11.7.8 Mitral disease

 It is not uncommon for mitral stenosis to be associated with some degree of insufficiency. It is important for the anaesthetist and intensivist to determine which condition is predominant as this will determine the haemodynamic behaviour of the patient. In general, stenosis is more restrictive than insufficiency because there is less room for adaptation; if significant, it dominates the clinical picture [1,2]. In addition to specific quantitative measurements, the silhouette of the 4 chambers shows the remodelling undergone by the heart and makes it possible to define the main component (Figure 11.99).

• If stenosis predominates, the LA is huge and the ventricle disproportionately small; spontaneous contrast is often absent as a result of mixing in the LA by the MI. The interatrial septum permanently bulges into the ventricle.
• If the insufficiency is predominant, the LV is dilated and hypertrophied; the LA is less voluminous, the interatrial septum bulges into the RV only in systole.

The volume regurgitated in systole increases the volume that must pass through the valve in diastole. This excess increases the gradient and leads to an overestimation of the degree of stenosis by the half-pressure time measurement. On the other hand, the combination of MI and MS keeps LV dimensions in the intermediate range and limits ventricular remodelling: the presence of MI reduces the risk of LV hypotrophy and the presence of MS reduces the risk of dilatation. This is particularly beneficial in patients weaning off ECC. However, the degree of haemodynamic disturbance is greater than for the same degree of severity in isolated pathology; therefore, the indication for surgery is generally based on the patient's symptoms during exercise rather than on calculated values [2].

 Figure 11.99: Comparative silhouettes of mitral regurgitation and stenosis. In the combination of the two conditions characteristic of mitral disease, the predominant condition is clearly identified by the general appearance of the left cavities.

 

Hemodynamics sought in mitral valve disease

High preload RAS ↑ if stenosis predominates, RAS ↓ if insufficiency predominates Normal rate Maintain sinus rhythm Inotropic support in ventricular dysfunction (Dts > 2.5 cm/m2, Dtd > 4 cm/m2) Pulmonary vasodilatation (PAR↓) Well tolerated positive ventilation

 

 

  © CHASSOT PG, BETTEX D, August 2011, last update November 2019