隨著微創心臟手術的發展，體外循環經由周邊血管插管建立已經越來越常被採用。由於空間受限的緣故，微創心臟手術無法輕易地如傳統心臟手術可在直視下建立中央體外循環。因此，經食道心臟超音波常被用來輔助周邊體外循環的建立。在此我們報告一位因嚴重二尖瓣閉鎖不全接受微創二尖瓣手術的個案。藉由經食道心臟超音波，我們發現了術前未被診斷的卵圓孔未閉，同時也避免了股靜脈插管通過卵圓孔。

With the advent of minimally invasive cardiac surgery (MICS), peripheral cannulation for cardiopulmonary bypass (CPB) has been increasingly used. Unlike conventional cardiac surgery, central cannulation for CPB under direct vision is difficult for MICS due to restricted space. Therefore, transesophageal echocardiography (TEE) is routinely used as guidance for peripheral CPB. We here present a case with severe mitral regurgitation receiving minimally invasive mitral valve surgery. Patent foramen ovale (PFO) was diagnosed by intraoperative TEE and femoral venous cannulation through PFO was avoided.