Annular Wall Research Articles

Experimental and numerical study of fluid flow and heat transfer in an annulus of inner twisted square duct and outer circular pipe

Heat transfer and friction factor characteristics of air flow in an annulus formed by an inner twisted square duct and an outer circular pipe is studied experimentally for Reynolds number range of 400–60,000. Experiments were conducted with air as working fluid. A uniform wall temperature at the inner wall of annulus was maintained while the outer pipe was kept insulated. Twist ratios (ratio of the pitch to outer width of twisted square duct) of 10.6 and 15 were used in the experiments. The transitional Reynolds number for laminar flow to turbulent flow was identified as 3000. Results were compared with the flow inside the annulus of an equivalent straight square duct in a circular pipe for identical pumping power. Results showed considerable enhancement in the heat transfer and pressure drop in both the laminar and turbulent flow regimes. The influence of the annulus parameter on the friction factor and heat transfer was also studied by varying the outer pipe diameter. At a given twist ratio, higher values of the friction factor and the Nusselt number were observed for smaller annulus parameters (ratio of cross section area of square twisted duct to cross section area of circular pipe). In order to extend the experimental results to a larger range of fluids, a numerical analysis was undertaken for fully developed flow inside the annulus for the experimental twist ratios. The parameters range covered in the simulations were Reynolds numbers of 100–100,000 and Prandtl numbers of 0.7–20. The local velocity distribution across the annulus cross-section were analysed. Empirical correlations for friction factor and Nusselt number are provided separately for laminar and turbulent regimes. Guidelines for selection of twisted square duct are provided in terms of Reynolds number and enhancement factor. The results are significant because it will contribute to the development of compact double pipe heat exchangers.

Hierarchical model for strain generalized streaming potential induced by the canalicular fluid flow of an osteon

A hierarchical model is developed to predict the streaming potential (SP) in the canaliculi of a loaded osteon. Canaliculi are assumed to run straight across the osteon annular cylinder wall, while disregarding the effect of lacuna. SP is generalized by the canalicular fluid flow. Analytical solutions are obtained for the canalicular fluid velocity, pressure, and SP. Results demonstrate that SP amplitude (SPA) is proportional to the pressure difference, strain amplitude, frequency, and strain rate amplitude. However, the key loading factor governing SP is the strain rate, which is a representative loading parameter under the specific physiological state. Moreover, SPA is independent of canalicular length. This model links external loads to the canalicular fluid pressure, velocity, and SP, which can facilitate further understanding of the mechanotransduction and electromechanotransduction mechanisms of bones.

ASSA14-02-06 Radiofrequency Catheter Ablation of Ventricular Tachycardia After Repair of Congenital Heart Disease

