THE INFLEXIBLE MITRAL ANNULUS AFTER VALVE PROSTHESIS - INHERENT RISK OF DYNAMIC LEFT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION

Although chordal preserving mitral valve replacement is beneficial to cardiac function, the loss of flexibility of the annulus and consequen t translational motion of the valve prosthesis during systole may caus e potential left ventricular outflow tract (LVOT) obstruction after su rgery. The extent of the flexibility of the mitral valve annulus (MVA) necessary for the prosthetic valve to prevent potential LVOT obstruct ion was determined. The three dimensional images of the MVA at 0, 100, 200, and 300 msec delay from the electrocardiogram R wave were recons tructed from cine-mode magnetic resonance images in eight normal subje cts. In the lateral view of the MVA, the dorsal flexion angle (DFA) wa s defined. This angle implies the extent of the flexion of the anterio r half of the MVA in relation to the posterior half. The data (mean +/ - SD) for the DFA were 31.7 +/- 5.4 degrees (0 msec), 36.4 +/- 4.5 deg rees (100 msec), 39.0 +/- 3.8 degrees (200 msec), and 43.6 +/- 2.6 deg rees (300 msec), whereas the systolic increase in DFA was 11.9 +/- 3.2 degrees. The flexibility observed in normal mitral annuli is relevant to prosthetic mitral valves.