Iatrogenic coronary ostial stenosis (ICOS) is a rare but potential fatal complication of valve surgery, with estimated instance of 0.3% to 5%. Here, we present a case of RCA ostium stenosis and consequent right heart failure, which is diagnose by TEE intraoperatively. A 69-year-old woman, with severe aortic stenosis, was admitted to hospital for elective aortic valve replacement. The resting ECG showed normal sinus rhythm. Preoperative coronary angiography revealed patent LM and insignificant narrowing of LAD, LCx, and RCA. The systolic function of both ventricles were adequate, without noticeable asynergy or hypokinesia. During operation, the aortic valve was approached via mini-sternotomy and aortotomy. A 21-mm porcine bioprosthesis (St. Jude Medical EpicTM) was implanted after aortic valve excised. After discontinuing the cardiopulmonary bypass (CPB), new-onset AV block and ST elevation in lead II occurred. TEE disclosed prominent RA and RV dilation with poor contractility. Pulsed wave (PW) TDI peak systolic velocity (PSV) of RV free wall significantly decreased down to 1.14 cm/sec, compared with 6.43 cm/sec measured preoperatively. However, LV regional wall motions were not impaired. The prosthesis was well positioned with appropriate motion. We found that calcified sinus and aortic wall around the RCA ostium remained, with inflow untraceable in proximal RCA. Under impression of right coronary ostial stenosis and consequent right heart failure, CPB was restarted to perform coronary artery bypass for RCA. After the procedure, RV regained systolic function with PSV improved up to 5.20 cm/sec. ECG showed gradually recovery from ST elevation to T wave inversion in lead II. CPB was discontinued uneventfully. The patient was extubated smoothly on day 1 after the operation and transferred to the ordinary ward right away with favorable hemodynamics and functional status. Mechanisms of ICOS have been postulated in previous reports, including traumatic insults on the coronary vessels by insertion of coronary cannulae, calcium emboli mobilized during the initial aorotomy, intimal thickening, turbulent blood flow around the prosthetic valves and consequent fibrous proliferation, immunological reaction to the graft, and genetic predisposition. Coronary angiography with revascularization for diagnosis and treatment has been shown with favorable immediate and long-term clinical outcomes. However, it is not be feasible to perform coronary angiography during operation. Thus, TEE can serve as a prompt and approachable diagnostic tool in this setting. We presented this case to highlight intraoperative application of pulsed wave TDI for diagnosing ICOS. Peak systolic velocities (PSV) changes in the basal segment of the free RV wall might serve as a valid indicator for infarction area, leading to prompt revascularization and favorable prognosis. We suggest that routine recording myocardial velocities preoperatively, especially for patients with prominently calcified aortic valves and at risk of iatrogenic coronary ostial stenosis during aortic valve surgery.