Objective This study was designed to discuss the mechanism, critical isthmus, the characteristics of surface electrocardiogram (ECG) and the strategy of ablation of ventricular tachycardia (VT) after repair of congenital heart disease in order to increase the success rate and safety of radiofrequency catheter ablation (RFCA). Methods Eleven consecutive patients (9 men and 2 women, aged 6∼41 years) with recurrent and symptomatic VT after repair of congenital heart disease were investigated. Nine patients had undergone surgical repair of tetralogy of Fallot (TOF), 1 patient had an operation for severe congenital pulmonary stenosis and patch closure of ventricular septal defect (VSD) and suture of atrial septal defect (ASD), and the remaining patient had repair of trilogy of Fallot combined with right ventricular cardiomyopathy. The ECG showed sustained VTs in 10 patients and unsustained VTs in 1 patient, and 4 patients had the histories of syncope. Substrate mapping of the right ventricle during sinus rhythm was performed in all 11 patients. Unexcitable tissue identified from bipolar voltage ( Results In 9 patients after surgical repair of TOF, 19 different monomorphic VTs (cycle length, 170∼350 ms) could be induced; 15 were documented as clinical VTs, 2 VTs were hemodynamically unstable. In 1 patient of having an operation for severe congenital pulmonary stenosis and patch closure of VSD and suture of ASD, 1 nonsustained VT could be induced, the clinical 2 VTs could not be induced. Five morphologies of nonsustained VT could be induced in the remaining patient who had repair of trilogy of Fallot combined with right ventricular cardiomyopathy. In 10 patients who had surgical repair of TOF or severe congenital pulmonary stenosis and patch closure of VSD and suture of ASD, mapping and ablation was performed during VTs in 4 patients. In the other 6 patients, mapping and ablation was performed during sinus rhythm. The sites of surgical correction of the right ventricle were associated with the origins of VTs in these 10 patients. Combined with QRS morphology during VT and the results of mapping and ablation, anatomic isthmus 2 were ablated in 8 patients, isthmus 3 ablated in 8 patients, isthmus 5 ablated in 4 patients, and isthmus 4 ablated in 1 patient. Isthmus 2 and 3 as the reentry circuit critical isthmuses were more common. In the patient of having repair of trilogy of Fallot combined with right ventricular cardiomyopathy, 5 morphologies of nonsustained VTs (cycle length, 250∼310 ms, left bundle-branch block) could be induced, 2 were clinical VTs. Combined with the information of surgical operation method and the result of electroanatomic mapping, these VTs were considered being relevant with right ventricular cardiomyopathy, but not the surgical operation of congenital heart disease. Radiofrequency energy was delivered around the scar of the right ventricle apex and at the sites with late potential within the scar. All the 25 VTs induced in the 11 patients were caused by scar related reentry. Catheter ablation achieved acute success in 10 patients, including elimination of all VTs in 9 patients, and elimination of the clinical VTs in 1 patient. Ablation of VTs failed in the remaining patient with TOF because of lacking of inferior vena cava. During 3 months to 9 years of follow up, VTs recurred in 3 patients. Two of them had a successful ablation of VTs in the second procedure, and 1 patient had success in the third procedure. Conclusions Reentry circuit isthmuses in VTs late after repair of congenital heart disease are located within anatomically defined isthmuses bordered by unexcitable tissue of scar, patch or valve annulus. The isthmuses between the pulmonary annulus and right ventricular free wall scar/patch (isthmus 2), and between the pulmonary annulus and septal scar/patch (isthmus 3) were more common. In addition, the boundary between the scar/patch in the anterior right ventricular outflow and septal scar/patch (isthmus 5) could also be the critical isthmus of VT. RFCA of these 3 isthmuses could increase the success rate of VT after repair of congenital heart disease. The information of surgical operation prior to ablation and ventricular angiogram during the procedure were very important to predict critical isthmuses and direct electroanatomic mapping. Based on the electroanatomic mapping, RFCA of critical isthmuses of VTs in patients after repair of congenital heart disease might have a high success rate and a low recurrence, especially for unmappable VTs.

Laccases direct lignification in the discrete secondary cell wall domains of protoxylem.

Plants precisely control lignin deposition in spiral or annular secondary cell wall domains during protoxylem tracheary element (TE) development. Because protoxylem TEs function to transport water within rapidly elongating tissues, it is important that lignin deposition is restricted to the secondary cell walls in order to preserve the plasticity of adjacent primary wall domains. The Arabidopsis (Arabidopsis thaliana) inducible VASCULAR NAC DOMAIN7 (VND7) protoxylem TE differentiation system permits the use of mutant backgrounds, fluorescent protein tagging, and high-resolution live-cell imaging of xylem cells during secondary cell wall development. Enzymes synthesizing monolignols, as well as putative monolignol transporters, showed a uniform distribution during protoxylem TE differentiation. By contrast, the oxidative enzymes LACCASE4 (LAC4) and LAC17 were spatially localized to secondary cell walls throughout protoxylem TE differentiation. These data support the hypothesis that precise delivery of oxidative enzymes determines the pattern of cell wall lignification. This view was supported by lac4lac17 mutant analysis demonstrating that laccases are necessary for protoxylem TE lignification. Overexpression studies showed that laccases are sufficient to catalyze ectopic lignin polymerization in primary cell walls when exogenous monolignols are supplied. Our data support a model of protoxylem TE lignification in which monolignols are highly mobile once exported to the cell wall, and in which precise targeting of laccases to secondary cell wall domains directs lignin deposition.

