A 55-year-old man with significant lesion of left anterior descending artery and left ventricular systolic dysfunction, became candidate for coronary artery bypass grafts surgery. Intraoperative transesophageal echocardiography (TEE) was done for evaluation of severity of mitral regurgitation. During surgery, suddently systolic blood pressure dropped to 50 mmHg and lasted for 2 minutes and grade III left ventricular (LV) diastolic dysfunction occurred. After restoring blood pressure to 110/60 mmHg, LV diastolic pattern returned to baseline pattern. The decreased coronary perfusion pressure and its effect on diastolic function may be responsible for this pattern of diastolic dysfunction.