Abstract
TTE evaluation of the heart valves requires both quantification of the severity of the pathology and identification of the underlying mechanism. This information will determine if surgical intervention is warranted and will guide the surgical decision as whether to repair or replace the diseased valve.
TTE evaluation of the heart valves requires both quantification of the severity of the pathology and identification of the underlying mechanism. This information will determine if surgical intervention is warranted and will guide the surgical decision as whether to repair or replace the diseased valve.
Aortic Valve
The normal AV is composed of three leaflets: right, left and non-coronary cusps. The normal AV area is 2.5–4.0 cm2. It is evaluated by TOE using long- and short-axis mid-oesophageal views and with Doppler in the deep transgastric view.
Aortic Stenosis
The most common aetiologies for AS are trileaflet AV calcification, bicuspid AV with calcific changes and rheumatic valve disease. A bicuspid AV is present in 1–2% of the general population and typically results from fusion of the right and left coronary cusps (80%) or the right and non-coronary cusps (20%). Rheumatic AS typically displays commissural fusion.
TOE assessment of severity (Table 34.1) involves measuring velocities across the valve to calculate mean and peak pressure gradients. The AV area (AVA) can be derived using the continuity equation once the LVOT area and peak velocity (LVOTVEL) have been determined:
The dimensionless index (DI) is more frequently used to grade the severity of AS, as it removes errors introduced during the LVOT area calculation (Figure 34.1):
Figure 34.1 CMD spectral display, showing a double envelope, used to calculate the DI
Aortic Regurgitation
AR can be classified according to its mechanism (Figure 34.2), which determines surgical repair or replacement. The severity of AR is based on qualitative and quantitative methods (Table 34.2). Under general anaesthesia, with reduced LV afterload, the severity of AR is often underestimated when determined by qualitative methods; quantitative techniques are largely unaffected by the changes in loading conditions.
Table 34.2 Grading severity of AV regurgitation
| Mild | Moderate | Severe | |
|---|---|---|---|
| Qualitative | |||
| Pressure half-time (ms) | >500 | 200–500 | <200 |
| PWD aortic diastolic flow reversal | Brief | Intermediate | Holodiastolic |
| Semi-quantitative | |||
| Jet width/LVOT diameter (%) | <25 | 25 – 65 | >65 |
| Vena contracta width (mm) | <3 | 3 – 6 | >6 |
| Quantitative | |||
| EROA (cm2) | <0.1 | 0.1 – 0.3 | >0.3 |
| Regurgitant volume (ml) | <30 | 30 – 60 | >60 |
| Regurgitant fraction (%) | <30 | 30 – 50 | >50 |
EROA, effective regurgitant orifice area.
Mitral Valve
The MV complex is comprised of the anterior and posterior valve leaflets, the annulus, the chordae tendinae and the papillary muscles. The LV myocardium also plays an important role in normal MV function. The MV is assessed in the mid-oesophageal views from 0° to 130° and in the transgastric basal views. 3D imaging of the MV is now standard for complex lesions (Figure 34.3).
Figure 34.3 3D en-face view of the MV, showing prolapse of segments P2 and P3. A: anterior; P: posterior.
Mitral Regurgitation
The mechanism of MR is divided into primary MR, where there is a leaflet abnormality, and secondary MR, due to annular dilatation or LV dysfunction, and is based on the Carpentier classification (Figure 34.4). Primary causes include myxomatous degeneration, fibroelastic deficiency, endocarditis, rheumatic disease and congenital abnormalities. Elucidating the mechanism will influence the surgical management and determine if valve repair is feasible and the type of repair technique.
Qualitative and quantitative methods are available to assess the severity of MR (Table 34.3). Quantitative methods are less affected by loading conditions and are recommended whenever feasible.
| Mild | Moderate | Severe | |
|---|---|---|---|
| Qualitative | |||
| CFD jet area | Small and narrow | Variable | Large (>50% of LA) |
| Semi-quantitative | |||
| Vena contracta width (mm) | <3 | 3–7 | >7 |
| PWD pulmonary vein flow | S-wave dominance | S-wave blunting | S-wave reversal |
| Quantitative | |||
| EROA (cm2) | <0.2 | 0.2–0.4 | >0.4 |
| Regurgitant volume (ml) | <30 | 30–60 | >60 |
| Regurgitant fraction (%) | <30 | 30 – 50 | >50 |
EROA, effective regurgitant orifice area; S, systolic.
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