Numerical research on relationship between flow pattern transition and condensation heat transfer in microchannel

Purpose– Based on the numerical research on the relationship between the flow pattern transition and the condensation heat transfer in circular microchannels, the purpose of this paper is to bring forward a concept of external separation circular microchannel to regulate and control the flow pattern for enhancing the condensation heat transfer.Design/methodology/approach– The numerical research is based on the volume of fluid method and the vapor-liquid phase change model proposed by the present authors.Findings– By numerical research on the condensation process of water in a general circular microchannel, it is discovered that, with the increase of the inlet velocity and the reduction of the temperature difference between the saturation temperature and the channel wall temperature, the bubble detachment frequency is raised and the water vapor condensation length is extended, representing an exponential growth. Therefore, for the condensation process with low temperature difference and high mass flow rate, it is in urgent need to regulate and control the flow pattern.Originality/value– To prevent the flow pattern in the general circular microchannel converted from annular flow to slug flow and then to bubble flow, this paper brings forward a concept of external separation circular microchannel, which regulates and controls the flow pattern by discharging partial liquid from the annular wall opening. After regulation and control, the flow pattern is converted from original periodic annular flow/slug flow/bubble flow to current stable annular flow. Accordingly, the heat transfer performance is enhanced and the condensation length is lowered remarkably.

How Healthy Discs Herniate

Microstructural investigation of compression-induced disruption of the flexed lumbar disc. To provide a microstructural analysis of the mechanisms of annular wall failure in healthy discs subjected to flexion and an elevated rate of compression. At the level of the motion segment failure of the disc in compression has been extensively studied. However, at the microstructural level the exact mechanisms of disc failure are still poorly understood, especially in relation to loading posture and rate. Seventy-two healthy mature ovine lumbar motion segments were compressed to failure in either a neutral posture or in high physiological flexion (10°) at a displacement rate of either 2 mm/min (low) or 40 mm/min (high). Testing at the high rate was terminated at stages ranging from initial wall tearing through to facet fracture so as to capture the evolution of failure up to full herniation. The damaged discs were then analyzed microstructurally. Approximately, 50% of the motion segments compressed in flexion at the high rate experienced annulus or annulus-endplate junction failure, the remainder failed via endplate fracture with no detectable wall damage. The average load to induce disc failure in flexion was 18% lower (P < 0.05) than that required to induce endplate fracture. Microstructural analysis indicated that wall rupture occurred first in the posterior mid-then-outer annulus. Disc wall failure in healthy motion segments requires both flexion and an elevated rate of compression. Damage is initiated in the mid-then-outer annular fibers, this a likely consequence of the higher strain burden in these same fibers arising from endplate curvature. Given the similarity in geometry between ovine and human endplates, it is proposed that comparable mechanisms of damage initiation and herniation occur in human lumbar discs. N/A.

B-type natriuretic peptide in patients after percutaneous trans-coronary-sinus mitral annuloplasty

Functional mitral regurgitation (MR) remains a significant clinical problem. Surgical valve repair carries a high procedural risk. Thus, percutaneous techniques are under development. One of the most advanced devices for percutaneous mitral annuloplasty (PTMA) is the Carillon™ device. B-type natriuretic peptide (BNP) is a marker of haemodynamic status in heart failure patients. So far, its usefulness in patients after PTMA is unknown. Thirteen consecutive patients after successful implantation of the Carillon™ device were enrolled. PTMA was achieved through the coronary sinus in order to improve leaflet coaptation. Before PTMA, immediately after, and at one month follow-up, transthoracic echocardiography was performed. Furthermore, plasma BNP levels, the six-minute walk test (6MWT) and the Naughton treadmill exercise test were evaluated before PTMA and after one month. In patients after successful PTMA, significant improvement in echocardiographic parameters was maintained at one-month follow-up: vena contracta (0.31 ± 0.03 vs. 0.64 ± 0.03 cm, p < 0.05), effective regurgitant orifice area (0.2 ± 0.02 vs. 0.32 ± 0.05 cm², p < 0.05), MR jet area/left atrial area (32.33 ± 1.98 vs. 47.06 ± 2.3%,p < 0.05) and regurgitant volume (27.84 ± 2.17 vs. 45.25 ± 7.47 mL, p < 0.05). Both the duration of the exercise test (4.3 ± 0.45 vs. 3.12 ± 0.18 min, p < 0.05) and 6MWT (320 ± 29.63 vs. 295.2 ± 13.4 m, p < 0.05) improved. Furthermore, improvement of the NYHA class was observed. Despite that, mean BNP levels remained unchanged (405.3 ± 133.9 vs. 596.5 ± 245.2 pg/mL, p = 0.191; after and before the procedure, respectively). In some patients with device located above the annulus level, an increase in BNP leve ls was observed. BNP seems to be useless for the assessment of patients after PTMA. This may be related to mechanical stress on the annulus and atrial wall caused by the device itself.

