Enhanced echocardiographic assessment of intracardiac flow in congenital heart disease.

BACKGROUND: 4D flow magnetic resonance imaging (4D flow MRI) can assess and measure the complex flow patterns of the right ventricle (RV) in congenital heart diseases, but its limited availability makes the broad application of intracardiac flow assessment challenging. Color Doppler imaging velocity reconstruction from conventional echocardiography is an emerging alternative, but its validity against 4D flow MRI needs to be established. OBJECTIVE: To compare intracardiac flow parameters measured by color Doppler velocity reconstruction (DoVeR) against parameters measured from 4D flow MRI. METHODS: We analyzed 20 subjects, including 7 normal RVs and 13 abnormal RVs (10 with repaired Tetralogy of Fallot, and 3 with atrial-level shunts). Intracardiac flow parameters such as relative pressure difference, vortex strength, total kinetic energy, and viscous energy loss were quantified using DoVeR and 4D flow MRI. The agreement between the two methods was determined by comparing the spatial fields and quantifying the cross-correlation and normalized difference between time-series measurements. RESULTS: The hemodynamic parameters obtained from DoVeR and 4D flow MRI showed similar flow characteristics and spatial distributions. The time evolutions of the parameters were also in good agreement between the two methods. The median correlation coefficient between the time-series of any parameter was between 0.87 and 0.92, and the median L2-norm deviation was between 10% to 14%. CONCLUSIONS: Our study shows that DoVeR is a reliable alternative to 4D flow MRI for quantifying intracardiac hemodynamic parameters in the RV.

Assessment of Cavitation Intensity in Accelerating Syringes of Spring-Driven Autoinjectors.

PURPOSE: Cavitation is an undesired phenomenon that may occur in certain types of autoinjectors (AIs). Cavitation happens because of rapid changes of pressure in a liquid, leading to the formation of small vapor-filled cavities, which upon collapsing, can generate an intense shock wave that may damage the device container and the protein drug molecules. Cavitation occurs in the AI because of the syringe-drug relative displacement as a result of the syringe's sudden acceleration during needle insertion and the ensuing pressure drop at the bottom of the container. Therefore, it's crucial to analyze the potential effect of cavitation on AI. The goal of the current study is to investigate the effects of syringe and AI design parameters such as air gap size, syringe filling volume, fluid viscosity, and drive spring force (syringe acceleration) on the risk and severity of cavitation. METHODS: A model autoinjector platform is built to record the syringe and cavitation dynamics which we use to estimate the cavitation intensity in terms of extension rate and to study the effects of design parameters on the severity of cavitation. RESULTS: Our results show the generation of an intense shock wave and a high extension rate upon cavitation collapse. The induced extension rate increases with syringe acceleration and filling volume and decreases with viscosity and air gap size. CONCLUSION: The most severe cavitation occurred in an AI device with the larger drive spring force and the syringe of a smaller air gap size filled with a less viscous fluid and a larger filling volume.

Assessment of left ventricular diastolic function using 4-dimensional phase-contrast cardiac magnetic resonance.

OBJECTIVES: Phase-contrast magnetic resonance imaging can potentially assess the dynamics of left ventricular (LV) early diastolic filling. METHODS: Fifteen participants underwent phase-contrast magnetic resonance imaging on a 1.5-T whole-body Avanto scanner (Siemens Healthcare, Erlangen, Germany). Left ventricular intracavitary velocities were measured in 3 orthogonal directions. Imaging parameters included a repetition time of 92.45 milliseconds, an echo time of 2.88 milliseconds, a flip angle of 30 degrees, and a velocity-encoding range of 100 to 150 cm/s. RESULTS: The color vector analysis provided a visual assessment of LV diastolic flow. In normal subjects, there was rapid organized early diastolic flow that extended from the mitral valve to the LV apex. In patients with LV diastolic dysfunction, organized high-velocity flow stopped in the mid-left ventricle. CONCLUSIONS: Four-dimensional phase-contrast cardiovascular magnetic resonance can differentiate between normal and abnormal diastolic flow propagation within the left ventricle.