No-react* anticalcification tissue treatment results with stentless heart valves in two adolescents

AbstractJ Thorac Cardiovasc Surg 1999;117:1222-

Spontaneous Echocardiographic Contrast (SPE) – An In-Vitro Study of the Impact of Cardiac-Output, Left-Ventricular DP/DT and Temperature

Recent clinical studies have indicated echocardiographic observations of gaseous emboli in the left ventricle (LV) and atrium (LA) during studies in patients with mechanical heart valves (MHV) in the mitral position. These reports have shown that the intensities of these gas bubbles in elderly patients are less than those in younger patients. These facts may indicate a correlation between formation of the gas bubbles and the LV functions. The goal was to utilize our pulse duplication system to create the corresponding physiologic conditions and to understand the impact of these parameters on SpE formation

Mitral mechanical heart valves: in vitro studies of their closure, vortex and microbubble formation with possible medical implications

Objective: The goal of the present work was to create the closest possible in vitro fluid dynamic environment in which prosthetic mitral valves in the patients’ hearts function, in order to demonstrate whether microbubbles are generated, and if yes, under what conditions and at which stage of the cardiac cycle. Microbubbles were observed in the blood of patients with mitral mechanical heart valves (MHV) by means of echocardiography. The phenomenon, often referred to as high-intensity transient signals (HITS), appears as bright, intense, high-velocity and persistent echoes detected by Doppler echocardiography at the instant of valve closure. The question is no longer whether microbubbles are being formed in patients with MHV. as an inherent aspect of their design, but rather how they evolve and when. The answer to this question was the objective of the present paper. Methods: Hemodynamic conditions in which microbubbles were observed in patients with mitral MHV were simulated in our laboratory. We were able to describe the bubble formation process, as one consisting of nucleation and microbubble growth. While mild growth of nuclei is governed by diffusion, extensive growth of microbubbles is controlled by pressure drop during deceleration of the leaflets on the housing on the atrial side of the mitral MHV. Results: The present study has shown that bubbles form in a fluid at the instant of closure of mechanical valves. The formation of vortices after valve closure, although clinically not yet observed, was also demonstrated in the present in vitro studies. We believe that impact of such vortices on the endothelial layer of the left atrial wall may have clinical significance. These two phenomena were not observed in bioprosthetic valves. Conclusions: As demonstrated, there exist two distinct phenomena characteristic of mechanical heart valves, which take place during valve closure, namely, that of vortex formation and that of microbubble growth. Both phenomena may have far reaching clinical implications

Pseudoaneurysm of the mitral-aortic intervalvular fibrosa following aortic valve replacement - diagnosis and dynamic evaluation with multidetector CT and transesophageal echocardiography

Sixteen-slice multidetector CT findings of a pulsatile pseudoaneurysm of the mitral-aortic intervalvular fibrosa, in a woman following aortic valve replacement, are presented. Multidetector CT depicted the pseudoaneurysm and enabled dynamic evaluation of its lumen through the cardiac cycle, documenting expansion during systole and almost complete collapse during diastole. This case illustrates the capabilities of multidetector cardiac CT in the evaluation of aortic valve pathology

Can regurgitant flow damage the left atrial endothelium in patients with prosthetic mechanical heart valves?

Background and aim of the study: Previous in-vitro studies of mechanical heart valves (MHVs) in the closed position demonstrated the formation of regurgitant flows, with bubbles and jets forming vortices during each systole. The study aim was to determine whether the regurgitant flow observed in patients with MHVs can damage the left atrial endothelium, due to shear stresses exerted on the endothelial layers. This objective has been accomplished by appropriate in-vitro simulation experiments. Methods: In these experiments, leakage flow through several commercial MHVs was investigated. The geometry of the set-up closely resembled that of the left atrial anatomy. Water was forced through the slit of a closed MHV and directed toward the hemispherical cup coated with fluorescent paint. The flow field between the valve and the cup was photographed using high-speed videography, from which local velocities were measured, using digital particle imaging velocimetry. Qualitative damage to the surface of the cup was assessed from the amount of fluorescent paint removed from the cup. Results: The experimental results and calculations indicated that flows through the gaps of the closed valves were sufficient to generate strong vortices, with velocities near the atrial wall in the range of 0.5 to 4.0 m/s, depending on the valve. This led to high shear stresses on the left atrial wall, which far exceeded physiologically acceptable levels. Conclusion: The calculated shear stresses exceeded by orders of magnitude the maximum physiologically tolerated stresses. This suggests that shear stresses associated with regurgitant jets in MHVs may damage the endothelial cells, leading to the activation of the inflammatory reaction, enhanced procoagulation, platelet activation and aggregation, and mechanical cell denudation

Bubble Formation on St. Jude Medical Mechanical Heart Valves: An In-Vitro Study

Background and aim of the study: Bubble formation in blood, which has been observed during valve closure in patients with mechanical heart valves (MHVs), raises concern because of cognitive changes and potential activation of blood elements associated with thromboembolic phenomena. Bubble formation in the vicinity of MHVs has been described previously; the present in-vitro study was undertaken to quantitate bubbles leaving the heart and entering the systemic circulation, and to gain a closer perspective of this phenomenon and its potential clinical implications. Methods: Experiments were performed in a left heart pulsed flow simulator with 29 mm mitral and 23 mm aortic St. Jude Medical MHVs; mitral and aortic bioprosthetic valves were used as controls. De-aerated water was pumped through the left heart pulsed flow simulator at a fixed rate of 70 beats/min and at different cardiac outputs. Bubble numbers and sizes were monitored photographically at the simulator exit. Results: Numbers of bubbles per frame generated in MHVs in the mitral position ranged from 8 to 14 at cardiac outputs of 3 to 6.5 l/min; this corresponded to gas volumetric flow rates of 330 to 830 mm^3/min. The number of bubbles per frame for the aortic MHV was 3 to 7, reflecting the less severe flow conditions and milder valve closure impact. The diameter of bubbles generated by the mitral valve was almost uniform (0.45 mm), while bubble diameters in the aortic valve ranged from 0.36 to 0.69 mm. Conclusion: Bubble formation was found to be an inherent flaw of the present generation of MHVs, and this problem should be addressed in future valve designs

Spontaneous Echocardiographic Contrast (SPE): Mechanical Heart Valve Closure and Extraction of Bubbles in Gas-Saturated Solutions – An In-Vitro Study

Recent clinical reports have indicated echocardiographic observations of bright mobile echoes in the left ventricle (LV) and in the left atrium (LA) during post-operative studies in patients with mechanical heart valves (MHV) in the mitral position. Depending on their Doppler spectrum signal intensities, some of these echoes have been categorized as gaseous emboli (GE). Our goal was to utilize the most recent innovations in heart pulsed flow simulator system designs combined with ultrasound and high-speed laser video flow imaging methods to understand the formation of gas microbubbles in a closure mechanism