50 mm Hg. Iškart po BVP spaudimo skirtumas per PA vožtuvą sumažėjo nuo 39,5 ± 5 iki 15,83 ± 8,37 mm Hg, tarpiniu laikotarpiu – iki 20 ± 6 mm Hg, vėlyvuoju – iki 21,5 ± 5 mm Hg. BPV atliktos 83 pacientams, kurių spaudimo per PA vožtuvą skirtumas > 50 mm Hg. Tiesiogiai po BVP vidutinis spaudimo skirtumas sumažėjo nuo 81,31 ± 21,28 iki 31,32 ± 13,82 mm Hg, tarpiniu laikotarpiu – iki 27,56 ± 12,71 mm Hg, vėlyvuoju – iki 19,89 ± 10,12 mm Hg. Esant liekamajam spaudimo skirtumui po BPV < 36 mm Hg (58 ligoniai), tarpiniu lakotarpiu vidutinis spaudimo skirtumas 23,66 ± 9,29 mm Hg, vėlyvuoju – 16,85 ± 7,98 mm Hg. Esant liekamajam spaudimo skirtumui po BPV > 36 mm Hg (21 ligonis), tarpiniu laikotarpiu vidutinis spaudimo skirtumas 51,99 ± 20,61 mm Hg, vėlyvuoju – 35,7 ± 16 mm Hg. Vėlyvuoju laikotarpiu spaudimo skirtumas mažėja, bet didėja PA nesandarumas. Tuoj po BPV nesandarumas nustatytas 7 %, tarpiniu laikotarpiu – 53 %, vėlyvuoju – 81,7 % ligonių. Išvados BPV yra gerai toleruojamas ir veiksmingas nechirurginis gydymo būdas. Daugumai ligonių išryškėja vėlyvasis nedidelis plaučių arterijos nesandarumas, kurį retai prireikia gydyti chirurginiu būdu. Mūsų studija rodo, kad tinkama ligonių atranka leidžia pasiekti gerų tiesioginių, tarpinius ir vėlyvųjų rezultatų. Reikšminiai žodžiai: įgimtos širdies ydos, įgimta plaučių arterijos vožtuvo stenozė, balioninė valvuloplastika. Balloon pulmonary artery valvuloplasty – immediate, mid-term and long-term follow-up results: 20-year experience Sigitas Čibiras, Eugenijus KosinskasVilnius University Clinic of Heart and Vascular Medicine, Vilnius University Hospital Santariškių Klinikos, Santariškių str. 2, LT-08661 Vilnius, LithuaniaE-mail: [email protected] Background To analyze immediate, mid-term and long-term follow-up results after percutaneous balloon pulmonary valvuloplasty (BPV) of congenital pulmonary artery (PA) stenosis for a 20-year period. Patients and methods During 1987–2007, in the Vilnius Clinic of Heart Diseases 101 BPV were performed, the patients’ age range being 1 day – 39 years. BPV was performed with the primary PA valvular pressure gradient > 30 mm Hg. Patients before BPV had been divided into two groups: (1) with primary PA pressure gradient < 50 mm Hg; (2) with primary PA pressure gradient > 50 mm Hg. Data were analyzed immediately after BPV, in a mid-term (2 years) and a long-term (more than 2 years) follow-up. The same patients after BPV were divided into two groups: with residual pressure gradient < 36 mmHg and > 36 mmHg. Results Eighteen BPV were performed with the primary PA pressure gradient < 50 mm Hg: the immediate mean pressure gradient decreased from 39.5  ±   5 to 15.83 ± 8.37 mm Hg, in the mid-term period to 20 ± 6 mm Hg, and in the long-term to 21.5 ± 5 mm Hg. Eighty-three BPV were performed with the primary PA pressure gradient > 50 mm Hg; the immediate mean pressure gradient decreased from 81.31 ± 21.28 mm Hg to 31.32 ± 13.82 mm Hg, in the mid-term period to 20 ± 6 mm Hg and in the long-term period to mm Hg. With the residual pressure gradient after BPV < 36 mm Hg (58 patients), in the mid-term period the pressure gradient decreased to 23.66 ± 9.29 mm Hg and in the long-term period to 16.85 ± 7.98 mm Hg. With the residual pressure gradient after BPV > 36 mm Hg (21 patients), in the mid-term period the pressure gradient decreased to 51.99 ± 20.61 mm Hg and in the long-term period to 35.7 ± 16 mm Hg. In the long-term follow-up, the pressure gradient decreased, but PA regurgitation (PAR) was progressive. Immediately after BPV, PAR was seen in 7%, in mid-term follow-up in 53 %, and in long-term follow-up in 81.7 % patients. Conclusions BPV is a well tolerated and effective non-surgical treatment method. Late trivial PAR develops in the majority of cases, but rarely requires surgical treatment. Our study has demonstrated that the appropriate patient selection enables achieving good immediate, mid-term and long-term follow-up results. Keywords: congenital heart defects, congenital pulmonary artery stenosis, balloon valvuloplasty.


