BACKGROUND: During clinical practice we found that left ventricular systolic function(LVSF) has been normalized in some patients with cardiomyopathy. We investigated the echocardiographic and clinical factors affecting normalization of LVSF in these patients. METHOD: The patients with LV systolic dysfunction(EF<40%) were evaluated with echocardiography, coronary angiography and/or 201-Thallium SPECT and follow-up echocardiography(FUE) one year later. They had no coronary, valvular, congenital heart diseases. Consecutive 50 patients with improved LVSF(EF> or =55%) in FUE were defined to Group 1(mean age 57+/-16, male 21, female 29, mean follow-up 18+/-6 month) and another consecutive 50 patients with sustained decreased LVSF(EF<40%) and no increment of EF over 10% in FUE were defined to Group 2(mean age 56+/-14, male 32, female 18, mean follow-up 20+/-6 month). RESULTS: By univariate analysis, significant factors affecting normalization of LVSF were female sex, non-smoker, first experience of dyspnea, absence of bundle branch block in ECG, end-diastolic dimension of LV(LVEDD), end-diastolic volume of LV(LVEDV), LA size, less sphericity, presence of pericardial effusion, peak and end systolic wall stress. By multivariate analysis, LVEDD(Group 1: 61+/-7, Group 2: 71+/-7mm, p<0.001), LVEDV(Group 1: 139+/-59, Group 2: 190+/-51ml, p<0.01), absence of bundle branch block in ECG and 1st attack of symptom were significant. By Receiver operating characteristics curve analysis, area under curve of LVEDD and LVEDV were 0.859(95%CI: 0.775-0.920) and 0.805(95%CI: 0.681-0.896), respectively. LVEDD< or =64mm predicted normalization of LVSF with a sensitivity 76% and a specificity 86%. CONCLUSION: Determination of cardiac dimension and volume by echocardiography is very important to predicting normalization of LV systolic function in primary myocardial disease. And this results suggest that myocardial structural integrity may be important for recovery of LV function in clinical setting.