Page 165 - Feline diagnostic imaging

166 10 Normal Cardiovascular Imaging
10.5 M-Mode

10.5.1 Right and Left Ventricles
M‐mode tracing of the RV and LV, aorta and LA, and the
E‐point septal separation (EPSS) is crucial for diagnosis
and treatment of cardiovascular disease. M‐mode of the RV
and LV is routinely performed from a right parasternal
short axis view. Although a right parasternal longitudinal
imaging plane can also be used for performing M‐mode, it
may be technically more difficult to obtain the same imag-
ing plane when performing sequential examinations. The
short axis view may lessen the variability in measurements.
In addition, measurement variability has been documented
Figure 10.12 A right parasternal long axis four-chamber view when measurements obtained from the short axis are com-
centered on the right atrium (RA) and left atrium (LA).
pared to those taken from the longitudinal axis [2]. It is best
to stay with one method of measurement as they are not
interchangeable and add variability and potential inaccu-
racy in evaluation of measurements over time, especially if
progression of disease or response to therapy is being
assessed.
The key to obtaining a diagnostic M‐mode study is to first
obtain a right parasternal short axis view at the level of the
papillary muscles with the right ventricular free wall
(RVFW) and chamber depicted in the near field. If you are
seeing the IVS and RVFW as one structure (Figure 10.15),
with no identifiable right ventricular lumen, move crani-
ally one intercostal space while continuing to hold the
probe perpendicular to the thoracic wall. If the septum is
still not separated from the RVFW, then move the probe
Figure 10.13 A right parasternal long axis four-chamber view slightly more dorsally. Offsetting the right ventricular
showing measurement of the right atrium (RA) and left atrium (LA). chamber and septum enables you to properly measure the

Figure 10.14 A right parasternal long axis five-chamber view Figure 10.15 In this image of the right and left ventricle (LV),
shows the right atrium (RA) in the near field. In the far field, the from a right parasternal short axis view, the right ventricular
left atrium (LA), left ventricle (LV), and left ventricular outflow free wall (RVFW) is in close proximity to the interventricular
tract (LVOT) can be assessed on the 2D image. This imaging septum (IVS). If M-mode is attempted at this level, the right
plane is useful for evaluating the LVOT for narrowing or focal ventricular free wall and the interventricular septum may be
thickening of the interventricular septum. mistakenly measured together.