Multidimensional flow mapping can measure the paths, compartmentalization and kinetic energy changes of blood flowing into the LV, demonstrating differences of KE loss between compartments, and potentially between the flows in normal and dilated left ventricles.

The flow patterns in the human heart are complex and difficult to visualize using conventional two‐dimensional (2D) modalities, whether they depict a single velocity component (Doppler echocardiography) or all three components in a few slices (2D phase contrast MRI). To avoid these shortcomings, a temporally resolved 3D phase contrast technique was used to derive data describing the intracardiac velocity fields in normal volunteers. The MRI data were corrected for phase shifts caused by eddy currents and concomitant gradient fields, with improvement in the accuracy of subsequent flow visualizations. Pathlines describing the blood pathways through the heart were generated from the temporally resolved velocity data, starting from user‐specified locations and time frames. Flow trajectories were displayed as 3D particle traces, with simultaneous demonstration of morphologic 2D slices. This type of visualization is intuitive and interactive and may extend our understanding of dynamic and previously unrecognized patterns of intracardiac flow. Magn Reson Med 41:793–799, 1999. © 1999 Wiley‐Liss, Inc.

A conventional 3D phase contrast acquisition generates images with good spatial resolution, but often gives rise to artifacts due to pulsatile flow. 2D cine phase contrast, on the other hand, can register dynamic flow, but has a poor spatial resolution perpendicular to the imaging plane. A combination of both high spatial and temporal resolution may be advantageous in some cases, both in quantitative flow measurements and in MR angiography. The described 3D cine phase contrast pulse sequence creates a temporally resolved series of 3D data sets with velocity encoded data.

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Understanding cardiac blood flow patterns is important in the assessment of cardiovascular function. Three-dimensional flow and relative pressure fields within the human left ventricle are demonstrated by combining velocity measurements with computational fluid mechanics methods. The velocity field throughout the left atrium and ventricle of a normal human heart is measured using time-resolved three-dimensional phase-contrast MRI. Subsequently, the time-resolved three-dimensional relative pressure is calculated from this velocity field using the pressure Poisson equation. Noninvasive simultaneous assessment of cardiac pressure and flow phenomena is an important new tool for studying cardiac fluid dynamics.

Objective-To study the time course and underlying mechanisms of right heart filling after cardiac surgery.Design-A prospective observational study of adult patients undergoing cardiac surgery.Setting-Echocardiography laboratory of the Stanford University Medical Center.Patients-Twenty six patients (mean age 54-9) undergoing cardiac surgery were studied before and two days, one week, six weeks, and six months after cardiac surgery.Main outcome measures-Flow in the hepatic veins and superior vena cava, tricuspid and mitral annulus motion, signs of tricuspid regurgitation, and right ventricular size were assessed by echocardiography.Results-Right heart filling, expressed as the ratio of systolic to diastolic forward flow Doppler velocity integrals in the superior vena cava and by tricuspid annulus motion, decreased in parallel from before surgery baseline values of 3*5 (SD 3-1) and 21-9 (3-4) mm, respectively to 02 (01) and 8-1 (2-3) mm two days after operation. A gradual increase towards baseline values was noted after six months, to 1-4 (1-3) and 15.1 (2 3) mm respectively; however, these values were still significantly less than those before operation. Similar changes were seen in the hepatic venous flow pattern. The decrease in total tricuspid annulus motion was most pronounced in its lateral segment and the atrial component of the tricuspid annulus motion showed similar changes.Conclusions-The pronounced decrease in tricuspid annulus motion during the early postoperative period suggests right atrial and right ventricular dysfunction as mechanisms responsible for the early changes-seen. The progressive return to a normal venous filling pattern and the partial recovery of annular motion six months after operation further support the influence ofthe above mechanisms, as well as their resolution with time. The persistent flow abnormalities and compromised motion of the free aspects of the tricuspid annulus, however, suggest long-term tethering of the right heart walL Right heart filling, reflected in the pattern of systemic venous return, becomes abnormal in patients who undergo cardiac surgery supported by cardiopulmonary bypass.'-' These changes were first described as an alteration in jugular venous pulse contours and flow velocities from the normal dominant systolic flow to an equal or dominant diastolic flow.45 Recently we have shown, using intraoperative transoesophageal echocardiography, that the venous flow pattern is normal before cardiopulmonary bypass even with the pericardium fully opened, but becomes abnormal immediately after termination of cardiopulmonary bypass.6 A mechanical impediment to cardiac motion and a combination of abnormalities in right heart function were suggested as possible mechanisms for these changes immediately after cardiopulmonary bypass. The present study was undertaken to further elucidate the time course and underlying mechanisms of these changes through repeated observations before and during a six month period after operation. Patients and methods PATIENT POPULATION...