The Role of (Intra-)Discal Treatments for Discogenic Low Back Pain

The intervertebral disc is believed to be the key pathology behind low back pain (LBP). The pain mechanisms include annular ruptures, fissures in the end plates, neural sensors on the disc surface ...

Effect of periodic excitation on alternating current electroosmotic flow in a microannular channel

The hydrodynamic behavior of time-periodic electro-kinetic-driven flow in a microannular channel is examined based on the linearized Poisson–Boltzmann equation and the Navier–Stokes equation under various periodic functions. The response of the flow field to excitation by more complex waveforms (than the sine wave) is investigated using Green’s function approach. It is shown that the velocity profiles are characterized by the geometric radius ratio, the wall zeta potential ratio, the electro-kinetic radius, and the dimensionless frequency. The influence of the particular excitation waveform is demonstrated to be more significant at lower frequencies, since the bulk fluid has more time to respond to instantaneous changes in the applied unsteady field. The square waveform yields higher local velocities (compared with the others), since the full strength of the electric field is applied for a longer time. In cases of high excitation frequency, large annulus size or small kinematic viscosity, the flow is demonstrated to be confined to a region near the annulus walls while the bulk fluid remains essentially stationary. As the dimensionless frequency becomes less than one, momentum diffusion is faster than the period of oscillation, and the plug-like velocity profiles (similar to steady-state electroosmotic flow) are observed at nearly all times. Impulsively started flows (from rest) exhibit transient behavior resulting in a net positive flow during the initial cycles for cases of high non-dimensional frequency.

Kinetic modelling of Escherichia coli inactivation in a photocatalytic wall reactor

A kinetic model of the photocatalytic inactivation of Escherichia coli in an annular wall reactor is presented. The model is based on a reaction scheme that involves a series of events in which bacteria are progressively damaged and eventually led to cell lysis. The model explicitly takes into account radiation absorption effects. Photocatalytic inactivation experiments were carried out in a photoreactor operated in a closed recirculating circuit with a reservoir tank and irradiated with a 6W black light lamp situated in the axis of the reactor. Immobilization of TiO2 Aeroxide P25 has been carried out by the dip-coating procedure onto the inner-tube wall of the annular reactor. Experimental results for different TiO2 layer thicknesses were used to estimate the kinetic parameters of the model. Good agreement between model predictions and inactivation experiments was achieved in the whole range of TiO2 thicknesses studied.

Pilot observational study on haemodynamic changes after surfactant administration in preterm newborns with respiratory distress syndrome

BackgroundSurfactant treatment reduces respiratory morbidity and mortality in preterm infants. Data on its haemodynamic consequences are conflicting. The aim was to characterise the haemodynamic effects of surfactant treatment on cardiac function in preterm newborns with respiratory distress syndrome (RDS).MethodsPreterm infants (gestational age <34 weeks, birth weight <2000 g) with RDS, who received surfactant within 72 hours of life, were recruited.Echocardiography was performed before surfactant, and 2 and 24 hours after. Left and right ventricular peak systolic, early diastolic and late diastolic myocardial velocities were measured using Tissue Doppler Imaging (TDI), while characteristics of the ductus arteriosus, pulmonary artery pressure, right ventricular (RVO) and left ventricular output were measured by standard echocardiography. Tricuspidal Annular Plane Systolic Excursion (TAPSE) was measured on the free wall of the tricuspid annulus.ResultsFourteen patients were studied. Surfactant was associated with a decrease in pulmonary pressure and an increase in RVO. The improvement of right ventricular function was also confirmed by a significant increase in right peak systolic velocity and in TAPSE. Left ventricular velocities did not change significantly after surfactant.ConclusionsSurfactant administration in preterm infants with RDS did not impair myocardial contractility and was followed by increased RVO, in agreement with other parameters of right ventricular function. TDI and TAPSE appeared to be reliable and feasible in this population. The addition of TDI and TAPSE to standard neonatal echocardiography may provide additional information about cardiac function.

