Aortic stenosis is the most frequent valvular heart disease. The mean systolic value of the transvalvular pressure gradient (TPG) is commonly utilized during clinical examination to evaluate its severity and it can be determined either by cardiac catheterization or by Doppler echocardiography. TPG is highly time-dependent over systole and is ...

BACKGROUND AND AIM OF THE STUDY: In-vitro studies on the ATS heart valve have indicated that valve opening is less in an expanding conduit than in a straight conduit. METHODS: Bileaflet valve behavior was studied using a new computational fluid-structure interaction model. A three-dimensional model of the ATS valve was ...

OBJECTIVE: We hypothesized that functional mitral and tricuspid valvular incompetence (MR and TR, respectively) are reversible causes of reduced cardiac output in decompensated heart failure (DF) that accompanies systolic dysfunction in ischemic or nonischemic cardiomyopathy. BACKGROUND: DF, defined as signs and symptoms of heart failure at rest, is rooted in ...

Biologically derived, chemically modified collagenous tissues are being increasingly used to fabricate cardiac valve prostheses and as biomaterials in cardiovascular repair. A stress-free state during chemical modification has been shown to preserve the collagen fiber architecture of the native tissue, potentially preserving native mechanical properties and improving prostheses durability. However, ...

BACKGROUND AND AIM OF THE STUDY: Conflicting data exist regarding the accuracy of echocardiographic Doppler gradients compared to invasive pressure gradients in the hemodynamic assessment of patients with prosthetic aortic valves. The study aim was to determine the correlation between these measurements for mechanical single- and double-leaflet aortic valve prostheses ...

We present a case of a patient scheduled for mitral valve replacement and possible aortic valve replacement. On Doppler examination, her peak transaortic pressure gradient measured on three separate occasions (pre-, intra-, and postoperatively) was approximately 60 mm Hg. In contrast, the peak-to-peak pressure gradient (cardiac catheterization) was 11 mm ...

The utility of tissue Doppler and propagation velocity in identifying patients with abnormal left ventricular filling pressures was assessed in 50 patients who underwent catheterization and echocardiography on the same day. The ratios of the peak velocity of early mitral inflow to early mitral annular velocity (E/Ea) and the velocity ...

OBJECTIVES: We sought to determine the impact of valve prosthesis-patient mismatch (PPM) on pulmonary arterial (PA) pressure after mitral valve replacement (MVR). BACKGROUND: Pulmonary arterial hypertension is a serious complication of mitral valve disease, and it is a major risk factor for poor outcome after MVR. We hypothesized that valve ...

A new valved conduit was developed using a canine aortic valve. The bioprosthetic valve was fixed with glutaraldehyde and epoxy compound (Denacol-EX313/810). A vascular graft composed of ultra-fine polyester fiber (10 mm in diameter, 200 mm in length) was used. Four dogs underwent apico-aortic valved conduit (AAVC) implantation and aortic ...

A 51-year-old woman was admitted with intractable congestive heart failure and progressive anemia. She had undergone mitral valve replacement for mitral regurgitation at age 23 years. Subsequently, her mitral prosthesis was replaced twice due to thrombotic stack and valve insufficiency. Signs of congestive heart failure became evident at age 46 ...

OBJECTIVE: To determine the effect of systemic arterial hypertension on the indices of aortic stenosis (AS) severity. METHODS: A severe supravalvar AS was created in 24 pigs. The maximum and mean pressure gradients across the stenosis were measured by Doppler echocardiography and by catheterisation. Both echocardiography and catheter data were ...

An 8-year-old child suffering from ventricular septal defect and severe valvular pulmonary stenosis was evaluated by echo-Doppler technique and cardiac catheterization. A peak instantaneous transventricular systolic gradient of 64 mmHg was recorded across the ventricular septal defect with an interesting M-shaped spectral pattern. However, cardiac catheterization revealed a peak-to-peak non-simultaneous ...

BACKGROUND: Tricuspid valve regurgitation occurs with other congenital heart defects, especially the right-sided obstructive lesions. We applied the selective annuloplasty technique for the treatment of tricuspid regurgitation in children. METHODS: Between 2001 and 2003, 15 patients whose ages averaged 7.6 +/- 3.1 years (range 4 to 17 years old) underwent ...

Petioles (up to 4 m tall) of huge solitary leaves of mature plants of Amorphophallus titanum and A. gigas resemble tree trunks supporting an umbrella-like crown. In a mechanical sense, the petiole is a shell, composed of compact parenchyma with embedded collenchyma strands. The core of the shell is filled ...

Certification tests currently employed by some industrialized nations to certify respirators require that when challenged with air flow at a constant suction head of 25 mmH2O, the leakage into the facepiece from the exhalation valve(s) should not exceed 30 ml min(-1). However, the test alone might not reflect the leakage ...

OBJECTIVES: The exact role of pressure gradient across the prosthetic valve estimated from Doppler flow velocity remains controversial. This in-vivo study was designed to assess the actual discrepancy between Doppler and catheter measurements of the pressure gradients for small bileaflet prosthetic valves in the aortic position. METHODS: Bileaflet prosthetic valves ...

