Since the total LV stroke volume can be calculated from planimetry of the LV end-diastolic and end-systolic contours (Figure 1), and the aortic forward flow can be calculated from phase-contrast CMR at the aortic root (Figure 4), the difference between these values
will be equal to the mitral insufficiency volume. This technique provides accurate calculations in the setting of isolated mitral insufficiency and coexisting aortic insufficiency, since aortic insufficiency increases both the LV stroke volume and aortic forward flow but leaves the difference between the two values unaffected. Selected validation Selleck BI-6727 studies are shown in Table 1. Calculation of regurgitant volumes Inhibitors,research,lifescience,medical by CMR also has low study variability as is demonstrated in several studies evaluating reproducibility of regurgitant volume assessment (Table 2). This makes CMR an optimal technique for serial assessment of mitral insufficiency in patients who are managed Inhibitors,research,lifescience,medical expectantly. Table 1 Mitral
insufficiency quantification: selected validation studies.14, 15, 17 Table 2 Mitral insufficiency quantification: reproducibility.14-16 Figure 5. Example of the method used to calculate mitral regurgitant volume (see text for details). AO: aorta; LA: left atrium; LV: left ventricle; EDV: Inhibitors,research,lifescience,medical end diastolic volume; ESV: end systolic volume; MR: mitral regurgitation Aortic Stenosis There are cases in which parallel alignment of the Doppler transducer Inhibitors,research,lifescience,medical with the aortic flow cannot be obtained, making it technically difficult to record the highest aortic transvalvular velocity with Doppler. In that regard, CMR is advantageous given its capability of slice selection at any angle and its ability to measure the velocity of the transaortic flow. The CMR SSFP cine images have excellent signal-to-noise ratio and spatial resolution that is better than transthoracic echocardiography
(TTE) and comparable to transesophageal echocardiography (TEE) for anatomic aortic valve assessment (planimetry Inhibitors,research,lifescience,medical and number of cusps).7 There are well-validated methods to assess aortic stenosis severity with CMR (Table 3), and it offers a wider field of view than TTE and DNA ligase TEE. En-face imaging of the aortic valve and the use of phase-contrast velocity mapping make it possible to determine the severity of the aortic stenosis by peak velocity.8 These assessments are done without the use of gadolinium-based contrast. Table 3 Aortic stenosis quantification: selected validation studies.18-21 Quantifying the Severity of Aortic Stenosis Phase-contrast velocity mapping makes it possible to measure the flow of interest by calculating a shift of the precession between the stationary protons and protons moving in a magnetic field. The magnitude of this phase shift is proportional to the velocity of interest. When the velocity assessed is higher than the velocity encoded in that particular phase, aliasing occurs. The velocities must be sampled at 25 to 50 cm/s intervals.