Assessment of left atrial function by volumetric indices and tissue Doppler imaging in ischaemic and idiopathic dilated cardiomyopathy

Left atrial (LA) contractility plays an important role in maintenance of cardiac output in patients with left ventricular systolic dysfunction. Although left atrial contractile dysfunction has been reported in dilated cardiomyopathy of ischemic and non-ischemic etiology, the mechanism of LA dysfunction and the pathophysiologic determinants of left atrial size and function have not been adequately investigated in these patients. The aim of this study was to evaluate LA size and contractile function in patients with dilated cardiomyopathy of ischemic and idiopathic etiology and to explore the mechanism and determinants of LA dilation and contractile dysfunction in these patients. 35 patients with ischemic dilated cardiomyopathy, 15 patients with idiopathic dilated cardiomyopathy and 30 control subjects were studied with transthoracic conventional echocardiography, tissue Doppler imaging (TDI) and coronary angiography (CA). Left ventricular (LV) size, systolic and diastolic functions as well as mitral regurgitation (MR) were evaluated. Left atrial volume at mitral valve opening (Vmax), onset of atrial systole, determined by onset of the P wave of the electrocardiogram (Vp) and mitral valve closure (Vmin) was determined with two-dimensional echocardiography. The left atrial contractile function was assessed by means of active emptying fraction (ACTEF = {Vp − Vmin}/Vp%) and TDI for assessment of late diastolic velocity of the mitral annulus and left atrial free wall. Left atrial Vmax was greater while ACTEF and left atrial wall velocity were lower in cardiomyopathy patients compared with the control subjects (79 ± 32 vs. 59 ± 18; P < 0.05, 27.6 ± 13 vs. 42 ± 15; P < 0.05 and 10.2 ± 4.7 vs. 16.2 ± 5.4; P < 0.05, respectively). Vmax , ACTEF and left atrial wall velocity were similarly affected in both types of cardiomyopathy, ischaemic and idiopathic, under the same loading conditions (74 ± 24 vs. 91 ± 46; P > 0.05, 29 ± 12 vs. 27 ± 13; P > 0.05 and 10 ± 5 vs. 11 ± 4; P > 0.05, respectively). The determinants of ACTEF were left atrial volume, left ventricular ejection fraction (EF), E/e’ and MR severity. Left atrial enlargement and contractile dysfunction are common in patients of dilated cardiomyopathy regardless of its aetiology, with the same degree of contractile dysfunction in both ischemic and idiopathic cardiomyopathies under similar loading conditions. This dysfunction is related to worse LV systolic and diastolic function, more severe mitral regurgitation and larger LA volume rather than to the aetiology of cardiomyopathy.

Assessment of left atrial function by volumetric indices and tissue Doppler imaging in ischaemic and idiopathic dilated cardiomyopathy

