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Figure 4 Color Doppler echocardiograms in the apical four-chamber view showing the method to determine the mitral inflow direction angle (right panel). Using Doppler color flow mapping at maximal early diastolic rapid filling, a line (straight arrow) is constructed to connect the center of the color Doppler inflow area at the mitral annular and chordal levels. The angle between this line and the mitral annular line (curved arrow) is the mitral inflow direction angle . The other two panels show markedly abnormal mitral inflow direction (directed posterolaterally) in an IMLC(+) patient and mildly abnormal direction in an IMLC(–) patient compared with normal direction in control subjects. LV, left ventricle; LA, left atrium; RV, right ventricle; RA, right atrium.