Abstract: One hundred cases of coronary heart disease were divided into the following three groups: CHDsinus rhythm group,paroxysmal Af group and permanent Af group. Results showed that the LADvalue of group 1 is shorter than that of group 2 with significant statistical difference(P<0.05).The occurrence of mitral regurgitation increases with the increase of LAD. The result of this article suggests that when paroxysmal atrial fibrillation(Af)happens in clinics, active measures should be taken to control the attack so as to prevent the worsening of ischemia and hypoxia of the patients' heart. Colour Doppler echocardiographic instrument is one of the simple and easy to operate means for dynamic inspection of LADand mitral regurgitation changes.

Key words: left atrium diameter(LAD), mitral regurgitation, atrium fibrillation