Left atrial (LA) contractility plays an important role in maintenance of cardiac output in patients with left ventricular systolic dysfunction. Although left atrial contractile dysfunction has been reported in dilated cardiomyopathy of ischemic and non-ischemic etiology, the mechanism of LA dysfunction and the pathophysiologic determinants of left atrial size and function have not been adequately investigated in these patients. The aim of this study was to evaluate LA size and contractile function in patients with dilated cardiomyopathy of ischemic and idiopathic etiology and to explore the mechanism and determinants of LA dilation and contractile dysfunction in these patients. 35 patients with ischemic dilated cardiomyopathy, 15 patients with idiopathic dilated cardiomyopathy and 30 control subjects were studied with transthoracic conventional echocardiography, tissue Doppler imaging (TDI) and coronary angiography (CA). Left ventricular (LV) size, systolic and diastolic functions as well as mitral regurgitation (MR) were evaluated. Left atrial volume at mitral valve opening (Vmax), onset of atrial systole, determined by onset of the P wave of the electrocardiogram (Vp) and mitral valve closure (Vmin) was determined with two-dimensional echocardiography. The left atrial contractile function was assessed by means of active emptying fraction (ACTEF = {Vp − Vmin}/Vp%) and TDI for assessment of late diastolic velocity of the mitral annulus and left atrial free wall. Left atrial Vmax was greater while ACTEF and left atrial wall velocity were lower in cardiomyopathy patients compared with the control subjects (79 ± 32 vs. 59 ± 18; P < 0.05, 27.6 ± 13 vs. 42 ± 15; P < 0.05 and 10.2 ± 4.7 vs. 16.2 ± 5.4; P < 0.05, respectively). Vmax , ACTEF and left atrial wall velocity were similarly affected in both types of cardiomyopathy, ischaemic and idiopathic, under the same loading conditions (74 ± 24 vs. 91 ± 46; P > 0.05, 29 ± 12 vs. 27 ± 13; P > 0.05 and 10 ± 5 vs. 11 ± 4; P > 0.05, respectively). The determinants of ACTEF were left atrial volume, left ventricular ejection fraction (EF), E/e’ and MR severity. Left atrial enlargement and contractile dysfunction are common in patients of dilated cardiomyopathy regardless of its aetiology, with the same degree of contractile dysfunction in both ischemic and idiopathic cardiomyopathies under similar loading conditions. This dysfunction is related to worse LV systolic and diastolic function, more severe mitral regurgitation and larger LA volume rather than to the aetiology of cardiomyopathy.

Cardiac structural and functional changes in old elderly patients with obstructive sleep apnoea–hypopnoea syndrome

To investigate cardiac structural changes in elderly patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and the impact on left ventricular systolic and diastolic function. The study enrolled elderly patients with OSAHS and age-matched healthy control subjects. Cardiac structure, left ventricular diastolic function and left ventricular systolic function were measured using a Doppler ultrasound scanner and compared between the two groups. The study included 136 patients with OSAHS and 50 healthy control subjects. There were significant differences in the echocardiography indicators that reflect cardiac structure, including interventricular septum, left ventricle posterior wall thickness, and left ventricular mass and mass index between the two groups. There were significant differences between the two groups in the ventricular septal early diastolic myocardial peak velocity/late diastolic myocardial peak velocity (Em/Am), mitral annulus Em/Am, and left ventricle posterior wall Em/Am. There were also significant differences in the indicators of interventricular septum, mitral annulus and left ventricular posterior wall systolic peak velocity between the two groups. Elderly patients with OSAHS demonstrated cardiac structural changes and their left ventricular diastolic and systolic functions were significantly diminished.

Numerical investigation on the impact of the converging angle of the suction chamber on annular jet pumps

The internal flow of an annular jet pump is an annular wall jet developed in a limited space, which is affected by its structure, shape, area ratio and flow rate ratio. In this paper, numerical simulation of an annular jet pump with area ratio A=1.75 was conducted based on realizable k-ε turbulence model. And the impact of the converging angle of the suction chamber to the pump performance and the expansion of annular jet is investigated. According to the simulated results, the following conclusion is obtained. With the converging angle of the suction chamber (α) being 20°, the pump performance turns out to be the best. And with the increasing α, the maximal axial velocity and the squeezing effect to the annular jet are larger, while the mixing level of the two flows drops. In addition, the half-width of the annular jet, in the suction chamber, is proportional to tan(α/2) which is the tangent of the half angle of the suction chamber.

Predictive value of atrial electromechanical delay for atrial fibrillation recurrence

