BACKGROUND AND OBJECTIVES: Some reports have suggested that coronary microvascular dysfunction plays a role in the recovery of myocardial function in patients with obstructive coronary artery disease. Thrombolysis in myocardial infarction (TIMI) frame count (TFC) is regarded as a simple, reliable method for evaluating microvascular function. We evaluated microvascular function using TFC immediately after coronary intervention and compared TFC with left ventricular systolic function eight months later. SUBJECTS AND METHODS: We studied 68 patients with obstructive coronary artery disease who underwent coronary intervention. Just after intervention, TFC was calculated with the standard method. Left ventricular systolic function was assessed with left ventricular diastolic dimension (LVEDd), ejection fraction (EF), and wall motion score index (WMSI). Eight months after intervention, we completed follow-up coronary angiography and echocardiography. We defined high TFC (HTFC) as a TFC greater than 18. RESULTS: Ten patients were in the HTFC group, and 58 patients were in the low TFC (LTFC) group. There was no difference between the two groups with regard to baseline cardiovascular characteristics and angiographic findings. Just after intervention, the HTFC group showed significantly higher LVEDd (56.6+/-8.9 mm) and WMSI (1.60+/-0.65) compared to the LTFC group (50.3+/-5.9 mm, p<0.05; 1.34+/-0.29, p<0.05, respectively), but there was no significant difference in EF between the groups (49.3+/-18.6% vs. 56.2+/-14.8%, p>0.05). Eight months after intervention, there was also a significant decrease in the WMSI in the LTFC group (1.23+/-0.25, p<0.05), but not in the HTFC group (1.57+/-0.62, p>0.05). CONCLUSION: Increased TFC immediately after coronary intervention is an important poor prognostic factor related to myocardial systolic function eight months after coronary intervention. Coronary microvascular dysfunction may influence myocardial recovery in the setting of obstructive coronary artery disease.