Assessment of transmitral and left atrial appendage flow rate from cardiac 4D-CT

Abstract

Background Cardiac time-resolved CT (4D-CT) acquisitions provide high quality anatomical images of the heart. However, some cardiac diseases require assessment of blood flow in the heart. Diastolic dysfunction, for instance, is diagnosed by measuring the flow through the mitral valve (MV), while in atrial fibrillation, the flow through the left atrial appendage (LAA) indicates the risk for thrombus formation. Accurate validated techniques to extract this information from 4D-CT have been lacking, however. Methods To measure the flow rate though the MV and the LAA from 4D-CT, we developed a motion tracking algorithm that performs a nonrigid deformation of the surface separating the blood pool from the myocardium. To improve the tracking of the LAA, this region was deformed separately from the left atrium and left ventricle. We compared the CT based flow with 4D flow and short axis MRI data from the same individual in 9 patients. Results For the mitral valve flow, good agreement was found for the time span between the early and late diastolic peak flow (bias: <0.1 s). The ventricular stroke volume is similar compared to short-axis MRI (bias 3 ml). There are larger differences in the diastolic peak flow rates, with a larger bias for the early flow rate than the late flow rate. The peak LAA outflow rate measured with both modalities matches well (bias: −6 ml/s). Conclusions Overall, the developed algorithm provides accurate tracking of dynamic cardiac geometries resulting in similar flow rates at the MV and LAA compared to 4D flow MRI.

Elevated atrial blood stasis in paroxysmal atrial fibrillation during sinus rhythm: a patient-specific computational fluid dynamics study

“…The radiation exposure from CT can be substantially reduced with advanced dose modulation (13). Although CT does not provide inherent motion information, we previously showed that it allows for the extraction of the endocardial wall motion and that flow rates calculated from those data agree well with measurements from 4D flow MRI (14). Thus, time-resolved cardiac CT is an excellent tool to investigate the left atrial shape and function.…”

“…For this, the endocardium of the LA and LV was segmented using ITK-SNAP version 3.8.0 ( www.itksnap.org ) ( 27 ) at the end diastolic time frame (0% RR) and the geometry was further processed with Ansys SpaceClaim version 2019 R3 (Ansys Inc, Canonsburg, PA 15317 USA). Then, the endocardial surface was deformed using a non-rigid iterative closed point algorithm to match threshold-based segmentations of the other 19 cardiac phases, as described previously ( 14 ). The approach yields similar flow rates as those obtained by 4D flow MRI ( 14 ).…”

“…Then, the endocardial surface was deformed using a non-rigid iterative closed point algorithm to match threshold-based segmentations of the other 19 cardiac phases, as described previously ( 14 ). The approach yields similar flow rates as those obtained by 4D flow MRI ( 14 ). The workflow of the process is visualized in Figure 1 .…”

Mechanisms and Prediction of Ischemic Stroke in Atrial Fibrillation Patients

“…Interestingly, first reports show that closing the LAA may improve the LA flow dynamics measured by four-dimensional magnetic resonance imaging [83]. Recently, LAA four-dimensional flow analysis has also been applied to cardiac CT, with similar outcomes to magnetic resonance imaging [84].…”

Impact of occluder device configurations in in-silico left atrial hemodynamics for the analysis of device-related thrombus

“…On the other hand, 4D flow MRI has a limited ability to capture rapid changes in blood flow dynamics and identify small or intricate flow features. An emerging alternative approach is the use of cardiac time-resolved CT (4D-CT), which offers better spatio-temporal resolution, but its validation is still in progress [22].…”