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Three-dimensional cross-sectional velocity distribution in the ascending aorta in cardiac patients
P Kvitting1, I Hessevik, K Matre
1Surgical Research Laboratory, Department of Surgery, University of Bergen, Haukeland Hospital, Norway.
Insights
Blood flow in the ascending aorta shows significant individual variation, with peak velocities often posterior. Reliable cardiac output estimates require large sampling volumes due to irregular flow patterns.
Area of Science:
- Cardiovascular Physiology
- Medical Imaging
- Hemodynamics
Background:
- Ascending aorta velocity distribution is crucial for cardiac output measurement, valve function assessment, and prosthetic valve evaluation.
- Understanding normal flow patterns is essential for diagnosing and managing cardiovascular conditions.
Purpose of the Study:
- To investigate the detailed spatial distribution of axial blood velocities in the human ascending aorta.
- To map flow patterns across a near-complete cross-section of the aorta lumen in a time-continuous manner.
Main Methods:
- Utilized pulsed Doppler ultrasound with an intraluminal probe (1 mm, 10 MHz) and a position-sensitive device.
- Measured blood velocities in the ascending aorta of 10 patients undergoing open-heart surgery with healthy aortic valves.
- Mapped velocities 6-8 cm above the aortic valve.
Main Results:
- Peak systolic flow was skewed and irregular, with maximum velocity typically located posteriorly.
- A positive correlation (r=0.854, P<0.002) was found between maximum skewness slope and stroke volume.
- Significant retrograde flow occurred in late systole/early diastole in the left posterior aorta; velocity patterns varied individually and lacked symmetry.
Conclusions:
- Ascending aorta velocity distribution exhibits considerable individual variation and lacks plane symmetry.
- Accurate mean velocity estimation necessitates large sampling volumes.
- Findings have implications for cardiac output calculations and prosthetic valve assessment.
Abstract:
Knowledge of the distribution of velocities across the ascending aorta is important for measurements of cardiac output; for understanding the function of normal and diseased valves and for the evaluation of prosthetic valves. The aim of this study was to investigate, in detail, the spatial distribution of axial velocities in the human ascending aorta, covering a nearly complete cross-section of the lumen in a time continuous modus. During open-heart surgery, blood velocities in the ascending aorta were mapped in 10 patients. All patients had aortic valves with no significant clinical evidence of disease. Pulsed Doppler ultrasound technique was used to measure blood velocity using an intraluminal probe with a 1 mm, 10 MHz crystal connected to a position-sensitive device. The distribution of blood velocity in the aorta 6-8 cm above the valve was characterized by a skewed and irregular peak systolic flow, with maximum velocity posteriorly. There was a positive correlation (r=0.854, P<0.002) between the maximum skewness slope and the stroke volume. Significant retrograde flow was recorded in all patients in the left posterior part of aorta in late systole and early diastole. The rotation of the point of maximal velocity was anticlockwise in six patients, clockwise in three and alternating in one. The present study shows that there is a considerable individual variation in the velocity distribution in the ascending aorta, with no plane symmetric features, and that large sampling volumes are required for reliable estimates of mean velocity.