INTRODUCTION: After shunt insertion there is commonly a disproportionate reduction in size of the lateral ventricle containing the catheter (shunted lateral ventricle), which is almost certainly related to shunt function. To explore the difference between two shunt types, the Differential Pressure Medium Pressure cylindrical (M.P.) and Delta 1.5 valves (manufactured ...

OBJECTIVE: Biological valves exhibit characteristic curves (CC) regarding transvalvular gradient, resistance, and effective orifice area when correlated with a physiological cardiac output range (CO). The slope of the curve of transvalvular resistance over a typical CO range characterizes the clinical performance of the valve. These information may support an individualized ...

BACKGROUND: Aortic valve sclerosis (AVS), a condition of thickening and calcification of the normal trileaflet aortic valve without the obstruction to left ventricular outflow, is likely the initial stage in the development of aortic stenosis and is associated with an increased incidence of cardiovascular events. The objective of this study ...

The purpose of this study was to evaluate the ex vivo effects of the Coapsys device upon functional mitral regurgitation (MR) in human hearts. We used seven excised hearts from patients who underwent cardiac transplantation. All patients had functional MR of grade 2 or greater associated with dilated (n = ...

Cavitation on a mechanical heart valve (MHV) is attributable to transient regional pressure drop at the instant of valve closure. As a cavitation bubble collapses, it emits shock waves, which have the characteristics of high frequency oscillations (HFO) on a pressure time trace. The potential for such HFO bursts to ...

In contrast to the widespread use of dobutamine stress Doppler echocardiography in the hemodynamic evaluation of the prosthetic valves in aortic position, it has been rarely, if ever, used for assessment of these valves in mitral position. Therefore, this pilot study was done to assess the hemodynamic performance of St. ...

In the past, several methods based on iterative solution of pressure-Poisson equation have been developed for measurement of pressure from phase-contrast magnetic resonance (PC-MR) data. In this paper, a non-iterative harmonics-based orthogonal projection method is discussed which can keep the pressures measured based on the Navier-Stokes equation independent of the ...

OBJECTIVE: Hydrostatic devices have considerable advantages compared to "conventional" differential-pressure-valves concerning overdrainage, but are thought to imply a tendency to underdrain or to clog. The aim of this study was to evaluate the ability of the hydrostatic gravitational Dual-Switch-Valve (DSV) to minimize overdrainage-related complications without increasing the danger of underdrainage. ...

OBJECTIVE: To assess the hydrodynamic properties of three new types of hydrocephalus valve. METHODS: Three new constructions have been recently tested in the UK shunt Evaluation Laboratory: the magnetically adjustable Strata Valve (Medtronic PS Medical), the gravitational Miethke Dual-Switch Valve (Aesculap) and the ventriculo-sinus SinuShunt (CSF Dynamics). Pressure-flow performance curves ...

BACKGROUND: The aim of the present study was to clarify whether programmable shunt valves are advantageous in the treatment of adults with communicating hydrocephalus with respect to valve-related shunt complications and surgical shunt revisions, in comparison with standard valves. METHODS: Adult patients with communicating hydrocephalus treated with Codman Hakim programmable ...

In patients with aortic stenosis, the left ventricular afterload is determined by the degree of valvular obstruction and the systemic arterial system. We developed an explicit mathematical model formulated with a limited number of independent parameters that describes the interaction among the left ventricle, an aortic stenosis, and the arterial ...

This paper presents the first systematic engineering study of the impact of chemical formulation and surface functionalization on the performace of free-standing microfluidic polymer elements used for high-pressure fluid control in glass microsystems. System design, chemical wet-etch processes, and laser-induced polymerization techniques are described, and parametric studies illustrate the effects ...

The structural and functional effects of the "edge-to-edge" technique on the human mitral valve have been investigated, paying particular attention to the diastolic phase. An advanced finite element model of the valve has been developed, using a hyperelastic material schematization, suitable geometry and constraint conditions, and an effective fluidodynamic analysis. ...

Physiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence that the ancestors of living crocodilians were active and endothermic, but the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. In endotherms, there is a functional nexus between high metabolic rates, high blood ...

An understanding of how mechanical forces impact cells within valve leaflets would greatly benefit the development of a tissue-engineered heart valve. Previous studies by this group have shown that exposure to constant static pressure leads to enhanced collagen synthesis in porcine aortic valve leaflets. In this study, the effect of ...

Continuous-wave (CW) Doppler recording of mitral regurgitation (MR) is a reflection of the left ventriculoatrial pressure gradient. Accordingly, this jet may yield information about pulmonary artery wedge pressure (PAWP). In this study, we derived and then evaluated a novel method for prediction of PAWP. Patients (n=80) with moderate to severe ...

The purpose of this study was to compare the Oxylator EM-100, a ventilator with a fixed flow and working pressure of 25 to 50 cm H(2)O, with a bag-valve device with respect to safety, efficiency, and efficacy when used by professionals. We conducted a prospective, controlled, caregiver-blind single center study. ...

