Normal Function
Video of normal cardiac function.
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Normal
History
47 year-old female was referred to cardiac MRI to evaluate the cardiac function.
Technique
Following the acquisition of sagittal, axial, aortic long axis localizers, a series of ECG-gated short axis FIESTA images are then prescribed perpendicular to the long-axis of the left ventricle. The planes for graphic prescription are shown schematically below.
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Long-axis views are then prescribed radially at 30-degree intervals off of a basal short axis image as shown below giving 2, 3 and 4-chamber radial images.
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Findings
Short axis FIESTA images show normal global and regional motion with appropriate myocardial thickening. Radial images (2, 3 and 4 chamber views) confirm normal wall motion.
Discussion
The wall-motion is assessed visually using the same principles applied to echocardiographic and nuclear ECG-gated images. Each segment’s motion and thickening are assessed. We use 16 segment model recommended by American Society of Echo to report the wall motion.
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Ventricular Function / Wall Motion is plotted on the 17 segment model bulls` eye:
- Normal: >50% thickening (end diastolic thickness is >50% of systolic), normal movement (coded in blue)
- Hypokinetic: <50% thickening, decreased movement (coded in green)
- Akinetic: no thickening, decreased or no movement (coded in yellow)
- Dyskinetic: no thickening, paradoxical movement (coded in red)
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Figure 1: 17-segment model
Measurements
The LV end-diastolic volume is calculated by tracing the endocardial surface of the LV at the end of diastole (Figure 2). LV End Diastolic dimension is measured at the highest level at which papillary muscles are visible (the 4th slice, Figure 2).
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Figure 2: LV End-diastolic volume traces.
The end-systolic volume is similarly calculated. Because the ventricle gets shorter longitudinally during systole, 1 less slice is traced for LVESV. In this particular case; because the longitudinal shortening of the LV during the systole was more pronounced, 2 less slices were traced (Figure 3). LV systolic dimension is measured at the same slice as the end-diastolic dimension was measured.
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Figure 3: LV End-systolic volume traces.
Stroke volume is the difference between the LVEDV and LVESV.
Ejection fraction is the ratio of the stroke volume to the LVEDV.
Fractional shortening is calculated as the ratio of LVEDD and LVESD.
Long-axis images provide important information about the LV apex, the mitral valve, and the left atrium. While it is possible to acquire many different long-axis orientations, three views are standard:
- Two-chamber view (2-Ch). The two-chamber view is helpful for evaluating the anterior and inferior walls of the left ventricle as well as the left atrial appendage.
- Four-chamber view (4-Ch). The four-chamber view is helpful for evaluating the septal and lateral walls of the left ventricle, the size and function of the right ventricle, and the tricuspid valve.
- Three-chamber view (3-Ch). The three-chamber view is helpful for assessing the anteroseptal and inferolateral walls of the left ventricle as well as the aortic valve.