2021 ◽  
Author(s):  
Arash Shokouhmand ◽  
Chenxi Yang ◽  
Nicole D. Aranoff ◽  
Elissa Driggin ◽  
Philip Green ◽  
...  

2021 ◽  
Author(s):  
Sonia B. Albanese Albanese

Background: Surgical treatment of isolated pulmonary valve stenosis in infants and children has evolved over the years, shifting from the original exclusive aim at lowering right ventricle pressure to the current concomitant focus on preserving pulmonary valve function. In our study, we sought to analyze the effect of such evolving philosophy on long-term results. Methods: All consecutive patients treated in our center between July 1983 and March 2019 were included. Patients were categorized into 2 groups based on the introduction into treatment practice of sparing valve techniques (1995). Actuarial survival, freedom from reintervention on the right outflow tract, transvalvular mean pressure gradient decrease, and pulmonary valve function at follow-up were analyzed. Results: One hundred twenty-three patients operated before (Group I, n=81) or since (Group II, n=42) 1995 were enrolled in the study. Mean age and weight were 3.0 ± 0.36 years and 16.6 ± 1.7kg, respectively. Early mortality occurred exclusively in 3 patients of Group 1. Transvalvular mean pressure gradient decreased in the entire patient population (from 63.28 ± 12.9mmHg to 16.46 ± 7.9mmHg). At a mean follow-up interval of 4.9 ± 33 years, freedom from death was comparable, but freedom from right ventricular outflow tract reintervention was significantly greater in Group II. Although the transvalvular gradient remained stable over time in non-reoperated survivors (mean value of 16.46 ± 7.9mmHg), pulmonary valve function on 2D-Echo showed severe incompetence in 2 patients of Group I and just mild to moderate incompetence in 20 patients of Group II, with a significantly negative effect of unsuccessful preoperative pulmonary balloon valvuloplasty (14/20 vs 6/20, p=0.025) in the latter. Conclusion: Current pulmonary valve sparing techniques are associated with better results, particularly in terms of freedom from re-interventions and pulmonary valve function at follow-up. Balloon valvuloplasty prior to surgery may worsen operative results, promoting pulmonary insufficiency and therefore should probably be avoided in all patients in whom anatomical characteristics predict failure of percutaneous therapy.


Author(s):  
Jae Woong Choi ◽  
Ho Young Hwang ◽  
Yeiwon Lee ◽  
Suk Ho Sohn ◽  
Kyung Hwan Kim ◽  
...  

