Valve prostheses

Echocardiographic evaluation of the function of valve prostheses has been and remains a difficult problem. These difficulties are connected with the following reasons: 1. the difference of many modifications of prostheses, which besides come in different sizes (in this connection, normal the values ​​of the pressure gradient on the aortic prosthesis vary from 12 to 30 mm Hg, and on the mitral – from 10 to 27 mm Hg. Art.); 2. The presence of a large number of acoustic artifacts that are difficult to distinguish from pathological echoes, especially in the area of ​​the ring. However, Doppler examination of the flow on prostheses and, especially, transesophageal echography, can provide valuable information in assessing their function. As a rule, the malfunction of the prosthesis is caused either by their stenosis (due to thrombosis, fibrosis, calcification, etc.), or failure (paraprosthetic fistulas, valvular insufficiency, etc.).

Since the standard values ​​of the pressure gradient on prostheses vary quite widely, it is possible to speak of stenosis only if there are results from previous studies (performed at best by the same doctor on the same machine). In the absence of concomitant regurgitation on the valves, a formula can be used to calculate the effective area of ​​the mitral opening of the prosthesis using the flow continuity equation, i.e. calculate the product of the LV outgoing path area and the flow rate in the outgoing path and divide by the flow rate through the MK prosthesis (Apv = Alvot X Vlvot / Vpv).

Attempting to quantify regurgitation through valve prostheses, especially in the mitral position, is extremely difficult with transthoracic access (due to the powerful acoustic shadow from the prosthetic material). In this case, the most informative may be color Doppler mapping or transesophageal examination. It should be remembered that a small stream of regurgitation (1 – 2 tbsp.) Can always be identified on a normally functioning prosthesis.

Thus, only using reference echocardiographic data, when the prosthesis is clearly functioning well (the results of postoperative echoCG studies), knowing the type and size of the prosthesis, one can evaluate its work in dynamics.

Prosthesis AK (paraprosthetic fistula with Prosthesis MK (ball prosthesis) regurgitation 2-3 tbsp.)

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