We investigated the predictive value of atrial electromechanical delay (AEMD) for recurrence of atrial fibrillation (AF) at 1-month after cardioversion. Seventy-seven patients with persistent AF were evaluated and finally 50 patients (12 men, 38 women) were included. All patients underwent transthoracic electrical DC cardioversion under amiodarone treatment. AEMD was measured as the time interval from the onset of the P wave on electrogram (ECG) to the beginning of late diastolic wave (Am) from the ventricular annulus and atrial walls on tissue Doppler imaging, in the apical 4-chamber view 24 h after cardiversion. P wave maximum-duration (Pmax), P wave minimum-duration (Pmin) and P wave dispersion-duration (Pdis) were calculated on the 12-lead ECG at 24-h postcardioversion. We followed the heart rate and rhythm by 12-lead ECG at 24-h, 1-week and 1-month. At 1-month follow-up after cardioversion, 28 (56%) patients were in sinus rhythm (SR), whereas 22 (44%) patients reverted to AF. The AEMD durations were longer in AF group than SR group (p < 0.001) and were signifi cantly correlated with Pmax and Pdis (p < 0.001 for both). For AF recurrence; duration of AF, left atrial (LA) diameter, maximum LA volume index, mitral A velocity and LA lateral AEMD were significant parameters in univariate-analysis, however LA lateral AEMD was the only significant parameter in multivariate-analysis (OR: 1.46; 95% CI 1.02-2.11; p = 0.03). Our results suggest that AEMD is associated with an increased risk of recurrence of AF within 1-month. These data may have implications for the identification of patients who are most likely to experience substantial benefit from cardiversion therapy for AF.

An Actuator Disk Model of Incidence and Deviation for RANS-Based Throughflow Analysis

Reynolds-averaged Navier–Stokes (RANS) equations with blade blockage and blade force source terms are solved in the meridional plane of complete axial flow turbomachinery using a finite-volume scheme. The equations of the compressible actuator disk (AD) are introduced to modify the evaluation of the convective fluxes at the leading and trailing edges (LEs and TEs). An AD behaves as a compact blade force which instantaneously turns the flow with no production of unphysical entropy. This avoids unphysical incidence loss across the LE discontinuity and allows for application of all of the desired deviation at the TE. Unlike previous treatments, the model needs no handmade modification of the throughflow (TF) surface and does not discriminate between inviscid and viscous meridional flows, which allows for coping with strong incidence gradients through the annulus wall boundary layers and with secondary deviation. This paper derives a generalized blade force term that includes the contribution of the LE and TE ADs in the divergence form of the TF equations and leads to generalized definitions of blade load, blade thrust, shaft torque, and shaft power. In analyzing a linear flat plate cascade with an incidence of 32 deg and a deviation of 21 deg, the proposed model provided a 105 reduction of unphysical total pressure loss compared to the numerical solution with no modeling. The computed mass flow rate, blade load, and blade thrust showed excellent agreement with the theoretical values. The complete RANS TF solver was used to analyze a four-stage turbine in design and off-design conditions with a spanwise-averaged incidence of up to 2 deg and 43 deg, respectively. Compared to a traditional streamline curvature solution, the RANS solution with incidence and deviation modeling provided a 0.1 to 0.7% accurate prediction of mass flow rate, shaft power, total pressure ratio, and adiabatic efficiency in both the operating conditions. It also stressed satisfactory agreement concerning the spanwise distributions of flow angle and Mach number at LEs and TEs. In particular, secondary deviation was effectively predicted. The RANS solution with no modeling showed acceptable performance prediction only in design conditions and could introduce no deviation.

The mechanical characterization study of mitral annulus at different sites in normal adults using ultrasonic dual pulse-wave Doppler

Objective To define the mechanical features of mitral annulus at various sites,and to investigate the specific mechanics characterization at different mitral annulus sites in evaluation consequences of left ventricular function by dual pulse-wave Doppler (DPW) technology.Methods The DPW spectrums were obtained at lateral and aboral interval,anterior and inferior and posterior mitral annular from 112 normal adults.The peak systolic velocity (Sm),peak early diastolic velocity (Em),peak late diastolic velocity (Am),the beginning time of the peak and the time to peak were measured,and E/A,Em/Am,E/Em,left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were computed.Results 1)Sm,Em,Am and Em/Am measured in the free wall annulus were significantly greater than measured in the interval annulus of mitral annular sites.However,E/Em was opposited (P ＜ 0.05).Sm of the posterior wall mitral annulus accelerated frist and experienced shortest duration in all the mitral annular sites (P ＜ 0.01).There were no significant differences of Em time parameters among different mitral annulus sites.Am of the beginning time and peak time in the free wall annulus were significantly longer than that in the interval annulus of anterior mitral annular sites.However,the acceleration time was opposited(P ＜0.05).2) Sm was correlated with LVEF and LVFS (r =0.243 and r =0.227,P ＜0.01) only at the posterior mitral annular site,Em/Am of anterior and posterior wall mitral annulus had the highest correlations with mitral orifice flow E/A(r =0.545 and 0.545 respectively,P ＜ 0.01).Conclusions There are significant differences among the mechanics patterns at different mitral annulus sites in normal adults.The mechanics characterization at different mitral annulus sites have different conclusions of left ventricular function. Key words: Echocardiography; Ventricular function,left; Mitral annulus; Dual pulse-wave Doppler

