A high-resolution method of spectral analysis, of the class generally called "maximum entropy method," was used in a study of aortic porcine valve closing sounds in 37 patients (ages 19 to 76). Spectra from 27 normal xenografts, implanted from 2 weeks to 61 months previously, were characterized by a dominant frequency peak, Fl, at 89 + 15 Hz (mean + SD), with a lower amplitude peak, F2, at 154 ...

OBJECTIVE The aims of this study were to compare opening and closing angles of normally functioning mechanical aortic valves measured on dual-source computed tomography (CT) with the manufacturers' values and to compare CT-measured opening angles according to valve function. MATERIALS AND METHODS A total of 140 patients with 10 different types of mechanical aortic valves, who underwent dual-s...

Phonocardiography is-often more valuable than electrocardiography in timing mechanical events in the cardiac cycle. This study shows that the opening and closing of the mitral valve are related to the length of the previous heart cycle as demonstrated by the variations occuring in aluricular fibrillation. These variations in valve action are controlled by the pressure gradient between left auri...

In this study, the operating processes of a four-stroke diesel marine engine from intake valve closing (IVC) to exhaust opening (EVO) at numerous different charge air conditions were simulated with AVL FIRE code. The CFD models validated shop-test technical data. results showed that increasing pressure without cooling decreased actual amount supplied cylinder. As result, combustion process was ...

Functional mitral regurgitation (MR) is a common finding in patients with global left ventricular (LV) dilatation and dysfunction. In these patients, the mitral leaflets are structurally normal and leaflet coaptation failure results from an imbalance between valve closing forces and valve tethering forces. Impaired LV contractility, global LV dyssynchrony, and reduced mitral annulus systolic co...

Auscultatory and echocardiographic and phonocardiographic studies were performed on 26 patients who had a total of 11 Lillehei-Kaster, 16 Björk-Shiley, and 18 St Jude heart valve prostheses functioning normally in the aortic or mitral positions or both. With all types and positions of prostheses a distinct closing sound was always detected. It was frequently heard in two parts which, according ...

Abstract Cylinder deactivation is well-known in spark-ignited (SI) engines and compression-ignited (CI) engines. The major reason why the efficiency of these decreased at part load due to flow restriction intake system caused by partially closing throttle valves, which causes increased pumping losses. In order resolve this issue, cylinder can be implemented SI with four cylinders developing a s...

During mitral valve surgery right pulmonary veins injury, subsequent to excessive traction (for better exposure of the mitral apparatus), is often unavoidable. This is more likely in patients with small left atrium. This common complication may cause severe intraoperative bleeding, while its surgical repair may lead to complications such as late stenosis or obstruction of the pulmonary veins. T...

Numerical analysis of the aortic valve has mainly been focused on the closing behaviour during the diastolic phase rather than the kinematic opening and closing behaviour during the systolic phase of the cardiac cycle. Moreover, the fluid-structure interaction in the aortic valve system is most frequently ignored in numerical modelling. The effect of this interaction on the valve's behaviour du...