Geometry of left ventricular contraction in the systolic click syndrome. Characterization of a segmental myocardial abnormality.

Left ventricular (LV) shape change during systole was characterized in nine patients with typical clinical findings of the systolic click syndrome (SCS) by means of cineangiographic measurements of three segmental diameters of the LV cavity and of the mitral valve ring (MVR) and contrasted with findings in eight patients with normal LV function. In the latter group, shortening of the proximal, midventricular, and apical segment diameters was comparable, averaging 38.6, 40.3, and 46.8%, respectively; MVR shortening averaged 31.8%. The velocity of fiber shortening, estimated as mean circumferential fiber shortening rate (mean FSR), was also similar in the three segments (1.66, 1.84, and 2.09 circ/sec). In patients with SCS, the extent of shortening and mean FSR in the proximal ventricular segment were consistently reduced (average 22.2%, P < 0.005; and 0.96 circ/sec, P <0.025 respectively), and the MVR exhibited either reduced extent of contraction (four patients) or was unchanged or increased in diameter during systole (five patients). However, shortening of the midventricular and apical segments was normal, averaging 37.5 and 40.5%, respectively, as was the mean FSR in these segments (averages 1.60 and 1.70 circ/sec). These findings are consistent with a primary disorder of the myocardium in SCS localized to the inflow region of the left ventricle.