Temporal relationship between early systolic closure of the aortic valve and aortic flow: experimental study with and without systolic anterior motion of the mitral valve.

To investigate the causative factors of typical early systolic closure (ESC) of the aortic valve (AoV), the temporal relationships of ESC with changes in blood pressures and aortic flow (AoF) were examined in dogs with experimentally induced ESC with and without systolic anterior motion (SAM) of the mitral valve. SAM was induced by dobutamine administration. Typical ESC was observed, but no SAM or left ventricular outflow obstruction, in five of the eight dogs treated with isoproterenol. Regardless of the presence or absence of SAM, the onset of ESC occurred before and the end of ESC immediately after the peak of AoF. A similar time relationship was noted between partial closure of the AoV, and pressure and flow changes before administration of isoproterenol, as well as after its termination. These results exclude a rapid decrease in flow velocity as the cause of ESC in our experimental preparation. The nearly uniform temporal relationship between ESC and changes in AoF observed under various conditions is considered to have important implications in the cause of ESC.