DYNAMIC CHANGE IN THE LEFT-VENTRICULAR BASE WITH OR WITHOUT A RIGID MITRAL-VALVE PROSTHESIS

To evaluate the narrowing of the left ventricular outflow tract (LVOT) during systole caused by a rigid mitral prosthesis, the geometric rel ationship between the prosthesis (or the mitral annulus) and the left ventricular base (LVB) was studied in five patients with mechanical mi tral valve prostheses and eight normal subjects. The images of the mit ral valve annulus (MVA) and the LVOT orifice reconstructed in three di mensions were projected on the plane of the LV base. Calculating the a reas of these projected images (i.e., those for MVA [Sm], LVOT orifice [So], the LVB [Sb; Sb = Sm + So]), the MVA-LVB ratio (Sm/Sb) was dete rmined. In the normal subject, the MVA-LVB ratio was nearly constant d uring systole (59 +/- 5% at 0 msec and 62 +/- 7% at 300 msec, respecti vely), whereas in the patients with prostheses, the ratio increased fr om 61 +/- 4% (0 msec) to 69 +/- 4% (300 msec). The increase in MVA-LVB ratio reduces the proportionate share of LVOT orifice in relation to the total LVB. The ideal mitral valve prosthesis should be flexible at the annulus to attain good performance in LVB dynamics.