Abstract
Ventricular dysfunction is associated with increased cardiovascular morbidity and mortality after both cardiac and non-cardiac surgery. Traditionally, invasive pressure monitoring has been used to make inferences regarding ventricular function. However, the relationship between pressure and organ perfusion may be affected by many variables in the dynamic intraoperative environment. TOE has the advantage of real-time visualization of ventricular filling, contractility and ischaemia. As such, TOE is now considered to be the ‘gold standard’ intraoperative monitor of ventricular function.
Ventricular dysfunction is associated with increased cardiovascular morbidity and mortality after both cardiac and non-cardiac surgery. Traditionally, invasive pressure monitoring has been used to make inferences regarding ventricular function. However, the relationship between pressure and organ perfusion may be affected by many variables in the dynamic intraoperative environment. TOE has the advantage of real-time visualization of ventricular filling, contractility and ischaemia. As such, TOE is now considered to be the ‘gold standard’ intraoperative monitor of ventricular function.
Left Ventricular Systolic Function
Fractional Shortening
Fractional shortening (FS) can be measured using either M-mode or 2D imaging. Measurements of internal LV dimensions are taken at end-diastole (LVIDd) and end-systole (LVIDs) from the transgastric two-chamber view at a level of the tips of the papillary muscles. The FS is then calculated as:
A normal value is 25–42%. However, as the FS is derived from linear measurements, it becomes inaccurate in the presence of regional wall motion abnormalities (RWMAs).
Ejection Fraction
The LV ejection fraction (LVEF) is derived from measurements of the LV end-diastolic volume (LVEDV) and end-systolic volume (LVESV):
The LVEDV and LVESV may be obtained from 2D images, using the biplane method of discs (modified Simpson’s method, Figure 33.1) or from reconstruction of 3D imaging. A normal LVEF is 52–74%.
Figure 33.1 Modified Simpson’s method to calculate the LVEF using mid-oesophageal four-chamber and two-chamber views.
Strain Imaging
Strain is defined as the change in length of an object (L1) compared to its baseline (L0):
Myocardial deformation analysis typically utilizes speckle-tracking echocardiography to assess the change of LV myocardial length from end-diastole to end-systole to derive the global longitudinal strain (GLS, Figure 33.2). A normal LV GLS is –20%.
Figure 33.2 Strain imaging of LV systolic function. The wavy lines at bottom represent strain from different LV regions (walls).
Regional Systolic Function
TOE is a highly sensitive tool for detecting myocardial ischaemia: RWMAs are usually present prior to ECG evidence of ischaemia. The 17-segment model is used to assess the regional LV function (Figure 33.3). Each myocardial segment is analyzed and scored according to both wall motion and thickening – see Table 33.1.
(A) Mid-oesophageal and TG views at basal, mid-papillary and apical levels, with anterior (A), anteroseptal (AS), inferoseptal (IS), inferior (I), inferolateral (IL) and anterolateral (AL) walls.