BACKGROUND: Functional mitral valve regurgitation plays a key role in the symptomatic severity and progression of heart failure. In an ovine model of dilated cardiomyopathy, we examined the chronic functional consequences of mitral regurgitation reduction using a recently developed novel percutaneous mitral annular reduction (PMAR) device. METHODS AND RESULTS: Fourteen ...

OBJECTIVE: There is little scientific basis for guidance in selecting the optimal valve for the treatment of normal pressure hydrocephalus. The aim of this study was to determine the programmable valve opening pressure setting that would result in a slight reduction in intracranial pressure (ICP) after a ventriculoperitoneal shunt is ...

The aim of this study was to assess the impact of stroke volume (SV) on mitral annular velocities derived from tissue Doppler imaging (TDI). To this end, conventional echocardiographic variables and TDI derived mitral annular velocities (S', E', A') were obtained in 14 patients (pts) with increased SV (due to ...

Several aspects of mechanical heart valve cavitation, in particular of "severe" vapor cavitation, have been investigated in order to describe the phenomenon of cavitation itself and to classify various mechanical heart valves with respect to their tendency to cavitation. Furthermore, following the results of the measurements, a model for determination ...

The aim of the present study was to assess the association between invasive PWV (pulse wave velocity), serum levels of MMPs (matrix metalloproteinases) and the echocardiographic severity and calcification score of degenerative AS (aortic stenosis). We enrolled 30 patients (16 males; age, 61.3+/-8.2 years) diagnosed with degenerative AS and an ...

Measurement of mitral valve area is still a challenge for the echocardiographers. Each method has its own limitations. In this study we assessed a different method and compared it with the other methods. The study included 50 consecutive patients with mitral stenosis. The reference method was planimetry. The suggested method ...

BACKGROUND: Cutting anterior mitral leaflet second-order chordae has been proposed for repair in ischemic mitral regurgitation (IMR). We examined the efficacy of such chordal cutting in preventing acute IMR. METHODS AND RESULTS: Six sheep underwent radiopaque marker placement (left ventricle, mitral annulus, papillary muscles [PMs], and leaflets). The largest second-order ...

OBJECTIVE: Vagus nerve stimulators and programmable shunt valves are used in the operative care of epilepsy and hydrocephalus, respectively. Both devices use magnetic fields to activate and program their various settings and functions. The authors conducted several ex vivo trials to better elucidate any interplay between the two systems. METHODS: ...

A high-pressure (> 3 MPa) on-chip injector has been developed for microchip applications including HPLC. The mechanical injector is implemented using in situ photopolymerization of fluorinated acrylates inside wet-etched silica microchips. The injector allows reproducible injections as small as 180 pL with < 250 ms duration. The injector operated robustly ...

We report a case of a 29-year-old male, who during workup of hypertension was found to have a malignant primary paraganglioma of the heart. The tumor arose from the site of the aortopulmonary window and right ventricular outflow tract (RVOT) and was removed with the aid of cardiopulmonary bypass. Reconstruction ...

In vitro testing of biological heart valves requires pressure and flow waveforms closely simulating natural conditions, which are mainly influenced by the characteristics of the vascular system. Simulation of the arterial function in artificial circulations was mostly performed by the useful Windkessel model but sometimes failed by generating inadequate systolic ...

OBJECTIVE: This retrospective study examined whether changes in ventricular volume correspond with changes in adjustable valve pressure settings in a cohort of patients who received shunts to treat idiopathic normal pressure hydrocephalus. We also examined whether these pressure-volume curves and other patient variables would co-occur with a positive clinical response ...

We sought to determine the hemodynamic performance of the Carpentier-Edwards Perimount pericardial valve in the mitral position. We reviewed the Doppler echocardiographic data on 189 patients (110 women; 68 +/- 12 years of age) who were implanted with this valve (7.6 days +/- 13 postoperatively) at our institution between September ...

High mean left atrial pressure (MLAP) due to canine degenerative mitral valve disease is associated with clinically relevant morbidity and mortality. The ability to noninvasively measure MLAP would assist in the diagnosis and treatment of disease. Doppler echocardiography allows measurement of early transmitral blood flow (E) and the velocity of ...

BACKGROUND: All indices of aortic stenosis (AS) rely on measurements of mean transvalvular pressure gradient (DeltaP) and flow rate. Because the gradient is reversed during late ejection, the late systolic left ventricular (LV)-aortic pressure crossover may be an erroneous landmark of end-ejection. The aortic incisura should be a better reference ...

Biologically active heart valves (tissue engineered and recellularized tissue-derived heart valves) have the potential to offer enhanced function when compared to current replacement value therapies since they can possibly remodel, and grow to meet the needs of the patient, and not require chronic medication. However, this technology is still in ...

Physiologists and cardiologists estimate peak transvalvular pressure gradients (DeltaP) by Doppler echocardiographic imaging of peak flow velocities using the simplified Bernoulli relationship: DeltaP (mm Hg) = 4V(2) (m/s). Because left ventricular filling is initiated by mechanical suction, V can be predicted by the motion of a simple harmonic oscillator by ...