Acute severe increase in afterload as a new mechanism for "stunning" in the right ventricle

Purpose: To determine the effects of an acute severe afterload increase on right ventricular (RV) function. Methods: Twelve patients (16±11 years old) with moderate or severe pulmonary regurgitation after Fallot correction in childhood underwent percutaneous pulmonary valve implantation (PPVI). Deployment of the valve with a balloon results in a complete occlusion of the RV outflow tract (RVOT) for a mean time of 15 seconds. Echocardiograms were taken before (Echo1) and immediately after (Echo2) balloon occlusion as well as at the end of the procedure (Echo 3). Conventional echocardiographic and tissue Doppler based deformation indices of the RV were assessed. Results: See figure. Acute severe increase in RV afterload during balloon inflation resulted in a significant decrease in fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE) and RV free wall deformation (Strain), the latter showing induced pronounced post-systolic shortening (PSS). All parameters had returned close to baseline at the end of the procedure. ![Figure][1] Conclusion: Acute severe increase in RV afterload induces a transient myocardial dysfunction which recovers within minutes. The underlying mechanism is unclear, but observed changes have similarities with ischemic stunning. Further studies are needed to explore this phenomenon. [1]: pending:yes

Electroanatomic mapping and catheter ablation of atrial tachycardia originating from the tricuspid annulus

We read with great interest with a recent case report from Cay et al. [1] published in International Journal of Cardiology. They reported an interesting case of successful radiofrequency ablation of idiopathic ventricular arrhythmia originating from the anterolateral free wall of tricuspid annulus (TA). We recently encountered a patient presenting with atrial tachycardia (AT) originating from the anterolateral free wall of the tricuspid annulus, who was successfully ablated using 3dimensional electroanatomic mapping system. A 62-year-old male patient was referred to our department for catheter ablation for symptomatic atrial tachycardia, which was resistant to metoprolol, propafenone, and amiodarone. He had a history of hypertension for 10 years. No underlying structural heart disease was detected by echocardiogram. P-wave morphology during tachycardia (Fig. 1) was “W” shape in the inferior leads, iso in lead I, and predominantly negative in lead V1, all suggesting the AT originating from the lateral free wall of the tricuspid annulus. During electrophysiologic study guided by the noncontact Ensite Array (EA) mapping system (St. Jude Medical, St. Paul, MN, USA), the tachycardia could be induced by atrial burst pacing. The cycle length of the tachycardia was 560 ms. The earliest atrial activation site during the arrhythmia was found near the anterolateral free wall of the TA (Movie). Activation mapping also showed the AT origin and its propagation to the other sites of the right atrium. Radiofrequency ablation using irrigated ablation catheter (Cool Path Ablation Catheter, St. Jude Medical) with average power of 30 W and maximum temperature of 43 °C at this site (Fig. 2) successfully terminated the tachycardia (Fig. 3), and AT was no longer inducible with and without isoproterenol infusion. The patient remained free from any atrial arrhythmias without anti-arrhythmic drugs during a follow-up period of one year. The focal atrial tachycardia originating from the TA is not commonly seen, and has been reported in separate cases [2–4] and case series [5,6] with an incidence of 9–10% of right atrial tachycardia. Furthermore, AT arising from the anterolateral free wall of the TA is relatively rare. Conventionally, intracardiac mapping of focal AT using 1 or 2 roving catheters was utilized to find the origin of AT. Noncontact mapping systems provide an accurate guidance for mapping and ablation of focal AT [7,8]. Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.ijcard.2013.06.084. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.