Abstract Background This study was conducted to evaluate the occurrence rate and risk factors of subaortic pannus (SAP) after bileaflet mechanical aortic valve (AV) replacement. Methods Between 1990 and 2014, 862 patients underwent primary AV replacement with bileaflet mechanical prosthesis. SAP was defined as (1) gradual increase in mean pressure gradient through mechanical AV without any evidence of motion limitation of the leaflets on echocardiography and (2) AV mean pressure gradient >40 mm Hg or AV peak velocity >4 m/s on echocardiography, and (3) any visible subaortic tissue ingrowth beneath the mechanical AV on echocardiography or computed tomography. Clinical and echocardiographic follow-up durations were 13.8 ± 8.0 and 10.7 ± 7.9 years, respectively. Results Mean age was 51.1 ± 12.1 years and concomitant surgeries were performed in 503 patients (58.4%). Overall survival at 10 and 20 years was 84.2 and 67.1%, respectively. SAP occurred in 33 patients, and in only 2 patients during the first 10 years after surgery. The cumulative incidence of SAP formation at 10, 20, and 25 years were 0.3, 5.0, and 9.9%, respectively. The Fine and Gray model demonstrated that small prosthetic valve size (hazard ratio [HR] [95% confidence interval, CI] = 0.738 [0.575–0.946]), young age (HR [95% CI] = 0.944 [0.909–0.981]), and concomitant mitral valve replacement (MVR) (HR [95% CI] = 3.863 [1.358–10.988]) were significant risk factors for the SAP formation. Conclusions SAP occurred gradually over time with 10- and 20-year cumulative incidence of 0.3 and 5.0%, respectively. Young age, small prosthetic valve size, and concomitant MVR were risk factors for SAP formation. Therefore, we recommend efforts to select large prostheses for young patients requiring concomitant MVR.


2020 ◽  
Vol 28 (04) ◽  
pp. 2050019
Author(s):  
Daren Zhou ◽  
Huancai Lu ◽  
D. Michael McFarland ◽  
Yongxiong Xiao

Vibrating structures are often mounted on or located near a passive plane surface with finite acoustic impedance, and hence the acoustic pressures measured in a half-space bounded by the surface consist of both the direct radiation from the structure and the reflection from the boundary surface. In order to visualize the direct radiation from the source into free space, a reconstruction method based on expansion in half-space spherical wave functions is proposed. First, the series of half-space spherical wave functions is derived based on the analytical solution of the sound field due to a multipole source located near an impedance plane. Then the sound field in the half-space is approximated by the superposition of a finite number of half-space expansion terms. The expansion coefficients are determined by solving an overdetermined linear system of equations obtained by matching this assumed solution to the total acoustic pressures in the half-space. The free-space radiation can finally be reconstructed via multiplying the free-space spherical wave functions by the corresponding coefficients. Numerical simulation examples of a vibrating sphere and a vibrating baffled plate are demonstrated. The effects of specific acoustic impedance of the boundary and the locations of the measurement points on the accuracy of reconstruction are examined.


2019 ◽  
Vol 21 (10) ◽  
pp. 1144-1151 ◽  
Author(s):  
Bálint Szilveszter ◽  
Daniel Oren ◽  
Levente Molnár ◽  
Astrid Apor ◽  
Anikó I Nagy ◽  
...  

Abstract Aims Cardiac CT is increasingly applied for planning and follow-up of transcatheter aortic valve implantation (TAVI). However, there are no data available on reverse remodelling after TAVI assessed by CT. Therefore, we aimed to evaluate the predictors and the prognostic value of left ventricular (LV) reverse remodelling following TAVI using CT angiography. Methods and results We investigated 117 patients with severe, symptomatic aortic stenosis (AS) who underwent CT scanning before and after TAVI procedure with a mean follow-up time of 2.6 years after TAVI. We found a significant reduction in LV mass (LVM) and LVM indexed to body surface area comparing pre- vs. post-TAVI images: 180.5 ± 53.0 vs. 137.1 ± 44.8 g and 99.7 ± 25.4 vs. 75.4 ± 19.9 g/m2, respectively, both P &lt; 0.001. Subclinical leaflet thrombosis (SLT) was detected in 25.6% (30/117) patients. More than 20% reduction in LVM was defined as reverse remodelling and was detected in 62.4% (73/117) of the patients. SLT, change in mean pressure gradient on echocardiography and prior myocardial infarction was independently associated with LV reverse remodelling after adjusting for age, gender, and traditional risk factors (hypertension, body mass index, diabetes mellitus, and hyperlipidaemia): OR = 0.27, P = 0.022 for SLT and OR = 0.22, P = 0.006 for prior myocardial infarction, OR = 1.51, P = 0.004 for 10 mmHg change in mean pressure gradient. Reverse remodelling was independently associated with favourable outcomes (HR = 0.23; P = 0.019). Conclusion TAVI resulted in a significant LVM regression on CT. The presence of SLT showed an inverse association with LV reverse remodelling and thus it may hinder the beneficial LV structural changes. Reverse remodelling was associated with improved long-term prognosis.


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