[Mechanism of an early diastolic posterior motion of the interventricular septum in patients with mitral stenosis: with special reference to left ventricular inflow velocity pattern].

The mechanism of an early diastolic posterior motion of the interventricular septum (IVS) was investigated by means of M-mode, two-dimensional and pulsed Doppler echocardiographies in 53 patients with pure mitral stenosis (MS). Velocity patterns of the blood flow at the inflow tract of the left ventricle (LVIT) were classified into three types as previously reported (cf. Fig.3). The results obtained were as follows: The mitral valve orifice area (MVA) was significantly smaller in patients with type III of the LVIT flow velocity pattern than in patients with type I (p less than 0.001). An amplitude ("a") of the posterior IVS motion in systole (P1) was significantly diminished in type III (4.2 +/- 1.1 mm) than in type I (6.6 +/- 1.5 mm) (p less than 0.001). An amplitude ("b") of the posterior IVS motion in early diastole (P3) showed a significant increase in type III (7.5 +/- 1.2 mm) than in type I (5.2 +/- 1.5 mm) (p less than 0.001). Difference of the amplitude between P1 and P3 ("a-b") was significantly greater in type III (-3.4 +/- 1.1 mm) than in type I (1.4 +/- 0.9 mm) (p less than 0.0001). MVA was correlated statistically with "a" (r = 0.58, p less than 0.001), "b" (r = -0.38, p less than 0.01) and "a-b" (r = 0.80, p less than 0.0001). Deformity of the left ventricular cavity due to the flattened IVS in early diastole was observed in severe MS with an augmented septal P3 dip. A case of severe MS with type III velocity pattern and an augmented P3 dip showed type II velocity pattern and a decreased P3 dip after the attack of acute myocardial infarction. These findings suggested a close relationship between type III of the LVIT flow velocity pattern and the prominent septal P3 dip. The importance of diastolic suction of the left ventricle in producing an early diastolic posterior motion of IVS (P3) was discussed.