© Haberal et al.; licensee BioMed Central.Background: We aimed at assessing the efficacy of the patch plasty technique without endarterectomy in patients with diffuse coronary artery. Long anastomosis of the left internal mammary artery graft (LIMA) to the left anterior descending (LAD) artery was performed and examined using transthoracic Doppler echocardiography to detect coronary flow reserve (CFR) and epicardial stenosis. Methods: Forty-one patients (6 women; mean age, 58 ± 9 years) who underwent coronary artery bypass surgery using the patch plasty technique without endarterectomy were included in the study. Presence of CFR was examined in each patient by transthoracic Doppler echocardiography. Results: One of the patients (2.4%) died on the first postoperative day. The remaining patients were divided into 2 groups: those with normal CFR (CFR ≥ 2) (n = 35, 88%) and those with low CFR (CFR < 2) (n = 5, 12.0%). The length of patch plasty (3.6 ± 0.82 cm) in the low CFR group was significantly longer than that in the normal CFR group (2.69 ± 0.75 cm). Coronary angiography was performed for the 3 patients with CFR < 2: Two patients showed normal grafts and anastomoses, but the third patient's distal LAD-LIMA anastomosis was almost 90% occluded. Conclusion: We elucidated the reliability of the patch plasty without endarterectomy method and transthoracic Doppler echocardiography for detecting the severity of coronary artery disease.